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Mobile Biplane X-Ray Imaging System for Measuring 3D Dynamic Joint Motion During Overground Gait
Abstract
Most X-ray fluoroscopy systems are stationary and impose restrictions on the measurement of dynamic joint motion; for example, knee-joint kinematics during gait is usually measured with the subject ambulating on a treadmill. We developed a computer-controlled, mobile, biplane, X-ray fluoroscopy system to track human body movement for high-speed imaging of 3D joint motion during overground gait. A robotic gantry mechanism translates the two X-ray units alongside the subject, tracking and imaging the joint of interest as the subject moves. The main aim of the present study was to determine the accuracy with which the mobile imaging system measures 3D knee-joint kinematics during walking. In vitro experiments were performed to measure the relative positions of the tibia and femur in an intact human cadaver knee and of the tibial and femoral components of a total knee arthroplasty (TKA) implant during simulated overground gait. Accuracy was determined by calculating mean, standard deviation and root-mean-squared errors from differences between kinematic measurements obtained using volumetric models of the bones and TKA components and reference measurements obtained from metal beads embedded in the bones. Measurement accuracy was enhanced by the ability to track and image the joint concurrently. Maximum root-mean-squared errors were 0.33 mm and 0.65° for translations and rotations of the TKA knee and 0.78 mm and 0.77° for translations and rotations of the intact knee, which are comparable to results reported for treadmill walking using stationary biplane systems. System capability for in vivo joint motion measurement was also demonstrated for overground gait.
... Guan et al. examined fluoroscopy data in functional mode [26], which were studied by Vergis et al. in static mode. Guan et al. measured real and functional performance to help with rehabilitation, diagnosis, and treatment decisions. ...
... Functional knee joint arthokinematics Guan et al. [26] The knees of each subject were scanned by computed Tomography (CT) (Light Speed Pro 16, GE Medical Systems) from 15 cm proximal to 15 cm distal to the joint line with a slice interval of 0.625 mm. Subject-specific CT-based bone models of the femur and tibia were matched to the biplane radiographs using an automated matching process. ...
... Bey et al. [24] Measuring in-vivo motion of the knee's patellofemoral Overall dynamic accuracy indicated errors of less than 0.395 mm for the patellar shift, 0.875° for flexion, 0.863° for tilt, and 0.877° for rotation Biplane x-ray imaging combined with model-based tracking Wu et al. [25] Arthro-kinematics through 3D motion tracking Indistinctive VICON 3D motion system Guan et al. [26] Functional knee joint arthokinematics ...
Context: The present study provides an analysis of methods in assessment and measurement of knee arthrokinematic movements. Evidence Acquisition: in this study, an exhaustive review of the methods for assessment of knee joint arthrokinematics is provided. For this, some known databases including Science Direct, PubMed, EMBASE, CINAHL, and Google Scholar, for the period 1985 to February 2020 are explored. Results: After the assessment steps, 14 articles were chosen based on the criteria and objectives of the research; 13 articles in entirety and one as a summary. Through a review of the studies, it was observed that various methods were used in assessment and measurement of the knee joint arthrokinematic movements. In the beginning, focus was on transitional motion in which knee arthrokinematic movements were studied in static state; but with time, knee transitional movement was studied in dynamic state as well. More recent studies scrutinized three main types of arthrokinematics: motion rolling, gliding and spinning. There were also studies that tried to implement tools which required minimum cost and scrutinized the knee arthrokinematic movements without complicated state-of-the-art equipment. All the said equipment were designed with the aim of diagnosis of how the arthrokinematic movements of an injured knee compared to a healthy one. Conclusion: Results of our analysis show that the literature is rich with a variety of instruments for measuring knee arthrokinematic movements. By classifying the instruments, it was found that studies of four different measurement methods including static, dynamic, functional and qualitative have examined the arthrokinematic movements of the knee.
... However, high cost, cumbersome setup, and limited field of view (FOV) impede routine usage in the clinical setting. Recently, several groups have been working on the development of mobile fluoroscopy systems [28,29]. Although using a robotic trolley or gantry carrying the fluoroscopic system following the movement of subject extends the FOV, the radiation exposure to the subject remains inevitable. ...
... A comparison with a skin-mounted marker measurement in a cadaveric setting has been conducted in our previous study. However, a critical comparison with a skin marker system under in vivo conditions is necessary, particularly if a ground truth method (e.g., an advanced mobile fluoroscopy system) [28,29] can be incorporated. Currently, the FOV of our system is the same as the conventional motion capture systems, since it only depends on the FOV of the employed motion capture system. ...
... Secondly, only five healthy subjects were involved in this study. Ideally, a cohort of living subject covering different patients and healthy groups with different sizes and BMIs accompanied with a ground truth measurements as a reference (e.g., advanced mobile fluoroscopy system) [28,29] could provide more valuable information with regard to the pathological patterns on kinematics. Thirdly, a standardized definition of the femoral and tibial ARF across different subjects is imperative for 6-DOF joint kinematics analysis. ...
Tracking joint motion of the lower extremity is important for human motion analysis. In this study, we present a novel ultrasound-based motion tracking system for measuring three-dimensional (3D) position and orientation of the femur and tibia in 3D space and quantifying tibiofemoral kinematics under dynamic conditions. As ultrasound is capable of detecting underlying bone surface noninvasively through multiple layers of soft tissues, an integration of multiple A-mode ultrasound transducers with a conventional motion tracking system provides a new approach to track the motion of bone segments during dynamic conditions. To demonstrate the technical and clinical feasibilities of this concept, an in vivo experiment was conducted. For this purpose the kinematics of healthy individuals were determined in treadmill walking conditions and stair descending tasks. The results clearly demonstrated the potential of tracking skeletal motion of the lower extremity and measuring six-degrees-of-freedom (6-DOF) tibiofemoral kinematics and related kinematic alterations caused by a variety of gait parameters. It was concluded that this prototyping system has great potential to measure human kinematics in an ambulant, non-radiative, and noninvasive manner.
... In addition to the radiation, a drawback of the fluoroscopic systems is the limited field of view that restricts the patient's natural movement. Recently, fluoroscopic systems that are mobilized by robots which can follow the patient during gait have been proposed, allowing for more natural kinematics [2,26] . These types of robotized fluoroscopic systems are, however, still radiative, high in cost and workload. ...
... Relative to our concept, the utilization of a fluoroscopy system to estimate the position and orientation of bone is different, since it relies on the radiological images and adequate modelbased techniques [24,39,40] . Fluoroscopy systems provide highly accurate measurements of tibiofemoral kinematics, especially for knee with implants [26,39] . Guan et al. reported that maximum root-mean-squared errors were 0.33 mm and 0.65 °for translations and rotations of the TKA knee and 0.78 mm and 0.77 °for translations and rotations of the intact knee [26] . ...
... Fluoroscopy systems provide highly accurate measurements of tibiofemoral kinematics, especially for knee with implants [26,39] . Guan et al. reported that maximum root-mean-squared errors were 0.33 mm and 0.65 °for translations and rotations of the TKA knee and 0.78 mm and 0.77 °for translations and rotations of the intact knee [26] . The maximum rootmean-squared errors were 4.20 mm and 3.30 °for translations and rotations of the intact knee for our one-channel ultrasound system, which is much less accurate than a biplane fluoroscopy system. ...
The purpose of this study is to investigate the technical feasibility of measuring relative positions and orientations of the tibia with respect to the femur in an in-vitro experiment by using a 3D-tracked A-mode ultrasound system and to determine its accuracy of angular and translational measurements. As A-mode ultrasound is capable of detecting bone surface through soft tissue in a non-invasive manner, the combination of a single A-mode ultrasound transducer with an optical motion tracking system provides the possibility for digitizing the 3D locations of bony points at different anatomical regions on the thigh and the shank. After measuring bony points over a large area of both the femur and tibia, the bone models of the femur and tibia that were segmented from CT or MRI images were registered to the corresponding bony points. Then the relative position of the tibia with respect to the femur could be obtained and the angular and translational components could also be measured. A cadaveric experiment was conducted to assess its accuracy compared to the reference measurement obtained by optical markers fixed to intra-cortical bone pins placed in the femur and tibia. The results showed that the ultrasound system could achieve 0.49 ± 0.83°, 0.85 ± 1.86° and 1.85 ± 2.78° (mean ± standard deviation) errors for Flexion-Extension, Adduction-Abduction and External-Internal rotations, respectively, and -2.22 ± 3.62 mm, -2.80 ± 2.35 mm and -1.44 ± 2.90 mm errors for Anterior-Posterior, Proximal-Distal and Lateral-Medial translations, respectively. It was concluded that this technique is feasible and facilitates the integration of arrays of A-mode ultrasound transducers with an optical motion tracking system for non-invasive dynamic tibiofemoral kinematics measurement.
... Biplane X-ray images (1024 9 1024 pixels, 200 frames/s, 1/200 s exposure time) of the right knee were acquired using a Mobile Biplane X-ray (MoBiX) imaging system. 10 The biplane X-ray images were then imported to custom software in MATLAB (Math-Works Inc., Natick, MA) to perform pose-estimation of the femur, tibia and patella and calculate TF and PF joint kinematics. Geometric models of each bone required for pose estimation were created from CT scans (0.35 9 0.35 9 0.50 mm) taken of the right knee. ...
... For example, the mean RMS error in predicting external tibial rotation using the 1-DOF knee model was 5.8°compared to an RMS error of 0.6°obtained from biplane X-ray imaging. 10 The relatively high errors in the model predictions can be explained firstly by the observation that no two kinematic parameters at either the TF or PF joint are perfectly coupled to each other 23 ; and secondly by the relatively high inter-participant variability in the knee kinematic data. 7 In addition, the model predictions are inextricably linked to the reference frame assigned to each bone. ...
Six kinematic parameters are needed to fully describe three-dimensional (3D) bone motion at a joint. At the knee, the relative movements of the femur and tibia are often represented by a 1-degree-of-freedom (1-DOF) model with a single flexion–extension axis or a 2-DOF model comprising a flexion–extension axis and an internal–external rotation axis. The primary aim of this study was to determine the accuracy with which 1-DOF and 2-DOF models predict the 3D movements of the femur, tibia and patella during daily activities. Each model was created by fitting polynomial functions to 3D tibiofemoral (TF) and patellofemoral (PF) kinematic data recorded from 10 healthy individuals performing 6 functional activities. Model cross-validation analyses showed that the 2-DOF model predicted 3D knee kinematics more accurately than the 1-DOF model. At the TF joint, mean root-mean-square (RMS) errors across all activities and all participants were 3.4°|mm (deg or mm) for the 1-DOF model and 2.4°|mm for the 2-DOF model. At the PF joint, mean RMS errors were 4.0°|mm and 3.9°|mm for the 1-DOF and 2-DOF models, respectively. These results indicate that a 2-DOF model with two rotations as inputs may be used with confidence to predict the full 3D motion of the knee-joint complex.
... Errors associated with STA can be avoided using pins screwed directly into the subjects' bones (Lafortune et al., 1992;Reinschmidt et al., 1997), but such procedures are highly invasive and therefore limited to small cohort studies. To directly assess tibio-femoral kinematics in a less invasive manner, single-plane (Dennis et al., 2001;Galvin et al., 2019;Grieco et al., 2016;List et al., 2017;Moewis et al., 2016;Moro-oka et al., 2008) and dual-plane (Anderst et al., 2009;Guan et al., 2016;Kozanek et al., 2009;Li et al., 2008) fluoroscopic analyses have provided valuable and accurate data. The predominant drawback of most systems, however, relates to the small size and static nature of the intensifier, hence restricting measurements to a limited field-of-view. ...
... To overcome the limitations of static imaging set-ups, procedures to enhance the fluoroscopic field-ofview have been investigated (Li et al., 2008). Moreover, mobile fluoroscopic systems have emerged that allow tracking of the knee during dynamic movements (Yamokoski and Banks, 2011) and consecutive cycles of gait activities (Guan et al., 2016;List et al., 2017). ...
Accurate assessment of 3D tibio-femoral kinematics is essential for understanding knee joint functionality, but also provides a basis for assessing joint pathologies and the efficacy of musculoskeletal interventions. Until now, however, the assessment of functional kinematics in healthy knees has been mostly restricted to the loaded stance phase of gait, and level walking only, but the most critical conditions for the surrounding soft tissues are known to occur during high-flexion activities. This study aimed to determine the ranges of tibio-femoral rotation and condylar translation as well as provide evidence on the location of the centre of rotation during multiple complete cycles of different gait activities.
Based on radiographic images captured using moving fluoroscopy in ten healthy subjects during multiple cycles of level walking, downhill walking and stair descent, 3D femoral and tibial poses were reconstructed to provide a comprehensive description of tibio-femoral kinematics.
Despite a significant increase in joint flexion, the condylar antero-posterior range of motion remained comparable across all activities, with mean translations of 6.3-8.3mm and 7.3-9.3mm for the medial and lateral condyles respectively. Only the swing phase of level walking and stair descent exhibited a significantly greater range of motion for the lateral over the medial compartment. Although intra-subject variability was low, considerable differences in joint kinematics were observed between subjects. The observed subject-specific movement patterns indicate that accurate assessment of individual pre-operative kinematics together with individual implant selection and/or surgical implantation decisions might be necessary before further improvement to joint replacement outcome can be achieved.
... Improved accuracy may be achieved by attaching markers to bone pins [11,14], however, use of this technique is limited due to its invasive nature. A less invasive technique is biplane radiography, which has demonstrated submillimeter accuracy in tracking bone motion during dynamic activities [15,16]. Processing biplane radiography data are extremely time-consuming, typically requiring hours to track motion from a single movement trial, which limits sample size using this technology. ...
... Processing biplane radiography data are extremely time-consuming, typically requiring hours to track motion from a single movement trial, which limits sample size using this technology. Biplane radiography also has a limited field of view which permits only a portion of the gait cycle to be imaged [15,[17][18][19] unless a mobile radiography system that moves with the participant is used [16,20]. ...
A dataset of knee kinematics in healthy, uninjured adults is needed to serve as a reference for comparison when evaluating the effects of injury, surgery, rehabilitation, and age. Most currently available datasets that characterize healthy knee kinematics were developed using conventional motion analysis, known to suffer from skin motion artifact. More accurate kinematics, obtained from bone pins or biplane radiography, have been reported for datasets ranging in size from 5 to 15 knees. The aim of this study was to characterize tibiofemoral kinematics and its variability in a larger sample of healthy adults. Thirty-nine knees were imaged using biplane radiography at 100 images/s during multiple trials of treadmill walking. Multiple gait trials were captured to measure stance and swing phase knee kinematics. 6DOF kinematics were determined using a validated volumetric model-based tracking process. A bootstrapping technique was used to define average and 90% prediction bands for the kinematics. The average ROM during gait was 7.0 mm, 3.2 mm, and 2.9 mm in AP, ML and PD directions, and 67.3°, 11.5° and 3.7° in FE, IE, and AbAd. Continuous kinematics demonstrated large inter-knee variability, with 90% prediction bands spanning approximately ±4 mm, ±10 mm, and ±5 mm for ML, AP, and PD translations and ±15°, ±10°, and ±6° in FE, IE, and AbAd. This dataset suggests substantial variability exists in healthy knee kinematics. This study provides a normative database for evaluating knee kinematics in patients who receive conservative or surgical treatment.
... Here we provide the first non-invasive measurements of the kinematics of the entire knee-joint complex for normal walking. We used a unique Mobile Biplane X-ray (MoBiX) imaging system 20 to track and image the three-dimensional motion of the femur, tibia, and patella as healthy young adults walked at their natural speeds over ground. Our specific aims were to (i) obtain simultaneous measurements of 6degree-of-freedom (6-DOF) tibiofemoral and patellofemoral joint kinematics and condylar motion for one complete stride cycle; (ii) examine the extent to which secondary rotations and translations of the femur, tibia, and patella are coupled to the knee flexion angle; and (iii) determine the location of the center of rotation of the knee in the transverse plane for the stance and swing phases of normal walking. ...
... Six-DOF tibiofemoral and patellofemoral joint kinematics were derived from the biplane X-ray images by following a pipeline of previously described procedures. 20 Image processing, pose estimation, and joint kinematic analysis were performed using a custom program developed in MATLAB (Mathworks Inc., Natick, MA). Maximum RMS errors associated with 6-DOF kinematic measurements for the healthy knee during overground walking were reported to be 0.78 mm and 0.77˚for translations and rotations of the tibiofemoral joint 20 and 0.37 mm and 1.46˚for translations and rotations of the patellofemoral joint. ...
Accurate knowledge of knee kinematics is important for a better understanding of normal joint function and for improving patient outcomes subsequent to joint reconstructive surgery. Limited information is available that accurately describes the relative movements of the bones at the knee in vivo, even for the most common of all activities: walking. We used a mobile X‐ray imaging system to measure the three‐dimensional motion of the entire knee‐joint complex – femur, tibia and patella – when humans walk over ground at their natural speeds. Data were recorded from 15 healthy individuals (9 males, 6 females; age 30.5 ± 6.2 years). The most pronounced rotational motion of the tibia was flexion‐extension followed by internal‐external rotation and abduction‐adduction (peak‐to‐peak displacements: 70.7°, 9.2° and 1.9°, respectively). Maximum anterior translation of the tibia was 6.5 mm and occurred in early swing, coinciding with peak knee flexion and peak internal rotation. The most prominent rotational motion of the patella was flexion‐extension (peak‐to‐peak displacement: 50.5°). The tibia pivoted about the medial compartment of the tibiofemoral joint, conferring greater movements of the contact centers in the lateral compartment than the medial compartment (15.4 mm and 9.7 mm, respectively). Internal‐external rotation, anterior‐posterior translation and medial‐lateral shift of the tibia as well as flexion‐extension and anterior‐posterior translation of the patella were each coupled to the knee flexion angle, as were movements of the contact centers at each joint. These fundamental data serve as a valuable resource for evaluating knee joint function in normal and pathological gait. The data are available in Supplementary_Material_Data.xlsx. This article is protected by copyright. All rights reserved
... Introduction Video-fluoroscopy in combination with 2D/3D registration allows an accurate quantification of 3D joint motion free of soft tissue artefact and has thus become a well-accepted imaging technique for the acquisition of kinematic information of single joints during functional movement tasks. Research using single plane video-fluoroscopic analysis [1][2][3][4][5][6][7], as well as dual orthogonal fluoroscopy [8][9][10], has provided valuable information on the three-dimensional motion of total knee arthroplasties (TKAs) and healthy knees. However, due to the limited field of view of the stationary image intensifier, static systems can only be applied for the analysis of highly restricted movements [11,12]. ...
... However, due to the limited field of view of the stationary image intensifier, static systems can only be applied for the analysis of highly restricted movements [11,12]. To overcome these limitations, mobile devices such as the robotic radiographic imaging platform [13,14], the mobile fluoroscopy system [15], the mobile biplane X-ray imaging system [9], and the moving fluoroscope [3,6,7,16], have all been developed to allow the tracking of the knee during complete gait cycles of level gait, stair and ramp walking. ...
Video-fluoroscopic analysis can provide important insights for the evaluation of outcome and functionality after total knee arthroplasty, allowing the in vivo assessment of tibiofemoral kinematics without soft tissue artefacts. To enable measurement of the knee throughout activities of daily living such as gait, robotic systems like the moving fluoroscope have been developed that follow the knee movement and maintain the joint in front of the image intensifier. Since it is unclear whether walking while being accompanied by moving fluoroscope affects normal gait, the objective of this study was to investigate its influence on gait characteristics in healthy subjects. In addition, the impact of the motors’ noise was analysed.
By means of skin markers analysis (VICON MX system, Oxford Metrics Group, UK) and simultaneous measurement of ground reaction forces (Kistler force plates, Kistler, Switzerland), gait characteristics when walking with and without the moving fluoroscope as well as with and without ear protectors in combination with the moving fluoroscope, were obtained in young (n = 10, 24.5y ± 3.0y) and elderly (n = 9, 61.6y ± 5.3y) subjects during level gait and stair descent. Walking with the moving fluoroscope significantly decreased gait velocity in level gait and stair descent over the respective movement without the fluoroscope. Statistical analysis, including gait velocity as a covariate, resulted in no differences on the ground reaction force parameters. However, some kinematic parameters (ankle, knee and hip ranges of motion, minimal knee angle in late stance phase, maximal knee angles in stance and swing phase) seemed to be modified by the presence of the moving fluoroscope, but statistical comparison was limited due to velocity differences between the conditions. Wearing ear protectors to avoid the influence of motor sound during walking with the moving fluoroscope caused no significant difference.
Walking with the moving fluoroscope has been shown to decrease gait velocity and small alterations in kinematic parameters were observed. Therefore, gait and movement alterations due to the moving fluoroscope cannot completely be excluded. However, based on the absence of differences in ground reaction force parameters (when adjusted for velocity within ANCOVA), as well as based on the comparable shape of the angular curves to the slow control condition, it can be concluded that changes in gait when walking with the moving fluoroscope are small, especially in comparison to natural slow walking. In order to allow assessment of joint replacement with the moving fluoroscope, including an understanding of the effects of joint pain, clinical analyses can only be compared to gait activities showing similarly reduced velocities. Importantly, the reduced gait speeds observed in this study are similar to those observed after total knee arthroplasty, suggesting that analyses in such subjects are appropriate. However, the moving fluoroscope would likely need to be optimized in order to detect natural gait characteristics at the higher gait velocities of healthy young subjects.
The moving fluoroscope can be applied for comparisons between groups measured with the moving fluoroscope, but care should be taken when comparing data to subjects walking at self-selected speed without the moving fluoroscope.
... trolled experimental scenario. As the results have shown, the ultrasound tracking system could achieve relatively high accuracies in flexion/extension (1.54°RMS error) and abduction/adduction (1.00°RMS error), which is close to the accuracy of the mobile fluoroscopic system with 0.77°RMS error (Guan et al., 2016a). In addition, the ultrasound tracking system showed the potential to Fig. 5. ...
... In this context, MRI scanning will be used to replace CT scanning for in-vivo application because of the radiation issue. With the high potential to implement further improvements associated with the ultrasound tracking system, we expect that a future ultrasound tracking system could estimate 6-DOF tibiofemoral kinematics with an accuracy within the range of fluoroscopy measurements (Guan et al., 2016a(Guan et al., , 2016b and provide a valid representation of bone segments in the knee joint, which will aid in gait analysis and disclosure of some pathological features. ...
Skin-mounted marker based motion capture systems are widely used in measuring the movement of human joints. Kinematic measurements associated with skin-mounted markers are subject to soft tissue artifacts (STA), since the markers follow skin movement, thus generating errors when used to represent motions of underlying bone segments. We present a novel ultrasound tracking system that is capable of directly measuring tibial and femoral bone surfaces during dynamic motions, and subsequently measuring six-degree-of-freedom (6-DOF) tibiofemoral kinematics. The aim of this study is to quantitatively compare the accuracy of tibiofemoral kinematics estimated by the ultrasound tracking system and by a conventional skin-mounted marker based motion capture system in a cadaveric experimental scenario. Two typical tibiofemoral joint models (spherical and hinge models) were used to derive relevant kinematic outcomes. Intra-cortical bone pins equipped with optical markers were inserted in the tibial and femoral bones to serve as a reference to provide ground truth kinematics. The ultrasound tracking system resulted in lower kinematic errors than the skin-mounted markers (the ultrasound tracking system: maximum root-mean-square (RMS) error 3.44° for rotations and 4.88 mm for translations, skin-mounted markers with the spherical joint model: 6.32° and 6.26 mm, the hinge model: 6.38° and 6.52 mm). Our proposed ultrasound tracking system has the potential of measuring direct bone kinematics, thereby mitigating the influence and propagation of STA. Consequently, this technique could be considered as an alternative method for measuring 6-DOF tibiofemoral kinematics, which may be adopted in gait analysis and clinical practice.
... This study is a prospective, double blinded, randomized trial to collect and measure subjective knee joint function using PROM, as well as three-dimensional knee joint kinematics utilizing biplane mobile fluoroscopy and video motion capture technologies as published by Guan et al. 26 in individuals who have undergone a total knee joint replacement. We will compare a medially stabilized construct design to standard fixed bearing conventional designs -posterior stabilized and cruciate retaining designs from a single joint implant manufacturer. ...
... Six-degree-of-freedom kinematics of the replaced knee will be measured at a sampling rate of 200 Hz using a mobile biplane x-ray (MoBiX) imaging system capable of measuring TKA rotations and translations to accuracies of 0.65° and 0.33 mm respectively. 26 The three dimensional coordinates of 45 retroreflective markers attached to predetermined bony landmarks of each subject will be recorded with a nine-camera video motion capture system (VICON, Oxford Metrics Ltd., Oxford) sampling at 120 Hz. Ground reaction forces acting on the subject's feet will be measured using two portable force plates (AMTI, Watertown, MA) sampling at 1080 Hz. ...
p class="abstract"> Background: No randomised trial exists to assess the relative prosthetic performance of three fixed bearing total knee joint replacement construct designs through clinical functional outcomes and biomechanical gait analysis at six months after the index procedure.
Methods: The design of a double blinded, prospective, randomised trial with three parallel patient groups is presented. Patients reviewed in consultant clinic with radiographic and clinical diagnosis of osteoarthritis of the knee, with the condition deemed severe enough to require a total knee joint replacement (TKJR) are eligible. Subjects enrolled in the trial are randomised to one of the three TKJR construct designs approximately ten days prior to scheduled date of surgery. Each subject is then followed up for at least twelve months. Repeated measure of Analysis of Variance (ANOVA), and Analysis of Covariance (ANCOVA) will be utilised to uncover any clinical functional differences in each trial group in each time interval.
Results: Differences in clinical functional scores at each time interval compared to pre-intervention, as well as between group differences in clinical functional scores at each time interval will be examined. At six months after the operation, biomechanical measurements of joint motion, ground reaction forces, and muscle electromyographic (EMG) activity will be recorded simultaneously from each subject for four test conditions: level walking, stair ascent, stair descent, and chair rise.
Conclusions: This randomised trial is designed to better understand the relationships between the clinical functional outcomes and replaced knee kinematics in three fixed bearing total knee replacement construct designs at six months postoperatively.</p
... A couple of research groups have been working on the development of mobile X-ray systems [6,[35][36][37][38], and recently Guan et el. [39] presented a mobile bi-plane X-ray system used for tracking of the knee joint during level walking. The system was capable of moving the Xray units 3.6 m horizontally and 0.5m vertically at peak velocities of 5 m/s and 1.2 m/s respectively with peak accelerations of 20 m/s 2 and 12 m/s 2 . ...
... While the influence of the wire on gait is expected to be very small (it only applies an external force of about 4N), a clear advantage is that the time delay is small enough to allow real-time control. In other systems [39] tracking includes a learned velocity profile and since, especially for pathological gait, gait repeatability can be reduced, this can lead to deficiencies in being able to keep the knee in the field of view. ...
Videofluoroscopy has been shown to provide essential information in the evaluation of the functionality of total knee arthroplasties. However, due to the limitation in the field of view, most systems can only assess knee kinematics during highly restricted movements. To avoid the limitations of a static image intensifier, a moving fluoroscope has been presented as a standalone system that allows tracking of the knee during multiple complete cycles of level- and downhill-walking, as well as stair descent, in combination with the synchronous assessment of ground reaction forces and whole body skin marker measurements. Here, we assess the ability of the system to keep the knee in the field of view of the image intensifier. By measuring ten total knee arthroplasty subjects, we demonstrate that it is possible to maintain the knee to within 1.8 ± 1.4 cm vertically and 4.0 ± 2.6 cm horizontally of the centre of the intensifier throughout full cycles of activities of daily living. Since control of the system is based on real-time feedback of a wire sensor, the system is not dependent on repeatable gait patterns, but is rather able to capture pathological motion patterns with low inter-trial repeatability.
... Wegen der genutzten Röntgenstrahlung ist die Fluoroskopie zwar invasiver als MRT-Untersuchungen, erlaubt aber eine höhere zeitliche Auflösung und findet zunehmend Einsatz bei der Untersuchung von rekonstruierten und ersetzten Kniegelenken (Clary et al. 2013;Dennis et al. 2005;. Mobile Fluoroskopien, die das Gelenk während der Fortbewegung verfolgen, ermöglichen komplett dynamische Betrachtungen der Gelenkkinematik (Guan et al. 2016;List et al. 2017). Mit einem solchen mobilen Fluoroskop wurde die 3D-Kniekinematik erfasst, während gleichzeitig die In-vivo-Kniekontaktkräfte mit instrumentierten Implantaten gemessen wurden (cams-knee.orthoload.com; ...
... ADLs of the prosthetic knee (List et al., 2017) and ankle (List et al., 2012) were analyzed invivo with moving single-plane fluoroscopy during ADLs. Recently, a moving biplane X-ray imaging system was tested in-vitro for total knee arthroplasty during simulated overground gait (Guan et al., 2016). ...
Introduction: Knowledge of the accurate in-vivo kinematics of total hip arthroplasty (THA) during activities of daily living can potentially improve the in-vitro or computational wear and impingement prediction of hip implants. Fluoroscopy- based techniques provide more accurate kinematics compared to skin marker-based motion capture, which is affected by the soft tissue artefact. To date, stationary fluoroscopic machines allowed the measurement of only restricted movements, or only a portion of the whole motion cycle.
Methods: In this study, a moving fluoroscopic robot was used to measure the hip joint motion of 15 THA subjects during whole cycles of unrestricted activities of daily living, i.e., overground gait, stair descent, chair rise and putting on socks.
Results: The retrieved hip joint motions differed from the standard patterns applied for wear testing, demonstrating that current pre-clinical wear testing procedures do not reflect the experienced in-vivo daily motions of THA.
Discussion: The measured patient-specific kinematics may be used as input to in vitro and computational simulations, in order to investigate how individual motion patterns affect the predicted wear or impingement.
... It has been suggested that the inclusion of gait analysis could improve clinical decision-making and treatment outcomes [7]. Current state-of-the-art technology includes both marker-based and markerless optical motion capture systems, as well as static and moving fluoroscopic systems [8,9]. While fluoroscopy offers the considerable advantage of not being affected by soft-tissue artefact, such systems are associated with substantial processing time requirements, infrastructure, expense and complexity, hence limiting their widespread adoption in clinical settings. ...
The success of kinematic analysis that relies on inertial measurement units (IMUs) heavily depends on the performance of the underlying algorithms. Quantifying the level of uncertainty associated with the models and approximations implemented within these algorithms, without the complication of soft-tissue artefact, is therefore critical. To this end, this study aimed to assess the rotational errors associated with controlled movements. Here, data of six total knee arthroplasty patients from a previously published fluoroscopy study were used to simulate realistic kinematics of daily activities using IMUs mounted to a six-degrees-of-freedom joint simulator. A model-based method involving extended Kalman filtering to derive rotational kinematics from inertial measurements was tested and compared against the ground truth simulator values. The algorithm demonstrated excellent accuracy (root-mean-square error ≤0.9°, maximum absolute error ≤3.2°) in estimating three-dimensional rotational knee kinematics during level walking. Although maximum absolute errors linked to stair descent and sit-to-stand-to-sit rose to 5.2° and 10.8°, respectively, root-mean-square errors peaked at 1.9° and 7.5°. This study hereby describes an accurate framework for evaluating the suitability of the underlying kinematic models and assumptions of an IMU-based motion analysis system, facilitating the future validation of analogous tools.
... Based on the resulting medial and lateral condylar A-P translations, the tibio-femoral centre of rotation (CoR) in the transverse plane can then be determined using either least-squares approaches (Banks and Hodge, 2004;Gray et al., 2019), sphere fitting (Gamage and Lasenby, 2002), or transformation techniques (Ehrig et al., 2006;Holzreiter, 1991). Application of these kinematic analysis approaches to bone poses captured using magnetic resonance imaging (MRI) (Vedi et al., 1999) or videofluoroscopy (Dennis et al., 2001;Galvin et al., 2019;Guan et al., 2016;Kozanek et al., 2009a;Li et al., 2008;List et al., 2017;Moro-oka et al., 2008) are able to provide access to the tibio-femoral joint motions in all degrees of freedom. However, while a general understanding of knee joint movement patterns has been achieved, including scientific and clinical agreement on the physiological range of A-P translation of the medial versus the lateral condyle as well as the location of the CoR during loaded knee flexion (Table 2), tibio-femoral kinematics during functional activities such as level walking remain controversially discussed (Table 3). ...
While there is general agreement on the transverse plane knee joint motion for loaded flexion activities, its kinematics during functional movements such as level walking are discussed more controversially. One possible cause of this controversy could originate from the interpretation of kinematics based on different analysis approaches. In order to understand the impact of these approaches on the interpretation of tibio-femoral motion, a set of dynamic videofluoroscopy data presenting continuous knee bending and complete cycles of walking in ten subjects was analysed using six different kinematic analysis approaches. Use of a functional flexion axis resulted in significantly smaller ranges of condylar translation compared to anatomical axes and contact approaches. All contact points were located significantly more anteriorly than the femur fixed axes after 70° of flexion, but also during the early/mid stance and late swing phases of walking. Overall, a central to medial transverse plane centre of rotation was found for both activities using all six kinematic analysis approaches, although individual subjects exhibited lateral centres of rotation using certain approaches. The results of this study clearly show that deviations from the true functional axis of rotation result in kinematic crosstalk, suggesting that functional axes should be reported in preference to anatomical axes. Contact approaches, on the other hand, can present additional information on the local tibio-femoral contact conditions. To allow a more standardised comparison and interpretation of tibio-femoral kinematics, results should therefore be reported using at least a functionally determined axis and possibly also a contact point approach.
... More invasive imaging techniques now enable the measurement of skeletal movement patterns, but these generally possess only a small field of view, therefore limiting the activities that can be captured (Anderst et al., 2009;Dennis et al., 2001;Galvin et al., 2019;Grieco et al., 2016;Kozanek et al., 2009;Li et al., 2008;Moewis et al., 2016;Moro-oka et al., 2008). More recently, however, mobile fluoroscopy systems have been introduced, hence allowing access to knee joint motion throughout full cycles of gait activities (Guan et al., 2016;List et al., 2017). Using such techniques, general agreement has been achieved for tibio-femoral kinematics during repetitive flexion tasks (DeFrate et al., 2004;Hamai et al., 2013;Hill et al., 2000;Moro-oka et al., 2008;Pinskerova et al., 2004;Tanifuji et al., 2011). ...
Background
A comparison of natural versus replaced tibio-femoral kinematics in vivo during challenging activities of daily living can help provide a detailed understanding of the mechanisms leading to unsatisfactory results and lay the foundations for personalised implant selection and surgical implantation, but also enhance further development of implant designs towards restoring physiological knee function. The aim of this study was to directly compare in vivo tibio-femoral kinematics in natural versus replaced knees throughout complete cycles of different gait activities using dynamic videofluoroscopy.
Methods
Twenty-seven healthy and 30 total knee replacement subjects (GMK Sphere, GMK PS, GMK UC) were assessed during multiple complete gait cycles of level walking, downhill walking, and stair descent using dynamic videofluoroscopy. Following 2D/3D registration, tibio-femoral rotations, condylar antero-posterior translations, and the location of the centre of rotation were compared.
Findings
The total knee replacement groups predominantly experienced reduced tibial internal/external rotation and altered medial and lateral condylar antero-posterior translations compared to natural knees. An average medial centre of rotation was found for the natural and GMK sphere groups in all three activities, whereas the GMK PS and UC groups experienced a more central to lateral centre of rotation.
Interpretation
Each total knee replacement design exhibited characteristic motion patterns, with the GMK Sphere most closely replicating the medial centre of rotation found for natural knees. Despite substantial similarities between the subject groups, none of the implant geometries was able to replicate all aspects of natural tibio-femoral kinematics, indicating that different implant geometries might best address individual functional needs.
... 2D/3D image registration techniques often use intensity or gradient measures to match silhouette projections or digitally reconstructed radiographs (DRRs). [9][10][11][12][13][14][15][16][17][18] Consequently, these methods are highly dependent on the geometrical shape, the intensities, and contrast to withhold the high accuracy. Theoretically, the registration may be affected by radiopaque metal implants and removal of bone, in terms of reduced bone model geometry and registration information, during insertion of implant components. ...
Radiostereometic analysis (RSA) is an accurate method for rigid body pose (position and orientation) in three‐dimensional space. Traditionally, RSA is based on insertion of periprosthetic tantalum markers and manual implant contour selection which limit clinically application. We propose an automated image registration technique utilizing digitally reconstructed radiographs (DRR) of computed tomography (CT) volumetric bone models (autorsa‐bone) as a substitute for tantalum markers. Furthermore, an automated synthetic volumetric representation of total knee arthroplasty implant models (autorsa‐volume) to improve previous silhouette‐projection methods (autorsa‐surface). As reference, we investigated the accuracy of implanted tantalum markers (marker) or a conventional manually contour‐based method (mbrsa) for the femur and tibia. The data are presented as mean (standard deviation). The autorsa‐bone method displayed similar accuracy of ‐0.013 (0.075) mm compared to the gold standard method (marker) of ‐0.013 (0.085). The autorsa‐volume with 0.034 (0.106) mm did not markedly improve the autorsa‐surface with 0.002 (0.129) mm, and none of these reached the mbrsa method of ‐0.009 (0.094) mm. In conclusion, marker‐free RSA is feasible with similar accuracy as gold standard utilizing DRR and CT obtained volumetric bone models. Furthermore, utilizing synthetic generated volumetric implant models could not improve the silhouette‐based method. However, with a slight loss of accuracy the autorsa methods provide a feasible automated alternative to the semi‐automated method. This article is protected by copyright. All rights reserved.
... The major limitation of these studies was that the muscle force was not controlled and, clearly, none of the experiments performed their assessments during highdemand sporting manoeuvres. However, EMG data can be processed to obtain in silico estimates of muscle force [72,88], and the highly accurate fluoroscopy technique [98,99] has been used to track tibiofemoral kinematics during drop landings [100]. These methods therefore warrant further research. ...
Anterior cruciate ligament (ACL) injuries are one of the most common knee pathologies sustained during athletic participation and are characterised by long convalescence periods and associated financial burden. Muscles have the ability to increase or decrease the mechanical loads on the ACL, and thus are viable targets for preventative interventions. However, the relationship between muscle forces and ACL loading has been investigated by many different studies, often with differing methods and conclusions. Subsequently, this review aimed to summarise the evidence of the relationship between muscle force and ACL loading. A range of studies were found that investigated muscle and ACL loading during controlled knee flexion, as well as a range of weightbearing tasks such as walking, lunging, sidestep cutting, landing and jumping. The quadriceps and the gastrocnemius were found to increase load on the ACL by inducing anterior shear forces at the tibia, particularly when the knee is extended. The hamstrings and soleus appeared to unload the ACL by generating posterior tibial shear force; however, for the hamstrings, this effect was contingent on the knee being flexed greater than ~ 20° to 30°. The gluteus medius was consistently shown to oppose the knee valgus moment (thus unloading the ACL) to a magnitude greater than any other muscle. Very little evidence was found for other muscle groups with respect to their contribution to the loading or unloading of the ACL. It is recommended that interventions aiming to reduce the risk of ACL injury consider specifically targeting the function of the hamstrings, soleus and gluteus medius.
... This method is due to the large errors in the measurement operation and manual reading and it is time-consuming and labor-intensive [3,4]. Castor reduces the industrial production efficiency [5,6]. Therefore, this paper proposes to use a camera to monitor the production line in real time, take pictures of each product regularly, and perform automatic processing [7,8]. ...
Aiming at the problems of manual testing of industrial products, a measurement method of industrial products based on three-dimensional dynamic imaging technology is proposed. The products on the production line are dynamically photographed from different angles and within a certain period of time by using cameras. Then the obtained Image denoising processing and contour tracking based on chain code table and line segment table to obtain boundary information and regional information of each enclosed area of the image. Experimental tests show that the test accuracy of this method is 100%, which is suitable for real-time detection. Fully automated research on product testing provides the foundation.
... The 3D pose of a skeleton can be determined by registering its CT model-projected digitally reconstructed radiographs (DRRs) to the X-ray images. The biplane imaging configuration is currently the most commonly used setup to capture the 3D movement of a single joint during particular tasks [22][23][24], as it can provide stereo X-ray images for 3D/2D image registration. The limited intersection volume of measurement and the higher ionizing radiation dose were considered the primary concerns of biplane configuration. ...
Model-based 3D/2D image registration using single-plane fluoroscopy is a common setup to determine knee joint kinematics, owing to its markerless aspect. However, the approach was subjected to lower accuracies in the determination of out-of-plane motion components. Introducing additional kinematic constraints with an appropriate anatomical representation may help ameliorate the reduced accuracy of single-plane image registration. Therefore, this study aimed to develop and evaluate a multibody model-based tracking (MbMBT) scheme, embedding a personalized kinematic model of the tibiofemoral joint for the measurement of tibiofemoral kinematics. The kinematic model was consisted of three ligaments and an articular contact mechanism. The knee joint activities in six volunteers during isolated knee flexion, lunging, and sit-to-stand motions were recorded with a biplane X-ray imaging system. The tibiofemoral kinematics determined with the MbMBT and mediolateral view fluoroscopic images were compared against those determined using biplane fluoroscopic images. The MbMBT was demonstrated to yield tibiofemoral kinematics with precision values in the range from 0.1 mm to 1.1 mm for translations and from 0.2° to 1.3° for rotations. The constraints provided by the kinematic model were shown to effectively amend the nonphysiological tibiofemoral motion and not compromise the image registration accuracy with the proposed MbMBT scheme.
... Biplane imaging with two x-ray units was demonstrated to topically address the issue with compromises on the effective field of view. Custom-built stereo radiography (Guan et al., 2016;Ivester et al., 2015;You et al., 2001), clinical asynchronous biplane x-ray imaging system (Akbari-Shandiz et al., 2018;Lin et al., 2020; and the configuration of two C-arm fluoroscopes (Barré and Aminian, 2018;Li, Van de Velde and Bingham, 2008) are commonly adopted. To the best knowledge of the authors, the combined effects of the number of image sources (single-plane vs. biplane) and the bone model compositions (homogeneous density vs. radiodensity) on the performance of the modelbased 3D/2D image registration remain unclear. ...
Model-based three-dimensional(3D)/two-dimensional(2D) image registration methods have been widely applied in measuring 3D kinematics of the knee during dynamic activities. However, the combined effects of bone model compositions (radiodensity vs. homogeneous-density) and the number of fluoroscopic views on the measurement accuracy remained unclear. The current study evaluated experimentally the accuracy of the four model-based 3D/2D image registration configurations on the accuracy of measured knee kinematics, namely homogeneous-density model/single-plane image (HS), radiodensity model/single-plane image (RS), homogeneous-density model/biplane images (HB), and radiodensity model/biplane images (RB). Computed tomography (CT) of the knee and asynchronous biplane fluoroscopic images of the simulated knee motions were collected from a cadaveric knee joint for the evaluation of the registration configurations. The results showed that the use of biplane fluoroscopic images ensured mean absolute errors (MAE) below 0.3 mm and 0.9° in each motion component regardless of the types of bone models. Application of radiodensity model could generate digitally reconstructed radiographs more similar to the fluoroscopic images, diminishing MAE in all motion components and measurement bias. As a result, the RS configuration was capable of reconstructing the 3D knee joint angles with MAE comparable to those obtained using the HB configuration. Among the four tested configurations, the RB configuration was most accurate and least affected by the fast skeleton motions.
... Defining this question clearly dictates the model's context of use and motivates the required modeling fidelity and relevant simulation scenarios. Commonly, anatomical imaging (computed tomography and magnetic resonance imaging) [11], in vitro mechanical testing (joint and tissue testing) [12], in vivo data collection [13], and research and clinical literature provide the foundational information to build the model. Geometries of tissues are usually generated through image segmentation [14] and discretized to generate a mesh for finite element analysis [6] or multibody dynamics simulations [15]. ...
The use of computational modeling to investigate knee joint biomechanics has increased exponentially over the last few decades. Developing computational models is a creative process where decisions have to be made, subject to the modelers' knowledge and previous experiences, resulting in the "art" of modeling. The long-term goal of the KneeHub project is to understand the influence of subjective decisions on the final outcomes and the reproducibility of computational knee joint models. In this paper, we report on the model development phase of this project, investigating model development decisions and deviations from initial modeling plans. Five teams developed computational knee joint models from the same dataset, and we compared each teams' initial uncalibrated models and their model development workflows. Variations in the software tools and modeling approaches were found, resulting in differences such as the representation of the anatomical knee joint structures in the model. The teams defined the boundary conditions in a consistent manner, and used the same anatomical coordinate system convention. However, deviations in the anatomical landmarks used to define the coordinate systems were present, resulting in a large spread in the kinematic outputs of the uncalibrated models. The reported differences and similarities in model development and simulation presented here illustrate the importance of the "art" of modeling and how subjective decision-making can lead to variation in model outputs. All teams deviated from their initial modeling plans, indicating that model development is a flexible process and difficult to plan in advance, even for experienced teams.
... Wegen der genutzten Röntgenstrahlung ist die Fluoroskopie zwar invasiver als MRT-Untersuchungen, erlaubt aber eine höhere zeitliche Auflösung und findet zunehmend Einsatz bei der Untersuchung von rekonstruierten und ersetzten Kniegelenken (Clary et al. 2013;Dennis et al. 2005;. Mobile Fluoroskopien, die das Gelenk während der Fortbewegung verfolgen, ermöglichen komplett dynamische Betrachtungen der Gelenkkinematik (Guan et al. 2016;List et al. 2017). Mit einem solchen mobilen Fluoroskop wurde die 3D-Kniekinematik erfasst, während gleichzeitig die In-vivo-Kniekontaktkräfte mit instrumentierten Implantaten gemessen wurden (cams-knee.orthoload.com; ...
... The application of standard X-ray fluoroscopy or newly developed mobile fluoroscopic imaging systems enable more dynamic kinematic measurements during functional tasks [21,22]. By numerically registering the subject-specific model of the prosthesis or bones to the single-plane fluoroscopic image, model-based tracking routines reproduce 6-dof kinematics of natural knee [23,24] and replacement joints [25,26]. ...
Model-based tracking of the movement of the tibiofemoral joint via a biplane X-ray imaging system has been commonly used to reproduce its accurate, three-dimensional kinematics. To accommodate the approaches to existing clinical asynchronous biplane fluoroscopy systems and achieve comparable accuracy, this study proposed an automated model-based interleaved biplane fluoroscopy image tracking scheme (MIBFT) by incorporating information of adjacent image frames. The MIBFT was evaluated with a cadaveric study conducted on a knee specimen. The MIBFT reproduced skeletal poses and tibiofemoral kinematics that were in good agreement with the standard reference kinematics provided by an optical motion capture system, in which the root-mean-squared (Rms) errors of the skeletal pose parameters ranged from 0.11 to 0.35 mm in translation and 0.18 to 0.49° in rotation. The influences of rotation speed on the pose errors were below 0.23 mm and 0.26°. The MIBFT-determined bias, precision, and Rms error were comparable to those of the reported model-based tracking techniques using custom-made synchronous biplane fluoroscopy. The results suggested that the further use of the clinical imaging system is feasible for the noninvasive and precise examination of dynamic joint functions and kinematics in clinical practice and biomechanical research.
... Two of these systems have been developed to image lower limb joints throughout complete activity cycles. 59,107 However, such systems may affect the subject's gait performance and introduce additional errors due to vibrations. 66 Currently, the virtual fibre elongation method is too time consuming for clinical translation due to the segmentation of the joint anatomy, definition of liga-ment attachment points, and 2D/3D images registration steps. ...
The critical clinical and scientific insights achieved through knowledge of in vivo musculoskeletal soft tissue strains has motivated the development of relevant measurement techniques. This review provides a comprehensive summary of the key findings, limitations, and clinical impacts of these techniques to quantify musculoskeletal soft tissue strains during dynamic movements. Current technologies generally leverage three techniques to quantify in vivo strain patterns, including implantable strain sensors, virtual fibre elongation, and ultrasound. (1) Implantable strain sensors enable direct measurements of tissue strains with high accuracy and minimal artefact, but are highly invasive and current designs are not clinically viable. (2) The virtual fibre elongation method tracks the relative displacement of tissue attachments to measure strains in both deep and superficial tissues. However, the associated imaging techniques often require exposure to radiation, limit the activities that can be performed, and only quantify bone-to-bone tissue strains. (3) Ultrasound methods enable safe and non-invasive imaging of soft tissue deformation. However, ultrasound can only image superficial tissues, and measurements are confounded by out-of-plane tissue motion. Finally, all in vivo strain measurement methods are limited in their ability to establish the slack length of musculoskeletal soft tissue structures. Despite the many challenges and limitations of these measurement techniques, knowledge of in vivo soft tissue strain has led to improved clinical treatments for many musculoskeletal pathologies including anterior cruciate ligament reconstruction, Achilles tendon repair, and total knee replacement. This review provides a comprehensive understanding of these measurement techniques and identifies the key features of in vivo strain measurement that can facilitate innovative personalized sports medicine treatment.
... These experiments can offer cues on the capability to quantity skeletal motions, which is crucial to understand vertebrate biomechanics, energetics, and motor control. These videos can capture 3D images directly or infer the 3D geometry from 2D frames [21][22][23][24][25][26][27][28]. ...
X-Ray Computed Microtomography (µCT or micro-CT) allows a non-destructive analysis of samples, which helps their reuse. The X-Ray µCT equipment offers the user several configuration options that change the quality of the images obtained, thus affecting the expected result. In this study, a methodology for analyzing X-Ray µCT images generated by the SkyScan1174 Compact Micro-CT equipment was developed. The basis of this analysis methodology is texture descriptors. Three sets of images were used, then degradations and noise were applied to the original images, generating new images. Subsequently, the following texture descriptors assisted in scrutinizing the sets: maximum probability , the moment of difference, the inverse difference moment, entropy, and uniformity. Experiments show the outcomes of some tests.
Cite this paper as:
Fernandes S.R. et al. (2021) Nondestructive Diagnosis and Analysis of Computed Microtomography Images via Texture Descriptors. In: Khelassi A., Estrela V.V. (eds) Advances in Multidisciplinary Medical Technologies ─ Engineering, Modeling and Findings. Springer, Cham. https://doi.org/10.1007/978-3-030-57552-6_16
First Online
08 November 2020
DOI
https://doi.org/10.1007/978-3-030-57552-6_16
Publisher Name
Springer, Cham
Print ISBN
978-3-030-57551-9
Online ISBN
978-3-030-57552-6
... Imaging studies have allowed a detailed analysis of the in vivo internal tibio-femoral kinematics throughout knee flexion, but are generally limited in the examination field of view, and therefore do not allow tracking of the knee joint during full cycles of dynamic gait activities, or are restricted to imaging only a portion of the whole motion. To overcome the constraints of such static imaging approaches, dynamic systems have been developed 25,26 that now allow investigation into tibio-femoral kinematics throughout complete cycles of level walking, downhill walking, and stair descent. The use of such a system has, for the first time, recently shown that tibio-femoral kinematics depend on the activity performed and that clear differences between the loaded stance and the unloaded swing phases of gait activities exist. ...
Joint stability is a primary concern in total knee joint replacement. The GMK Sphere prosthesis was specifically designed to provide medial compartment anterior‐posterior (A‐P) stability, while permitting rotational freedom of the joint through a flat lateral tibial surface. The objective of this study was to establish the changes in joint kinematics introduced by the GMK Sphere prosthesis during gait activities in comparison to conventional posterior‐stabilized (PS) fixed‐bearing and ultra‐congruent (UC) mobile‐bearing geometries. The A‐P translation and internal/external rotation of three cohorts, each with 10 good outcome subjects (2.9±1.6y postop), with a GMK Sphere, GMK PS or GMK UC implant were analysed throughout complete cycles of gait activities using dynamic videofluoroscopy. The GMK Sphere showed the smallest range of medial compartment A‐P translation for level walking, downhill walking, and stair descent (3.6±0.9mm, 3.1±0.8mm, 3.9±1.3mm), followed by the GMK UC (5.7±1.0mm, 8.0±1.7mm, 8.7±1.9mm) and the GMK PS (10.3±2.2mm, 10.1±2.6mm, 11.6±1.6mm) geometries. The GMK Sphere exhibited the largest range of lateral compartment A‐P translation (12.1±2.2mm), and the largest range of tibial internal/external rotation (13.2±2.2°), both during stair descent. This study has shown that the GMK Sphere clearly restricts A‐P motion of the medial condyle during gait activities while still allowing a large range of axial rotation. The additional comparison against the conventional GMK PS and UC geometries, not only demonstrates that implant geometry is a key factor in governing tibio‐femoral kinematics, but also that the geometry itself probably plays a more dominant role for joint movement than the type of gait activity. This article is protected by copyright. All rights reserved.
... As a result, these techniques provide little or no access to functional measurement of activities that involve either loading and unloading, toe-off and heel strike impact, or muscle activation and deactivation, and especially not throughout multiple consecutive cycles. To overcome these limitations of a static image intensifier, dynamic single and dual plane systems have been introduced [12,21,22]. The moving fluoroscope developed at the Institute for Biomechanics, ETH Zü rich, allows not only tracking of free-level gait but also tracking of the knee joint during stair descent, which is considered to be a challenging daily activity for subjects with knee disorders [3,23]. ...
Although total knee arthroplasty (TKA) has become a standard surgical procedure for relieving pain, knowledge of the in vivo knee joint kinematics throughout common functional activities of daily living is still missing. The goal of this study was to analyse knee joint motion throughout complete cycles of daily activities in TKA subjects to establish whether a significant difference in joint kinematics occurs between different activities. Using dynamic videofluoroscopy, we assessed tibio-femoral kinematics in six subjects throughout complete cycles of walking, stair descent, sit-to-stand and stand-to-sit. The mean range of condylar anterior–posterior translation exhibited clear task dependency across all subjects. A significantly larger anterior–posterior translation was observed during stair descent compared to level walking and stand-to-sit. Local minima were observed at approximately 30° flexion for different tasks, which were more prominent during loaded task phases. This characteristic is likely to correspond to the specific design of the implant. From the data presented in this study, it is clear that the flexion angle alone cannot fully explain tibio-femoral implant kinematics. As a result, it seems that the assessment of complete cycles of the most frequent functional activities is imperative when evaluating the behaviour of a TKA design in vivo.
... Many techniques have been used to investigate the kinematics of the knee using gait analysis, mechanical measurement, magnetic resonance imaging, fluoroscopy, and radiostereomatoghrapic imaging [11,[17][18][19][20][21]. A well recognised method used to assess the kinematics of total knee arthroplasty is 2D to 3D reconstruction of fluoroscopic imaging [11,14,15] which has also been used to study kinematics of native knees [22]. ...
Background:
Many different measures have been used to describe knee kinematics. This study investigated the changes of two measures, the patellar tendon angle and the patellar flexion angle, in response to variations in the geometry of the knee due to surgical technique or implant design.
Methods:
A mathematical model was developed to calculate the equilibrium position of the extensor mechanism for a particular tibiofemoral position. Calculating the position of the extensor mechanism allowed for the determination of the patellar tendon angle and patellar flexion angle relationships to the knee flexion angle. The model was used to investigate the effect of anterior-posterior position of the femur, change in joint line, patellar thickness (overstuffing, understuffing), and patellar tendon length; these parameters were varied to determine the effect on the patellar tendon angle/knee flexion angle and patellar flexion angle/knee flexion angle relationships.
Results:
The patellar tendon angle was a good indicator of anterior-posterior femoral position and change in patellar thickness, and the patellar flexion angle a good indicator of change in joint line, and patellar tendon length.
Conclusions:
The patellar tendon angle/knee flexion angle relationship was found to be an effective means of identifying abnormal kinematics post-knee arthroplasty. However, the use of both the patellar tendon angle and patellar flexion angle together provided a more informative overview of the sagittal plane kinematics of the knee.
... There are several reasons for the lack of a consensus. First, STA quantification is a cumbersome, expensive, and time-consuming process which requires the determination of a virtually error-free bone pose using either invasive techniques such as pins inserted into the bones (Benoit et al., 2006;Cereatti et al., 2009;Dal Maso et al., 2015;Lafortune et al., 1992;Reinschmidt et al., 1997) or bio-imaging techniques such as fluoroscopy and magnetic resonance (MR) imaging (Bey et al., 2008;Garling et al., 2008;Guan et al., 2016;Stagni et al., 2005). The need for complex experimental set-ups and procedures (e.g. ...
Soft tissue artefact (STA) represents one of the main obstacles for obtaining accurate and reliable skeletal kinematics from motion capture. Many studies have addressed this issue, yet there is no consensus on the best available bone pose estimator and the expected errors associated with relevant results. Furthermore, results obtained by different authors are difficult to compare due to the high variability and specificity of the phenomenon and the different metrics used to represent these data. Therefore, the aim of this study was twofold: firstly, to propose standards for description of STA; and secondly, to provide illustrative STA data samples for body segments in the upper and lower extremities and for a range of motor tasks specifically , level walking, stair ascent, sit-to-stand, hip-and knee-joint functional movements, cutting motion, running, hopping, arm elevation and functional upper-limb movements. The STA dataset includes motion of the skin markers measured in vivo and ex vivo using stereophotogrammetry as well as motion of the underlying bones measured using invasive or bio-imaging techniques (i.e., X-ray fluoroscopy or MRI). The data are accompanied by a detailed description of the methods used for their acquisition, with information given about their quality as well as characterization of the STA using the proposed standards. The availability of open-access and standard-format STA data will be useful for the evaluation and development of bone pose estimators thus contributing to the advancement of three-dimensional human movement analysis and its translation into the clinical practice and other applications.
... The current gold standard for the determination of bone kinematics is biplane fluoroscopy. This technique allows the acquisition of functional information during physiologically relevant tasks, such as stair rising 4 and gait, 28 with very high temporal and spatial resolution. ...
Anatomical (static) magnetic resonance imaging (MRI) is the most useful imaging technique for the evaluation and assessment of internal derangement of the knee, but does not provide dynamic information and does not allow the study of the interaction of the different tissues during motion. As knee pain is often only experienced during dynamic tasks, the ability to obtain four-dimensional (4D) images of the knee during motion could improve the diagnosis and provide a deeper understanding of the knee joint. In this work, we present a novel approach for dynamic, high-resolution, 4D imaging of the freely moving knee without the need for external triggering. The dominant knee of five healthy volunteers was scanned during a flexion/extension task. To evaluate the effects of non-uniform motion and poor coordination skills on the quality of the reconstructed images, we performed a comparison between fully free movement and movement instructed by a visual cue. The trigger signal for self-gating was extracted using principal component analysis (PCA), and the images were reconstructed using a parallel imaging and compressed sensing reconstruction pipeline. The reconstructed 4D movies were scored for image quality and used to derive bone kinematics through image registration. Using our method, we were able to obtain 4D high-resolution movies of the knee without the need for external triggering hardware. The movies obtained with and without instruction did not differ significantly in terms of image scoring and quantitative values for tibiofemoral kinematics. Our method showed to be robust for the extraction of the self-gating signal even for uninstructed motion. This can make the technique suitable for patients who, as a result of pain, may find it difficult to comply exactly with instructions. Furthermore, bone kinematics can be derived from accelerated MRI without the need for additional hardware for triggering.
... One biplane video sequence per leg was acquired at 70 AE 3.2 kV, 103 AE 13.2 mA and 500 frames/s with a shutter of 0.5 ms and a resolution of 1280 9 1024 pixels. The source-to-image distance was 1.4 m and the interbeam angle approximately 60°simulating an in vivo experimental set-up in which the walkway would have to be kept clear of equipment [28]. ...
Reason for performing study:
Biplane high-speed fluoroscopy is a new method for gait analysis of the equine distal extremity. This is the first study validating the noninvasive tracking possibilities (Autoscoping and Scientific Rotoscoping) taking equine anatomy into account.
Objectives:
To determine the resolution with which Autoscoping and Scientific Rotoscoping depict motion of the equine phalanges in comparison to the invasive gold standard marker-based registration.
Study design:
Comparative ex vivo study.
Methods:
In 5 distal extremities of slaughtered ponies, 3 or 4 tantalum beads with 1 mm diameter were implanted in each of the proximal, middle and distal phalangeal bones. Three-dimensional models of the bones were reconstructed using computed tomographic data (120 kV, 50 mA, slice thickness 1 mm, increment 0.5). The beads were digitally removed from the bone models. Biplane fluoroscopic videos were taken at 69.5 ± 3.5 kV, 102.5 ± 22.5 mA, 500 frames/s and 0.5 ms shutter speed. The 5 specimens were moved in the trial field of the biplane fluoroscopic setup in a step-like motion (simulation of landing, main stance phase, lift-off). Marker-based registration, Autoscoping and Scientific Rotoscoping were carried out. For statistical analysis agreement was computed as percentiles, mean and s.d.
Results:
The medians of Scientific Rotoscoping ranged from 0.16 to 0.66 mm in translations and 0.43 to 2.78° in rotations, while values for Autoscoping were 0.13-0.70 mm and 0.28-2.39° respectively. With 2 exceptions, all differences between methods were statistically significant. Scientific Rotoscoping is more time efficient than Autoscoping and results in smaller maximum errors.
Main limitations:
The experimental set-up was specifically designed to accommodate in vivo requirements. Autoscoping was not manually corrected but rather expected to work automatically.
Conclusions:
It is possible to noninvasively apply both Autoscoping and Scientific Rotoscoping for gait analysis of the equine phalanges with high precision. The summary is available in Chinese - see supporting information.
In clinical movement biomechanics, kinematic data are often depicted as waveforms (i.e. signals), characterising the motion of articulating joints. Clinically meaningful interpretations of the underlying joint kinematics, however, require an objective understanding of whether two different kinematic signals actually represent two different underlying physical movement patterns of the joint or not. Previously, the accuracy of IMU-based knee joint angles was assessed using a six-degrees-of-freedom joint simulator guided by fluoroscopy-based signals. Despite implementation of sensor-to-segment corrections, observed errors were clearly indicative of cross-talk, and thus inconsistent reference frame orientations. Here, we address these limitations by exploring how minimisation of dedicated cost functions can harmonise differences in frame orientations, ultimately facilitating consistent interpretation of articulating joint kinematic signals. In this study, we present and investigate a frame orientation optimisation method (FOOM) that aligns reference frames and corrects for cross-talk errors, hence yielding a consistent interpretation of the underlying movement patterns. By executing optimised rotational sequences, thus producing angular corrections around each axis, we enable a reproducible frame definition and hence an approach for reliable comparison of kinematic data. Using this approach, root-mean-square errors between the previously collected (1) IMU-based data using functional joint axes, and (2) simulated fluoroscopy-based data relying on geometrical axes were almost entirely eliminated from an initial range of 0.7°–5.1° to a mere 0.1°–0.8°. Our results confirm that different local segment frames can yield different kinematic patterns, despite following the same rotation convention, and that appropriate alignment of reference frame orientation can successfully enable consistent kinematic interpretation.
Study design:
Prospective cohort.
Objective:
Determine if total hip arthroplasty (THA) changes lumbar spine kinematics during gait in a manner that explains the improvements in back pain seen in patients with hip-spine syndrome.
Summary of background data:
For patients with hip-spine syndrome, improvements in both hip and back pain have been demonstrated after THA, however, the exact mechanism of improvement in back pain remains unknown, as no corresponding changes in lumbar spine static radiographic parameters have been identified.
Methods:
Thirteen patients with severe, unilateral hip osteoarthritis scheduled to undergo THA with concomitant back pain and disability were tested at baseline and 6 months after THA. Harris Hip Score (HHS) and Oswestry Disability Index (ODI) questionnaires were completed, static orientation of the spine and pelvis were measured on standing radiographs, and lumbar spine kinematics were measured during treadmill walking using a validated measurement system that matched subject-specific bone models created from CT scans to dynamic biplane radiographs.
Results:
After THA, both the ODI (36.3 to 11.3, P<0.001) and HHS (55.7 to 77.9, P<0.001) improved, however, there were no changes in static intervertebral or pelvis orientation. During gait after THA, the overall lumbar spine (L1 to L5) was less lordotic from heel strike to contralateral toe off (P<0.001), the L4 and L5 vertebra were less anteriorly tilted by 3.9° (P=0.038) from midstance to contralateral heel strike and by 3.9° (P=0.001) during stance, respectively.
Conclusion:
The decreased anterior tilt of the 2 lowest lumbar vertebrae and corresponding loss of lumbar lordosis may reduce facet loading during the stance phase of gait after THA. This change in lumbar spine kinematics during gait is a potential mechanism to explain the observed improvements in back pain and disability after THA.
Level of evidence:
4.
Model-based tracking (MBT) is a time-consuming and semiautomatic approach, and thus subject to errors during the tracking process. The present study aimed primarily to quantify the effects that interpolation and intra-user variability associated with MBT have on the kinematic and arthrokinematic measurements in comparison to a gold standard radiostereometric analysis (RSA). Cadaveric knee specimens were imaged at 125 Hz while simulating standing, walking, jogging, and lunging motions. (Arthro)kinematic metrics were calculated via MBT without interpolation, MBT with two interpolation techniques when every fifth or tenth frame was analyzed, and RSA. Tracking the same activity multiple times affected (p-value, largest mean difference) the flexion-extension (FE) joint angle during walking (0.03, 0.6°), and the internal-external joint angle during jogging (0.048, -0.9°). Only during jogging for the FE joint angle was there an effect of interpolation (0.046, 0.3°). Neither tracking multiple times nor interpolation affected arthrokinematic metrics (contact path locations and excursions). The present study is the first to quantify the effects that intra-user variability and interpolation have on the (arthro)kinematic measurement accuracy using MBT. Results suggest interpolation may be used without sacrificing (arthro)kinematic outcome measurement accuracy and the errors associated with intra-user variability, while small, were larger than errors due to interpolation.
The aim of this randomized controlled trial was to measure and compare six-degree-of-freedom (6-DOF) knee joint motion of three total knee arthroplasty (TKA) implant designs across a range of daily activities. Seventy-five TKA patients were recruited to this study and randomly assigned a posterior-stabilized (PS), cruciate-retaining (CR) or medial-stabilized (MS) implant. Six months after surgery, patients performed five activities of daily living: level walking, step-up, step-down, sit-to-stand and stand-to-sit. Mobile biplane X-ray imaging was used to measure 6-DOF knee kinematics and the center of rotation of the knee in the transverse plane for each activity. Mean 6-DOF knee kinematics were consistently similar for PS and CR, whereas MS was more externally rotated and abducted, and lateral shift was lower across all activities. Peak-to-peak anterior drawer for MS was also significantly lower during walking, step-up and step-down (p<0.017). The center of rotation of the knee in the transverse plane was located on the medial side for MS, whereas PS and CR rotated about the lateral compartment or close to the tibial origin. The kinematic function of MS was more similar to that of the healthy knee than PS and CR based on reduced paradoxical anterior translation at low flexion angles and a transverse center of rotation located in the medial compartment. Overall, 6-DOF knee joint motion for PS and CR were similar across all daily activities, whilst that measured for MS was appreciably different. The kinematic patterns observed for MS reflects a highly conforming medial articulation in the MS design. This article is protected by copyright. All rights reserved.
Background
The ability of the quadriceps muscles to extend the knee depends on the moment arm of the knee-extensor mechanism, which is described by the moment arm of the patellar tendon at the knee. The knee-extensor moment may be altered by a change in quadriceps force, a change in the patellar tendon moment arm (PTMA), or both. A change in quadriceps muscle strength after anterior-cruciate-ligament-reconstruction (ACLR) surgery is well documented, however, there is limited knowledge on how this procedure affects the PTMA.
Research Question
Does ACLR surgery alter the moment arm of the knee-extensor mechanism during gait?
Methods
We measured the PTMA in both the ACLR knee and the uninjured contralateral knee in 10 young active individuals after unilateral ACLR surgery. Mobile biplane X-ray imaging was used to measure the three-dimensional positions of the femur, tibia and patella during level walking and downhill walking over ground. The PTMA was found from the location of the instantaneous axis of rotation at the knee and the line-of-action of the patellar tendon.
Results
There was a small but statistically significant difference in the mean PTMA calculated over one cycle of level walking between the ACLR knee and the contralateral knee, with the mean PTMA in the ACLR knee being 1.5 mm larger (p<0.01). In downhill walking, statistically significant differences were found in the range 15° to 25° of knee flexion, where the PTMA was 4.7 mm larger in the ACLR knee compared to the contralateral knee (p<0.01).
Significance
Significant differences were evident in the mean PTMA between the ACLR knee and the contralateral knee in both activities, however, the magnitudes of these differences were relatively small (range: 3-10%), indicating that ACLR surgery successfully restores the moment arm of the knee-extensor mechanism during dynamic activity.
Fluoroscopy is a dynamic video X-ray imaging technology widely used in the field of orthopedic biomechanics for assessing joint or implant motion in conjunction with object tracking techniques. While many biomechanical models are driven by surface-based motion capture systems, when assessing joint biomechanics these surface-based systems are inherently flawed since they measures the motion of the skin over the bone rather than the bone itself. Fluoroscopy overcomes this by visualizing the positions of radiopaque objects (such as bones or implants) inside the body in near real time. The locations of these objects as they move can be quantified postprocessing and reported in 2D or 3D coordinate systems. This chapter describes the methods and applications of fluoroscopy in orthopedic biomechanics and provides examples of its utility in assessing kinematics in the foot, knee, and spine.
We combined mobile biplane X-ray imaging and magnetic resonance imaging to measure the regions of articular cartilage contact and cartilage thickness at the tibiofemoral and patellofemoral joints during six functional activities: standing, level walking, downhill walking, stair ascent, stair descent, and open-chain (non-weight-bearing) knee flexion. The contact centers traced similar paths on the medial and lateral femoral condyles, femoral trochlea, and patellar facet in all activities while their locations on the tibial plateau were more varied. The translations of the contact centers on the femur and patella were tightly coupled to the tibiofemoral flexion angle in all activities (r² > 0.95) whereas those on the tibia were only moderately related to the flexion angle (r² > 0.62). The regions of contacting cartilage were significantly thicker than the regions of non-contacting cartilage on the patella, femoral trochlea, and the medial and lateral tibial plateaus in all activities (p < 0.001). There were no significant differences in thickness between contacting and non-contacting cartilage on the medial and lateral femoral condyles in all activities, except open-chain knee flexion. Our results provide partial support for the proposition that cartilage thickness is adapted to joint load and do not exclude the possibility that other factors, such as joint congruence, also play a role in regulating the structure and organization of healthy cartilage. The data obtained in this study may serve as a guide when evaluating articular contact motion in osteoarthritic and reconstructed knees.
We measured the moment arm of the knee-extensor mechanism as ten healthy young individuals performed six functional activities: level walking, downhill walking, stair ascent, stair descent, open-chain (non-weight-bearing) knee flexion, and open-chain knee extension. The moment arm of the knee-extensor mechanism was described by the moment arm of the patellar-tendon force, which acts to rotate the tibia about the instantaneous axis of rotation (screw axis) of the knee. A mobile biplane X-ray imaging system enabled simultaneous measurements of the three-dimensional movements of the femur, tibia and patella during each activity, from which the position and orientation of the screw axis and the patellar-tendon moment arm (PTMA) were determined. Mean PTMA across all activities and all participants remained nearly constant (∼46 mm) from 0° to 70° of knee flexion and decreased by no more than 20% at higher flexion angles. The magnitude of the PTMA varied more substantially across individuals than across activities, indicating that the moment arm is more heavily influenced by differences in knee-joint geometry than muscle loading. Hence, PTMA measurements obtained for a given activity performed by one individual may be used with good confidence to describe the PTMA for any other activity performed by the same individual. Caution is advised when using PTMA measurements obtained from one individual to describe the moment arm in another individual even once the data are normalized by knee bone size, as the PTMA varied by as much as 13% from the mean across individuals.
The purpose of this study was to measure the three-dimensional movements of the femur, tibia and patella in healthy young people during activities of daily living. A mobile biplane X-ray imaging system was used to obtain simultaneous measurements of six-degree-of-freedom (6-DOF) tibiofemoral and patellofemoral kinematics and femoral condylar motion in ten participants during standing, level walking, downhill walking, stair ascent, stair descent and open-chain (non-weightbearing) knee flexion. Seven of the eleven secondary motions at the knee—three translations at the tibiofemoral joint, three translations at the patellofemoral joint, and patellar flexion—were coupled to the tibiofemoral flexion angle (r2 ≥ 0.71). Tibial internal–external rotation, tibial abduction–adduction, patellar rotation, and patellar tilt were each weakly related to the tibiofemoral flexion angle (r2 ≤ 0.45). The displacements of the femoral condyles were also coupled to the tibiofemoral flexion angle (r2 ≥ 0.70), with the lateral condyle translating further on the tibial plateau than the medial condyle. The center of rotation of the tibiofemoral joint in the transverse plane was located on the medial side in all activities. These findings expand our understanding of the kinematic function of the healthy knee and may be relevant to a range of applications in biomechanics, including the design of prosthetic knee implants and the development of knee models for use in full-body simulations of movement.
X-ray computed microtomography (μCT or micro-CT) allows a nondestructive analysis of samples, which helps their reuse. The X-ray μCT equipment offers the user several configuration options that change the quality of the images obtained, thus affecting the expected result. In this study, a methodology for analyzing X-ray μCT images generated by the SkyScan 1174 Compact Micro-CT equipment was developed. The basis of this analysis methodology is texture descriptors. Three sets of images were used, and then degradations and noise were applied to the original images, generating new images. Subsequently, the following texture descriptors assisted in scrutinizing the sets: maximum probability, the moment of difference, the inverse difference moment, entropy, and uniformity. Experiments show the outcomes of some tests
Background
Paradoxical anterior translation in mid-flexion is reduced in total knee arthroplasties (TKA) with a gradually reducing femoral radius, when compared to a two-radii design. This reduction has been shown in FE model simulations, in vitro tests, intraoperatively, as well as recently also in vivo during a lunge and unloaded flexion-extension. However, TKA kinematics are task dependent and this reduction has not been tested for gait activities.
Methods
30 good outcome subjects (≥ 1y postop) with a unilateral cruciate-retaining TKA with a gradually reducing (n=15) or dual (n=15) femoral radius design were assessed during five complete cycles of level walking, stair descent (0.18m steps), deep knee bend and sitting down onto and standing up from a chair, using a moving fluoroscope (25Hz, 1ms shutter time). Kinematic data were extracted by 2D/3D image registration.
Results
Tibiofemoral ranges of motion (ROM) for flexion/extension, ab-/adduction, internal/external rotation as well as anterioposterior (AP) translation were similar for both groups, whereas the pattern of AP translation-flexion-coupling differed. The subjects with the dual-radii design showed a sudden change of direction of AP translation around 30° of flexion, which was not present in the subjects with the gradually reducing femoral radius design.
Conclusion
Through the unique ability of moving fluoroscopy, the present study confirmed that the gradually reducing femoral radii eliminated the paradoxical sudden anterior translation at 30° present in the dual-radii design in vivo during daily activities, including gait and stair descent.
Accurate knowledge of knee joint motion is needed to evaluate the effects of implant design on functional performance and component wear. We conducted a randomized controlled trial to measure and compare 6-degree-of-freedom (6-DOF) kinematics and femoral condylar motion of posterior-stabilized (PS), cruciate-retaining (CR) and medial-stabilized (MS) knee implant designs for one cycle of walking. A mobile biplane X-ray imaging system was used to accurately measure 6-DOF tibiofemoral motion as patients implanted with PS (n = 23), CR (n = 25) or MS (n = 26) knees walked over ground at their self-selected speeds. Knee flexion angle (maximum, minimum, and peak-to-peak range) did not differ significantly between the three designs. Relative movements of the femoral and tibial components were generally similar for PS and CR with significant differences observed only for anterior tibial drawer. Knee kinematic profiles measured for MS were appreciably different: external rotation and abduction of the tibia were increased while peak-to-peak anterior drawer was significantly reduced for MS compared to PS and CR. Anterior-posterior drawer and medial-lateral shift of the tibia were strongly coupled to internal-external rotation for MS, as was anterior-posterior translation of the contact center in the lateral compartment. MS exhibited the least amount of paradoxical anterior translation of the femur relative to the tibia during knee flexion. The joint center of rotation in the transverse plane was located in the lateral compartment for PS and CR and in the medial compartment for MS. Substantial differences were evident in 6-DOF knee kinematics between the healthy knee and all three prosthetic designs. Overall, knee kinematic profiles observed for MS resemble those of the healthy joint more closely than PS and CR. This article is protected by copyright. All rights reserved.
The accurate quantification of in-vivo tibio-femoral kinematics is essential for understanding joint functionality, but determination of the 3D pose of bones from 2D single-plane fluoroscopic images remains challenging. We aimed to evaluate the accuracy, reliability and repeatability of an intensity-based 2D/3D registration algorithm.
The accuracy was evaluated using fluoroscopic images of 2 radiopaque bones in 18 different poses, compared against a gold-standard fiducial calibration device. In addition, 3 natural femora and 3 natural tibiae were used to examine registration reliability and repeatability.
Both manual fitting and intensity-based registration exhibited a mean absolute error of <1 mm in-plane. Overall, intensity-based registration of the femoral bone model revealed significantly higher translational and rotational errors than manual fitting, while no statistical differences (except for y-axis translation) were found for the tibial bone model. The repeatability of 108 intensity-based registrations showed mean in-plane standard deviations of 0.23–0.56 mm, but out-of-plane position repeatability was lower (mean SD: femur 7.98 mm, tibia 6.96 mm). SDs for rotations averaged 0.77–2.52°.
While the algorithm registered some images extremely well, other images clearly required manual intervention. When the algorithm registered the bones repeatably, it was also accurate, suggesting an approach that includes manual intervention could become practical for efficient and accurate registration.
The primary aim of this study was to validate predictions of human knee-joint contact mechanics derived from finite-element models of the tibiofemoral and patellofemoral joints (specifically, contact pressure, contact area and contact force) against corresponding measurements obtained in vitro during simulated weight-bearing activity. A secondary aim was to perform sensitivity analyses of the model calculations to identify those parameters that most significantly affect model predictions of joint contact pressure, area and force. Joint pressures in the medial and lateral compartments of the tibiofemoral and patellofemoral joints were measured in vitro during two simulated weight-bearing activities: stair descent and squatting. Model-predicted joint contact pressure distribution maps were consistent with those obtained from experiment. Normalized root-mean-square errors between the measured and calculated contact variables were on the order of 15%. Pearson correlations between the time histories of model-predicted and measured contact variables were generally above 0.8. Mean errors in the calculated centre-of-pressure locations were 3.1 mm for the tibiofemoral joint and 2.1 mm for the patellofemoral joint. Model predictions of joint contact mechanics were most sensitive to changes in the material properties and geometry of the meniscus and cartilage, particularly estimates of peak contact pressure. The validated FE modelling framework offers a useful tool for non-invasive determination of knee-joint contact mechanics during dynamic activity under physiological loading conditions.
Knee kinematics is an analysis of motion pattern that is utilized to assess a comparative, biomechanical performance of healthy nonimplanted knees, injured nonimplanted knees, and various prosthetic knee designs. Unfortunately, a consensus between implanted knee kinematics and outcomes has not been reached. One might hypothesize that the kinematic variances between the nonimplanted and implanted knee might play a role in patient dissatisfaction following TKA. There is a wide range of TKA designs available today. With such variety, it is important for surgeons and engineers to understand the various geometries and kinematic profiles of available prostheses. The purpose of this review is to provide readers with the pertinent information related to TKA kinematics.
Recent explorations of knee biomechanics have benefited from computational modeling, specifically leveraging advancements in finite element analysis and rigid body dynamics of joint and tissue mechanics. A large number of models have emerged with different levels of fidelity in anatomical and mechanical representation. Adapted modeling and simulation processes vary widely, based on justifiable choices in relation to anticipated use of the model. However, there are situations where modelers' decisions seem to be subjective, arbitrary, and difficult to rationalize. Regardless of the basis, these decisions form the "art" of modeling, which impact the conclusions of simulation-based studies on knee function. These decisions may also hinder the reproducibility of models and simulations, impeding their broader use in areas such as clinical decision making and personalized medicine. This document summarizes an ongoing project that aims to capture the modeling and simulation workflow in its entirety - operation procedures, deviations, models, by-products of modeling, simulation results, and comparative evaluations of case studies and applications. The ultimate goal of the project is to delineate the "art" of a cohort of knee modeling teams through a publicly accessible, transparent approach and begin to unravel the complex array of factors that may lead to a lack of reproducibility. This manuscript outlines our approach along with progress made so far. Potential implications on reproducibility, on science, engineering, and training of modeling and simulation, on modeling standards, and on regulatory affairs are also noted.
Existing “off-the-shelf” musculoskeletal models are problematic when simulating movements that involve substantial hip and knee flexion, such as the upstroke of pedalling, because they tend to generate excessive passive fibre force. The goal of this study was to develop a refined musculoskeletal model capable of simulating pedalling and fast running, in addition to walking, which predicts the activation patterns of muscles better than existing models. Specifically, we tested whether the anomalous co-activation of antagonist muscles, commonly observed in simulations, could be resolved if the passive forces generated by the underlying model were diminished. We refined the OpenSim™ model published by Rajagopal et al. (IEEE Trans Biomed Eng 63:1–1, 2016) by increasing the model’s range of knee flexion, updating the paths of the knee muscles, and modifying the force-generating properties of eleven muscles. Simulations of pedalling, running and walking based on this model reproduced measured EMG activity better than simulations based on the existing model—even when both models tracked the same subject-specific kinematics. Improvements in the predicted activations were associated with decreases in the net passive moments; for example, the net passive knee moment during the upstroke of pedalling decreased from 36.9 N m (existing model) to 6.3 N m (refined model), resulting in a dramatic decrease in the co-activation of knee flexors. The refined model is available from SimTK.org and is suitable for analysing movements with up to 120° of hip flexion and 140° of knee flexion.
Accurate measurement of in vivo joint kinematics is important for understanding normal and pathological human motion and for evaluating the outcome of surgical procedures. Biplane videoradiography is currently the most accurate method available for measuring in vivo joint kinematics noninvasively. The method uses two X-ray images obtained from different perspectives to deduce precise three-dimensional spatial information of the bones that meet at a joint. The abilities to collect high-quality X-ray images at high frame rates and to process these images in a time efficient manner are key factors determining the feasibility of using modern biplane videoradiography systems to measure human joint motion in vivo. The latest developments in this field include improvements in image quality, software for more efficient and accurate data processing, and the advent of mobile biplane videoradiography systems. Mobile systems enable data capture for a wider range of joints and activities by increasing the effective image capture volume, thereby addressing a major limitation of stationary systems.
This chapter summarizes the most recent advances in human motion measurement using biplane videoradiography (also commonly referred to as biplane X-ray fluoroscopy). We begin with some basic considerations related to hardware setup, data capture, and data processing and then describe methods commonly used to evaluate system accuracy. The chapter concludes with a discussion of the relative merits of mobile versus stationary systems as well as some thoughts on potential future applications of biplane videoradiography in human joint motion measurement.
Understanding the functionality of total ankle arthroplasties (TAA) requires thorough knowledge of the kinematics during activities of daily life. Videofluoroscopy enables the in vivo measurement of the 3D kinematics of implant components more accurately than by means of skin marker tracking. The aim of the present preliminary study was to quantify the 3D kinematics of a TAA during the stance phase of level and slope walking using single plane videofluoroscopy.
The experimental set up consisted of a videofluoroscopy system (BV Pulsera, Philips Medical Systems, Switzerland, 25 Hz, 1 ms shutter time) integrated in a walkway, allowing the assessment of free level gait, uphill, downhill and cross-slope walking. 2D/3D registration was performed using the CAD models of the TAA. In a preliminary feasibility study, the presented method was applied on four patients with successful unilateral TAA (Mobility™ Total Ankle, DePuy) with good outcomes.
Isolated 3D TAA kinematics was quantified with a rotational and translational error of 0.2 degrees and 0.4 mm in plane and 1.3 degrees and 2.1 mm out of plane. In the feasibility study it was found that only minor limitations occurred in sagittal plane motion. Any restrictions were caused by a limitation in dorsiflexion, whereas plantarflexion was for all gait conditions sufficiently provided. Transverse and frontal plane rotation was marginal, the main rotation occurred around the talar construction axis itself.
The presented method enabled accurate estimation of the 3D TAA kinematics in vivo, without being limited by skin movement artifacts and isolated from subtalar motion. Since the available amount of dorsiflexion is the crucial factor to allow unrestrictive gait, walking uphill is an appropriate motion task to challenge and evaluate the performance of the TAA.
The presented method has the potential to identify specific kinematic patterns and thereby help clinicians and implant developers to evaluate current designs and future design modifications.
Fluoroscopic imaging, using single plane or dual plane images, has grown in popularity to measure dynamic in vivo human shoulder joint kinematics. However, no study has quantified the difference in spatial positional accuracy between single and dual plane image-model registration applied to the shoulder joint. In this paper, an automatic 2D-3D image-model registration technique was validated for accuracy and repeatability with single and dual plane fluoroscopic images. Accuracy was assessed in a cadaver model, kinematics found using the automatic registration technique were compared to those found using radiostereometric analysis. The in vivo repeatability of the automatic registration technique was assessed during the dynamic abduction motion of four human subjects. The in vitro data indicated that the error in spatial positional accuracy of the humerus and the scapula was less than 0.30mm in translation and less than 0.58° in rotation using dual plane images. Single plane accuracy was satisfactory for in-plane motion variables, but out-of-plane motion variables on average were approximately 8 times less accurate. The in vivo test indicated that the repeatability of the automatic 2D-3D image-model registration was 0.50mm in translation and 1.04° in rotation using dual images. For a single plane technique, the repeatability was 3.31mm in translation and 2.46° in rotation for measuring shoulder joint kinematics. The data demonstrate that accurate and repeatable shoulder joint kinematics can be obtained using dual plane fluoroscopic images with an automatic 2D-3D image-model registration technique; and that out-of-plane motion variables are less accurate than in-plane motion variables using a single plane technique.
We propose an image restoration technique exploiting regularized inversion and the recent block-matching and 3D filtering (BM3D) denoising filter. The BM3D employs a non-local modeling of images by collecting similar image patches in 3D arrays. The so-called collaborative filtering applied on such a 3D array is realized by transform- domain shrinkage. In this work, we propose an extension of the BM3D filter for colored noise, which we use in a two-step deblurring algorithm to improve the regularization after inversion in discrete Fourier domain. The first step of the algorithm is a regularized inversion using BM3D with collaborative hard-thresholding and the seconds step is a regularized Wiener inversion using BM3D with collaborative Wiener filtering. The experimental results show that the proposed technique is competitive with and in most cases outperforms the current best image restoration methods in terms of improvement in signal-to-noise ratio.
The anterior cruciate ligament (ACL) has been well defined as the main passive restraint to anterior tibial translation (ATT) in the knee and plays an important role in rotational stability. However, it is unknown how closely the ACL and other passive and active structures of the knee constrain translations and rotations across a set of functional activities of increasing demand on the quadriceps.
Anterior tibial translation and internal rotation of the tibia relative to the femur would increase as the demand on the quadriceps increased.
Controlled laboratory study.
The in vivo 3-dimensional knee kinematics of 10 adult female patients (height, 167.8 ± 7.1 cm; body mass, 57 ± 4 kg; body mass index [BMI], 24.8 ± 1.7 kg/m(2); age, 29.7 ± 7.9 years) was measured using biplane fluoroscopy while patients completed 4 functional tasks. The tasks included an unloaded knee extension in which the patient slowly extended the knee from 90° to 0° of flexion in 2 seconds; walking at a constant pace of 90 steps per minute; a maximum effort isometric knee extension with the knee at 70° of flexion; and landing from a height of 40 cm in which the patient stepped off a box, landed, and immediately performed a maximum effort vertical jump.
Landing (5.6 ± 1.9 mm) produced significantly greater peak ATT than walking (3.1 ± 2.2 mm) and unweighted full extension (2.6 ± 2.1 mm) (P < .01), but there was no difference between landing and a maximum isometric contraction (5.0 ± 1.9 mm). While there was no significant difference in peak internal rotation between landing (19.4° ± 5.7°), maximum isometric contraction (15.9° ± 6.7°), and unweighted full knee extension (14.5° ± 7.7°), each produced significantly greater internal rotation than walking (3.9° ± 4.2°) (P < .001). Knee extension torque significantly increased for each task (P < .01): unweighted knee extension (4.7 ± 1.2 N·m), walking (36.5 ± 7.9 N·m), maximum isometric knee extension (105.1 ± 8.2 N·m), and landing (140.2 ± 26.2 N·m).
Anterior tibial translations significantly increased as demand on the quadriceps and external loading increased. Internal rotation was not significantly different between landing, isometric contraction, and unweighted knee extension. Additionally, ATT and internal rotation from each motion were within the normal range, and no excessive amounts of translation or rotation were observed.
This study demonstrated that while ATT will increase as demand on the quadriceps and external loading increases, the knee is able to effectively constrain ATT and internal rotation. This suggests that the healthy knee has a safe envelope of function that is tightly controlled even though task demand is elevated.
The experimental study of joint kinematics in three dimensions requires the description and measurement of six motion components. An important aspect of any method of description is the ease with which it is communicated to those who use the data. This paper presents a joint coordinate system that provides a simple geometric description of the three-dimensional rotational and translational motion between two rigid bodies. The coordinate system is applied to the knee and related to the commonly used clinical terms for knee joint motion. A convenient characteristic of the coordinate system shared by spatial linkages is that large joint displacements are independent of the order in which the component translations and rotations occur.
We used fluoroscopy to study the kinematics of the knee in 47 patients with total knee arthroplasty (TKA) and four control subjects with normal knees while performing a single-leg deep-knee bend. The videos were analysed using still photographs taken at 5 degrees increments of flexion. Femorotibial contact points, patellar ligament rotation, and patellar rotation were calculated from each image. Maximum weight-bearing flexion was determined for each knee. Compared with the control group, posterior-cruciate-retaining TKA did not reproduce normal knee kinematics in any case, but showed a starting point posterior to the tibial midline which translated anteriorly with flexion. The curves from successive knee bends could not be consistently reproduced. Under weight-bearing conditions, the maximum flexion for any PCR TKA was 98 degrees and several patients could not flex beyond 70 degrees.
Current noninvasive or minimally invasive methods for evaluating in vivo knee kinematics are inadequate for accurate determination of dynamic joint function due to limited accuracy and/or insufficient sampling rates. A three-dimensional (3-D) model-based method is presented to estimate skeletal motion of the knee from high-speed sequences of biplane radiographs. The method implicitly assumes that geometrical features cannot be detected reliably and an exact segmentation of bone edges is not always feasible. An existing biplane radiograph system was simulated as two separate single-plane radiograph systems. Position and orientation of the underlying bone was determined for each single-plane view by generating projections through a 3-D volumetric model (from computed tomography), and producing an image (digitally reconstructed radiograph) similar (based on texture information and rough edges of bone) to the two-dimensional radiographs. The absolute 3-D pose was determined using known imaging geometry of the biplane radiograph system and a 3-D line intersection method. Results were compared to data of known accuracy, obtained from a previously established bone-implanted marker method. Difference of controlled in vitro tests was on the order of 0.5 mm for translation and 1.4 degrees for rotation. A biplane radiograph sequence of a canine hindlimb during treadmill walking was used for in vivo testing, with differences on the order of 0.8 mm for translation and 2.5 degrees for rotation.
Dynamic assessment of three-dimensional (3D) skeletal kinematics is essential for understanding normal joint function as well as the effects of injury or disease. This paper presents a novel technique for measuring in-vivo skeletal kinematics that combines data collected from high-speed biplane radiography and static computed tomography (CT). The goals of the present study were to demonstrate that highly precise measurements can be obtained during dynamic movement studies employing high frame-rate biplane video-radiography, to develop a method for expressing joint kinematics in an anatomically relevant coordinate system and to demonstrate the application of this technique by calculating canine tibio-femoral kinematics during dynamic motion. The method consists of four components: the generation and acquisition of high frame rate biplane radiographs, identification and 3D tracking of implanted bone markers, CT-based coordinate system determination, and kinematic analysis routines for determining joint motion in anatomically based coordinates. Results from dynamic tracking of markers inserted in a phantom object showed the system bias was insignificant (-0.02 mm). The average precision in tracking implanted markers in-vivo was 0.064 mm for the distance between markers and 0.31 degree for the angles between markers. Across-trial standard deviations for tibio-femoral translations were similar for all three motion directions, averaging 0.14 mm (range 0.08 to 0.20 mm). Variability in tibio-femoral rotations was more dependent on rotation axis, with across-trial standard deviations averaging 1.71 degrees for flexion/extension, 0.90 degree for internal/external rotation, and 0.40 degree for varus/valgus rotation. Advantages of this technique over traditional motion analysis methods include the elimination of skin motion artifacts, improved tracking precision and the ability to present results in a consistent anatomical reference frame.
Little is known about the three-dimensional behavior of the anterior cruciate ligament (ACL) reconstructed knee during dynamic, functional loading, or how dynamic knee function changes over time in the reconstructed knee. We hypothesized dynamic, in vivo function of the ACL-reconstructed knee is different from the contralateral, uninjured knee and changes over time. We measured knee kinematics for 16 subjects during downhill running 5 and 12 months after ACL reconstruction (bone-patellar tendon-bone or quadrupled hamstring tendon with interference screw fixation) using a 250 frame per second stereoradiographic system. We used repeated-measures ANOVA to ascertain whether there were differences between the uninjured and reconstructed limbs and over time. We found no differences in anterior tibial translation between limbs, but reconstructed knees were more externally rotated and in more adduction (varus) during the stance phase of running. Anterior tibial translation increased from 5 to 12 months after surgery in the reconstructed knees. Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic, functional loading and some degradation of graft function occurred over time. These abnormal motions may contribute to long-term joint degeneration associated with ACL injury and reconstruction.
The purpose of this study was to investigate glenohumeral translation in-vivo during active shoulder abduction in the scapular plane. Three-dimensional (3D) models of 9 shoulders were created from CT scans. Fluoroscopic views aligned to the plane of the scapula were recorded during active arm abduction with neutral rotation. 3D motions were determined using model-based 3D-to-two-dimensional (2D) registration. Humeral translation was referenced to the glenoid center in the superior/inferior direction. The humerus moved an average of 1.7 mm superior with arm abduction, from an inferior location to the glenoid center. The humeral head was centered within 1 mm from the glenoid center above 80 degrees abduction. Variability in glenohumeral translation between shoulders decreased significantly from initial to final arm abduction. Our findings agree with some authors' observations of inferior-to-central translation of the humerus and behavior as a congruent ball and socket. We believe this information will help improve the understanding of shoulder function.
The purpose of this study was to determine the accuracy of a radiographic model-based tracking technique that measures the three-dimensional in vivo motion of the tibio-femoral joint during running. Tantalum beads were implanted into the femur and tibia of three subjects and computed tomography (CT) scans were acquired after bead implantation. The subjects ran 2.5m/s on a treadmill positioned within a biplane radiographic system while images were acquired at 250 frames per second. Three-dimensional implanted bead locations were determined and used as a "gold standard" to measure the accuracy of the model-based tracking. The model-based tracking technique optimized the correlation between the radiographs acquired via the biplane X-ray system and digitally reconstructed radiographs created from the volume-rendered CT model. Accuracy was defined in terms of measurement system bias, precision and root-mean-squared (rms) error. Results were reported in terms of individual bone tracking and in terms of clinically relevant tibio-femoral joint translations and rotations (joint kinematics). Accuracy for joint kinematics was as follows: model-based tracking measured static joint orientation with a precision of 0.2 degrees or better, and static joint position with a precision of 0.2mm or better. Model-based tracking precision for dynamic joint rotation was 0.9+/-0.3 degrees , 0.6+/-0.3 degrees , and 0.3+/-0.1 degrees for flexion-extension, external-internal rotation, and ab-adduction, respectively. Model-based tracking precision when measuring dynamic joint translation was 0.3+/-0.1mm, 0.4+/-0.2mm, and 0.7+/-0.2mm in the medial-lateral, proximal-distal, and anterior-posterior direction, respectively. The combination of high-speed biplane radiography and volumetric model-based tracking achieves excellent accuracy during in vivo, dynamic knee motion without the necessity for invasive bead implantation.
Patellofemoral joint pain is a common problem experienced by active adults. However, relatively little is known about patellofemoral joint load and its distribution across the medial and lateral facets of the patella. In this study, biomechanical experiments and computational modeling were used to study patellofemoral contact mechanics in four healthy adults during stair ambulation. Subject-specific anatomical and gait data were recorded using magnetic resonance imaging, dynamic X-ray fluoroscopy, video motion capture, and multiple force platforms. From these data, in vivo tibiofemoral joint kinematics and knee muscle forces were computed and then applied to a deformable finite-element model of the patellofemoral joint. The contact force acting on the lateral facet of the patella was 4-6 times higher than that acting on the medial facet. The peak average patellofemoral contact stresses were 8.2±1.0MPa and 5.9±1.3MPa for the lateral and medial patellar facets, respectively. Peak normal compressive stress and peak octahedral shear stress occurred near toe-off of the contralateral leg and were higher on the lateral facet than the medial facet; furthermore, the peak compressive stress (11.5±3.0MPa) was higher than the peak octahedral shear stress (5.2±0.9MPa). The dominant stress pattern on the lateral patellar facet corresponded well to the location of maximum cartilage thickness. Higher loading of the lateral facet is also consistent with the clinical observation that the lateral compartment of the patellofemoral joint is more prone to osteoarthritis than the medial compartment. Predicted cartilage contact stress maps near contralateral toe-off showed three distinctly different patterns: peak stresses located on the lateral patellar facet; peak stresses located centrally between the medial and lateral patellar facets; and peak stresses located superiorly on both the medial and lateral patellar facets.
A precise and comprehensive definition of "normal" in vivo cervical kinematics does not exist due to high intersubject variability and the absence of midrange kinematic data. In vitro test protocols and finite element models that are validated using only end range of motion data may not accurately reproduce continuous in vivo motion.
The primary objective of this study was to precisely quantify cervical spine intervertebral kinematics during continuous, functional flexion-extension in asymptomatic subjects. The advantages of assessing continuous intervertebral kinematics were demonstrated by comparing asymptomatic controls with patients with single-level anterior arthrodesis.
Cervical spine kinematics were determined during continuous in vivo flexion-extension in a clinically relevant age group of asymptomatic controls and a group of patients with C5-C6 arthrodesis.
The patient sample consisted of 6 patients with single-level (C5-C6) anterior arthrodesis (average age: 48.8±6.9 years; 1 male, 5 female; 7.6±1.2 months postsurgery) and 18 asymptomatic control subjects of similar age (average age: 45.6±5.8 years; 5 male, 13 female).
Outcome measures included the physiologic measure of continuous kinematic motion paths at each cervical motion segment (C2-C7) during flexion-extension.
Participants performed flexion-extension while biplane radiographs were collected at 30 images per second. A previously validated tracking process determined three-dimensional vertebral positions with submillimeter accuracy. Continuous flexion-extension rotation and anterior-posterior translation motion paths were adjusted for disc height and static orientation of each corresponding motion segment.
Intersubject variability in flexion-extension angle was decreased 15% to 46% and intersubject variability in anterior-posterior translation was reduced 14% to 33% after adjusting for disc height and static orientation angle. Average intersubject variability in continuous motion paths was 1.9° in flexion-extension and 0.6 mm in translation. Third-order polynomial equations were determined to precisely describe the continuous flexion-extension and anterior-posterior translation motion path at each motion segment (all R(2)>0.99).
A significant portion of the intersubject variability in cervical kinematics can be explained by the disc height and the static orientation of each motion segment. Clinically relevant information may be gained by assessing intervertebral kinematics during continuous functional movement rather than at static, end range of motion positions. The fidelity of in vitro cervical spine mechanical testing protocols may be evaluated by comparing in vitro kinematics to the continuous motion paths presented.
Older adults walk more slowly, take shorter steps, and spend more time with both legs on the ground compared to young adults. Although many studies have investigated the effects of aging on the kinematics and kinetics of gait, little is known about the corresponding changes in muscle function. The aim of this study was to describe and compare the actions of the lower-limb muscles in accelerating the body's center of mass (COM) in healthy young and older adults. Three-dimensional gait analysis and subject-specific musculoskeletal modeling were used to calculate lower-limb muscle forces and muscle contributions to COM accelerations when both groups walked at the same speed. The orientations of all body segments during walking, except that of the pelvis, were invariant to age when these quantities were expressed in a global reference frame. The older subjects tilted their pelves more anteriorly during the stance phase. The mean contributions of the gluteus maximus, gluteus medius, vasti, gastrocnemius and soleus to the vertical, fore-aft and mediolateral COM accelerations (support, progression and balance, respectively) were similar in the two groups. However, the gluteus medius contributed significantly less to support (p<0.05) while the gluteus maximus and contralateral erector spinae contributed significantly more to balance (p<0.05) during early stance in the older subjects. These results provide insight into the functional roles of the individual leg muscles during gait in older adults, and highlight the importance of the hip and back muscles in controlling mediolateral balance.
While measuring knee motion in all six degrees of freedom is important for understanding and treating orthopaedic knee pathologies, traditional motion capture techniques lack the required accuracy. A variety of model-based biplane fluoroscopy techniques have been developed with sub-millimeter accuracy. However, no studies have statistically evaluated the consistency of the accuracy across motions of varying intensity or between degrees of freedom. Therefore, this study evaluated the bias and precision of a contour-based tracking technique by comparing it to a marker-based method (gold standard) during three movements with increasing intensity. Six cadaveric knees with implanted tantalum markers were used to simulate knee extension, walking and drop landings, while motion was recorded by a custom biplane fluoroscopy system. The 3D geometries of the bones were reconstructed from CT scans and anatomical coordinate systems were assigned. The position and orientation of the bone and marker models were determined for an average of 27 frames for each trial and knee joint kinematics were compared. The average bias and precision was 0.01±0.65° for rotations and 0.01±0.59mm for joint translations. Rotational precision was affected by motion (p=0.04) and depended on the axis of rotation (p=0.02). However, the difference in average precision among motions or axes was small (≤0.13°) and not likely of consequence for kinematic measurements. No other differences were found. The contour-based technique demonstrated sub-millimeter and sub-degree accuracy, indicating it is a highly accurate tool for measuring complex three dimensional knee movements of any intensity.
This paper deals with the experimental problems related to the reconstruction of the position and orientation of the lower limb bones in space during the execution of locomotion and physical exercises. The inaccuracies associated with the relative movement between markers and underlying bone are analysed. Quantitative information regarding this movement was collected by making experiments on subjects who had suffered fractures and were wearing either femoral or tibial external fixators. These latter devices provided frames that were reliably rigid with the bone involved, and hence the possibility of assessing the relative movement between markers mounted on the skin and this bone. Anatomical frames associated with thigh and shank were reconstructed using technical frames based on different clusters of skin markers and their rotation with respect to the relevant bone evaluated. Marker movement was also assessed in subjects with intact musculoskeletal structures using digital videofluoroscopy.
Knowledge of three-dimensional skeletal kinematics during functional activities such as walking, is required for accurate modelling of joint motion and loading, and is important in identifying the effects of injury and disease. For example, accurate measurement of joint kinematics is essential in understanding the pathogenesis of osteoarthritis and its symptoms and for developing strategies to alleviate joint pain. Bi-plane X-ray fluoroscopy has the capacity to accurately and non-invasively measure human joint motion in vivo. Joint kinematics obtained using bi-plane X-ray fluoroscopy will aid in the development of more complex musculoskeletal models, which may be used to assess joint function and disease and plan surgical interventions and post-operative rehabilitation strategies. At present, however, commercial C-arm systems constrain the motion of the subject within the imaging field of view, thus precluding recording of motions such as overground gait. These fluoroscopy systems also operate at low frame rates and therefore cannot accurately capture high-speed joint motion during tasks such as running and throwing. In the future, bi-plane fluoroscopy systems may include computer-controlled tracking for the measurement of joint kinematics over entire cycles of overground gait without constraining motion of the subject. High-speed cameras will facilitate measurement of high-impulse joint motions, and computationally efficient pose-estimation software may provide a fast and fully automated process for quantification of natural joint motion.
People who have undergone total knee replacement (TKR) experience difficulties in some daily activities including walking. Walking at faster speeds requires more knee flexion and may therefore present a greater challenge following TKR. The aim of this study was to compare the knee kinematics of patients following TKR and unimpaired controls during comfortable and fast walking speeds. Forty patients (22 women, 18 men) 12 months following TKR and 40 control participants (matched for age and sex) were assessed during walking at self-selected comfortable and fast speeds using three dimensional motion analysis. The group averages of spatiotemporal and peak kinematic characteristics in the sagittal, coronal and transverse movement planes were compared using univariate analysis of variance with walking speed as a co-variate. The TKR group walked with significantly reduced cadence (p < 0.001 at both speeds) and reduced stride length (p < 0.001 at both speeds), less knee flexion during stance and swing phases (p < 0.001 for both speeds) and less knee extension during stance phase (p < 0.024 for comfortable speed; p < 0.042 for fast speed). The TKR group also walked with less peak knee external rotation than controls at both speeds (p < 0.001 for both speeds). Both groups increased their velocity, cadence and stride length by a similar proportion when walking at fast speed. When walking at a faster speed, spatiotemporal gait parameters and knee motion are altered in a similar manner for both TKR patients and controls. However, at both walking speeds, TKR patients exhibit residual deficits 12 months following surgery.
The soft-tissue interface between skin-mounted markers and the underlying bones poses a major limitation to accurate, non-invasive measurement of joint kinematics. The aim of this study was twofold: first, to quantify lower limb soft-tissue artifact in young healthy subjects during functional activity; and second, to determine the effect of soft-tissue artifact on the calculation of knee joint kinematics. Subject-specific bone models generated from magnetic resonance imaging (MRI) were used in conjunction with X-ray images obtained from single-plane fluoroscopy to determine three-dimensional knee joint kinematics for four separate tasks: open-chain knee flexion, hip axial rotation, level walking, and a step-up. Knee joint kinematics was derived using the anatomical frames from the MRI-based, 3D bone models together with the data from video motion capture and X-ray fluoroscopy. Soft-tissue artifact was defined as the degree of movement of each marker in the anteroposterior, proximodistal and mediolateral directions of the corresponding anatomical frame. A number of different skin-marker clusters (total of 180) were used to calculate knee joint rotations, and the results were compared against those obtained from fluoroscopy. Although a consistent pattern of soft-tissue artifact was found for each task across all subjects, the magnitudes of soft-tissue artifact were subject-, task- and location-dependent. Soft-tissue artifact for the thigh markers was substantially greater than that for the shank markers. Markers positioned in the vicinity of the knee joint showed considerable movement, with root mean square errors as high as 29.3mm. The maximum root mean square errors for calculating knee joint rotations occurred for the open-chain knee flexion task and were 24.3 degrees , 17.8 degrees and 14.5 degrees for flexion, internal-external rotation and abduction-adduction, respectively. The present results on soft-tissue artifact, based on fluoroscopic measurements in healthy adult subjects, may be helpful in developing location- and direction-specific weighting factors for use in global optimization algorithms aimed at minimizing the effects of soft-tissue artifact on calculations of knee joint rotations.
Accurate knowledge of the dynamic knee motion in-vivo is instrumental for understanding normal and pathological function of the knee joint. However, interpreting motion of the knee joint during gait in other than the sagittal plane remains controversial. In this study, we utilized the dual fluoroscopic imaging technique to investigate the six-degree-of-freedom kinematics and condylar motion of the knee during the stance phase of treadmill gait in eight healthy volunteers at a speed of 0.67 m/s. We hypothesized that the 6DOF knee kinematics measured during gait will be different from those reported for non-weightbearing activities, especially with regards to the phenomenon of femoral rollback. In addition, we hypothesized that motion of the medial femoral condyle in the transverse plane is greater than that of the lateral femoral condyle during the stance phase of treadmill gait. The rotational motion and the anterior-posterior translation of the femur with respect to the tibia showed a clear relationship with the flexion-extension path of the knee during the stance phase. Additionally, we observed that the phenomenon of femoral rollback was reversed, with the femur noted to move posteriorly with extension and anteriorly with flexion. Furthermore, we noted that motion of the medial femoral condyle in the transverse plane was greater than that of the lateral femoral condyle during the stance phase of gait (17.4+/-2.0mm vs. 7.4+/-6.1mm, respectively; p<0.01). The trend was opposite to what has been observed during non-weightbearing flexion or single-leg lunge in previous studies. These data provide baseline knowledge for the understanding of normal physiology and for the analysis of pathological function of the knee joint during walking. These findings further demonstrate that knee kinematics is activity-dependent and motion patterns of one activity (non-weightbearing flexion or lunge) cannot be generalized to interpret a different one (gait).
Understanding the effect of weightbearing on subtalar and ankle joint kinematics is critical for the diagnosis and treatment of foot disorders. However, dynamic in vivo kinematics of these joints are not well studied. The purpose of this study was to compare in vivo kinematics during nonweightbearing and weightbearing activities in healthy subjects.
Seven healthy subjects with a mean age of 32 (range, 23 to 42) years were enrolled. Oblique lateral fluoroscopic images of nonweightbearing and weightbearing dorsiflexion-plantarflexion activities were recorded. Three dimensional subtalar, ankle, and ankle-subtalar joint complex kinematics were determined using 3D-2D model registration techniques with 3D bone models and single-plane fluoroscopy.
During the weightbearing activity from 20 degrees dorsiflexion to 15 degrees plantarflexion, the subtalar joint was significantly more everted, dorsiflexed, and abducted, and the calcaneus showed a significantly more posterior position, than during the nonweightbearing activity. The ankle joint was significantly more plantarflexed and adducted during the weightbearing activity than the nonweightbearing activity. The ankle-subtalar joint complex was significantly more everted, and the calcaneus showed significantly greater posterior position than the nonweightbearing activity.
These observations provide basic quantitative descriptions of weightbearing and nonweightbearing kinematics for healthy joints.
These data can serve as the basis for comparison with pathologic feet for both diagnostic and therapeutic purposes.
The problem of determining skeletal movements in three dimensions by using a number of landmarks is treated. We present a method that determines the motion of a rigid body by using the positions of the landmarks in least-squares sense. The method uses the singular value decomposition of a matrix derived from the positions of the landmarks. We show how one can use this method to express movement of skeleton segments relative to each other. As many others have pointed out, the movement can be very ill determined if the landmarks are badly configured. We present a condition number for the problem with good geometrical properties. The condition number depends on the configuration of the landmarks and indicates how to distribute the landmarks in a suitable way.
A simple extension of a previously reported object recognition technique has been used to implement a six-degree-of-freedom position/orientation estimator for the measurement of knee replacement motion from two-dimensional (2-D) fluoroscopic images. Computer modeling studies and controlled mechanical tests were performed to assess the accuracy of the technique. The results indicate that knee rotations can be measured with an accuracy of approximately one degree and that sagittal plane translations can be measured with an accuracy of approximately 0.5 mm. The measurement technique is uniquely well suited for performing dynamic kinematic measurements on individuals with knee replacements, and for performing comparative studies among subjects with different designs of knee replacements.
The objective of the current study was to use fluoroscopy and computed tomography to accurately determine the three-dimensional, in vivo, weightbearing kinematics of five normal knees. Three-dimensional computer-aided design models of each subject's femur and tibia were recreated from the three-dimensional computed tomography bone density data. Three-dimensional motions for each subject then were determined for five weightbearing activities. During gait, the lateral condyle experienced -4.3 mm (range, -1.9--10.3 mm) of average motion, whereas the medial condyle moved only -0.9 mm (range, 3.4--5.8 mm). One subject experienced 5.8 mm of medial condyle motion. On average, during deep flexion activities, subjects experienced -12.7 mm (range, 1.4--29.8 mm) of lateral condyle motion, whereas the medial condyle motion only was -2.9 mm (range, 3.0--9.0 mm). One subject experienced 5.8 and 9.0 mm of medial condyle motion during gait and a deep knee bend, respectively leading to the occurrence of a lateral pivot motion. During the deep flexion activities, the subjects experienced significantly more axial rotation (> 13 degrees) than gait (< 5 degrees). During all five activities, the lateral condyle experienced significantly more anteroposterior translation, leading to axial rotation of the tibia relative to the femur.
It remains unknown if and how the polyethylene bearing in mobile bearing knees moves during dynamic activities with respect to the tibial base plate. Marker Configuration Model-Based Roentgen Fluoroscopic Analysis (MCM-based RFA) uses a marker configuration model of inserted tantalum markers in order to accurately estimate the pose of an implant or bone using single plane Roentgen images or fluoroscopic images. The goal of this study is to assess the accuracy of (MCM-Based RFA) in a standard fluoroscopic set-up using phantom experiments and to determine the error propagation with computer simulations. The experimental set-up of the ph