Tibiofemoral kinematic analysis of kneeling after total knee arthroplasty

Some surgeons warn against kneeling after total knee arthroplasty (TKA), because limited clinical data exist. We describe the tibiofemoral contact position of TKA components during kneeling in vivo. Ten posterior-substituting (PS) and 10 cruciate-retaining (CR) designs were examined using a radiographic image-matching technique. Movement from standing to kneeling at 90 degrees produced different responses. CR knees translated anteriorly (medial, 4 +/- 4 mm; lateral, 2 +/- 6 mm). PS knees underwent little posterior translation (medial, 0.2 +/- 3 mm; lateral, 1 +/- 4 mm). Movement from 90 degrees to maximum flexion produced femoral posterior translation (CR medial, 5 +/- 4 mm; CR lateral, 5 +/- 4 mm; PS medial, 6 +/- 4 mm; PS lateral, 6 +/- 3 mm). The relationship between tibiofemoral contact position and flexion angle was more variable for CR (r2=.38) than for PS (r2=.64). Knee kinematics was similar to other deep-flexion weight-bearing activities.     

In vivo kneeling biomechanics after posterior stabilized total knee arthroplasty

Background Kneeling is one of the activities sought by patients after total knee arthroplasty (TKA). This study investigated the six degrees of freedom (DOF) kinematics and three-dimensional (3D) contact during weight-bearing kneeling. Methods A total of 16 South Korean female patients (22 knees) after posteriorly stabilized (PS) TKA (LPS-Flex) were randomly recruited and had the same surgeon. The patients were imaged using a dual fluoroscopic technique while they kneeled from initial to maximum flexion. The acquired images and 3D models were then used to recreate the in vivo pose of the components. Contact was determined by locating the surface intersections in the tibiofemoral and cam/post (between the femoral cam and tibial post) articular compartments. Results Patients flexed, on average, from 107.3° to 128.0° during the kneeling activity. Changes in kinematics included 1.0 mm of proximal, 0.9 mm of medial, and 7.6 mm of posterior translation and 1.7° of varus rotation (P < 0.04). A difference in internal tibial rotation was not detected. Articular contact moved posteriorly by 5.9 mm and 6.4 mm in the medial and lateral compartments, respectively. Contact also moved medially by 3.2 mm and 5.8 mm in the medial and lateral compartments. A decrease in articular contact was observed in both condyles, and lateral condylar lift-off increased with flexion (P = 0.0001). More than 80% of the patients demonstrated cam/post engagement, which always occurred in the distal portion of the post. Conclusions In this patient cohort, the knee joint was constrained during the weight-bearing activity such that femoral subluxation and dislocation were not observed. Furthermore, posterior cam/post engagement occurred only in the distal portion of the tibial post, which may improve the longevity of the post. The tibiofemoral and cam/post articular contact data presented in this study further suggest that kneeling may be performed by patients after clinically successful PS TKA who feel comfortable with the activity and are free of pain.     

Detrimental kinematics of a flat on flat total condylar knee arthroplasty

Fourteen subjects having a flat on flat condylar posterior cruciate retaining total knee arthroplasty were evaluated under different in vivo weightbearing conditions, with six performing a deep knee bend and eight walking at normal gait. An interactive model fitting algorithm was used to convert two-dimensional fluoroscopic images into three-dimensional computer aided design solid model images. The femorotibial contact positions for the medial and lateral condyle started posterior at full extension. With a deep knee bend the lateral condyle acted as a pivot, and the medial condyle slid in the anterior direction. Five of six had lateral condyle liftoff (maximum 1.6 mm) and abnormal positive screw home motion was seen from 0 degree to 90 degrees flexion. During gait, all femorotibial contact positions were posterior in extension and throughout the cycle. Six of eight patients experienced lateral condyle liftoff (maximum 3.5 mm), but minimal screw home motion was seen. Abnormal medial condyle posteroanterior sliding, lateral condyle liftoff, and erratic screw home motion may be related to abnormal wear characteristics of this flat on flat condylar design.     

Anterior tibial post impingement in a posterior stabilized total knee arthroplasty.

Despite the numerous long-term success reports of posterior stabilized (PS) total knee arthroplasty (TKA), recent retrieval studies of various PS TKA designs revealed wear and deformation on the anterior side of the tibial post. This study investigated the mechanisms of anterior impingement of the post with the femoral component. Seven cadaveric knees were tested to study kinematics and tibial post biomechanics during simulated heel strike using an in vitro robotic testing system. Intact knee kinematics and in situ anterior cruciate ligament (ACL) forces were determined at hyperextension (0 degree to -9 degrees) and low flexion angles (0 degrees to 30 degrees) under the applied loads. The same knee was reconstructed using a PS TKA. The kinematics and the tibial post contact forces of the TKA were measured under the same loading condition. The ACL in the intact knee carried load and contributed to knee stability at low flexion angles and hyperextension. After TKA, substantial in situ contact forces (252.4 +/- 173 N at 9 degrees of hyperextension) occurred in the tibial post, indicating anterior impingement with the femoral component. Consequently, the TKA showed less posterior femoral translation compared to the intact knee after the impingement. At 9 degrees of hyperextension, the medial condyle of the intact knee translated 0.1 +/- 1.1 mm whereas the medial condyle of the TKA knee translated 5.6 +/- 6.9 mm anteriorly. The lateral condyle of the intact knee translated 1.5 +/- 1.0 mm anteriorly whereas the lateral condyle of the TKA knee translated 2.1 +/- 5.8 mm anteriorly. The data demonstrated that anterior tibial post impingement functions as a substitute for the ACL during hyperextension, contributing to anterior stability. However, anterior post impingement may result in additional polyethylene wear and tibial post failure. Transmitted impingement forces might cause backside wear and component loosening. Understanding the advantages and disadvantages of the tibial post function at low flexion angles may help to further improve component design and surgical techniques and thus enhance knee stability and component longevity after TKA.     

Effects of the Medial Plateau Bearing Insert Conformity on Mid-Flexion Paradoxical Motion in a Posterior-Stabilized Total Knee Arthroplasty Design

BackgroundOne of the most common kinematic abnormalities reported for posterior-stabilized (PS) total knee arthroplasty (TKA) design is paradoxical anterior sliding during early and mid-flexion. PS TKAs have been designed such that the cam-post mechanism does not engage until later in flexion, making these implants vulnerable to anterior sliding during early and mid-flexion. The objective of this study is to investigate the biomechanical effect of increasing bearing conformity on a PS TKA.MethodsUsing a validated computational model of the knee joint, the sagittal conformity of the medial plateau of a PS TKA design was altered. Three scenarios were created and evaluated for mechanics: (1) baseline conformity, (2) increased conformity, and (3) decreased conformity.ResultsFrom full extension to approximately 70° of knee flexion, the medial condyle demonstrated minimal anterior sliding for the increased medial conformity design but revealed anterior sliding of 2 and 4 mm for the baseline and decreased conformity designs, respectively. After cam-post engagement, the medial condyle consistently rolled back for all 3 designs. The lateral condyle experienced consistent rollback throughout the entire flexion range for all 3 designs. However, femorotibial contact force was higher for the increased conformity design, peaking at 3.13 times body weight (×BW) compared to 3.0 × BW contact force for other 2 designs.ConclusionIncreasing medial conformity of the bearing insert appears to reduce mid-flexion sliding for PS TKA designs, although this comes at the expense of increased femorotibial forces. This could be due to kinematic conflicts that may be introduced with highly constraining designs.     

In vivo kinematic comparison of posterior cruciate-retaining and posterior stabilized total knee arthroplasties under passive and weight-bearing conditions

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.     

Kinematic comparison of posterior cruciate sacrifice versus substitution in a mobile bearing total knee arthroplasty

Interest in mobile bearing total knee arthroplasty (TKA) has increased significantly. The objective of this in vivo study was to analyze 2 different mobile bearing TKAs during gait and during a knee bend from 0 degrees to 90 degrees flexion. Femorotibial contact positions for 10 subjects, implanted by a single surgeon, were analyzed using videofluoroscopy. Five subjects were implanted with a posterior-stabilized mobile bearing TKA (PS), and 5 subjects were implanted with a posterior cruciate-sacrificing mobile bearing TKA (PCS). Each subject, while under fluoroscopic surveillance, performed 2 weight-bearing activities: i) normal gait and ii) deep-knee bend. This study showed that the kinematic patterns for subjects having either a PS or PCS mobile bearing TKA were similar during gait but different during a deep-knee bend. Subjects having a PS TKA experienced more posterior femoral rollback of the lateral condyle during the deep-knee bend. Findings of kinematic similarities in gait and differences in a deep-knee bend between these 2 mobile bearing designs are similar to previously published findings of fixed bearing posterior cruciate-retaining and PS TKA.     

Magnetic resonance image analysis of meniscal translation and tibio‐menisco‐femoral contact in deep knee flexion

The purpose of this study was to clarify meniscal displacement and cartilage–meniscus contact behavior in a full extension position and a deep knee flexion position. We also studied whether the meniscal translation pattern correlated with the tibiofemoral cartilage contact kinematics. Magnetic resonance (MR) images were acquired at both positions for 10 subjects using a conventional MR scanner. Subjects achieved a flexion angle averaging 139° ± 3°. Both medial and lateral menisci translated posteriorly on the tibial plateau during deep knee flexion. The posterior translation of the lateral meniscus (8.2 ± 3.2 mm) was greater than the medial (3.3 ± 1.5 mm). This difference was correlated with the difference in tibiofemoral contact kinematics between medial and lateral compartments. Contact areas in deep flexion were approximately 75% those at full extension. In addition, the percentage of area in contact with menisci increased significantly due to deep flexion. Our results related to meniscal translation and tibio‐menisco‐femoral contact in deep knee flexion, in combination with information about force and pressure in the knee, may lead to a better understanding of the mechanism of meniscal degeneration and osteoarthritis associated with prolonged kneeling and squatting. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:673–684, 2008     

Kinematic analysis of kneeling in cruciate‐retaining and posterior‐stabilized total knee arthroplasties

Kneeling is an important function of the knee for many activities of daily living. In this study, we evaluated the in vivo kinematics of kneeling after total knee arthroplasty (TKA) using radiographic based image‐matching techniques. Kneeling from 90 to 120° of knee flexion produced a posterior femoral rollback after both cruciate‐retaining and posterior‐stabilized TKA. It could be assumed that the posterior cruciate ligament and the post‐cam mechanism were functioning. The posterior‐stabilized TKA design had contact regions located far posterior on the tibial insert in comparison to the cruciate‐retaining TKA. Specifically, the lateral femoral condyle in posterior‐stabilized TKA translated to the posterior edge of the tibial surface, although there was no finding of subluxation. After posterior‐stabilized TKA, the contact position of the post‐cam translated to the posterior medial corner of the post with external rotation of the femoral component. Because edge loading can induce accelerated polyethylene wear, the configuration of the post‐cam mechanism should be designed to provide a larger contact area when the femoral component rotates. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:435–442, 2008     

Functional comparison of posterior cruciate-retaining versus posterior stabilized total knee arthroplasty

A prospective, randomized comparison of posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasties (TKAs) was conducted in 20 patients who underwent bilateral TKAs for osteoarthritis. All procedures were performed by a single surgeon. One knee was implanted with a PCR TKA, and a contralateral knee with a PS TKA. Both prosthetic designs were of the same TKA series, with comparable surface geometries. Patients had a clinical and radiographic evaluation at a mean of 31.7 months for PCR TKAs and 30.6 months for PS TKAs postoperatively. There were no significant differences between the PCR and PS TKAs in postoperative knee scores. However, postoperative improvement in range of motion was significantly superior in the PS group.     

Posterior condylar offset and flexion in posterior cruciate-retaining and posterior stabilized TKA

Background Anterior tibial translation associated with posterior impingement has been reported to be one of the factors limiting flexion after posterior cruciate-retaining (CR) total knee arthroplasty (TKA), especially when posterior condylar offset is decreased postoperatively. On the other hand, its effect on postoperative motion in posterior-stabilized (PS) TKA remains unknown. It has been demonstrated that PS TKA exhibits a consistent posterior femoral rollback during flexion. Thus, we hypothesized that the problem of posterior impingement can be avoided by use of PS TKA. In this study, we examined the relationship between postoperative posterior condylar offset and knee flexion in CR and PS TKAs. Methods In this study, analysis was performed for 20 subjects who underwent bilateral TKAs (one CR and one PS TKA) as well as another group of 50 PS TKAs. All patients could be tracked for a minimum of 2 years. The range of flexion was measured before operation and at follow-up. Preoperative and postoperative posterior condylar offset was evaluated on true lateral radiographs. Results At the follow-up examination, the mean flexion angle was 123° in the CR knees and 131° in the PS knees with a significantly greater improvement observed for the latter group. In the roentgenographic measurement of the posterior condylar offset, no significant difference was observed between the preoperative and postoperative values both in the CR and PS knees. We divided the patients into two groups according to the change of posterior condylar offset. The first group (Group I) showed a decrease in the posterior condylar offset after surgery and the second group (Group II) showed no change or an increase. Subsequently, postoperative change in flexion was compared between Groups I and II for the CR and PS knees. A significant difference between Groups I and II was observed in the CR knees, while no difference was observed in the PS knees. The magnitude of postoperative posterior condylar offset did not correlate with an improvement in maximum flexion angle in the 50 PS knees. Conclusions It was shown that the magnitude of posterior condylar offset correlated with a postoperative change in flexion angle in CR knees, while no such correlation was observed in PS knees.     

固定平台后稳定型假体全膝关节置换术后的运动学研究

 目的 探讨固定平台后稳定型假体全膝关节置换(total knee arthroplasty,TKA)术后膝关节在负重屈膝下蹲时的运动学特征。方法 选取10名健康志愿者和10例固定平台后稳定型假体TKA术后患者。制作骨骼及膝关节假体三维模型,在持续X线透视下完成负重下蹲动作,膝关节屈曲度每增加15°截取一幅图像。通过荧光透视分析技术完成三维模型与二维图像的匹配,再现股骨与胫骨在屈膝过程中的空间位置,通过连续的图像分析比较正常与固定平台后稳定型假体TKA术后膝关节在负重下蹲时股骨内、外髁前后移动及胫骨内外旋转幅度。结果 负重下蹲时,正常膝关节平均屈曲136°,股骨内、外髁分别后移(7.3±1.2) mm和(19.3±3.1) mm,胫骨平均内旋23.8°±3.4°;TKA术后膝关节平均屈曲125°,股骨内、外髁分别后移(1.4±1.6) mm和(6.4±1.7) mm,胫骨平均内旋8.5°±3.4°。结论 固定平台后稳定型假体TKA术后膝关节运动与正常膝关节相似,均表现出股骨内、外髁后移及胫骨内旋运动,但幅度小于正常膝关节,且在屈膝过程中存在股骨矛盾性前移及胫骨外旋现象。     

In vivo comparison of knee kinematics for subjects having either a posterior stabilized or cruciate retaining high-flexion total knee arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112 degrees of weight-bearing (WB) flexion, -6.4 mm of posterior femoral rollback, and 2.9 degrees of axial rotation. The CR subjects averaged 117 degrees of WB flexion, -4.9 mm of posterior femoral rollback, and 4.8 degrees of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.     

Evaluation of joint laxity against distal traction force upon flexion in cruciate-retaining and posterior-stabilized total knee arthroplasty

Background  Several studies have reported varus-valgus stability in the extension position after total knee arthroplasty (TKA). However, few studies have evaluated joint laxity in the flexion position postoperatively. The purpose of the study was to evaluate joint laxity against distal traction force on flexion after cruciate-retaining and posterior-stabilized total knee arthroplasties. Methods  A total of 44 knees (22 knees cruciate-retaining, 22 knees posterior-stabilized) in 40 patients with osteoarthritis were tested in this study. The subjects were seated at a table and their knee joints were fixed at 80° of flexion to avoid overlapping images of condyles and the femoral shaft. Tibial shafts were adjusted to be parallel to the radiographic films, and posteroanterior radiographs were obtained. Flexion stress tests were performed with a distal traction of 100 N at a neutral foot position. Radiographs were obtained at neutral and traction positions. The distance from the perpendicular line of the top of the polyethylene insert to the midpoint on the tangential line of the femoral condyle was measured (joint space distance) at each side. Results  In the flexion-neutral position, average joint space distances were 0.1 ± 0.2 mm in cruciate-retaining (CR) TKA knees and 0.2 ± 0.3 mm in posterior-stabilized (PS) TKA knees. With flexion-traction stress tests, the average joint space distances were 0.5 ± 0. 5 mm in CR TKA knees 2.4 ± 1.2 mm in PS TKA knees. Average changes of joint space distances between the two positions were 0.3 ± 0.4 mm (CR TKA) and 2.2 ± 1.5 mm (PS TKA). The changes in joint space distances between neutral and traction positions of PS TKA knees were significantly larger than those of CR TKA knees in flexion stress tests (P < 0.01). Conclusion  The posterior cruciate ligament acted as a stabilizer against distal traction force in the CR-TKA knees. However, the laxity of PS-TKA knees against distal force differed among individual cases.     

膝骨关节炎患者股骨后髁软骨磨损差异对人工全膝关节置换术中股骨假体旋转定位的影响

目的通过测量膝骨关节炎患者股骨内、外侧后髁软骨厚度以及后髁角(posterior condylar angle,PCA),探讨其对人工全膝关节置换(total knee arthroplasty,TKA)术中截骨的影响。方法选择2011年5月-12月拟行TKA治疗的53例(60膝)膝骨关节炎患者作为研究对象(骨关节炎组),男12例(14膝),女41例(46膝);年龄57～82岁,平均71.9岁。胫股角为(183.2±2.6)°。以15例(30膝)健康志愿者膝关节作为对照(对照组),男6例,女9例;年龄59～68岁,平均66.3岁。将MRI扫描膝关节获得数据导入Mimics10.01交互式医学影像控制系统,测量内、外侧股骨后髁软骨厚度和包括与不包括后髁软骨时的PCA,进行统计学分析。结果对照组股骨内、外侧后髁软骨厚度分别为(1.85±0.33)mm及(1.92±0.27)mm,包括与不包括后髁软骨时的PCA分别为(5.0±0.9)°和(5.1±0.8)°,差异均无统计学意义(P>0.05)。骨关节炎组股骨内、外侧后髁软骨厚度分别为(0.45±0.40)mm及(1.78±0.51)mm,包括与不包括后髁软骨时的PCA分别为(3.3±1.7)°和(4.8±1.8)°,差异均有统计学意义(P<0.05)。骨关节炎组股骨内、外侧后髁软骨厚度差为(1.33±0.45)mm,与包括与不包括后髁软骨时的PCA角度差(1.5±1.3)°成正相关(r=0.75,P=0.01)。结论膝骨关节炎患者股骨后髁软骨磨损程度存在差异,导致内、外侧后髁软骨厚度和包括与不包括后髁软骨时的PCA存在差异,TKA术中行截骨时,应将股骨后髁软骨厚度差异纳入考虑范围内。     

Comparison of Contact Kinematics in Posterior-Stabilized and Cruciate-Retaining Total Knee Arthroplasty at Long-Term Follow-Up

BackgroundThere is controversy regarding the superiority of posterior-stabilizing (PS) total knee arthroplasty (TKA) and cruciate-retaining (CR) TKA. Substantial work has made comparisons between PS and CR TKA at follow-ups of less than 5 years. It was the goal of the present study to compare the kinematics at greater than 5 years postoperatively between CR and PS TKA, with a secondary goal of comparing patient function.MethodsA total of 42 knees were investigated, with equal representation in the PS and CR TKA groups. Patients underwent radiostereometric analysis imaging at 0°, 20°, 40°, 60° 80°, and 100° of flexion. Contact position, magnitude of excursion, and condylar separation on each condyle were measured. A Timed-Up-and-Go functional test was also performed by patients, with the total test time being measured. Preoperative and postoperative clinical outcome scores were also collected.ResultsThere were differences in contact position on both the medial and lateral condyles at multiple angles of flexion (P < .05). There was no difference (P = .89) in medial excursion; however, PS TKA had greater lateral excursion than CR TKA (P < .01). No difference (P > .99) was found in frequency of condylar separation. PS TKA was associated with faster (P = .03) total Timed-Up-and-Go test times. There were no differences in clinical outcome scores between the groups preoperatively or postoperatively.ConclusionWe found kinematic and functional differences that favor PS TKA. Our results suggest posterior cruciate ligament insufficiency in CR TKA, indicating that perhaps the cam/post systems in PS TKA better maintain knee kinematics and function long term.     

In-vivo kinematics of high-flex posterior-stabilized total knee prosthesis designed for Asian populations

Purpose

The purpose of this study was to determine in-vivo kinematics of our developed posterior-stabilized (PS) total knee prosthesis for Asian populations in comparison with a popular high-flexion PS prosthesis.

Methods

We analyzed 62 osteoarthritic knees: 31 knees with the new PS prosthesis (group A) and 31 knees with a popular high-flexion PS prosthesis (group B). Radiographic knee images were taken during standing, lunge, and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-based shape matching techniques.

Results

Group A showed slightly greater implant flexion angles compared with knees with conventional prosthesis at maximum lunge (average: 119 vs. 110°, p?=?0.001), and at maximum kneeling (121 vs. 114°, p?=?0.004), although the range of motion was not significantly different. The femoral centre positions were more posterior in group A at standing, at 90° lunge, at maximum lunge (-9 and -7 mm, p?=?0.004), at 90° kneeling, and at maximum kneeling (-9 vs. -7 mm, p?=?0.016), and posterior translations of the femoral center were greater at 90° knee flexion postures. The femoral centre positions had a strong negative correlation with implant flexion angles at maximum lunge in group B (r?=?-0.893, p?<?0.001), but not in group A (p?=?0.242).

Conclusions

The new PS prosthesis designed for Asian knee morphology achieved flexion angles and range of motion at least comparable to that of conventional high-flexion PS prosthesis. The femoral roll-back pattern, however, is different from a conventional knee, reflecting the post/cam design.

     

A recession of posterior cruciate ligament in posterior cruciate-retaining total knee arthrosplasty

The range of motion, the stability of the knee, and the prevalence of radiolucent lines in 68 posterior cruciate-retaining (CR) total knee arthroplasties (TKAs) with a retained, but balanced, posterior cruciate ligament were compared with those in 68 knees with a posterior cruciate-substituting (PS) TKAs in the 60 patients who were managed with simultaneous bilateral TKAs. The average range of motion in both groups (126 degrees vs 129 degrees) at the latest follow-up was not significantly different (P = .359). No significant difference in the sagittal laxity of the knee was seen between 2 groups. The prevalence of radiolucent lines was 7% in the CR TKA with a recession posterior cruciate ligament and 12% in the PS TKA group (P = .108). We feel that posterior stabilization is unnecessary in the PS flex knees.