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Erratum: Tibiofemoral force following total knee arthroplasty: Comparison of four prosthesis designs in vitro
Abstract
Despite ongoing evolution in total knee arthroplasty (TKA) prosthesis design, restricted flexion continues to be common postoperatively. Compressive tibiofemoral force during flexion is generated through the interaction between soft tissues and prosthesis geometry. In this study, we compared the compressive tibiofemoral force in vitro of four commonly used prostheses: fixed-bearing PCL (posterior cruciate ligament)-retaining (PFC), mobile-bearing posterior-stabilized (PS), posterior-stabilized with a High Flex femoral component (HF), and mobile-bearing PCL-sacrificing (LCS). Fourteen fresh-frozen cadaver knee joints were tested in a passive motion rig, and tibiofemoral force measured using a modified tibial baseplate instrumented with six load cells. The implants without posterior stabilization displayed an exponential increase in force after 90° of flexion, while PS implants maintained low force throughout the range of motion. The fixed-bearing PFC prosthesis displayed the highest peak force (214 ± 68 N at 150° flexion). Sacrifice of the PCL decreased the peak force to a level comparable with the LCS implant. The use of a PCL-substituting post and cam system reduced the peak force up to 78%, irrespective of whether it was a high-flex or a standard PS knee. However, other factors such as preoperative range of motion, knee joint kinematics, soft tissue impingement, and implantation technique play a role in postoperative knee function. The present study suggests that a posterior-stabilized TKA design might be advantageous in reducing soft tissue tension in deep flexion. Further research is necessary to fully understand all factors affecting knee flexion after TKA. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
... Therefore, a 41 means to evaluate contact force imbalance and contact kinematics 42 in vitro after specific improvements is necessary to determine 43 whether a specific improvement measurably affects knee function 44 hence offering the potential to improve a patient's outcome. 45 A tibial force sensor is a commonly used device to evaluate 46 contact forces and/or contact kinematics after improvements to 47 the surgical procedure and/or the design of the implants [8][9][10][11][12][13][14][15]. 48 To maximize the usefulness of such a sensor for in vitro evalua-49 tions of innovations in TKA, six major design criteria should be 50 satisfied. ...
... Sixth, the sensor must withstand forces in each compart-75 ment up to 450 N, which is adequate for evaluating contact force 76 imbalance after TKA in vitro [8]. 77 Because none of the previous designs [8][9][10][11][12][13][14][15] Both the contact force and contact location in each compartment 117 were expressed in terms of the coordinate system for each com-118 partment (Fig. 4). During the calibration procedure, the applied (i.e., 0 N, 45 N,…, 405 N, 128 450 N, 405 N,…, 45 N, 0 N), the six Wheatstone bridge voltage 129 outputs were recorded. ...
... The inde-313 pendent transducer arrays, trays, and articular surface inserts were 314 incorporated to meet this design criterion, and the independence of 315 the compartments was confirmed by the low contact force cross-talk 316 between the compartments ( 2.0 N). Only two of the previous sen-317 sors incorporated independent medial and lateral compartments, but 318 neither quantified the cross-talk [8,10] (Table 2). 319 The fourth major design criterion was that the contact forces be 320 measured with sufficiently low errors to detect clinically impor-321 tant imbalances (i.e., ! ...
Contact force imbalance and contact kinematics (i.e. motion of the contact location in each compartment during flexion) of the tibiofemoral joint are both important predictors of a patient's outcome following total knee arthroplasty (TKA). Previous tibial force sensors (TFS) have limitations in that they either did not determine contact force and contact location independently in the medial and lateral compartments or only did so within restricted areas of the tibial insert, which prevented them from thoroughly evaluating contact force imbalance and contact kinematics in vitro. Accordingly, the primary objective of this study was to present the design and verification of an improved TFS which overcomes these limitations. The improved TFS consists of a modified tibial baseplate which houses independent medial and lateral arrays of three custom tension-compression transducers each. This TFS is interchangeable with a standard tibial component because it accommodates tibial articular surface inserts with a range of sizes and thicknesses. This TFS was verified by applying known loads at known locations over the entire surface of the tibial insert to determine the errors in the computed contact force and contact location in each compartment. The root-mean-square errors (RMSE) in contact force are =6.1N which is 1.4% of the 450N full scale. The RMSEs in contact location are =1.6mm. This improved TFS overcomes the limitations of previous sensors and therefore should be useful for in vitro evaluation of new alignment goals, new surgical techniques, and new component designs in TKA.
... However, concerns exist regarding high stress imparted onto the cam-mechanism in PS designed implants, potentially leading to increased polyethylene wear, tibial loosening or fracture of the post [4]. Furthermore, bone stock is sacrificed due to the need for intercondylar bone resection [5,6]. Implant design with low constraint such as a condylar constrained (CS) (ultra-congruent, deep dished, lipped liner) bearing insert theoretically offer stability through a highly conforming articulation and raised anterior and posterior lips [7]. ...
... Conflicting results have been published using CS prosthesis in TKA, with some studies previously reporting instability with the use of a CS implant [7][8][9], whilst others have reported good medium-term survival without increased risk of revision for instability [10]. Further, concerns remain that the increased conformity of deep-dished liners may come at the expense of flexion range and increased sheer forces across the polyethylene may be experienced due to the increased sagittal laxity observed compared to PS designed prosthesis [5,6,8,11]. ...
Purpose:
Prosthesis design influences stability in total knee arthroplasty and may affect maximum knee flexion. Posterior-stabilised (PS) and condylar-stabilised (CS) designed prosthesis do not require a posterior-cruciate ligament to provide stability. The aim of the current study was to compare the range of motion (ROM) and clinical outcomes of patients undergoing cemented total knee arthroplasty (TKA) using either a PS or CS design prosthesis.
Methods:
A total of 167 consecutive primary TKAs with a CS bearing (mobile deep-dish polyethylene) were retrospectively identified and compared to 332 primary TKA with a PS constraint, with similar design components from the same manufacturer. Passive ROM was assessed at last follow-up with use of a handheld goniometer. Clinical scores were assessed using Patient-Reported Outcome Measures (PROMs); International Knee Society (IKS) knee and function scores and satisfaction score. Radiographic assessment was performed pre and post operatively consisting of mechanical femorotibial angle (mFTA), femoral and tibial mechanical angles measured medially (FMA and TMA, respectively) on long leg radiographs, tibial slope and patella height as measured by the Blackburne-Peel index (BPI).
Results:
Both groups had a mean follow-up of 3 years (range 2-3.7 years). Mean post-operative maximum knee flexion was 117° ± 4.9° in the PS group and 119° ± 5.2° in the CS group (p = 0.29). Postoperative IKS scores were significantly improved in both groups compared to preoperative scores (p < 0.01). The mean IKS score in the PS group was 170.9 ± 24.1 compared to 170.3 ± 22.5 in the CS group (p = 0.3). Both groups had similar radiographic outcomes as determined by coronal and sagittal alignment, tibial slope and posterior condylar offset ratio measurements. When considering the size of tibial slope change and posterior-condylar offset ratio, there was no differences between groups (p = 0.4 and 0.59 respectively). The PS group had more interventions for post-operative stiffness (arthrolysis or manipulation under anaesthesia) 8 (2.7%) compared to 1 (0.6%) in the CS group (p = 0.17).
Conclusion:
Condylar-stabilised TKA have similar patient outcomes and ROM at a mean follow-up of 3 years compared to PS TKA. Highly congruent inserts could be used without compromising results in TKA at short term.
Level of evidence:
Level IV, retrospective case control study.
... As with any measurement instrument, tibial force sensors must be calibrated to minimize the errors in the contact location computed using the sensor. Although the typical calibration procedure is performed by applying forces normal to the tibial baseplate [10][11][12][13][14][15][16], contact between the curved articular surfaces of the components occurs normal to the articular surfaces during use. Hence, the typical calibration procedure only accounts for one source of error, which is the error caused by imperfections in the design, manufacturing, and assembly of the sensor. ...
... Based on a static analysis, the curved articular surface will introduce bias (i.e., average or systematic error) in the computed contact location, which is directed toward the periphery of the tibial articular surface and is greater in regions of high curvature (see Appendix 1, which is available under the "Supplemental Materials" tab for this paper on the ASME Digital Collection). However, errors in the computed contact locations caused by the curved articular surface of the tibial component have not been accounted for previously [10][11][12][13][14][15][16]. It is important that these errors be accounted for to prevent incorrect interpretations of contact kinematics based on the computed contact locations. ...
Previous reports of tibial force sensors have neither characterized nor corrected errors in the computed contact location between the femoral and tibial components in total knee arthroplasty (TKA) that are theoretically caused by the curved articular surface of the tibial component. The objectives were to experimentally characterize there errors and to develop and validate an error correction algorithm. The errors were characterized by calculating the difference between the errors in the computed contact location when forces were applied normal to the tibial articular surface and those when forces were applied normal to the tibial baseplate. The algorithm generated error correction functions to minimize these errors and was validated by determining how much the error correction functions reduced the errors in the computed contact location caused by the curved articular surface. The curved articular surfaces primarily caused bias which ranged from 1.0 to 2.7 mm in regions of high curvature. The error correction functions reduced the bias in these regions to negligible levels ranging from 0.0 to 0.6 mm (p < 0.001). Bias in the computed contact locations caused by the curved articular surface of the tibial insert needs to be accounted for because it may inflate the computed internal-external rotation and anterior-posterior translation of femur on the tibia leading to false identifications of clinically undesirable contact kinematics (e.g. external rotation and anterior translation). Our novel error correction algorithm is an effective method to account for this bias to more accurately compute contact kinematics.
... These studies compared contact mechanics of different designs in fixtured-only tests 7,10 or in cadaveric experiments. [12][13][14] Others used computational models to predict the effect of post-cam design on contact mechanics. 8,9,15 However, these mechanical, in vitro, and in silico investigations typically studied component performance in a small number of static positions, and thus did not report engagement velocity. ...
... Those studies that measured contact area, pressure, and forces on the post were limited to a small number of static poses. 7,10,12 Additionally, mechanical or in vitro experiments typically did not assess or compare devices under physiological loading; Nicholls et al. 13 tested cadaveric knees during passive motion, with a 40 N load applied to the quadriceps in deepest flexion; Nakayama et al. 10 and Akasaki et al. 7 evaluated components under a 500 N posterior force, without any compressive force applied to the TF articular surface. We present post-cam mechanics and engagement velocity under dynamic physiological conditions. ...
Posterior-stabilized (PS) total knee arthroplasty (TKA) components employ a tibial post and femoral cam mechanism to guide anteroposterior knee motion in lieu of the posterior cruciate ligament. Some PS TKA patients report a clicking sensation when the post and cam engage, while severe wear and fracture of the post; we hypothesize that these complications are associated with excessive impact velocity at engagement. We evaluated the effect of implant design on engagement dynamics of the post-cam mechanism and resulting polyethylene stresses during dynamic activity. In vitro simulation of a knee bend activity was performed for four cadaveric specimens implanted with PS TKA components. Post-cam engagement velocity and flexion angle at initial contact were determined. The experimental data were used to validate computational predictions of PS mechanics using the same loading conditions. A lower limb model was subsequently utilized to compare engagement mechanics of eight TKA designs, relating differences between implants to geometric design features. Flexion angle and post-cam velocity at engagement demonstrated considerable ranges among designs (23°-89°, and 0.05-0.22 mm/°, respectively). Post-cam velocity was correlated (r = 0.89) with tibiofemoral condylar design features. Condylar geometry, in addition to post-cam geometry, played a significant role in minimizing engagement velocity and forces and stresses in the post. This analysis guides selection and design of PS implants that facilitate smooth post-cam engagement and reduce edge loading of the post. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res.
... The design is not a factor in these cases, because this complication occurs in all different designs, especially in the ones who retain the posterior cruciate ligament [2][3][4][5]. Even more, Jeffcote et al. and Nicholls et al. describe that except for the initial choice for the constraint, for example, a cruciate retaining design with an insufficient cruciate ligament, the design is not a factor anymore for dislocation, especially not in the newer posterior stabilized design [13,14]. Tibiofemoral dislocation after total knee replacement with disengagement of the polyethylene liner is a rare complication [4], first reported by Insall et al. in 1979 after total condylar knee replacement in four patients out of a series of 220 patients [15]. ...
Introduction:
Dislocation of a total knee arthroplasty is a rare complication that has rarely been described, while the total knee arthroplasty is frequently performed. From literature, we know patient-related factors, like obesity, neuropsychiatric disease, and severe valgus or varus deformity, are associated with higher risk of dislocation. We show our cases for awareness of the risk factors for surgeons. Case Presentations. We present four patients with a dislocation after a total knee arthroplasty. We compare these case reports with previous literature and show the most important risk factors for these dislocations. In our cases, three of them suffered from obesity, which possibly has contributed to the dislocation. Three patients did have instability which emphasizes the importance of ligament balancing while performing a total knee replacement. In all cases, an exchange of the polyethylene liner was performed.
Conclusion:
Implant-related factors and surgical technique as well as patient-related factors can contribute to this uncommon complication. Obesity, neuropsychiatric disorders, and a severe valgus or varus deformity are important patient-related risk factors. Our cases show these risk factors too. Some of these risk factors were encountered as well as other comorbidity factors. Such risk factors must be taken into consideration when deciding whether to perform a total knee arthroplasty. This stresses the importance of patient education and shared decision-making before performing a total knee replacement.
... As the reaction forces are measured through deformation of the bridges, the location and amplitude of the compartmental loads can be computed. Nicholls et al. 17) used a customized device with 3 sensors embedded in the medial and lateral compartments of a base plate with identical dimensions of standard tibial components. ...
Wireless intraoperative load sensors have been used to improve the quality of soft-tissue balancing during total knee arthroplasty(TKA). Recent studies using the sensors have demonstrated reductions in gap imbalance, as well as early improvement of patient-reported clinical outcomes and low rates of arthrofibrosis. However, well-designed prospective studies are needed to determine whether the application of the sensor technology for TKA will have clinical benefits and improve the survival of prosthesis. Knowledge of the load-sensing technology (advantages and disadvantages, potential pitfalls, and future prediction) is crucial to apply this new TKA technique successfully. Herein, we conduct a narrative review of previous studies on this technique.
... Higher heel squat contact force is in part due to the higher estimated muscle forces. Total knee replacements have demonstrated higher compressive tibial force as knee flexion increased (Nicholls et al., 2007). Maximum forces were 2.2 times bodyweight (BW) during gait and 2.5 five times bodyweight during stair climb (D'Lima et al., 2006). ...
... Reduced range of motion (ROM) remains a problem in total knee arthroplasty (TKA). Factors influencing postoperative ROM are preoperative and intraoperative ROM [24], patient age [20], body mass index (BMI) [6], type of prosthesis [21], Insall-Salvati ratio [19] and femoral posterior condylar offset [5]. ...
Purpose
Increased range of motion (ROM) while maintaining joint stability is the goal of modern total knee arthroplasty (TKA). A biomechanical study has shown that small increases in flexion gap result in decreased tibiofemoral force beyond 90° flexion. The purpose of this paper was to investigate clinical implications of controlled increased flexion gap.
Methods
Four hundred and four TKAs were allocated into one of two groups and analysed retrospectively. In the first group (n = 352), flexion gap exceeded extension gap by 2.5 mm, while in the second group (n = 52) flexion gap was equal to the extension gap. The procedures were performed from 2008 to 2012. The patients were reviewed 12 months postoperatively. Objective clinical results were assessed for ROM, mediolateral and sagittal stability. Patient-reported outcome measures were the WOMAC score and the Forgotten Joint Score (FJS-12).
Results
After categorizing postoperative flexion into three groups (poor < 90°, satisfactory 91°–119°, good ≥ 120°) significantly more patients in group 1 achieved satisfactory or good ROM (p = 0.006). Group 1 also showed a significantly higher mean FJS-12 (group 1: 73, group 2: 61, p = 0.02). The mean WOMAC score was 11 in the first and 14 in the second group (n.s.). Increase in flexion gap did not influence knee stability.
Conclusions
The clinical relevance of this study is that a controlled flexion gap increase of 2.5 mm may have a positive effect on postoperative flexion and patient satisfaction after TKA. Neither knee stability in the coronal and sagittal planes nor complications were influenced by a controlled increase in flexion gap.
Level of evidence
III.
... the most important goals for normal daily activities [1,10,22]. Preoperative ROM is reportedly the most important factor influencing postoperative ROM [9,13,26], but many other factors, including implant design [6,23], mediolateral (ML) soft tissue balance [32], flexion-extension gap balance [11,18], joint-line height [20], femoral posterior condylar offset [3,8], and PCL tension [24,39], also influence postoperative ROM. ...
Background:
Joint gaps and mediolateral (ML) soft tissue balance have long been known to affect clinical scores and patient function after TKA, but the relationship between gaps and soft tissue balance remain poorly defined. If specific relationships exist between soft tissue tension and patient function, then objective targets could be established to assist surgeons in achieving more consistent postoperative knee function.
Questions/purposes:
By performing instrumented gap measurements during TKA, we sought to quantify the relationships between intraoperative soft tissue tension and clinical scores and patient function.
Methods:
We prospectively followed 57 patients with 63 primary TKAs with posterior-stabilized prostheses. Joint gaps and ML soft tissue balance were measured intraoperatively from 0° to 135° with the patella reduced after independent bone cuts and soft tissue releases. We determined the relationships between these intraoperative measurements and postoperative ROM and Knee Society scores at minimum 2-year followup.
Results:
Larger joint gaps at 120° and 135° flexion predicted larger postoperative knee flexion (r=0.296 and r=0.393, respectively), whereas larger gaps at 10° flexion predicted greater postoperative knee extension (r=0.285). Knees with rectangular joint gaps did not show better ROM or Knee Society scores compared with knees with trapezoidal joint gaps. In the range of normal surgical variation, neither joint gaps nor gap asymmetry affected the incidence of postoperative instability.
Conclusions:
Avoiding small joint gaps in extension and in deep flexion should allow patients who undergo TKAs to obtain maximum ROM.
Level of evidence:
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
... Among them, the preoperative ROM has a major effect, and patients with a good preoperative ROM have been reported to show good motion postoperatively [12]. Various other factors including the design of the prosthesis [8, 14], ratio between the patella and patellar tendon lengths [7], femoral posterior condylar offset [2, 5] and posterior cruciate ligament (PCL) stiffness [9, 18] have also been evaluated. Recently, mobile bearing TKA, in which the platform rotates or moves anteroposteriorly, has been devised, and its clinical results are under discussion [6, 16] . ...
The objective of this study was to investigate the range of motion (ROM) of the knee before and four years after total knee arthroplasty (TKA) with a mobile or fixed type of platform and to prospectively evaluate whether there was a difference in ligament balance between the platform types. The subjects were 68 patients involving 76 joints. The mobile type was used in 31 joints and fixed type in 45 joints by employing a prospective randomised method. The passive maximum ROM was measured using a goniometer before and four years after surgery. Also, the intraoperative knee ligament balance was measured. The postoperative extension ROM was significantly improved after TKA using a mobile bearing type compared with that employing a fixed bearing type. In TKA using the former, the intraoperative gap difference was not related to the postoperative flexion angle of the knee. However, they were related in TKA using a fixed bearing type, with a positive correlation regarding the flexion gap.
... To overcome this lack of loading data, several studies to measure the in vitro and in vivo loading conditions of the knee joint have been performed. Some of them have used tibial baseplates instrumented with force transducers to measure loads in cadaveric studies or intraoperatively (Crottet et al., 2007(Crottet et al., , 2005Jeffcote et al., 2007;Kaufman et al., 1996;Nicholls et al., 2007;Singerman et al., 1999Singerman et al., , 1994. However, these implants were not suited for in vivo measurements. ...
Background:
Detailed information about the loading of the knee joint is required for various investigations in total knee replacement. Up to now, gait analysis plus analytical musculo-skeletal models were used to calculate the forces and moments acting in the knee joint. Currently, all experimental and numerical pre-clinical tests rely on these indirect measurements which have limitations. The validation of these methods requires in vivo data; therefore, the purpose of this study was to provide in vivo loading data of the knee joint.
Methods:
A custom-made telemetric tibial tray was used to measure the three forces and three moments acting in the implant. This prosthesis was implanted into two subjects and measurements were obtained for a follow-up of 6 and 10 months, respectively. Subjects performed level walking and going up and down stairs using a self-selected comfortable speed. The subjects' activities were captured simultaneously with the load data on a digital video tape. Customized software enabled the display of all information in one video sequence.
Findings:
The highest mean values of the peak load components from the two subjects were as follows: during level walking the forces were 276%BW (percent body weight) in axial direction, 21%BW (medio-lateral), and 29%BW (antero-posterior). The moments were 1.8%BW*m in the sagittal plane, 4.3%BW*m (frontal plane) and 1.0%BW*m (transversal plane). During stair climbing the axial force increased to 306%BW, while the shear forces changed only slightly. The sagittal plane moment increased to 2.4%BW*m, while the frontal and transversal plane moments decreased slightly. Stair descending produced the highest forces of 352%BW (axial), 35%BW (medio-lateral), and 36%BW (antero-posterior). The sagittal and frontal plane moments increased to 2.8%BW*m and 4.6%BW*m, respectively, while the transversal plane moment changed only slightly.
Interpretation:
Using the data obtained, mechanical simulators can be programmed according to realistic load profiles. Furthermore, musculo-skeletal models can be validated, which until now often lacked the ability to predict properly the non-sagittal load values, e.g. varus-valgus and internal-external moments.
... 1,4--6 During knee motion, tensions in the ligaments, capsule, and extensor envelope may restrict flexion and affect implant wear. 6,7 Awareness of the role of the extensor retinaculum in patellofemoral kinematics is increasing. 8 While studies to date have focused on its role in patellar instability, [8][9][10][11] the influence of TKR is unknown. ...
Patellofemoral dysfunction following total knee replacement (TKR) is a significant clinical problem, but little information exists on the mechanics of the patellofemoral retinacula or the effects of TKR on these structures. We hypothesized that TKR would cause significant elongation of the retinacula. Retinacular length changes were measured by threading sutures along the retinacula, fixing the sutures to the patella and the iliotibial band (ITB), and attaching the femoral ends to displacement transducers. The intact knee was flexed-extended while the quadriceps and ITB were tensed and the retinacular length change patterns were recorded. The measurements were repeated post-TKR. The medial patellofemoral ligament (MPFL) was close to isometric, stretching 2 mm in terminal knee extension, whereas the lateral retinaculum slackened 8 mm from 110 degrees to 0 degrees flexion. TKR did not cause significant elongation of either of the retinacula, the largest change being 3 mm elongation of the MPFL around 40 degrees , which stretched the MPFL by 1.4 mm above its maximum natural length. Thus, this work did not support the hypothesis that TKR causes significant elongation of the retinacula sufficient to affect knee function.
... However, determination of in vivo tibiofemoral contact forces has been a challenging issue in biomechanics. Instrumented tibial implants have been used to measure tibiofemoral forces in-vitro (Kaufman, et al., 1996, Nicholls, et al., 2007. Computational models using inverse dynamic optimization have also been used to estimate joint reaction forces (Crowninshield and Brand, 1981, Li, et al., 1999, Taylor, et al., 2004. ...
Analysis of polyethylene component wear and implant loosening in total knee arthroplasty (TKA) requires precise knowledge of in vivo articular motion and loading conditions. This study presents a simultaneous in vivo measurement of tibiofemoral articular contact forces and contact kinematics in three TKA patients. These measurements were accomplished via a dual fluoroscopic imaging system and instrumented tibial implants, during dynamic single leg lunge and chair rising-sitting. The measured forces and contact locations were also used to determine mediolateral distribution of axial contact forces. Contact kinematics data showed a medial pivot during flexion of the knee, for all patients in the study. Average axial forces were higher for lunge compared to chair rising-sitting (224% vs. 187% body weight). In this study, we measured peak anteroposterior and mediolateral forces averaging 13.3% BW during lunge and 18.5% BW during chair rising-sitting. Mediolateral distributions of axial contact force were both patient and activity specific. All patients showed equitable medial-lateral loading during lunge but greater loads at the lateral compartment during chair rising-sitting. The results of this study may enable more accurate reproduction of in vivo loads and articular motion patterns in wear simulators and finite element models. This in turn may help advance our understanding of factors limiting longevity of TKA implants, such as aseptic loosening and polyethylene component wear, and enable improved TKA designs.
Endoprosthetic knee replacement surgery is nowadays an effective procedure for the treatment of high-grade gonarthrosis. A subjectively satisfactory functional result is based, among other factors, on the reconstruction of the natural joint kinematics and consideration of the individual geometric data of the distal femur as well as the proximal tibia. As the importance of the dorsal inclination of the tibia (i.e. posterior tibial slope, TS) for the stability of the native knee joint has been repeatedly proven, its influence on the function and long-term durability after total knee arthroplasty (TKA) is currently under consideration. According to the current literature, the reconstruction of the native TS using a unicondylar or bicondylar cruciate ligament-retaining TKA is preferred. In contrast, the use of procedures which replace the cruciate ligament minimizes this association as the design per se is associated with a stricter kinematic guidance.
Objective: In order to evaluate the influence of kinematics by two different design concepts of cruciate-retaining total knee arthroplasties (TKAs), we compared intra-operative findings of compressive forces on the tibial joint surface in terminal procedure after assembling each component.
Methods: We developed a tibial metal tray containing six load cells to directly measure compressive forces on the tibio-femoral joint surface. Utilizing both a navigation system and our developed force sensor, 13 NexGen® CR TKAs (Z group) and 9 NRG® CR TKAs (S group) were compared with axial rotation, distribution of six local forces, subtotal forces of lateral/medial tibial compartment and kinematic pathway (gravity axes) which jointed a lateral/medial gravity point to be made by three local forces.
Results: The two groups showed different findings except the axial rotation pattern. Z group's subtotal force had a higher lateral force than the medial force (P < 0.05), but lateral roll back (6 mm) which was similar to medial roll back in the kinematic pathway. These findings indicated an undesirable influence of asymmetric condyle and dual contact design in the NexGen® TKA. Conversely, S group's subtotal force showed a similar lateral force compared to the medial force and internal rotation with medial pivot which indicated a more lateral roll back (7 mm) than medial roll back (4 mm) in the kinematic pathway. These findings support the superiority of single radius and spherical arc design in the NRG® TKA.
Moreover, well gap balances in Z group were shown at 20° and 110° of knee flexion. Because the spacer block was inserted into the gap spaces between the aspect of the femoral bone cut and the tibial bone cut with 6.5° of posterior slope, this finding indicated that gap balances were not adjusted at full extension and 90° knee flexion, and this led us to observe the gap balance was inclined to laxity of the medial cruciate ligament.
Conclusions: Our developed force sensor showed that two different design concepts of TKAs enable there to be different ligament balance, gap balance and kinematic pathways, except in axial rotation.
In vitro testing of the human knee provides valuable insight that contributes to further understanding knee biomechanics. Cadaveric testing correlates well with clinical trials because the tissue has similar properties to that of live subjects. In addition, in vitro testing allows studies to be performed that would otherwise be unethical to evaluate in vivo. Due to their many advantages, cadaveric testing has been utilized to evaluate many of medical devices and surgical techniques that have been developed in recent decades. This article aims to review the current technologies and methodologies utilized in experimental in vitro testing of the human knee. The article provides a summary of the different rigs and machines that are currently used to examine the biomechanics of the knee. It also highlights the variable experimental techniques and measurement systems that are used to collect the kinematics and kinetics of the knee joint. As technologies advance so do the measurement systems and equipment in the experimental biomechanics field. The influence of improvements to these testing equipment and measurement devices on in vitro testing of the knee will also be discussed in this review.
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Despite standardized surgical procedures, failure constitutes a substantial problem after total joint arthroplasty. Besides infection, loosening and fracture, postoperative instability prevails as a major complication in daily clinical practice. Both its obscurity and the severe consequences for patients, especially in case of dislocation, make it difficult for clinicians to find appropriate countermeasures. In this context, there is little evidence in how exactly soft tissue structures contribute to stability of total hip (THRs) and knee replacements (TKRs). The same applies to dynamic effects of certain parameters such as implant design and positioning. Therefore, biomechanical investigations seem invaluable which at best meet with the demands of in vivo analyses, even for instability-associated maneuvers.
As measurements in patients are afflicted with ethical objections, the purpose of this work is to present a comprehensive approach capable of testing total joint stability under dynamic, reproducible and physiological conditions. The approach is based on a hardware-in-the-loop (HiL) simulation where the anatomic and physiological environment of the implant is extracted into a simulation model described by a multibody systems formulation. Interaction between the model and the real implant components is achieved by a physical setup composed of an industrial robot equipped with a force-torque sensor and a compliant support with displacement sensors attached to. An essential aspect of this work represents the validation of the HiL test system as regards THR and TKR testing. This includes developing specific multibody models of the musculoskeletal system which reproduce physiological test conditions within the HiL environment. In this sense, the HiL test system extends the repertoire of approaches and methods commonly used in orthopedic research by combining the advantages of real implant testing and model-based simulation.
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Accurate knowledge of in vivo articular contact kinematics and contact forces is required to quantitatively understand factors limiting life of total knee arthroplasty (TKA) implants, such as polyethylene component wear and implant loosening [1]. Determination of in vivo tibiofemoral contact forces has been a challenging issue in biomechanics. Historically, instrumented tibial implants have been used to measure tibiofemoral forces in vitro [2] and computational models involving inverse dynamic optimization have been used to estimate joint forces in vivo [3]. Recently, D’Lima et al. reported the first in vivo measurement of 6DOF tibiofemoral forces via an instrumented implant in a TKA patient [4]. However this technique does not provide a direct estimation of tibiofemoral contact forces in the medial and lateral compartments. Recently, a dual fluoroscopic imaging system has been used to accurately determine tibiofemoral contact locations on the medial and lateral tibial polyethylene surfaces [5]. The objective of this study was to combine the dual fluoroscope technique and the instrumented TKAs to determine the dynamic 3D articular contact kinematics and contact forces on the medial and lateral tibial polyethylene surfaces during functional activities.
Currently, the number of Total Knee Arthroplasty (TKA) in Japan is 70,000. Because it is easy to expect increasing the number due to super-aging society, the clinical outcome of TKA surgery has been important The surgery requires proper soft tissue balance to avoid shortening fatigue life of prosthesis. Thus, a measurement system of force concentration about contacting region between femur component and polyethylene insert contributes to prolong the prosthesis. This study examined the force concentration by using our developed measurement system. This study performed two experiment consists of physical and simulated experiment As a result, our developed system could localize the force concentration point A future work is to apply this measurement system to the cadaveric knee.
The effects of valgus load on cadaveric knees following total knee arthroplasty (TKA) were investigated using a custom testing system. TKAs were performed on 8 cadaveric knees and tested at 0°, 30°, and 60° knee flexion in both neutral and 5° valgus. Fuji pressure sensitive film was used to quantify contact areas and pressures and MCL strain was determined using a Microscribe digitizing system. Lateral tibiofemoral pressures increased (P<0.05) at all knee flexion angles with valgus loading. Patellofemoral contact characteristics did not change significantly (P>0.05). Significant increases in strain were observed along the anterior and posterior border of the MCL at all knee flexion angles. These findings suggest that valgus loading increases TKA joint contact pressures and MCL strain with increasing knee flexion which may increase implant instability.
Background:
Posterior cruciate ligament (PCL) retaining (CR) and -sacrificing (PS) total knee arthroplasties (TKA) are widely-used to treat osteoarthritis of the knee joint. The PS design substitutes the function of the PCL with a cam-spine mechanism which may produce adverse changes to joint kinematics and kinetics.
Methods:
CR- and PS-TKA were performed on 11 human knee specimens. Joint kinematics were measured with a dynamic knee simulator and motion tracking equipment. In-situ loads of the PCL and cam-spine were measured with a robotic force sensor system. Partial weight bearing flexions were simulated and external forces were applied.
Results:
The PS-TKA rotated significantly less throughout the whole flexion range compared to the CR-TKA. Femoral roll back was greater in the PS-TKA; however, this was not correlated with lower quadriceps forces. Application of external loads produced significantly different in-situ force profiles between the TKA systems.
Conclusions:
Our data demonstrate that the PS-design significantly alters kinematics of the knee joint. Our data also suggest the cam-spine mechanism may have little influence on high flexion kinematics (such as femoral rollback) with most of the load burden shared by supporting implant and soft-tissue structures.
Purpose:
To compare intra-operative knee joint kinematic measurements immediately after total knee replacement with those of the same patients post-operatively at 6-month follow-up.
Methods:
Fifteen patients who underwent total knee arthroplasty were analysed retrospectively. Eight were implanted with one prosthesis design and seven with another. The intra-operative measurements were performed by using a standard knee navigation system. This provided accurate three-dimensional positions and orientations for the femur and tibia by corresponding trackers pinned into the bones. At 6-month follow-up, the patients were analysed by standard three-dimensional video-fluoroscopy of the replaced knee during stair climbing, chair rising and step-up. Relevant three-dimensional positions and orientations were obtained by an iterative shape-matching procedure between the silhouette contours and the CAD-model projections. A number of traditional kinematic parameters were calculated from both measurements to represent the joint motion.
Results:
Good post-operative replication of the intra-operative measurements was observed for most of the variables analysed. The statistical analysis also supported the good consistency between the intra- and post-operative measurements.
Conclusions:
Intra-operative kinematic measurements, accessible by a surgical navigation system, are predictive of the following motion performance of the replaced knees as experienced in typical activities of daily living.
Level of evidence:
Prognostic studies--investigating natural history and evaluating the effect of a patient characteristic, Level II.
Purpose of review: The aim of this article is to review recent publications regarding the results of posterior cruciate ligament retaining total knee arthroplasty, the most commonly implanted type of knee replacement used worldwide. Recent developments in understanding of the kinematics of these implants are discussed together with clinical follow-up studies.
Recent findings: The cruciate retaining total knee arthroplasty is a successful implant design and can be safely used in patients with rheumatoid arthristis. Infection, aseptic loosening or wear of the insert continue to be the main modes of failure of cruciate retaining total knee arthroplasty. All polyethylene and metal-backed tibias have similar outcome at 10 years. Presence of a ipsilateral planovalgus foot can increase the risk of failure of cruciate retaining total knee arthroplasty. Mobile bearing knees tend to have low-grade wear whereas high-grade wear is more common in the fixed bearing designs. High-flex designs might improve tibiofemoral contact biomechanics if high flexion is achievable, although their clinical advantages are still unproven.
Summary: Fixed bearing cruciate retaining total knee arthroplasty have a good track record. Advances are being made in the field of implant design although as yet no obvious clinical advantages have been proven.
High-flexion total knee arthroplasty is considered flexion beyond 125 degrees . Certain activities and a number of workplace demands benefit from this greater range of motion. Some cultures and religions place more emphasis on deep knee flexion. Important patient factors include preoperative motion, body mass index, and previous knee surgery. Component design modifications focus on lengthening the radius of curvature through the posterior condyles, increasing the posterior condylar offset, recessing the tibial insert, lengthening the trochlear groove, and altering the cam-post design. These changes allow increased femoral rollback, translation, and thus clearance in deep flexion. Surgical techniques focus on soft tissue balancing, component sizing and position, removal of impinging osteophytes, and reestablishment of the flexion gap. A number of outcome studies have demonstrated benefits for high flexion after standard total knee and high-flexion designs.
Restricted range of motion and excessive laxity are both potential complications of total knee arthroplasty (TKA). During TKA surgery, the surgeon is frequently faced with the question of how tightly to implant the prosthesis. The most common method of altering implantation tightness is to vary the thickness of the polyethylene inlay after the bone cuts have been made and the trial components inserted. We have sought to quantify how altering the polyethylene thickness may affect post-operative soft tissue tension for a range of prosthetic designs. Four different prosthetic designs were implanted into fresh-frozen cadaveric knee joints. All four designs were implanted in the standard manner, with a 100 Newton distraction force used to set soft tissue balance. The tibiofemoral force was then recorded at 15° intervals throughout the passive flexion range. After the standard implantation of each prosthesis, the tibial component was raised or lowered to mimic increasing and decreasing the polyethylene thickness by 2mm and the force measurements repeated. Tibiofemoral force in extension correlated with implantation tightness for all prosthesis designs. Between 15° and 90° of knee flexion, all four designs were insensitive to changes in implantation tightness. Beyond 90° the effect was more notable in rotating platform mobile-bearing and cruciate-retaining prostheses than in posterior-stabilised mobile-bearing designs. The findings of this research may be useful in assisting surgical decision-making during the implantation of TKA prostheses.
Vorderer Knieschmerz nach Implantation einer KTEP wird für eine Vielzahl von Revisionseingriffen verantwortlich gemacht. Eine veränderte Kniegelenkkinematik mit unphysiologischem patellofemoralem Kontaktdruckverhalten und erhöhtem Aufwand des M. quadriceps kommen unter anderem als Ursache in Betracht. Ziel der vorliegenden in vitro-Studie war es, das patellofemorale Druckverhalten und die aufzubringende Quadricepskraft nach kreuzbanderhaltender (CR flat, DD) und kreuzbandersetzender (PS) Knie-TEP mittels dynamischer Druckmessung zu untersuchen. Weiterhin sollte neben Höhe und Konformität des PE-Gleitlagers der Einfluss des HKB auf die Kniegelenkkinematik untersucht werden. Methode: In einem Laborexperiment wurden 8 Leichenkniegelenke in einem Kniegelenkskinemator einem isokinetischen Extensionsversuch mit 31 Nm von 120° Flexion bis zur vollständigen Extension unter Simulation aktiver Muskelzüge untersucht. Zur Druckmessung wurde eine drucksensitive Messfolie (Tekscan-System, Boston, USA) auf der patellofemoralen Gelenkfläche angebracht, sodass neben patellofemoralem Kontaktdruck auch Spitzendruck und Druckzentrumlokalisation während der Extensionsbewegung aufgezeichnet werden konnten. Es folgte die Implantation einer bikompartimentellen „Genesis II“-KTEP (Smith & Nephew, Schenefeld, Deutschland) mit Applikation unterschiedlicher PE-Inlays bei intaktem HKB (CR 11, CR 9, DD) und nach Resektion des HKB (CR 11, DD, PS). Zur statistischen Analyse wurde ein Zweistichproben T-Test angewandt (Signifikanzniveau p ≤ 0,05). Ergebnisse: Nur nach Implantation des PS-Designs zeigte sich ein patellofemorales Kontaktdruckverhalten, das große Ähnlichkeit mit dem physiologischer Kniegelenke zeigte, während kreuzbanderhaltende Prothesendesigns bestenfalls dazu in der Lage waren, die physiologische Gelenkkinematik qualitativ zu reproduzieren (mittlerer Kontaktdruck: PS: 3,58 ± 1,25 MPa; CR 11: 4,31 ± 1,40 MPa; CR 9: 4,23 ± 1,40 MPa; DD: 4,27 ± 1,34 MPa; CR 11 ohne HKB: 4,18 ± 1,26 MPa; DD ohne HKB: 3,99 ± 1,44 MPa bzw. Spitzendruck: PS: 6,12 ± 2,37 MPa; CR 11: 7,17 ± 2,41 MPa; CR 9: 7,05 ± 2,45 MPa; DD: 7,12 ± 2,53 MPa; CR 11 ohne HKB: 6,89 ± 2,30 MPa; DD ohne HKB: 6,63 ± 2,52 MPa). Dabei waren die Unterschiede für den reduzierten Kontaktdruck der PS-Gleitlager gegenüber allen anderen Designs signifikant oder verfehlten eine Signifikanz meist nur relativ knapp (p ≤ 0,006, p ≤ 0,02, p ≤ 0,01, p ≤ 0,03 und p ≤ 0,18 bzw. p ≤ 0,02, p ≤ 0,02, p ≤ 0,01, p ≤ 0,07 und p ≤ 0,39). Bezüglich der Drucklokalisation zeigte sich nur eine Tendenz für die PS-Prothesen hin zu einer physiologischeren medialeren und proximaleren Lokalisation. Im Vergleich zeigte sich weiterhin für PS-Kniegelenke gegenüber den HKB resezierten Kniegelenken ein signifikant niedrigerer Kraftaufwand des M. quadriceps (PS: 1131 ± 108 N; CR 11 ohne HKB: 1203 ± 92 N; DD ohne HKB: 1192 ± 80 N; p ≤ 0,01, p ≤ 0,01). Für die maximal aufgebrachte Muskelkraft zeigte sich für die PS-Kniegelenke gegenüber allen anderen untersuchten Kniegelenken ein signifikant besserer mechanischer Wirkungsgrad (PS: 1560 ± 145 N; CR 11: 1683 ± 156 N; CR 9: 1712 ± 157 N; DD: 1685 ± 175 N; CR 11 ohne HKB: 1729 ± 162 N; DD ohne HKB: 1689 ± 123 N; p ≤ 0,04, p ≤ 0,008, p ≤ 0,02, p ≤ 0,01 und p ≤ 0,02). Höhe (11 mm versus 9 mm) und Konformität (CR flat versus DD) des PE-Gleitlagers zeigten keinen relevanten Einfluss auf die Kniegelenkkinematik, wohingegen die Integrität des HKB die Gelenkmechanik beeinflusste. Nach Resektion des HKB zeigten die Kniegelenke unabhängig von CR-Design (CR flat 11/9, DD) signifikant ungünstigere mechanische Wirkungsgrade (CR 11: 1147 ± 88 N; CR 9: 1151 ± 83 N; DD: 1150 ± 98 N; CR 11 ohne HKB: 1203 ± 92 N; DD ohne HKB: 1192 ± 80 N; CR 11 ohne HKB versus CR 11: p ≤ 0,009; CR 11 ohne HKB versus CR 9: p ≤ 0,02 bzw. DD ohne HKB versus CR 11: p ≤ 0,05; DD ohne HKB versus CR 9: p ≤ 0,01; DD ohne HKB versus DD: p ≤ 0,03). Weitere Auswirkungen einer HKB Resektion auf die patellofemorale Kinematik konnten allerdings nicht nachgewiesen werden. Schlussfolgerung: Die Ergebnisse der vorliegenden Studie lassen den Schluss zu, dass kreuzbandersetzende Prothesen eher eine physiologische Gelenkkinematik wiederherstellen als kreuzbanderhaltende Designs, was sich über ein besser reproduzierbares „roll-back“ erklären lässt. Bei hoch konformen Gleitlagern (DD), für die bei HKB Insuffizienz eine verbesserte AP-Stabilität postuliert wird, konnte nach Resektion des HKB keine physiologischere Kinematik beobachtet werden. Höhe und Konformität der PE-Inlays haben keinen relevanten Effekt auf die Gelenkmechanik, während ein intaktes HKB auch nach Implantation einer KTEP eine wichtige Rolle für das AP-Verhalten spielt. Bei insuffizientem HKB oder Gelenkinstabilität sollten den HKB erhaltenden Designs daher HKB substituierende Designs vorgezogen werden. Anterior knee pain after Total Knee Arthroplasty (TKA) is one of the most common patient complaints leading to numerous revision procedures. Changing the kinematic behaviour of patello-femoral joint with increased patello-femoral contact pressure and quadriceps extension force could add to its sequelae. The aim of this in vitro study was to compare the influence of different prosthesis designs on patello-femoral contact mechanics and quadriceps extension force after implantation of cruciate retaining (CR flat, DD) and posterior stabilized (PS) TKA under dynamic conditions. Furthermore, the influence of the PCL and both height and conformity of the inlay on knee kinematics were investigated. Methods: 8 fresh frozen human cadaveric knee specimens underwent testing in a kinematic device simulating an isokinetic knee extension cycle from 120° of flexion to full extension. Knee motion was driven by a hydraulic cylinder applying sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm. Patello-femoral contact pressure was measured by means of a pressure sensitive film (Tekscan®, Inc., Boston, USA). Both patello-femoral contact pressure and quadriceps extension force were recorded after implantation of a TKA (Genesis II, Smith & Nephew, Schenefeld, Germany) with application of different polyethylene inlays. First, different cruciate retaining (CR) designs were tested before (CR 11, CR 9, DD) and after (CR 11, DD) resection of the PCL. The CR TKA was then removed to be replaced by a posterior stabilized (PS) design and measurements were repeated with an 11 mm PE inlay. The patella remained unresurfaced. A paired sampled t-test to compare means (significance, P ≤ 0.05) was used for statistical analysis. Results: After implantation of the posterior stabilized design (PS) patello-femoral contact kinematics were comparable to physiological knee kinematics whereas cruciate retaining TKA showed higher patello-femoral contact pressures (mean contact pressure: PS: 3,58 ± 1,25 MPa; CR 11: 4,31 ± 1,40 MPa; CR 9: 4,23 ± 1,40 MPa; DD: 4,27 ± 1,34 MPa; CR 11 without PCL: 4,18 ± 1,26 MPa; DD without PCL: 3,99 ± 1,44 MPa respectively peak pressure: PS: 6,12 ± 2,37 MPa; CR 11: 7,17 ± 2,41 MPa; CR 9: 7,05 ± 2,45 MPa; DD: 7,12 ± 2,53 MPa; CR 11 without PCL: 6,89 ± 2,30 MPa; DD without PCL: 6,63 ± 2,52 MPa). The patello-femoral contact pressure in PS TKA was mostly significantly lower compared with the cruciate retaining (CR) design (p ≤ 0,006, p ≤ 0,02, p ≤ 0,01, p ≤ 0,03 and p ≤ 0,18 respectively p ≤ 0,02, p ≤ 0,02, p ≤ 0,01, p ≤ 0,07 and p ≤ 0,39). There was a trend to a more physiological patello-femoral contact pressure area (medialized, proximalized). Quadriceps extension force decreased significantly with the PS TKA compared to the CR type after resection of the PCL (PS: 1131 ± 108 N; CR 11 without PCL: 1203 ± 92 N; DD without PCL: 1192 ± 80 N; p ≤ 0,01, p ≤ 0,01). Regarding to maximal quadriceps extension force PS TKA decreased significantly in comparison with all other TKA designs (PS: 1560 ± 145 N; CR 11: 1683 ± 156 N; CR 9: 1712 ± 157 N; DD: 1685 ± 175 N; CR 11 without PCL: 1729 ± 162 N; DD without PCL: 1689 ± 123 N; p ≤ 0,04, p ≤ 0,008, p ≤ 0,02, p ≤ 0,01 und p ≤ 0,02). Height (11 mm versus 9 mm) and conformity (CR flat versus DD) of the polyethylene inlay did not influence knee kinematics whereas integrity of the PCL affected knee kinematics. After resection of the PCL in cruciate retaining TKA (CR flat 11/9, DD) quadriceps extension force increased significantly (CR 11: 1147 ± 88 N; CR 9: 1151 ± 83 N; DD: 1150 ± 98 N; CR 11 without PCL: 1203 ± 92 N; DD without PCL: 1192 ± 80 N; CR 11 without PCL versus CR 11: p ≤ 0,009; CR 11 without PCL versus CR 9: p ≤ 0,02 respectively DD without PCL versus CR 11: p ≤ 0,05; DD without PCL versus CR 9: p ≤ 0,01; DD without PCL versus DD: p ≤ 0,03). An effect on patello-femoral kinematics could not be detected. Conclusions: The results of this in vitro study suggest that a posterior stabilized TKA design can reproduce more physiological knee kinematics in comparison with a cruciate retaining design. It is hypothesized that this could be due to a better reproducible rollback of a PS design. High conforming inlays (DD) which are supposed to improve ap-stability in case of an insufficient PCL did not show physiological knee kinematics after resection of the PCL. Height and conformity of the inlay could not influence knee mechanics whereas the PCL is important for ap-stability after implantation of a TKA. In case of insufficiency of the PCL or instability of the knee joint posterior stabilized TKA designs therefore should be prefered to cruciate retaining TKA.
Intraoperative stress testing is required for the detection of syndesmosis instability following an ankle fracture. The present study compared two stress tests for the detection of syndesmotic injury.
A true mortise radiograph of the ankle was made for fourteen cadaver joints. Specimens were randomized into two groups to simulate ligament and syndesmosis injury on the basis of the Danis-Weber classification system. In the first group, the anterior inferior tibiofibular ligament was divided first (Weber B(r)), followed sequentially by division of the interosseous membrane (Weber C) and the deltoid ligament. In the second group, the deltoid ligament was divided first, followed by the anterior inferior tibiofibular ligament. Radiographs were made at each stage with use of two methods of stressing the ankle mortise: (1) external rotation of the foot with an external moment of 7.5 Nm, and (2) application of a lateral force of 100 N. Tibiofibular overlap, tibiofibular clear space, and medial clear space were measured.
Lateral stress produced a significantly greater increase in the tibiofibular clear space than did the external rotation test for Weber C injuries and Weber C plus deltoid ligament injuries. A greater increase in the tibiofibular clear space was noted during the lateral stress test when both the deltoid and the anterior inferior tibiofibular ligament had been sectioned (p < 0.05). The external rotation stress test produced a significant increase in the medial clear space in the presence of isolated anterior inferior tibiofibular ligament and deltoid ligament injuries (p < 0.05).
For the detection of syndesmotic instability at the site of ankle fractures on stress radiographs, the lateral stress test appeared to be superior to the external rotation stress test in this cadaver model.
Musculoskeletal modeling and optimization theory are often used to determine muscle forces in vivo. However, convincing quantitative evaluation of these predictions has been limited to date. The present study evaluated model predictions of knee muscle forces during walking using in vivo measurements of joint contact loading acquired from an instrumented implant. Joint motion, ground reaction force, and tibial contact force data were recorded simultaneously from a single subject walking at slow, normal, and fast speeds. The body was modeled as an 8-segment, 21-degree-of-freedom articulated linkage, actuated by 58 muscles. Joint moments obtained from inverse dynamics were decomposed into leg-muscle forces by solving an optimization problem that minimized the sum of the squares of the muscle activations. The predicted knee muscle forces were input into a 3D knee implant contact model to calculate tibial contact forces. Calculated and measured tibial contact forces were in good agreement for all three walking speeds. The average RMS errors for the medial, lateral, and total contact forces over the entire gait cycle and across all trials were 140 +/- 40 N, 115 +/- 32 N, and 183 +/- 45 N, respectively. Muscle coordination predicted by the model was also consistent with EMG measurements reported for normal walking. The combined experimental and modeling approach used in this study provides a quantitative framework for evaluating model predictions of muscle forces in human movement.
Total knee arthroplasty (TKA) relies on soft tissue to regulate joint stability after surgery. In practice, the exact balance of the gaps can be difficult to measure, and various methods including intra-operative spreaders or distraction devices have been proposed. While individual ligament strain patterns have been measured, no data exist on the isometricity of the soft tissue envelope as a whole. In this study, a novel device was developed and validated to compare isometricity in the entire soft tissue envelope for both the intact and TKA knee. A spring-loaded rod was inserted in six cadaver knee joints between the tibial shaft and the tibial plateau or tibial tray after removing a 7 mm slice of bone. The displacement of the rod during passive flexion represented variation in tissue tension around the joint. The rod position in the intact knee remained within 1 mm of its initial position between 15 degrees and 135 degrees of flexion, and within 2 mm (+/-1.2 mm) throughout the entire range of motion (0-150 degrees). After insertion of a mobile-bearing TKA, the rod was displaced a mean of 6 mm at 150 degrees (p<0.001). The results were validated using a force transducer implanted in the tibial baseplate of the TKA, which showed increased tibiofemoral force in the parts of the flexion range where the rod was most displaced. The force measurements were highly correlated with the displacement pattern of the spring-loaded rod (r=-0.338; p=0.006). A simple device has been validated to measure isometricity in the soft tissue envelope around the knee joint. Isometricity measurements may be used in the future to improve implantation techniques during TKA surgery.
One of the most commonly cited reasons for retaining the posterior cruciate ligament (PCL) during total knee arthroplasty is to preserve femoral rollback and theoretically improve extensor mechanism efficiency (lengthening the moment arm). This study was undertaken to assess PCL function in this regard and to delineate the effects of joint line elevation that can be manipulated intraoperatively by the surgeon. The anterior movement of tibiofemoral contact following PCL resection at flexion angles 60 degrees demonstrated the beneficial effect of the PCL on extensor function. This anterior translation and the concomitant increases in quadriceps tendon load and patellofemoral contact pressures were consistently observed. This study demonstrated that small changes of the joint line position significantly influenced PCL strain and knee kinematics. In order to preserve the desired functions that would be lost with an overly lax PCL and to avoid the potential adverse effects of an overly tight PCL (posterior edge loading and increased tibiofemoral contact), the surgeon should make every effort to restore the preoperative joint line. If this is not possible, consideration should be given to posterior cruciate recession or use of a posterior cruciate substituting design.
We have investigated the ability to kneel after total knee replacement. We asked 75 patients (100 knees) at least six months after routine uncemented primary total knee replacement, to comment on and to demonstrate their ability to kneel. Differences between the perceived and actual ability to kneel were noted. In 32 knees patients stated that they could kneel without significant discomfort. In 54 knees patients avoided kneeling because of uncertainties or recommendations from third parties (doctors, nursing staff, friends, etc). A total of 64 patients was actually able to kneel without discomfort or with mild discomfort only and 12 of the remainder were unable to kneel because of problems which were not related to the knee. Twenty-four patients therefore were unable to kneel because of discomfort in the knee. There was no difference between the 'kneelers' and 'non-kneelers' with regard to overall knee score, range of movement and the presence of patellar resurfacing.
To improve the ligament balancing procedure during total knee arthroplasty a force-sensing device to intraoperatively measure knee joint forces and moments has been developed. It consists of two sensitive plates, one for each condyle, a tibial base plate and a set of spaces to adapt the device thickness to the patient-specific tibiofemoral gap. Each sensitive plate is equipped with three deformable bridges instrumented with thick-film piezoresistive sensors, which allow accurate measurements of the amplitude and location of the tibiofemoral contact forces. The net varus-valgus moment is then computed to characterize the ligamentous imbalance. The developed device has a measurement range of 0-500 N and an intrinsic accuracy of 0.5% full scale. Experimental trials on a plastic knee joint model and on a cadaver specimen demonstrated the proper function of the device in situ. The results obtained indicated that the novel force-sensing device has an appropriate range of measurement and a strong potential to offer useful quantitative information and effective assistance during the ligament balancing procedure in total knee arthroplasty.
Mobile-bearing posterior-stabilised knee replacements have been developed as an alternative to the standard fixed- and mobile-bearing designs. However, little is known about the in vivo kinematics of this new group of implants. We investigated 31 patients who had undergone a total knee replacement with a similar prosthetic design but with three different options: fixed-bearing posterior cruciate ligament-retaining, fixed-bearing posterior-stabilised and mobile-bearing posterior-stabilised. To do this we used a three-dimensional to two-dimensional model registration technique. Both the fixed- and mobile-bearing posterior-stabilised configurations used the same femoral component. We found that fixed-bearing posterior stabilised and mobile-bearing posterior-stabilised knee replacements demonstrated similar kinematic patterns, with consistent femoral roll-back during flexion. Mobile-bearing posterior-stabilised knee replacements demonstrated greater and more natural internal rotation of the tibia during flexion than fixed-bearing posterior-stabilised designs. Such rotation occurred at the interface between the insert and tibial tray for mobile-bearing posterior-stabilised designs. However, for fixed-bearing posterior-stabilised designs, rotation occurred at the proximal surface of the bearing. Posterior cruciate ligament-retaining knee replacements demonstrated paradoxical sliding forward of the femur. We conclude that mobile-bearing posterior-stabilised knee replacements reproduce internal rotation of the tibia more closely during flexion than fixed-bearing posterior-stabilised designs. Furthermore, mobile-bearing posterior-stabilised knee replacements demonstrate a unidirectional movement which occurs at the upper and lower sides of the mobile insert. The femur moves in an anteroposterior direction on the upper surface of the insert, whereas the movement at the lower surface is pure rotation. Such unidirectional movement may lead to less wear when compared with the multidirectional movement seen in fixed-bearing posterior-stabilised knee replacements, and should be associated with more evenly applied cam-post stresses.
In six unloaded cadaver knees we used MRI to determine the shapes of the articular surfaces and their relative movements. These were confirmed by dissection.
Medially, the femoral condyle in sagittal section is composed of the arcs of two circles and that of the tibia of two angled flats. The anterior facets articulate in extension. At about 20° the femur ‘rocks’ to articulate through the posterior facets. The medial femoral condyle does not move anteroposteriorly with flexion to 110°.
Laterally, the femoral condyle is composed entirely, or almost entirely, of a single circular facet similar in radius and arc to the posterior medial facet. The tibia is roughly flat. The femur tends to roll backwards with flexion.
The combination during flexion of no antero-posterior movement medially (i.e., sliding) and backward rolling (combined with sliding) laterally equates to internal rotation of the tibia around a medial axis with flexion. About 5° of this rotation may be obligatory from 0° to 10° flexion; thereafter little rotation occurs to at least 45°. Total rotation at 110° is about 20°, most if not all of which can be suppressed by applying external rotation to the tibia at 90°.
A study was conducted to determine in vivo femorotibial contact patterns for subjects having a posterior cruciate retaining or posterior cruciate substituting total knee arthroplasty. Femorotibial contact of 72 subjects implanted with a total knee replacement, performed by five surgeons, was analyzed using video fluoroscopy. Thirty-one subjects were implanted with a posterior cruciate retaining total knee replacement with a flat polyethylene posterior lipped insert, 12 with a posterior cruciate retaining total knee replacement with a curved insert, and 29 with a posterior cruciate substituting total knee replacement. Each subject performed successive deep knee bends to maximum flexion. Video images at 0 degrees, 30 degrees, 60 degrees, and 90 degrees flexion were downloaded onto a workstation computer. Femorotibial contact paths were determined for the medial and lateral condyles using an interactive model fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative. Analysis of average femorotibial contact pathways of both posterior cruciate retaining designs revealed posterior femorotibial contact in full extension with anterior translation of femorotibial contact commonly observed in midflexion and terminal flexion. In posterior cruciate substituting designs, anterior femoral translation was seen medially at 30 degrees to 60 degrees flexion but rarely was observed laterally. Posterior femoral rollback laterally from full extension to 90 degrees flexion was seen in 100% of subjects implanted with a posterior cruciate substituting total knee replacement, versus 51.6% (posterior lipped polyethylene insert) and 58.3 % (curved insert) of those with a posterior cruciate retaining total knee replacement. Data from this multicenter study are remarkably similar to previous fluoroscopy data from a single surgeon series, showing a lack of customary posterior femoral rollback in both posterior cruciate retaining designs, and conversely showing an average anterior femoral translation with knee flexion. Posterior femoral rollback, less than in normal knees, routinely was observed in posterior cruciate substituting total knee arthroplasty, attributed to engagement of the femoral component cam with the tibial post. The abnormal anterior femoral translation observed in posterior cruciate retaining total knee arthroplasty may be a factor in premature polyethylene wear observed in retrieval studies.
The objective of this study was to measure three-dimensional knee motion or functional laxity with implants which either retained the posterior cruciate ligament (PCL+) in ten patients, or substituted for excised PCL with a posterior stabilized articulating surface (PCL-S) in ten patients. The intent was to identify the specific influence and significance of the presence of the PCL under active flexion and extension. Internal-external rotation (screw home movement) and anterior-posterior translation (femoral rollback phenomena) with active extension and flexion were chosen to characterize knee joint functional laxity, and were measured using an instrumented spatial linkage. Knees with a PCL+ implant exhibited both screw home movement and femoral rollback, while knees with a PCL-S design exhibited only femoral rollback. A knee with a PCL+ implant was more able to reproduce the normal kinematics of the screw home movement and femoral rollback, compared to a PCL-S design.
To define the physiologic status of a retained posterior cruciate ligament (PCL) after total knee arthroplasty (TKA), PCL strain was measured in the operating room before and after prosthetic insertion. Strain patterns in the PCL were measured throughout the range of motion before and after resection of the anterior cruciate ligament (ACL) and after completion of the TKA. Strain patterns before and after resection of the ACL changed little. However, after the completed arthroplasty, repeat measurements indicated that only one of 10 knees had a PCL strain pattern consistent with its original pattern. The ligament failed to achieve preoperative strain levels in six knees and had increased strain early inflexion in three.
These findings demonstrate the difficulty of consistently preserving normal function of the PCL after TKA. In many cases, the ligament will be too lax and function in a variable pattern. In other cases, the PCL may be too tight and thereby increase contact stress on the posterior aspect of the polyethylene insert, resulting in limited flexion and increased wear. Orthopedic surgeons should appreciate that the varying function of the PCL after TKA may require accurate balancing to achieve consistent success with PCL-retaining devices.
The purpose of this article is to give a general overview of total knee replacement: when it should and should not be used, the differences among various implants, how certain anatomic situations are dealt with, the complications, realistic goals, and finally developments to be anticipated. The ideas and results to be described are a compendium of the current thoughts of many surgeons involved in knee replacement surgery. They are presented to provide a basic framework to which one can add as new developments occur.
A three-dimensional computer model of the knee was formulated based on sectional and coordinate data from knee specimens. The model was consistent with published data in terms of contact points and ligament length patterns. Prosthetic components were designed, and surgical placement was simulated. Maximum flexion was limited by tension in the posterior cruciate ligament. Increased dishing of the tibial surface reduced flexion, but some dishing was considered necessary for reduction of contact stresses. Anteroposterior translation of the tibial component had little effect on flexion. Femoral translation had some offset, and posterior positioning reduced flexion. The most important surgical variable was tibial component tilt in the sagittal plane. Posterior tilt increased motion, while anterior tilt decreased motion. The results apply to the choice of total knee system, instrument design, and surgical technique.
The arguments for resection of the (anterior and) posterior cruciate ligament(s), as a step in total knee arthroplasty, are reviewed on the basis of the authors' personal experience and the work of others published in the literature.
The strain developed in the posterior cruciate ligament (PCL) of eight fresh cadaveric knees was measured before and after total knee arthroplasty using a loading technique that simulated stair ascent and descent. Each knee was instrumented with a Hall Effect strain gauge (Micro-Strain, Burlington, VT) in the PCL, a load cell in the quadriceps tendon, an electrogoniometer, and an array of linear displacement transducers to measure femoral rollback. Testing was undertaken with each knee in its normal state with the anterior cruciate cut and with a cruciate-retaining prosthesis, a cruciate-excising prosthesis, and a cruciate-substituting prosthesis. Normal PCL strain levels were produced in only 37% of the trials following implantation of the cruciate-retaining knee arthroplasties. With a cruciate-retaining prosthesis, femoral rollback decreased by an average of 36% and was associated with a 15% loss in extensor efficiency. In the procedures performed with excision of the PCL, rollback decreased by 70% and extensor efficiency by 19%. Cruciate substitution resulted in a 12% loss in rollback and an 11% decrease in extensor efficiency. The strain developed within the PCL during knee flexion was found to be extremely sensitive to the thickness of the polymeric tibial insert. In the majority of cases, it was not possible to restore normal ligament loading with flexion while simultaneously maintaining acceptable varus/valgus stability of the knee joint. Using a range of contemporary knee arthroplasties, the authors were unable to consistently reproduce normal function of the PCL.
To determine the role of the posterior cruciate ligament in total knee arthroplasty, 242 consecutive primary total knee arthroplasties were included in 1 of 3 sequential groups. Group I included 77 Press Fit Condylar total knee replacements in which the posterior cruciate ligament was completely released from its tibial attachment. In Group II, there were 80 Press Fit Condylar total knee replacements in which the posterior cruciate ligament was retained. Group III consisted of 85 total knee replacements with a posterior cruciate-substituting device (Insall-Burstein II). All patients were observed at least 2 years and evaluated by the Knee Society's Clinical and Functional Scoring System, including a radiographic evaluation. No differences were found between the posterior cruciate ligament sacrificed group and the posterior cruciate ligament preserved group. The 1 significant difference among the 3 groups was in range of motion (ROM). Groups I and II averaged 103 degrees and 104 degrees motion respectively, whereas Group III, the posterior cruciate-substituting group, averaged 112 degrees (p = 0.001). In addition, only in Group III was the lower 95% confidence limit of the mean ROM > 90 degrees. These findings suggest that preserving the posterior cruciate ligament does not consistently lead to improved functional ROM. The posterior cruciate ligament-substituting device historically has demonstrated excellent survivorship and appears to offer greater ROM.
A satisfactory design of the patellar component used in total knee arthroplasty and a general understanding of the effects of orthopedic procedures require, in part, an accurate description of patellofemoral contact forces. Experimental determination of the contact stress distribution requires integration to estimate the contact forces. Due to complex patellar geometry, the determination of the components of the resultant load is difficult. Current techniques for the direct measurement of contact loads either report a single load component or require sequential experiments to fully describe the contact force. The present study describes the development of a six-degree-of-freedom patellofemoral force transducer. This transducer allows the simultaneous determination of the three components of the contact force with an increase in accuracy over available devices. The contact forces components are accurate to 1% of full scale (900 N anterior-posterior, +/- 200 N medial-lateral and inferior-superior). The location on the patella where the resultant force acts is determined to within 1 mm. Relative movement of this point as a function of either normal change in knee flexion angle or as a result of a typical orthopedic procedure is determined to within 0.1 mm. A protocol is presented that allows the contact forces to be determined for either the anatomically normal patella or a patella following total knee arthroplasty.
Experimental measurement of loads occurring in the human knee joint will allow validation of analytical models and provide data for the design of total knee implants. A customized transducer was developed to measure the dynamic tibiofemoral force and center of pressure after total knee arthroplasty. The transducer consists of a standard tibial component to which four uniaxial load cells and an additional tibial tray have been added. The transducer was calibrated using a loading device traceable to the National Institute of Standards and Technology (NIST). The transducer was accurate to within 1% in magnitude, 0.07 mm in medial/lateral location and 0.24 m in anterior/posterior location.
Wear at the polyethylene tibial plateau in total knee arthroplasty (TKR) is one of the primary concerns with these devices. The artificial bearing of a TKR has to sustain large forces while allowing the mobility for normal motion, typically, rolling, gliding and rotation. The tractive forces during the rolling motion at the knee joint were analyzed to determine which factors cause these forces to increase in TKR. The implications of these tractive forces to polyethylene wear were considered. Traction forces were calculated using a model of the knee to evaluate the effect of variations in the coefficient of friction, gait characteristics, antagonistic muscle contraction and patellofemoral mechanics. The model was limited to the sagittal plane motion of the femur on the tibia. The input for the model was the shape of the articulating surface, coefficient of friction, contact path, muscle anatomy and gait kinetics common to patients with a total knee replacement. The generation of tractive forces on the tibial polyethylene plateau was highly dependent on the static and dynamic coefficient of friction between the femur and the tibia. A peak tractive force of approximately 0.4 body weight was calculated with a peak normal force of 3.3 body weight. Tractive rolling occurred during most of stance phase when the static coefficient was 0.2. Alterations in gait patterns had a substantial effect on the generation of tractive forces at the knee joint. When an abnormal gait pattern (often seen following TKR) was input to the model the posteriorly directed tractive force on the tibial surface was reduced. It was also found that variations in muscle contractions associated with antagonistic muscle activity as well as the angle of pull of the patellar tendon affected the magnitude of tractive forces. The results of the study suggest that there are feasible conditions following total knee replacement which can lead to tractive forces during rolling motion at the tibiofemoral articulation that should be considered in the analysis of factors leading to polyethylene damage in total knee replacement.
Numerous studies indicate that total knee arthroplasty (TKA) achieves excellent long-term success whether the posterior cruciate ligament (PCL) is saved or excised. In 13 patients, 16 PCL-retaining TKAs were identified with incapacitating instability secondary to early PCL deficiency. Patients with clinical PCL insufficiency present with a triad of subjective complaints: persistent swelling/effusions, anterior knee pain, and giving-way or instability episodes with activities of daily living. Of 13 patients, 12 had at least three postoperative visits with identical subjective complaints before PCL deficiency was diagnosed. On examination all patients exhibited effusion, posterior sag, positive quadriceps active test, and a visible anterior translation of the tibia on the femur while extending the leg from a seated, 90 degree flexed position. This sign has not been previously described to our knowledge but was present in all of our study patients. No patients had radiographic evidence of loosening or osteolysis. Joint aspiration was negative for infection in all patients. No patient had lateral patellofemoral maltracking. By radiographic measurement, the PCL-deficient knees had an average joint line elevation of 10.3 mm, compared with well-functioning TKAs which had an average joint line elevation of 5.0 mm. There was no correlation of PCL deficiency with excessive proximal tibial resection. Nonsurgical intervention provided no improvement in pain or instability. Six patients had improvement of pain, effusion, and stability after revision to a cruciate-substituting implant. We believe that this complication occurs more frequently than is currently being identified and should be considered in problem TKAs with normal radiographs.
A prospective, observational cohort investigation was performed to help understand the impact of knee replacement on patients with knee osteoarthritis in community practice. Of those, 291 patients (330 knees) were eligible and willing to participate. Forty-eight orthopaedic surgeons referred 563 patients from 25 institutions within the state of Indiana. Demographics, patient completed health status, satisfaction, independent radiographic measures, surgeon reported intraoperative factors, hospital discharge factors, and independent physical examinations were recorded. A minimum 2-year followup was obtained in 92% of the patients. At followup, 88% were satisfied, 3% were neutral, and 9% were dissatisfied with the results of their knee surgery. The physical composite score improved from 27.4 +/- 0.4 (range, 13.3-50.3) to 37.7 +/- 0.7 (range, 12.9-61.3) at two years. Maximal improvement in physical composite score was seen in patients who had their surgery performed in institutions that performed greater than 50 knee replacements per year in patients with Medicare insurance; who had a better mental health status at baseline; who had surgery performed on Monday, Friday, or Saturday; who were older; who were treated with a posterior cruciate sparing device; and who had worse preoperative function. A lower likelihood of complications were found with surgeons who performed greater than 20 knee replacements per year; midweek surgeries; in patients with more severe preoperative knee dysfunction; patients with fewer comorbidities; patients with less preoperative stiffness; patients being treated by younger surgeons; and in patients undergoing unilateral knee replacement. Among voluntarily participating physicians, knee replacement can be a highly effective medical technology with high levels of patient satisfaction and low rates of complications.
A study was conducted to determine in vivo femorotibial contact patterns for subjects having a posterior cruciate retaining or posterior cruciate substituting total knee arthroplasty. Femorotibial contact of 72 subjects implanted with a total knee replacement, performed by five surgeons, was analyzed using video fluoroscopy. Thirty-one subjects were implanted with a posterior cruciate retaining total knee replacement with a flat polyethylene posterior lipped insert, 12 with a posterior cruciate retaining total knee replacement with a curved insert, and 29 with a posterior cruciate substituting total knee replacement. Each subject performed successive deep knee bends to maximum flexion. Video images at 0 degree, 30 degrees, 60 degrees, and 90 degrees flexion were downloaded onto a workstation computer. Femorotibial contact paths were determined for the medial and lateral condyles using an interactive model fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative. Analysis of average femorotibial contact pathways of both posterior cruciate retaining designs revealed posterior femorotibial contact in full extension with anterior translation of femorotibial contact commonly observed in midflexion and terminal flexion. In posterior cruciate substituting designs, anterior femoral translation was seen medially at 30 degrees to 60 degrees flexion but rarely was observed laterally. Posterior femoral rollback laterally from full extension to 90 degrees flexion was seen in 100% of subjects implanted with a posterior cruciate substituting total knee replacement, versus 51.6% (posterior lipped polyethylene insert) and 58.3% (curved insert) of those with a posterior cruciate retaining total knee replacement. Data from this multicenter study are remarkably similar to previous fluoroscopy data from a single surgeon series, showing a lack of customary posterior femoral rollback in both posterior cruciate retaining designs, and conversely showing an average anterior femoral translation with knee flexion. Posterior femoral rollback, less than in normal knees, routinely was observed in posterior cruciate substituting total knee arthroplasty, attributed to engagement of the femoral component cam with the tibial post. The abnormal anterior femoral translation observed in posterior cruciate retaining total knee arthroplasty may be a factor in premature polyethylene wear observed in retrieval studies.
A computerised, real time, thin-film pressure transducer method is used to measure tibiofemoral contact area in total knee arthroplasty (TKA) devices that is easier and more reliable and reproducible as compared to the Fuji pressure-sensitive film technique. Many authors have suggested that contact areas and pressures within TKA devices can be a predictor of wear and failure of the ultra-high molecular weight polyethylene (UHMWPE) tibial insert. In this study, two contact area measurement techniques (Fuji pressure-sensitive Film and K-scan sensor system) were compared using a custom TKA testing jig designed for freedom of movement so that in any loading configuration the component found and seated in its own "home" position. The K-scan system was used to measure contact areas of one TKA design at several angles from 0 to 110 degrees flexion with loads equating to 4, 4.5, and 5 times body weight. For comparison, four ranges of Fuji film were used to measure areas at the same flexion angles but at 5 times body weight only. Contact areas measured with the Fuji films were 11-36% (p < 0.05) lower than those measured by the K-scan sensor.
Mobile bearing total knee arthroplasty kinematically allows the advantages of large and congruent surface contact and low contact pressures, while preserving flexion, extension, and rotation in knee motion. In allowing for these degrees of freedom, the interface between bone and component also is protected from high stress. The Self Aligning I total knee arthroplasty initially was implanted in patients after its development at the authors' institution in 1990. Between 1990 and 1994, 141 patients with osteoarthritis of the knee underwent 172 total knee replacements using this system. At average followup of 5.6 years (range, 5-8 years), clinical results using this system showed a 94% satisfaction rate (good or very good). Two revision surgeries have been performed for polyethylene wear, with none of the remaining knees showing evidence of discernible wear. Complications included four cases of deep infection, four cases where a press fit femoral component failed (nonporous coated) and the patients required revision surgery, four traumatic fractures (three patellar and one supracondylar), one popliteal artery occlusion, and one revision for stiffness. Three patients required manipulation under anesthesia for arthrofibrosis. Kaplan-Meier survival curves show the probability of survival to be 91.7%, with revision surgery for any reason as an end point, and 98.8% for revision surgery because of polyethylene wear as an end point. Following the initial learning curve with this prosthesis, the medium term results using this system show maintenance of clinical success. No progressive evidence of polyethylene wear with time has been found, supporting the concept of mobile bearing arthroplasty in extending the service life of total knee arthroplasty.
This cadaver study was undertaken to gain insight into the effects that posterior cruciate ligament retention and sacrifice would have on the amount of deformity correction obtained with medial and lateral structure release during total knee arthroplasty. Twenty-seven cadaveric specimens were used to sequentially release medial and lateral structures with and without posterior cruciate support. Each release sequence was tested in full extension and 90 degrees flexion. In full extension, the resulting change into valgus after release of the posterior cruciate ligament, posteromedial capsule/oblique ligament complex, superficial medial collateral ligament, and pes anserinus and semimembranosus tendons was 6.9 degrees, and it increased to 13.4 degrees in 90 degrees flexion. With preservation of the posterior cruciate ligament this decreased to 5.2 degrees in extension and 8.7 degrees in flexion. Changes seen in 90 degrees flexion were significantly greater than those in full extension. For the valgus knee model with release of the posterior cruciate ligament, posterolateral capsule, lateral collateral ligament, iliotibial band, popliteus tendon, and lateral head of the gastrocnemius, 8.9 degrees of change into varus was seen in extension and 18.1 degrees in 90 degrees flexion. With posterior cruciate ligament retention 5.4 degrees and 4.9 degrees of change into varus was seen in extension and flexion, respectively. Significantly less change with retention of the posterior cruciate ligament was seen with both medial and lateral release and more opening of the flexion gap was seen on the release side of the joint for all groups except those with lateral release with sacrifice of the posterior cruciate ligament.
In six unloaded cadaver knees we used MRI to determine the shapes of the articular surfaces and their relative movements. These were confirmed by dissection. Medially, the femoral condyle in sagittal section is composed of the arcs of two circles and that of the tibia of two angled flats. The anterior facets articulate in extension. At about 20 degrees the femur 'rocks' to articulate through the posterior facets. The medial femoral condyle does not move anteroposteriorly with flexion to 110 degrees. Laterally, the femoral condyle is composed entirely, or almost entirely, of a single circular facet similar in radius and arc to the posterior medial facet. The tibia is roughly flat. The femur tends to roll backwards with flexion. The combination during flexion of no anteroposterior movement medially (i.e., sliding) and backward rolling (combined with sliding) laterally equates to internal rotation of the tibia around a medial axis with flexion. About 5 degrees of this rotation may be obligatory from 0 degrees to 10 degrees flexion; thereafter little rotation occurs to at least 45 degrees. Total rotation at 110 degrees is about 20 degrees, most if not all of which can be suppressed by applying external rotation to the tibia at 90 degrees.
Increasing femoral rollback in flexion is thought to reduce patellofemoral contact load in total knee arthroplasty (TKA). The objectives of this study were to quantify the dependence of patellar load on rollback and to assess the effectiveness of posterior cruciate ligament (PCL)-retaining, PCL-sacrificing, and PCL-substituting TKA types in generating rollback. Nine cadaver knees were tested in simulated squatting. Six TKAs that were expected to produce varying amounts of femoral rollback were evaluated: PCL-retaining TKA, PCL-sacrificing TKA, a commercially available PCL-substituting TKA, and 3 modified PCL-substituting TKAs in which the anteroposterior position of the tibial post was varied. Kinematics, quadriceps loads, and patellofemoral contact loads were recorded. Significant differences in rollback were observed in the 30 degrees to 90 degrees flexion range. PCL-sacrificing TKAs generated the least rollback. PCL-retaining TKAs produced greater rollback but had the most variability. PCL-substituting TKAs produced the greatest and most reproducible rollback. Moving the tibial post posteriorly further increased rollback. Increased rollback correlated with reduced patellar load (-2.2%/mm). Reductions in patellar load of 17.6% were observed. Quadriceps loads were reduced by increasing rollback but to a smaller degree (-0.9%/mm). Rollback primarily affects patellar load rather than quadriceps load or efficiency.
Video fluoroscopy and computer photogrammetry was used to evaluate 20 knees with posterior cruciate ligament (PCL) retaining and 19 knees with PCL sacrificing total knee arthroplasties (TKAs) with a mobile bearing total condylar prosthesis compared with 10 normal patients. In extension, femorotibial contact was posterior for TKA patients (P<.05) and demonstrated anterior translation from 60 degrees-90 degrees flexion. However, posterior rollback with limited translation was seen from 0 degrees-40 degrees, which may reflect the high congruity of this prosthesis. Fifty percent of meniscal bearing implants demonstrated bearing translation. Kinematics and weight-bearing range of motion were similar with PCL retention or sacrifice.
In vitro dynamic simulation of knee flexion was performed to quantify knee kinematics for a mobile bearing prosthesis that allows the tibial insert to translate and rotate with respect to the baseplate. Six cadaver knees were tested in the intact state, after implanting a fixed platform prosthesis, and after implanting a mobile bearing prosthesis. The mobile bearing prosthesis significantly increased the tibial internal rotation and medial shift compared with the intact knee, near 90 degrees of flexion. Both prostheses increased the patellar medial shift near 90 degrees of flexion. The patellar flexion was significantly larger for the mobile bearing prosthesis than for the fixed platform prosthesis for most of flexion. Motion of the insert with respect to the baseplate may have contributed to the variations in tibiofemoral kinematics, whereas tibiofemoral kinematic changes influenced the patellofemoral kinematics. Although the kinematics were similar for the 2 types of prosthesis, the possibility of complications related to increased patellar flexion and backside wear of the tibial insert should be considered.
This study evaluated the improvement in range of motion after revision total knee arthroplasty (TKA) in a consecutive series of patients with TKAs presenting with pain and limited range of motion. Eleven stiff (range of motion <70 degrees ) and painful TKAs were revised with a posterior stabilized condylar prosthesis and reviewed after an average of 37.6 months (range, 24-53 months). The average range of motion increased from 39.7 degrees preoperatively to 83.2 degrees postoperatively. The mean flexion contracture decreased from 13.2 degrees to 0.9 degrees. Pain scores improved from 4.5 to 44.1, and all 11 patients were satisfied. This study shows that knee range of motion can improve significantly after revision TKA.
Currently available knee prostheses can provide 100 degrees to 110 degrees of knee flexion, which is usually good enough for most daily activities, such as ascending or descending stairs and rising from chairs. Many activities require deep knee flexion, however. In Asian countries, deep knee flexion also is needed for special cultural activities. Preoperative range of motion, surgical technique, prosthesis design, and postoperative rehabilitation are important factors that influence postoperative range of motion.
Many factors affect or predict the flexion range achieved after total knee arthroplasty. While the knees that have good preoperative flexion have better final flexion, knees with good preoperative flexion do lose some flexion whereas those with poor preoperative flexion can gain flexion. Although studies of different prosthetic designs have produced conflicting results, recent studies appear to favour posterior cruciate ligament (PCL)--substituting over PCL-retaining prostheses. Several factors related to surgical techniques have been found to be important. These include the tightness of the retained posterior cruciate ligament, the elevation of the joint line, increased patellar thickness, and a trapezoidal flexion gap. Vigorous rehabilitation after surgery appears useful, while continuous passive motion has not been found to be effective. Obesity and previous surgery are poor prognostic factors; certain cultural factors, such as the Japanese style of sitting, offer 'unintentional' passive flexion and result in patients with better range. If the flexion after surgery is unsatisfactory, manipulation under anaesthesia within 3 months of the total knee arthroplasty can be beneficial.
Using a step-by-step procedure, we measured joint gap during surgery using a simple device with a torque meter in 45 osteoarthritis knee joints (43 patients) with varus deformity. The effects of specific cuts or releases of the anatomic portion on joint gaps were investigated. Each cut or release resulted in various increases in the medial gap from 1.2 to 3.8 mm on average. The final gap measurements averaged 24.1 mm medially and 27.6 mm laterally in extension, and 24.6 mm medially and 27.2 mm laterally in flexion. The results of the measurements showed that each step-by-step procedure had a tendency of gap increase. The results led us to measure soft tissue balancing in a step-by-step procedure during total knee arthroplasty.
We investigated the relationship of knee range of motion (ROM) and function in a prospective, observational study of primary total knee arthroplasty (TKA). Preoperative and 12-month data were collected on 684 patients, including knee ROM, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function questionnaire scores, patient satisfaction, and perceived improvement in quality of life (QOL). Only modest correlations were found between knee ROM and WOMAC function (r<0.34). At 12 months we found significantly worse WOMAC function scores for patients with <95 degrees flexion compared with patients with > or =95 degrees (mean, 61.9 vs 75.0; P<.0001). In linear regression models, WOMAC pain and function scores at 12 months were both correlates of patient satisfaction and perceived improvement in QOL (standardized beta>3.5; P<.0001), but knee flexion was not. For assessment of these outcomes, WOMAC function appears to be more important than knee flexion.
Range of motion is a crucial measure of the outcome of total knee arthroplasty. The purpose of this study was to determine which factors are predictive of the postoperative range of motion.
We retrospectively studied 3066 patients (4727 knees) who had a primary total knee arthroplasty with the same type of implant at the same center between 1983 and 1998. Statistical clustering analysis paired with log-linear regression was used to determine groupings along continuous variables. Regression tree analysis was used to characterize the combinations of variables influencing the postoperative range of motion. The variables considered were preoperative and intraoperative flexion and extension, preoperative alignment, age, gender, and soft-tissue releases.
Preoperative flexion was the strongest predictor of the postoperative flexion regardless of preoperative alignment. Other factors that were significantly related to reduced flexion were intraoperative flexion (p < 0.0001), gender (p < 0.0001), preoperative tibiofemoral alignment (p = 0.0005), age (p < 0.0001), and posterior capsular release (p < 0.0001). The removal of posterior osteophytes was related to the greatest increase in postoperative flexion in the group of patients with a varus tibiofemoral alignment preoperatively.
The principal predictive factor of the postoperative range of motion was the preoperative range of motion. Removal of posterior osteophytes and release of the deep medial collateral ligament, the semimembranosus tendon, and the pes anserinus tendon in patients with large preoperative varus alignment and the attainment of a good intraoperative range of motion improved the likelihood that a good postoperative range of motion would be achieved.
Five hundred ninety-eight consecutive primary low contact stress total knee replacements were done in 502 patients between 1985 and 1990. Clinical review was available for 495 knees (406 patients), 228 knees with meniscal-bearing prostheses and 267 knees with rotating-platform prostheses. The average followup was 12 years (range, 10-15 years). The average postoperative knee and functional scores were 87 points and 75 points, respectively. The average postoperative range of motion was 110 degrees. Fifty-six knees (11%) required revision for excessive wear of the tibial insert (41), dislocation (10), patellar polyethylene breakage (one), component loosening (one patellar, one tibial), and infection (two). During revision, osteolysis (20 knees), patellar polyethylene failure (33), and femoral component fracture (one) were seen. The overall survivorship was 88.1% at 15 years using Kaplan-Meier analysis. The survival rate was 83% for the meniscal-bearing prostheses and 92.1% for the rotating-platform prostheses. The Low Contact Stress mobile-bearing knee prosthesis has no superiority over that of fixed-bearing knees, especially for the meniscal-bearing design in prevention of polyethylene failure or revision. Based on the results of this study, the use of the LCS meniscal-bearing prosthesis does not appear to be justified.
Pain-free flexion of as much as 155 degrees with stability is the ultimate goal of total knee replacement (TKR). Achieving this amount of flexion depends on implant design, surgical technique, preoperative range of motion (ROM), and patient cooperation. Current design trends are focusing on shortening the radii of curvature; such shortening, in turn, thickens the posterior femoral condyle, and increases the height of the posterior-stabilized box, both of which require removal of more bone. The end results may be excessive wear, increased patellofemoral complications, and difficult revisions. Several studies have indicated preoperative ROM is more predictive of postoperative ROM than any other criteria, including implant design. Based on currently available information, if full or almost full preoperative ROM is required for the high flex total knee design, few patients would qualify for the high flex TKA.
The evaluation of contact areas and pressures in total knee prosthesis is a key issue to prevent early failure. The first part of this study is based on the hypothesis that the patterns of contact stresses on the tibial insert of a knee prosthesis at different stages of the gait cycle could be an indicator of the wear performances of a knee prosthesis. Contact stresses were calculated for a mobile bearing knee prosthesis by means of finite element method (FEM). Contact areas and stresses were also measured through in vitro tests using Fuji Prescale film in order to support the FEM findings. The second part of this study addresses the long-term structural integrity of metal tibial components in terms of fatigue life by means of experimental tests and FEM simulations. Fatigue experimental evaluations were performed on Cr-Co alloy tibial tray, based on ISO standards. FEM models were used to calculate the stress patterns. The failure risk was estimated with a standard fatigue criterion on the basis of the results obtained from the FEM calculations. Experimental and computational results showed a positive matching.
Correct ligamentous balancing is an important determinant of the clinical outcome in total knee arthroplasty (TKA). Many surgeons prefer a tight rather than a lax knee during implantation of a TKA. The hypothesis in this study was that patients with a slightly laxer knee joint might perform better than patients with a tight knee joint after implantation of a TKA.
Twenty-two patients with bilateral knee arthroplasties were clinically and radiologically evaluated at a mean follow-up of 4.5 years, ranging from 2 to 7 years. There were 12 women and 10 men with an average age of 68.9 years (range 32-82 years) at the time of surgery. A modified HSS score (excluding laxity), varus and valgus stress X-rays in 30 degrees of knee flexion, and the subjective outcome of both knees were compared. A knee was considered tight when it opened less than 4 degrees and lax if it opened 4 degrees or more on stress X-ray.
There was a trend towards improved range of motion and HSS score for the laxer knee joints. However, the difference did not achieve statistical significance. Eleven of the 22 patients considered one side subjectively better than the other side. In 10 out of these 11 TKA, the slacker knee joint was the preferred side ( p<0.05).
As the present study compared bilateral knee joints after TKA, the same patient could act as a control group, and subtle subjective differences were revealed which are not quantifiable. The results showed that patients with a preferred side felt significantly more comfortable on the laxer side, indicating that during intraoperative ligamentous tensioning, some varus and valgus laxity at 20-30 degrees of flexion might be preferable to an over-tight knee joint. Further biomechanical and prospective investigations will be necessary to establish the correct soft-tissue tensioning.
Limitation of motion after knee arthroplasty can be the result of a multiplicity of factors. Among these are malpositioning of the components, especially in the sagittal plane; oversizing at the patellofemoral or tibiofemoral joint spaces; retaining posterior osteophytes; and persisting with a tight posterior cruciate ligament. Postoperatively, problems with physical therapy likewise can cause limitation of both extension and flexion. Specific patient factors also may affect the range of motion after surgery. Although most patients achieve a postoperative flexion that is highly correlated to that which was present preoperatively, factors such as pain, obesity, and deformities of adjacent joints may limit such motion.
Stiffness is an uncommon but disabling problem after total knee arthroplasty. The prevalence of stiffness after knee replacement has not been well defined in the literature. In addition, the outcomes of revision surgery for a stiff knee following arthroplasty have not been evaluated in a large series of patients, to our knowledge. The purposes of this study were to define the prevalence of stiffness after primary total knee arthroplasty and to evaluate the efficacy of revision surgery for treatment of the stiffness.
We defined a stiff knee as one having a flexion contracture of >/=15 degrees and/or <75 degrees of flexion. Two separate groups were evaluated. First, the results of 1000 consecutive primary total knee replacements were reviewed to determine the prevalence of stiffness. Second, the results of fifty-six revisions performed because of stiffness, sometimes associated with pain or component loosening, after primary total knee arthroplasty were evaluated.
The prevalence of stiffness was 1.3%, at an average of thirty-two months postoperatively. The patients with a stiff knee had had significantly less preoperative extension and flexion than did those without a stiff knee (p < 0.0001). There were no significant differences in age, gender, implant design, diagnosis, or the need for lateral release between the patients with and without stiffness. The second cohort, of knees revised because of stiffness, were followed for an average of forty-three months. The mean Knee Society score improved from 38.5 points preoperatively to 86.7 points at the time of follow-up; the mean Knee Society function score, from 40.0 to 58.4 points; and the mean Knee Society pain score, from 15.0 to 46.9 points. The mean flexion contracture decreased from 11.3 degrees to 3.2 degrees, the mean flexion improved from 65.8 degrees to 85.4 degrees, and the mean arc of motion improved from 54.6 degrees to 82.2 degrees. The arc of motion improved in 93% of the knees, and flexion increased in 80%. Extension improved in 63%, and it remained unchanged in 30%.
The prevalence of stiffness in our series of 1000 primary knee arthroplasties was 1.3%. Revision surgery was a satisfactory treatment option for stiffness, as the Knee Society scores improved, the flexion contractures diminished, and 93% of the knees had an increased arc of motion. However, the results suggest that the benefits are modest.
Fluoroscopy has recently been used to analyze postoperative kinematics in total knee arthroplasty (TKA). These analyses have reported varying results even in patients with similar implant design. In addition, patterns of wear in retrieved tibial polyethylene inserts of similar design have been found to vary substantially. These findings suggest that surgical technique, especially soft tissue balancing, may play a role in postoperative kinematics and implant failure. Accurate soft-tissue balancing is hypothesized to result in similar pressures within the medial and lateral compartments of the knee. However, a method of easily measuring these pressures at TKA has not been developed. In the present study, 32 patients were implanted with a mobile-bearing LCS TKA utilizing the balanced gap technique. An electronic pressure sensor, developed specifically to record pressure magnitude and distribution in the medial and lateral compartments, was incorporated into the implant trials. The knee was then passively taken through a range of motion while pressure data was recorded via computer. Postoperatively, 16 patients underwent active fluoroscopic kinematic analysis to assess for condylar liftoff and femorotibial translation. We found that abnormal compartment pressures and distributions as recorded by the intraoperative pressure sensor were correlated with inappropriate or paradoxical postoperative kinematics. In addition, subjects having similar pressures in both compartments throughout a range of motion did not experience condylar liftoff values greater than 1.0 mm. These data suggest that surgical technique influences the magnitude and distribution of forces at the articulation, postoperative kinematics, and likely, implant longevity.
In designing a posterior-stabilized total knee arthroplasty (TKA) it is preferable that when the cam engages the tibial spine the contact point of the cam move down the tibial spine. This provides greater stability in flexion by creating a greater jump distance and reduces the stress on the tibial spine. In order to eliminate edge loading of the femoral component on the posterior tibial articular surface, the posterior femoral condyles need to be extended. This provides an ideal femoral contact with the tibial articular surface during high flexion angles. To reduce extensor mechanism impingement in deep flexion, the anterior margin of the tibial articular component should be recessed. This provides clearance for the patella and patella tendon. An in vivo kinematic analysis that determined three dimensional motions of the femorotibial joint was performed during a deep knee bend using fluoroscopy for 20 subjects having a TKA designed for deep flexion. The average weight-bearing range-of-motion was 125 degrees . On average, TKA subjects experienced 4.9 degrees of normal axial rotation and all subjects experienced at least -4.4 mm of posterior femoral rollback. It is assumed that femorotibial kinematics can play a major role in patellofemoral kinematics. In this study, subjects implanted with a high-flexion TKA design experienced kinematic patterns that were similar to the normal knee. It can be hypothesized that forces acting on the patella were not substantially increased for TKA subjects compared with the normal subjects.
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Range of motion after total knee arthroplasty is an important variable in determining clinical outcome. The goal of this study was to assess range of motion across five types of posterior-stabilized knee prostheses used sequentially in the same institution during 17 years. The hypothesis was that absolute flexion would improve in newer models of this basic prosthesis design. Only primary knee arthroplasties in patients with osteoarthritis were evaluated. A retrospective analysis was done. Three hundred fifty-eight knees with osteoarthritis were reviewed. The average arc of motion was 103 degrees before surgery and 111 degrees after surgery. Absolute flexion was clinically similar but improved from before surgery (110 degrees ) to after surgery (113 degrees ). No difference was found when comparing improvements in range of motion among the different types of prostheses used. This study did not show that any knee system made a difference in determining the final range of motion postoperatively. Height emerged as a predictive factor of absolute flexion. Preoperative range of motion is the most important variable in determining improvements in range of motion, with height playing a secondary role.
Level of evidence:
Prognostic study, Level II-1.
Despite the advanced age of many patients having total knee arthroplasty, previous attempts to quantify patient function postoperatively have not allowed for normal deterioration of musculoskeletal function that occurs with aging. We determined the effects of aging on knee function, thereby providing a realistic level of normal, healthy knee function for patients and surgeons after total knee arthroplasties. A self-administered, validated knee function questionnaire consisting of 55 scaled multiple choice questions was used in this study. Responses were collected from 243 patients at least 1 year after they had total knee arthroplasties, and from 257 individuals (age- and gender-matched) who had no previous history of knee disorders. Many of these latter subjects reported that they could do most of the activities cited in the questionnaire without symptoms attributable to their knees. However, knee symptoms were experienced more frequently during activities that placed greater loads on the extremity. There was no difference in the knee function of men and women, and both groups had continuous deterioration in knee function with increasing age. There were large differences in the functional capacity to do activities involving the knee between the group of patients who had total knee arthroplasties and the age- and gender-matched patients with no previous knee disorders. Overall, 52% of the patients who had total knee arthroplasties reported some degree of limitation in doing functional activities, versus 22% of subjects with no previous knee disorders. Two groups of activities were identified: activities in which the patients and control subjects had essentially similar knee function (swimming, golfing, and stationary biking), and activities in which the function scores of the control group exceeded the scores of the patients who had total knee arthroplasties (kneeling, squatting, moving laterally, turning and cutting, carrying loads, stretching, leg strengthening, tennis, dancing, gardening, and sexual activity). Our data show that many of the limitations reported by patients after total knee arthroplasties are shared by individuals with no previous knee disorders. However, only approximately 40% of the functional deficit present after a total knee arthroplasty seems to be attributable to the normal physiologic effects of aging. Patients who had total knee replacements still experienced substantial functional impairment compared with their age- and gender-matched peers, especially when doing biomechanically demanding activities. This suggests that significant improvements in the procedure and prosthetic designs are needed to restore normal knee function after a total knee arthroplasty.
Wear of the insert backside occurs ostensibly because of micromotion at the undersurface articulation that occurs with loading. When a cyclic axial load was applied to contemporary knee implants, all inserts tested moved 2 to 25 microm in the shear plane relative to the metal backing suggesting that undersurface motion may be inevitable. Variables that increase the forces between the insert and metal backing can worsen relative micromotion and backside wear. Forces at the undersurface articulation, created during physiologic loading, are influenced by insert type, articular design, and surgical technique. Increasing articular insert constraint can cause forces at the main articulation to be resisted and transferred to this and the other interfaces. Designs with a cam post mechanism that force rollback at a certain flexion angle create a significant force in this shear plane. Inserts with highly conforming articular geometries can have a similar affect if used to inhibit anteroposterior or mediolateral motion of the femur on the tibial insert. Component alignment and position, and ligament balance also may influence backside wear as suggested by the great variability of wear patterns seen on like insert retrievals and by kinematic differences observed in fluoroscopic studies of the same implant design. Only by understanding these potential causes of backside motion and subsequent wear, can backside wear be mitigated.
This study examined the kinematics of a cruciate-retaining (CR) total knee arthroplasty (TKA) component that attempts to enhance knee flexion by improving posterior tibiofemoral articular contact at high-flexion angles. Using an in vitro robotic experimental setup, medial and lateral femoral translations of this CR design were compared with that of a conventional CR TKA design and intact knee under a combined quadriceps and hamstring muscle load. Both CR TKA designs showed similar kinematics throughout the range of flexion (0 degrees -150 degrees ). The TKAs restored nearly 80% of the posterior femoral translation of the intact knee at 150 degrees . The posterior cruciate ligament (PCL) forces measured for the high-flexion CR TKA component indicate that the PCL is important in the mid-flexion range but has little effect on knee kinematics at high flexion.
An in vivo comparison of flexion kinematics for posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasty (TKA) was performed. Twenty patients who underwent bilateral paired TKAs were included in this prospective study. Both PCR and PS prostheses were from the same TKA series with comparable surface geometries, and all were implanted by a single surgeon. Of these 20 patients, 3-dimensional kinematics during flexion could be analyzed using a computer model fitting technique in 18 patients. The follow-up period ranged from 18 to 53 months. In the PCR TKA, an anterior femoral translation from 30 degrees to 60 degrees of flexion was observed in the weight-bearing condition. In contrast, flexion kinematics for the PS TKA was characterized by the maintenance of a constant contact position under weight-bearing conditions and posterior femoral rollback in passive flexion.
The functional and clinical results to support the choice whether or not to retain the posterior cruciate ligament (PCL) during total knee arthroplasty have not been gathered and analysed so far. There are at least some trials showing no difference.
To identify the difference in functional, clinical, and radiological outcome between retention and sacrifice of the PCL in total knee arthroplasty in patients with osteoarthrosis and other non-traumatic diseases.
A search was conducted in MEDLINE(Through PubMed; 1966 - March 2004), EMBASE (1980 - March 2004), Cochrane Central Register of Controlled Trials (CENTRAL Issue 2004 - 1), and Current Contents (1996 - March 2004). Also, references of selected articles were checked and citation tracking on the articles selected was performed.
Randomised controlled trials comparing retention to sacrifice of the PCL during total knee arthroplasty with regard to functional, radiological and clinical outcome in patients with osteoarthritis and other non-traumatic diseases were selected by two independent reviewers.
Methodological quality was assessed with the checklist by van Tulder and the Jadad list. Data was collected with a predeveloped form. Meta-analysis was performed with subgroup analyses on age, gender, disease severity, and follow-up time, if allowed by adequate power.
Eight randomised controlled trials were found. Two treatment options were compared against PCL retention: PCL sacrifice without additional stabilisation (post and cam mechanism) (2 studies), and PCL sacrifice with posterior stabilized design (5 studies). One study included all three options. Range of motion was found to be 8.1 degrees higher in the posterior stabilized group compared to the PCL retention group (p=0.01, 95% confidence interval [1.7, 14.5]), although the heterogeneity was high (I(2 )= 66.3%). PCL resection without substituting the PCL with a posterior stabilised prosthesis showed no difference compared to PCL retention (p=0.31, I(2) = 83.2%). On clinical scores, only Hospital for Special Surgery score revealed a significant difference of 1.6 points (p=0.03, 95% confidence interval [-3.1, -0.1]) between PCL retention versus PCL sacrifice and substitution combined favouring the latter group. The necessary subgroup analyses could not be performed for the clinical scores.
These results should be interpreted with caution as the methodological quality of the studies was highly variable. We conclude that there is, so far, no solid base for the decision to either retain or sacrifice the PCL with or without use of a posterior stabilized design during total knee arthroplasty. The technique of PCL retention is difficult because the normal configuration and tension need to be reproduced with ligament tensioners. Knowledge of the technique needs to be improved before it can yield superior results compared to the more straightforward techniques of PCL sacrifice or use of a posterior stabilized design. Also, studies evaluating the effect of both techniques should address the right outcome parameters such as range of motion, contact position, and anterior-posterior stability. Suggestions are given to improve future research on this specific topic of knee arthroplasty.
Retrospective review of 1216 primary total knee arthroplasties (TKAs) to evaluate incidence and predictors of arthrofibrosis, defined as flexion less than 90 degrees 1 year post-TKA. Incidence of stiffness post-TKA was 3.7% (45/1216). A matched case-control study was then conducted to identify predictive factors for this outcome. Preoperative flexion and intraoperative flexion were predictive of ultimate postoperative flexion (P = .001 and P = .039, respectively). There was no correlation between postoperative stiffness and specific medical comorbidities, including diabetes. Preoperative and postoperative relative decreased patellar height and stiffness postoperative were significantly correlated (P = .001). Although stiffness post-TKA is multifactorial, careful attention to surgical exposure, restoring gap kinematics, minimizing surgical trauma to the patellar ligament/extensor mechanism, appropriate implant selection, and physiotherapy combined with a well-motivated patient may all serve to reduce the incidence of stiffness post-TKA.
Total knee arthroplasty imposes abnormal tension on local soft tissues
- Nicholls Rl Bo Jeffcote
- Kuster
- Ms
Nicholls RL, Jeffcote BO, Kuster MS. 2005. Total knee arthroplasty imposes abnormal tension on local soft tissues. In: Cavanagh PR, editor. Proceedings of the XXth Congress of the International Society of Biomechanics, July 31–August 5, Cleveland, OH, Ohio State University.
Proceedings of the XXth Congress of the International Society of Biomechanics, July 31–August 5, Cleveland, OH, Ohio State University
- Nicholls RL
- Jeffcote BO
- Kuster MS
Daniel's knee injuries: ligament & cartilage structure, function, injury & repair
- Hogervorst T
- Brand RA