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ABSTRACT: Current clinical evaluations often rely on static anatomic imaging modalities for diagnosis of mechanical low back pain, which provide anatomic snapshots and a surrogate analysis of a functional disease. Three dimensional in vivo motion is available with the use of digital fluoroscopy, which was used to capture kinematic data of the lumbar spine in order to identify coefficients of motion that may assist the physician in differentiating patient pathology. Forty patients distributed among 4 classes of lumbar degeneration, from healthy to degenerative, underwent CT, MRI, and digital x-ray fluoroscopy. Each patient underwent diagnosis by a neurosurgeon. Fluoroscopy was taken as the patient performed lateral bending (LB), axial rotation (AR) and flexion-extension (FE). Patient specific models were registered with the fluoroscopy images to obtain in vivo kinematic data. Motion coefficients, C(LB), C(AR), C(FE), were calculated as the ratio of in-plane motion to total out-of-plane motion. Range of motion (ROM) was calculated about the axis of motion for each exercise. Inter- and Intra- group statistics were examined for each coefficient and a flexible Bayesian classifier was used to differentiate patients with degeneration. The motion coefficients C(LB) and C(FE) were significantly different (p<0.05) in 4 of 6 group comparisons. In plane motion, ROM(LB), was significantly different in only 1 of 6 group comparisons. The classifier achieved 95% sensitivity and specificity using (C(FE), C(LB), ROM(LB)) as input features, and 40% specificity and 80% sensitivity using ROM variables. The new coefficients were better correlated with patient pathology than ROM measures. The coefficients suggest a relationship between pathology and measured motion which has not been reported previously.
Journal of biomechanics 12/2012; · 2.66 Impact Factor
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ABSTRACT: Fluoroscopy along with image registration techniques is widely used to study the in vivo kinematic behavior observed in total knee arthroplasties (TKAs). This study provides and overview of the basic principles associated with the process and the protocols commonly followed using this technique. A summary of the data collected for more than 2000 patients implanted with 25 different types of TKAs are also provided and compared with the kinematics observed in normal knees. Some of the characteristics of TKA behavior when compared with normal knees include: (1) incidence of reduced posterior translations or paradoxical anterior slide of the femoral condyles with respect to the tibia; (2) reverse axial rotation patterns, where the femur rotates internally relative to the tibial component with increasing flexion; and (3) incidence of condylar lift-off where one of the condyles separate and loses contact. Comparison of patients who achieve higher flexion with those who achieve lower flexion revealed that the condylar contact location remains more posterior in the higher flexing group even at the same flexion angles.
Techniques in Knee Surgery 05/2011; 10(2):66–72.
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ABSTRACT: In vivo studies have suggested Caucasians achieve lower average knee flexion than non-Western populations. Some previous studies have also suggested gender may influence condylar AP translation and axial rotation, while others report an absence of such an influence.
We determined whether different ethnic and gender groups residing in the United States had different knee translations and rotations.
Three-dimensional knee rotations and translations were determined for 72 healthy subjects (24 Caucasian men, 24 Caucasian women, 13 Japanese men, 11 Japanese women) from full extension to maximum flexion using a fluoroscopic technique, under in vivo, weightbearing conditions.
Although we observed substantial variability in all groups, small differences between groups were found, especially in deep flexion. Japanese women and men and Caucasian women achieved higher maximum flexion (153°, 151°, and 152°, respectively) than Caucasian men (146°). External rotation was higher for these three groups than for Caucasian men. The medial condyle remained more anterior for Caucasian women and all Japanese subjects than for Caucasian men, possibly leading to greater axial rotation and flexion, observed for these three groups.
We identified small differences in maximum flexion between genders and ethnic groups. While no differences were identified in the lateral condyle translation, the medial condyle remained more stationary and more anterior for the groups that achieved highest (and similar) maximum flexion. Therefore, it may be important for future implant designs to incorporate these characteristics, such that only the lateral condyle experiences greater posterior femoral rollback, while the medial condyle remains more stationary throughout flexion.
Clinical Orthopaedics and Related Research 01/2011; 469(1):95-106. · 2.53 Impact Factor
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ABSTRACT: In vivo video fluoroscopies of well-functioning total hip arthroplasties (THA) have shown that femoral head separation from the medial articular bearing surface occurs during gait. Other activities may cause the same phenomenon. We examined this while patients performed the following 4 activities of daily living: pivoting to each side in stance, shoe tying, sitting down, and standing up. Ten healthy patients (5 men, 5 women, average age 66 years) all 1 year or more after cementless THA performed for degenerative arthritis, with Harris Hip Scores ≥90, were studied. Each patient performed the activities of daily living while data was captured using video fluoroscopy. Based on previously reported criteria, femoral head separation (the femoral head sliding lateral to the acetabular liner) was determined to be reliably predicted if the distance between the femoral head and acetabular cup was ≥0.5. Results showed that the greatest femoral head separation occurred during the pivoting activity (mean, 1.53 mm; range, 0.00-3.34 mm; SD, 1.05 mm). The separation values identified during pivoting occurred at the extremes of internal or external rotation for all patients. The other 3 activities showed lower separation distances. Separation during the pivoting activity exceeded the reported separations occurring during walking. This finding was seen in a small group of patients, and the data should be interpreted with caution. We conclude from this study that the evaluation of gait alone may not be sufficient to accurately assess femoral head separation occurring during activities of daily living for healthy, active patients.
Orthopedics 01/2011; 34(6):127. · 2.66 Impact Factor
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ABSTRACT: The performance evaluation of THA outcome is difficult and surgeons often use invasive methods to investigate effectiveness. A non-invasive acoustic and vibration analysis technique has recently been developed for more-in-depth evaluation of in vivo hip conditions. Gait kinematics, corresponding vibration and sound measurement of five THA subjects were analyzed post-operatively using video-fluoroscopy, sound and accelerometer measurements while walking on a treadmill. The sound sensor and a pair of tri-axial accelerometers, externally attached to the pelvic and femoral bone prominences, detected frequencies that are propagated through the femoral head and acetabular cup interactions. A data acquisition system was used to amplify the signal and filter out noise generated by undesired frequencies. In vivo kinematics and femoral head sliding quantified using video fluoroscopy were correlated to the sound and acceleration measurements. Distinct variations between the different subjects were identified. A correlation of sound and acceleration impulses with separation has been achieved. Although, in vivo sounds are quite variable in nature and all correlated well with the visual images. This is the first study to document and correlate visual and audible effects of THA under in-vivo conditions. This study has shown that the development of the acoustic and vibration technique provides a practical method and generates new possibilities for a better understanding of THA performance.
Journal of biomechanics 11/2009; 43(3):426-32. · 2.66 Impact Factor
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ABSTRACT: This study compares the in vivo patellar kinematics of high-flexion posterior cruciate ligament-retaining and posterior-stabilized total knee arthroplasty (TKA) implants with that of the healthy knee. Twenty-seven subjects performing weight-bearing deep knee bends were analyzed under fluoroscopic surveillance from full extension to maximum flexion. The patellofemoral contact positions and patellar flexion were similar for both TKAs. At low flexion, the patellofemoral contact was significantly more distal on the healthy patella than on the TKA patella, but in deeper flexion, there was no difference among the 3 groups. The tibiopatellar angle was similar for all 3 groups, except at deep flexion where the healthy patella rotated significantly more than the implanted ones. Patellofemoral separation was observed in some TKA knees, whereas it was absent in the healthy knees.
The Journal of arthroplasty 03/2009; 25(3):398-404. · 1.79 Impact Factor
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ABSTRACT: This study analyzed three dimensional (3D) in vivo kinematic data from the squatting to standing position for 18 Japanese subjects (18 knees) implanted with either Legacy((R)) Posterior Stabilized (LPS) Flex Fixed Bearing TKA or LPS Flex Mobile Bearing TKA. Under weight-bearing conditions, for all patients, the average roll-forward motions for the medial and lateral condyles were 4.0+/-3.6 mm and 6.3+/-3.4 mm, and the average external axial rotation was 3.1 degrees +/-4.1 degrees . For both groups, the weight-bearing range-of-motion (ROM) (110.7 degrees +/-12.7 degrees ) was less than pre (127.2+/-15.5 degrees ) and post (135.6+/-5.4 degrees ) operative non-weight bearing ROM. As hypothesized, the incidence, average and maximum lift off for the squatting to standing activity were much less than those of deep knee bend (DKB), and condylar motions and kinematics were opposite that of the DKB. There was little statistical difference of their kinematic patterns during this activity between the LPS fixed and mobile TKA implants.
The Knee 01/2009; 16(2):116-20. · 1.74 Impact Factor
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ABSTRACT: Recent technological advancements in total ankle arthroplasty (TAA) have included the introduction of the mobile bearing concept. This bearing has several advantages, but researchers have questioned whether or not increased mobility sacrifices joint stability or durability of the implant. The present study evaluated the kinematics of this type of prosthesis implanted in patients.
Fluoroscopy and 3D-to-2D registration techniques were used to determine the in vivo kinematics for 20 TAA subjects performing two activities: gait and step-up. The motion of the prostheses was described in terms of clinical rotations and as rotation about the helical (screw) axis. Then, the anterior-posterior translation and axial rotation of the mobile bearing insert were determined.
Among the clinical rotations, the dorsi-/plantarflexion was the most dominant, revealing the greatest pattern change and the largest magnitude. During gait, the orientation of the prosthetic components changed smoothly from plantarflexion to dorsiflexion. The average range of this motion was 9.2 degrees. For step-up activity, the range was 8.0 degrees. However, between 33% and 66% of stance phase, the talar component's orientation changed from dorsiflexion to plantarflexion. The average absolute range of anterior-posterior translation of the mobile bearing insert was 1.5 mm and 2.3 mm for gait and step-up, respectively.
These measured translations were relatively small and may suggest that the rotational portion of the motion was more dominant than translational and provided sufficient mobility.
The Foot and Ankle Online Journal 12/2008; 29(11):1117-25. · 1.22 Impact Factor
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The Journal of Bone and Joint Surgery 12/2008; 90 Suppl 4:85-9. · 3.27 Impact Factor
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The Journal of Bone and Joint Surgery 12/2008; 90 Suppl 4:112-20. · 3.27 Impact Factor
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ABSTRACT: The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112 degrees of weight-bearing (WB) flexion, -6.4 mm of posterior femoral rollback, and 2.9 degrees of axial rotation. The CR subjects averaged 117 degrees of WB flexion, -4.9 mm of posterior femoral rollback, and 4.8 degrees of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.
The Journal of arthroplasty 04/2008; 23(7):1057-67. · 1.79 Impact Factor
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ABSTRACT: Minimally invasive surgery has been developed to reduce incision length, muscle damage, and rehabilitation time. However, reduced exposure of anatomical landmarks may result in technical errors and inferior implant survivorship. The objective of this study was to compare in vivo motions and hip joint contact forces during gait in total hip arthroplasty subjects, performed with either minimally invasive surgery or standard surgical approaches.
Fifteen subjects implanted using either minimally invasive surgery anterolateral, minimally invasive surgery posterolateral, or traditional posterolateral total hip arthroplasty were evaluated using fluoroscopy while performing gait on a treadmill. Kinematics, obtained using 3D-to-2D image registration technique, were input as temporal functions in a 3D inverse dynamic mathematical model that determines in vivo soft tissue and hip contact forces.
The subjects implanted with posterolateral and anterolateral minimally invasive surgery demonstrated significantly less separation than those implanted with the traditional approach (P<0.01). The minimally invasive surgery subjects also experienced lower average maximum peak forces, with 3.2 body weight for the anterolateral minimally invasive surgery and 2.9 body weight for the posterolateral minimally invasive surgery subjects, compared to 3.5 body weight for the traditional subjects (P=0.02 and P=0.03, respectively).
This is the first study to compare in vivo weight-bearing kinematics, separation and kinetics for traditional, anterolateral minimally invasive surgery and posterolateral minimally invasive surgery total hip arthroplasty subject groups. Our data indicated in all analyzed parameters differences between the minimally invasive surgery and the traditional groups, with favorable results for the minimally invasive surgery subjects. This may be related, to a reduction in stabilizing soft tissues after a minimally invasive surgery procedure, leading to lower bearing surface forces at the femoral head--acetabular cup interface.
Clinical Biomechanics 02/2008; 23(2):127-34. · 2.07 Impact Factor
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ABSTRACT: The objective of this study was to determine if consistent posterior femoral rollback of an asymmetrical posterior cruciate retaining (PCR) total knee arthroplasty was mostly influenced by the implant design, surgical technique, or presence of a well-functioning posterior cruciate ligament (PCL). Three-dimensional femorotibial kinematics was determined for 80 subjects implanted by 3 surgeons, and each subject was evaluated under fluoroscopic surveillance during a deep knee bend. All subjects in this present study having an intact PCL had a well-functioning PCR knee and experienced normal kinematic patterns, although less in magnitude than the normal knee. In addition, a surprising finding was that, on average, subjects without a PCL still achieved posterior femoral rollback from full extension to maximum knee flexion. The findings in this study revealed that implant design did contribute to the normal kinematics demonstrated by subjects having this asymmetrical PCR total knee arthroplasty.
The Journal of Arthroplasty 02/2008; 23(1):41-50. · 2.38 Impact Factor
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ABSTRACT: This study compares the in vivo patellofemoral contact forces generated in high flexion fixed bearing posterior cruciate retaining Nexgen CR-Flex (PCR) and high flexion posterior stabilized Nexgen LPS-Flex (LPS) TKAs with that of normal knees from full knee extension to maximum weight bearing flexion. Ten patients with the PCR total knee arthroplasty (TKA), ten with the LPS TKA and seven patients having normal knees were fluoroscoped while performing a deep knee bend activity. In vivo femorotibial kinematics, obtained from 3D-to-2D registration technique, and patellar kinematics obtained by direct measurements from the fluoroscopic images were entered into a 3D inverse dynamics mathematical model to determine the in vivo contact forces at the knee. The variation in the patellofemoral and quadriceps forces with flexion were found to be similar across the three groups-increasing from full extension to 90 degrees of flexion, reaching a maximum between 90 degrees and 120 degrees of flexion and then decreasing until maximum flexion. At maximum knee flexion, these forces were found to be significantly lower in the normal knees than in the TKAs. The patellar ligament to quadriceps force ratio decreased with the increase in knee flexion while the patellofemoral to quadriceps force ratio increased. A strong correlation was found to exist between the patellofemoral forces, the femorotibial contact forces and the forces in the extensor mechanism. The PCR TKA in this study exhibited greater resemblance to the normal patients with respect to the patellofemoral forces than the LPS TKA though significant differences in the two implant types were not observed.
Journal of Biomechanics 02/2008; 41(3):642-8. · 2.43 Impact Factor
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ABSTRACT: In this cervical spine kinematics study the authors evaluate the motions and forces in the normal, degenerative, and fused states to assess how alteration in the cervical motion segment affects adjacent segment degeneration and spondylosis.
Fluoroscopic images obtained in 30 individuals (10 in each group with disease at C5-6) undergoing flexion/extension motions were collected. Kinematic data were obtained from the fluoroscopic images and analyzed with an inverse dynamic mathematical model of the cervical spine that was developed for this analysis.
During 20 degrees flexion to 15 degrees extension, average relative angles at the adjacent levels of C6-7 and C4-5 in the fused patients were 13.4 degrees and 8.8 degrees versus 3.7 degrees and 4.8 degrees in the healthy individuals. Differences at C3-4 averaged only about 1 degrees. Maximum transverse forces in the fused spines were two times the skull weight at C6-7 and one times the skull weight at C4-5, compared with 0.2 times the skull weight and 0.3 times the skull weight in the healthy individuals. Vertical forces ranged from 1.6 to 2.6 times the skull weight at C6-7 and from 1.2 to 2.5 times the skull weight at C4-5 in the patients who had undergone fusion, and from 1.4 to 3.1 times the skull weight and from 0.9 to 3.3 times the skull weight, respectively, in the volunteers.
Adjacent-segment degeneration may occur in patients with fusion due to increased motions and forces at both adjacent levels when compared with healthy individuals in a comparable flexion and extension range.
Journal of Neurosurgery Spine 12/2007; 7(5):509-13. · 1.53 Impact Factor
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ABSTRACT: Results of total knee arthroplasty have demonstrated excellent pain relief and increased patient function, particularly in activities such as walking. This procedure has not always met the needs of certain ethnic and religious groups as well as younger patients who require greater magnitudes of knee flexion. This has resulted in the introduction of new implant designs engineered to improve postoperative flexion. We reviewed factors known to influence postoperative flexion after total knee arthroplasty. An in vivo, weightbearing fluoroscopic kinematic analysis of multiple high-flexion total knee arthroplasty designs was performed, and demonstrated high levels of weightbearing flexion (125 degrees) can be obtained in some, but not all, evaluated designs. Multiple evaluations of the same high-flexion total knee arthroplasty design performed by different surgeons and involving different patient populations revealed one study group with high weightbearing flexion and other groups that did not achieve high flexion. This suggests numerous factors other than implant design influence eventual flexion, including the patient, surgical technique, knee kinematics, perioperative complications, and postoperative physiotherapy. LEVEL OF EVIDENCE: Level V, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Clinical Orthopaedics and Related Research 12/2007; 464:53-60. · 2.53 Impact Factor
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ABSTRACT: In vivo human and biomechanical study.
To quantify the in vivo kinematic and kinetic variations in the normal, fused, and disc replacement cervical spines.
Clinical and cadaveric studies have reported the motions and forces after an anterior cervical decompression and fusion (ACDF) or implantation of a cervical artificial disc replacement (CADR). However, there is no current study that describes the in vivo dynamic data of these 2 groups and compares them with that of a normal group.
Ten normal subjects, 10 patients treated with an ACDF (C5-C6), and 10 patients having CADR (C5-C6) performed full flexion to extension motions under fluoroscopic surveillance. Kinematic data were obtained from the fluoroscopic images. Kinetic data were derived based on an inverse dynamic model of the entire cervical spine.
Even though the range of motion was larger for the normal group than for the ACDF group, the intersegmental rotations at the adjacent C6-C7 and C4-C5 levels in the ACDF group were 13.4 degrees and 8.8 degrees compared with 3.7 degrees and 4.8 degrees in the normal group, respectively, during the neck motion from 20 degrees flexion to 15 degrees extension. The difference at the C3-C4 level was 1 degree on average. Both the transverse contact forces and the soft tissue forces in the ACDF group were significantly larger than those in the normal group. The vertical forces in the ACDF group were smaller than those in the normal group, but there were no statistical differences. The CADR group exhibited kinematic and kinetic results similar to the normal group.
In terms of restoring the normal dynamic motion of the cervical spine, CADR may be an alternative to the ACDF.
Spine 12/2007; 32(23):2578-84. · 2.08 Impact Factor
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ABSTRACT: To accommodate for high flexion, new total knee arthroplasties (TKAs) have been designed. Unlike older designs which have been found to exhibit decreasing contact area with increasing flexion, we hypothesized the new designs would be associated with improved contact mechanics. We compared in vivo contact mechanics for 10 subjects having a fixed-bearing high-flexion posterior-stabilized (LPS-Flex) TKA and 10 subjects having a fixed-bearing high-flexion posterior cruciate-retaining (CR-Flex) TKA. All subjects performed deep knee bends to maximum flexion while under fluoroscopic surveillance. In vivo kinematics obtained using a three-dimensional to two-dimensional registration technique, were input into a three-dimensional inverse dynamic mathematical model to determine the contact forces. The contact areas and contact stresses were determined using a deformable contact model. The contact forces, contact areas, and contact stresses in both these implants increased with increasing flexion. The medial contact area in the LPS-Flex was higher than the CR-Flex for most of the flexion cycle. The lateral contact area was higher in the CR-Flex than the LPS-Flex in early and midflexion ranges. Although the lateral contact stresses were similar in both implants, the CR-Flex experienced higher medial contact stress than the LPS-Flex throughout flexion. However, both these implants were able to maintain sufficient contact area so the contact stress values were well below the yield strength of crosslinked polyethylene.
Clinical Orthopaedics and Related Research 12/2007; 464:117-26. · 2.53 Impact Factor
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ABSTRACT: This study determined the relationship between the in vivo kinematics and joint laxity of mobile-bearing knees.
Ten subjects who were judged clinically successful after a posterior-cruciate-ligament-retaining mobile-bearing total knee arthroplasty were analyzed under dynamic conditions using fluoroscopy, following a quantitative evaluation of coronal and sagittal laxity using Telos and KT-2000 arthrometers under static conditions.
Under static conditions, the anteroposterior laxity averaged 10.3 mm at 30 degrees of flexion, and 8.3 mm at 75 degrees . Abduction and adduction at full extension averaged 3.7 and 4.4 mm, respectively. Under dynamic conditions, 7/10 subjects demonstrated posterior femoral rollback of their lateral condyle moving from full extension to maximum knee flexion, and 8/10 experienced normal axial rotation patterns during deep knee bend activity. Furthermore, 7/10 subjects exhibited screw-home motion. 4/10 subjects experienced greater than 1.0 mm of condylar liftoff.
We could not predict a consistent relationship between the laxity and kinematics. The activity of the muscles and ligamentous tension under dynamic conditions might have a much greater effect on the kinematics with currently used prosthetic designs than the laxity of ligamentous structures under static conditions.
The Knee 09/2007; 14(4):269-74. · 1.74 Impact Factor
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ABSTRACT: This study compared the in vivo femoropolyethylene contact pressures generated in fixed-bearing total knee arthroplasty (TKAs) with those in mobile-bearing TKAs. In vivo kinematics obtained from a 2-dimensional to 3-dimensional registration technique and soft tissue locations derived from computed tomographic scans were entered into a 3-dimensional inverse dynamics mathematical model to determine the in vivo bearing contact forces. The contact areas were obtained from the assembly of computer-aided design models of the components. The contact pressure was defined as the ratio of the contact forces to the contact areas. The results indicate that the in vivo contact pressures in each TKA are greater for the medial condyle than for the lateral condyle. The ability of the mobile-bearing TKA to rotate maintains higher femoropolyethylene contact, resulting in lesser contact pressures, as compared with the fixed-bearing TKA.
The Journal of Arthroplasty 04/2007; 22(3):404-16. · 2.38 Impact Factor
