Biomechanical comparison of fixed‐ and mobile‐bearing for unicomparmental knee arthroplasty using finite element analysis

Unicomparmental knee arthroplasty (UKA) is a popular alternative to total knee arthroplasty (TKA) and high tibial osteotomy for unicompartmental knee conditions, especially in young patients. However, failure of UKA occurs due to either progressive osteoarthritis (OA) in the other compartment or wear on the polyethylene (PE) insert. This study used finite element (FE) analysis to investigate the effects of PE insert contact pressure and stress in opposite compartments for fixed‐ and mobile‐bearing UKA. Analysis was performed using high kinematics displacement and rotation inputs, which were based on the kinematics of the natural knee. ISO standards were used for axial load and flexion. The mobile‐bearing PE insert had lower contact pressure than the fixed‐bearing PE insert. With the mobile‐bearing UKA, lower stress on the opposite compartment reduces the overall risk of progressive OA in the knee. The fixed‐bearing UKA increases the overall risk of progressive OA in the knee due to higher stress on the opposite compartment. However, the PE insert of mobile‐bearing showed pronounced backside stress at the inferior surface. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:338–345, 2014.     

Importance of joint line preservation in unicompartmental knee arthroplasty: Finite element analysis

Unicompartmental knee arthroplasty (UKA) is an effective surgical technique for pain relief and functional restoration in patients with localized osteoarthritis of the knee joint. However, the role of the joint line in UKA, especially its biomechanical effect, has not been previously investigated. This study numerically evaluates the effects of the joint line on the contact stresses in polyethylene (PE) inserts, articular cartilage, and lateral meniscus using the finite element (FE) analysis. The FE model for joint line was modeled as the orthogonal projection line from the medial tibial plateau to the anatomical axis. The joint line was varied from −6 to +6 mm in 2 mm intervals, and the seven FE models were analyzed and compared under ISO gait loading conditions. The contact stresses in the PE insert, articular cartilage, and lateral meniscus matched those of the reference joint line (0 mm) in the ±2 and ±4 mm joint line cases but significantly differed from the reference in the ±6 mm joint line cases. On the +6 mm joint line, the contact stress was greater on the PE insert than on the articular cartilage, whereas the reverse occurred on the −6 mm joint line. This study confirms the post‐operative significance of joint line preservation in UKA implantation surgery. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:347–352, 2017.

     

Multicenter determination of in vivo kinematics after total knee arthroplasty

A summation analysis of more than 70 individual kinematic studies involving normal knees and 33 different designs of total knee arthroplasty (TKA) was done with the objective of analyzing implant design variables that affect knee kinematics. Eight hundred eleven knees (733 subjects) were analyzed either during the stance phase of gait or a deep knee bend maneuver while under fluoroscopic surveillance. Fluoroscopic videotapes then were downloaded onto a workstation computer and anteroposterior (AP) femorotibial translational patterns were determined using an automated three-dimensional model fitting technique. The highest magnitude of translation was found in the normal and ACL-retaining TKA groups. Paradoxical anterior femoral translation during deep flexion was most commonly observed in PCL-retaining TKA. Substantial variability in kinematic patterns was observed in all groups. The least variability during gait was observed in mobile-bearing TKA designs, whereas posterior-stabilized TKA designs (fixed or mobile-bearing) showed the least variability during a deep knee bend. A medial pivot kinematic pattern was observed in only 55% of knees during deep knee flexion. Kinematic patterns of fixed versus mobile-bearing designs were similar with the exception of mobile-bearing TKA during gait in which femorotibial contact remained relatively stationary with minimal AP femorotibial translation.     

Edge loading of patellar components after total knee arthroplasty.

Patellofemoral joint kinematics, contact areas, contact pressures, and contact patterns were assessed after total knee arthroplasty (TKA) using human cadaver knees. Two contemporary TKA systems with anatomic patellofemoral joints were implanted and tested under anatomically based loading conditions. An electromagnetic tracking system was used to evaluate patellofemoral kinematics, and Fuji pressure-sensitive film was used to determine contact areas, pressures, and patterns. Edge loading of patellar components was observed at higher knee flexion angles with both TKA systems. Peak contact pressures seen at the regions of edge loading exceeded the yield strength of ultra-high-molecular weight polyethylene. Efforts to reduce edge loading and contact pressures may decrease the incidence of patellofemoral joint complications and component failure after TKA.     

Effects of knee simulator loading and alignment variability on predicted implant mechanics: a probabilistic study.

Inherent variability in total knee arthroplasty loading and alignment, present in vivo and in simulator testing, may ultimately influence polyethylene tibial insert wear and long-term performance. The effect of this variability was quantified on implant kinematics and contact mechanics during simulated gait loading conditions using semi-constrained and unconstrained fixed bearing, cruciate retaining implants. A probabilistic finite element model of the Stanmore knee wear simulator was utilized to estimate the envelope of anterior-posterior (AP) and internal-external (IE) position and contact pressure and to evaluate the variability in corresponding ranges of motion (ROM). Variability levels were represented by standard deviations of up to 10% of the maximum value for load inputs and 0.25 mm and 0.5 degrees for component alignment inputs. Model predictions compared well with experimental simulator results for the semi-constrained implant, with predicted positional envelopes of up to 1.8 mm (AP) an 3.4 degrees (IE) for the semi-constrained and up to 2.6 mm (AP) and 3.7 degrees (IE) for the unconstrained implant at the variability levels evaluated. ROM varied by up to 22%, while peak contact pressure variations averaged less than 2 MPa for both designs. For each implant, loading variability was more influential during the swing phase of gait, while alignment variability affected kinematics more during stance. The relative rank of sensitivities showed differences between the two designs, providing insight into critical parameters affecting kinematics and contact characteristics.     

Changed gait pattern in patients with total knee arthroplasty but minimal influence of tibial insert design

Introduction Previous radiostereometric studies have revealed abnormal anterior-posterior translation of the femur in patients operated with AMK (DePuy, Johnson and Johnson, Leeds, UK) total knee arthroplasty (TKA). Based on these observations, we hypothesized that patients with TKA have an abnormal gait pattern, and that there are differences in kinematics depending on the design of the tibial joint area.

Method We used a gait analysis system to evaluate the influence of joint area design on the kinematics of the hip and knee during level walking. 39 TKA patients (42 knees) and 18 healthy age-matched controls were studied. Patients with 5° varus/valgus alignment or less were randomized to receive either a relatively flat or a concave tibial insert with retention of the posterior cruciate ligament. Patients who had more than 5° varus-valgus alignment and/or extension defect of 10° or more were randomized to receive the concave or a posterior-stabilized tibial component with resection of the posterior cruciate ligament.

Results Patients with TKA tended to have less hip and knee extension and decreased knee and hip extension moment than controls. They also tended to walk more slowly. TKA altered the gait pattern, but choice of implant design had little influence.

Interpretation In patients with a similar degree of degenerative joint disease and within the limits of the constraints offered by the prostheses under study, the choice of joint area constraint has little influence on the gait pattern.     

垫片改良设计对膝关节置换术后临床功能和膝关节运动的影响

目的 探讨膝关节假体垫片设计对膝关节置换术后临床功能和膝关节运动学的影响.方法 分析2007年7月至2009年6月使用GENESIS Ⅱ假体行全膝关节置换术的28例膝关节骨关节炎患者的临床资料,共42膝,平均随访27.7个月.按照使用垫片的种类分为高屈曲垫片组(男性1例,女性14例,23膝;年龄54～74岁,平均62.8岁)和标准组(男性1例,女性12例,19膝;年龄54～74岁,平均64.3岁).通过膝关节评分比较两组的临床功能.采用循环透视和软件分析的方法比较两组病例在膝关节屈伸活动时股骨后滚、伸膝装置力臂等参数,评价垫片设计对膝关节运动的影响.结果 标准组和高屈曲垫片组的术后活动度分别为120°和123°,差异无统计学意义.两组在膝关节学会评分上没有差异.高屈曲垫片组术后的Feller评分高于标准组,差异有统计学意义(P=0.012).在影像学测量上,两组病例在0～120°范围活动时股骨后滚和伸膝装置力臂的差异均无统计学意义;活动范围达到130°时,两组的伸膝装置力臂差异有统计学意义(P=0.034).结论 高屈曲垫片的改良设计在减少膝关节置换术后膝前痛的发生、改善膝关节功能方面有一定的作用;但可能会减小伸膝装置的力臂,从而影响股四头肌的做功.     

Bi‐Cruciate Retaining Total Knee Arthroplasty Does Not Restore Native Tibiofemoral Articular Contact Kinematics During Gait

Bi‐cruciate retaining (BCR) total knee arthroplasty (TKA) design preserves both anterior and posterior cruciate ligaments with the potential to restore normal posterior femoral rollback and joint kinematics. Abnormal knee kinematics and “paradoxical” anterior femoral translation in conventional TKA designs have been suggested as potential causes of patient dissatisfaction. However, there is a paucity of data on the in vivo kinematics and articular contact behavior of BCR‐TKA. This study aimed to investigate in vivo kinematics, articular contact position, and pivot point location of the BCR‐TKA during gait. In vivo kinematics of 30 patients with unilateral BCR‐TKA during treadmill walking was determined using validated dual fluoroscopic imaging tracking technique. The BCR‐TKA exhibited less extension than the normal healthy knee between heel strike and 48% of gait cycle. Although the average external rotation trend observed for BCR TKA was similar to the normal healthy knee, the range of motion was not fully comparable. The lowest point of the medial condyle showed longer anteroposterior translation excursion than the lateral condyle, leading to a lateral‐pivoting pattern in 60% of BCR TKA patients during stance phase. BCR‐TKA demonstrated no statistical significant differences in anterior–posterior translation as well as varus rotation, when compared to normal healthy knees during the stance phase. However, sagittal plane motion and tibiofemoral articular contact characteristics including pivoting patterns were not fully restored in BCR TKA patients during gait, suggesting that BCR TKA does not restore native tibiofemoral articular contact kinematics. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1929–1937, 2019     

Changed gait pattern in patients with total knee arthroplasty but minimal influence of tibial insert design: gait analysis during level walking in 39 TKR patients and 18 healthy controls

INTRODUCTION: Previous radiostereometric studies have revealed abnormal anterior-posterior translation of the femur in patients operated with AMK (DePuy, Johnson and Johnson, Leeds, UK) total knee arthroplasty (TKA). Based on these observations, we hypothesized that patients with TKA have an abnormal gait pattern, and that there are differences in kinematics depending on the design of the tibial joint area. METHOD: We used a gait analysis system to evaluate the influence of joint area design on the kinematics of the hip and knee during level walking. 39 TKA patients (42 knees) and 18 healthy age-matched controls were studied. Patients with 5 degrees varus/valgus alignment or less were randomized to receive either a relatively flat or a concave tibial insert with retention of the posterior cruciate ligament. Patients who had more than 5 degrees varus-valgus alignment and/or extension defect of 10 degrees or more were randomized to receive the concave or a posterior-stabilized tibial component with resection of the posterior cruciate ligament. RESULTS: Patients with TKA tended to have less hip and knee extension and decreased knee and hip extension moment than controls. They also tended to walk more slowly. TKA altered the gait pattern, but choice of implant design had little influence. INTERPRETATION: In patients with a similar degree of degenerative joint disease and within the limits of the constraints offered by the prostheses under study, the choice of joint area constraint has little influence on the gait pattern.     

Which one restores in vivo knee kinematics effectively-medial or lateral pivot?

IntroductionTotal knee arthroplasty (TKA) usually provides good pain relief and improved function but has generally been unable to fully restore normal knee kinematics. Does Medial or Lateral Pivot TKA designs guide us to native knee kinematics needs to be elucidated?MethodsKinematic assessment of 13 knees with Medial Pivot TKA and 13 knees with Lateral Pivot TKA was done. The subjects were asked to perform step-up and weight bearing deep knee bend exercise under fluoroscopy for kinematic assessment. Patellar Tendon Angle (PTA) was measured after correcting f luoroscopic images for distortion against Knee Flexion Angle (KFA).ResultsDuring the weight bearing deep knee bend, the average active maximum flexion achieved with Medial Pivot design was 113.8 ͦ as compared to 102.9 ͦ with Lateral Pivot design. There was no significant difference in PTA in step up and deep knee bend exercise between both the designs.ConclusionThe kinematic assessment of both the Medial and Lateral Pivot TKA designs revealed linear trend of PTA with increasing KFA as described for normal knee. Both the designs were able to achieve functional knee range of motion.     

Functional comparison of posterior cruciate-retained versus cruciate-sacrificed total knee arthroplasty

Gait of 11 patients with bilateral paired posterior cruciate-retaining and cruciate-sacrificing total knee arthroplasties (TKA) was studied preoperatively and two years postoperatively on walking and stair climbing. Five-year clinical and roentgenographic examinations were included in the study. Differences between the two prostheses were noted both in level walking and in stair climbing. On level walking, cruciate-sacrificed TKA had more flexion in loading response and increased flexion and varus moments with increased muscle activity of quadriceps and biceps femoris. Abnormal gaits common to both types of knee were decreased flexion in stance and decreased single-limb stance. Both knees had a stiff-legged gait during stance. On stairs, the cruciate-sacrificed TKA substituted soleus muscle activity for knee stability. The single-limb stance and range of motion were similar for both knees. In clinical terms, the cruciate-sacrificed TKA is less efficient and has greater medial loading and higher joint reaction forces that may affect durability of the prosthesis. The five-year knee scores, patient satisfaction, and roentgenographic examinations were equal for both sets of knees.     

Gait after unilateral total knee arthroplasty: Frontal plane analysis

After unilateral total knee arthroplasty (TKA), osteoarthritis (OA) in the non‐operated knee often progresses. The altered gait mechanics exhibited by patients after TKA increase the loading on the non‐operated knee and predispose it to disease progression. Therefore, our objective was to examine the potentially detrimental changes in frontal plane kinetics and kinematics during walking in patients who underwent unilateral TKA. Thirty‐one subjects 6 months after TKA, 24 subjects 1 year after unilateral TKA, and 20 control subjects were recruited. All subjects underwent 3D gait analysis. In the TKA groups, the non‐operated knee had a higher adduction angle and higher dynamic loading, knee adduction moment and impulse, compared to the operated knee. This increased loading may be an underlying reason for OA progression in the non‐operated knee. Measures of loading in the control knee did not differ from that of the non‐operated knee in the TKA group, but the TKA group walked with shorter step length. While the non‐operated knee loading was not different from controls, there may be greater risk of cumulative loading in the non‐operated knee of the TKA group given the shorter step length. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:647–652, 2011     

Kinematics of the patellofemoral joint in total knee arthroplasty

Sagittal plane patellofemoral kinematics was determined for 81 subjects while performing a weight-bearing deep knee bend under fluoroscopic surveillance. Fourteen normal knees, 12 anterior cruciate ligament (ACL)-deficient knees, and 55 total knee arthroplasties (TKAs) were assessed. Of TKAs, 39 had resurfacing with a dome-shaped patella, 8 had resurfacing with an anatomic mobile-bearing patella, and 8 were unresurfaced. TKA patellae experienced more superior patellofemoral contact and higher patellar tilt angles compared with the normal knees and ACL-deficient knees (P <.05). Patellofemoral separation at 5 degrees (+/-3 degrees ) extension was seen in 86% cruciate-retaining and 44% cruciate-stabilized TKAs and 8% ACL-deficient knees but not in the normal knees or mobile-bearing TKAs (P <.05). The patellar kinematic patterns for subjects having a TKA were more variable than subjects having either a normal knee or an ACL-deficient knee. Kinematic abnormalities of the prosthetic patellofemoral joint may reduce the effective extensor moment after TKA.     

A mechanical comparison of 2 posterior-stabilizing designs: Insall/Burstein 2 knee and Bisurface knee

A posterior-stabilizing knee prosthesis, called the Bisurface knee (Kyocera Corp, Kyoto, Japan), with a ball-and-socket joint installed in the midposterior portion of the tibiofemoral joint, has been developed to satisfy 2 conflicting demands in knee joint design: kinematics and wear resistance. To confirm if the prosthesis has achieved its design objectives, a contact area and stress study was done throughout the range of motion and compared with results obtained for the Insall-Burstein 2 knee. The posterior-stabilizing ability of the ball-and-socket joint also was assessed. This study showed that the ball-and-socket joint could provide sufficient posterior stability, earlier start of flexion, and lower contact stress in the tibial polyethylene insert in flexion. The design of the Bisurface knee could provide a good balance between kinematics, stability, and wear resistance.     

In vivo six‐degree‐of‐freedom knee‐joint kinematics in overground and treadmill walking following total knee arthroplasty

No data are available to describe six‐degree‐of‐freedom (6‐DOF) knee‐joint kinematics for one complete cycle of overground walking following total knee arthroplasty (TKA). The aims of this study were firstly, to measure 6‐DOF knee‐joint kinematics and condylar motion for overground walking following TKA; and secondly, to determine whether such data differed between overground and treadmill gait when participants walked at the same speed during both tasks. A unique mobile biplane X‐ray imaging system enabled accurate measurement of 6‐DOF TKA knee kinematics during overground walking by simultaneously tracking and imaging the joint. The largest rotations occurred for flexion‐extension and internal‐external rotation whereas the largest translations were associated with joint distraction and anterior‐posterior drawer. Strong associations were found between flexion‐extension and adduction‐abduction (R ² = 0.92), joint distraction (R ² = 1.00), and anterior‐posterior translation (R ² = 0.77), providing evidence of kinematic coupling in the TKA knee. Although the measured kinematic profiles for overground walking were grossly similar to those for treadmill walking, several statistically significant differences were observed between the two conditions with respect to temporo‐spatial parameters, 6‐DOF knee‐joint kinematics, and condylar contact locations and sliding. Thus, caution is advised when making recommendations regarding knee implant performance based on treadmill‐measured knee‐joint kinematic data. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1634–1643, 2017.

     

Biomechanical influence of deficient posterolateral corner structures on knee joint kinematics: A computational study

The posterolateral corner (PLC) structures including the popliteofibular ligament (PFL), popliteus tendon (PT) and lateral collateral ligament (LCL) are important soft tissues for posterior translational, external rotational, and varus angulation knee joint instabilities. The purpose of this study was to determine the effects of deficient PLC structures on the kinematics of the knee joint under gait and squat loading conditions. We developed subject‐specific computational models with full 12‐degree‐of‐freedom tibiofemoral and patellofemoral joints for four male subjects and one female subject. The subject‐specific knee joint models were validated with computationally predicted muscle activation, electromyography data, and experimental data from previous study. According to our results, deficiency of the PFL did not significantly influence knee joint kinematics compared to an intact model under gait loading conditions. Compared with an intact model under gait and squat loading conditions, deficiency of the PT led to significant increases in external rotation and posterior translation, while LCL deficiency increased varus angulation. Deficiency of all PLC structures led to the greatest increases in external rotation, varus angulation, and posterior translation. These results suggest that the PT is an important structure for external rotation and posterior translation, while the LCL is important for varus angulation under dynamic loading conditions. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2202–2209, 2018.

     

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.     

人工全膝关节置换术治疗类风湿性关节炎的疗效分析

目的探讨人工全膝关节置换术治疗类风湿性关节炎的临床效果。方法对35例类风湿性关节炎患者(64膝)进行全膝关节置换。根据软组织平衡情况采用后稳定型膝关节非限制性假体(58膝)或者限制性假体(6膝)。根据HSS评分系统对患者手术前后的膝关节功能进行评分。结果 35例均获随访,时间6个月~7年。关节功能明显改善,尤其是在畸形矫正方面效果显著。HSS评分:优27例,良4例,可4例,优良率达88.5%。无感染发生及深静脉血栓形成。结论类风湿性关节炎病理改变复杂,手术难度大,需要很好的软组织平衡技术,韧带损伤严重者需要采用限制性假体才能取得满意的疗效。     

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     

Tibiofemoral force following total knee arthroplasty: comparison of four prosthesis designs in vitro.

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 degrees 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 degrees 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.