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。     

Knee kinematics in medial osteoarthritis during in vivo weight‐bearing activities

Dynamic knee kinematics were analyzed for medial osteoarthritic (OA) knees in three activities, including two types of maximum knee flexion. Continuous x‐ray images of kneeling, squatting, and stair climbing motions were taken using a large flat panel detector. CT‐derived bone models were used for the model registration‐based 3D kinematic measurements. Three‐dimensional joint kinematics and contact locations were determined using two methods: bone‐fixed coordinate systems and by interrogation of CT‐based bone model surfaces. The femur exhibited gradual external rotation with knee flexion for kneeling and squatting activities, and gradual internal rotation with knee extension for stair climbing. From 100° to 120° flexion, contact locations showed a medial pivot pattern similar to normal knees. However, knees with medial OA displayed a femoral internal rotation bias and less posterior translation when compared with normal knees. A classic screw‐home movement was not observed in OA knees near extension. Decreased variability with both activities and methods of calculation were demonstrated for all three activities. In conclusion, the weight‐bearing kinematics of patients with medial OA differs from normal knees. Pathological changes of the articulating surfaces and the ligaments correspond to observed abnormalities in knee kinematics. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1555–1561, 2009     

Changes in Knee Kinematics Reflect the Articular Geometry after Arthroplasty

We hypothesized changes in rotations and translations after TKA with a fixed-bearing anterior cruciate ligament (ACL)-sacrificing but posterior cruciate ligament (PCL)-retaining design with equal-sized, circular femoral condyles would reflect the changes of articular geometry. Using 8 cadaveric knees, we compared the kinematics of normal knees and TKA in a standardized navigated position with defined loads. The quadriceps was tensed and moments and drawer forces applied during knee flexion-extension while recording the kinematics with the navigation system. TKA caused loss of the screw-home; the flexed tibia remained at the externally rotated position of normal full knee extension with considerably increased external rotation from 63° to 11° extension. The range of internal-external rotation was shifted externally from 30° to 20° extension. There was a small tibial posterior translation from 40° to 90° flexion. The varus-valgus alignment and laxity did not change after TKA. Thus, navigated TKA provided good coronal plane alignment but still lost some aspects of physiologic motion. The loss of tibial screw-home was related to the symmetric femoral condyles, but the posterior translation in flexion was opposite the expected change after TKA with the PCL intact and the ACL excised. Thus, the data confirmed our hypothesis for rotations but not for translations. It is not known whether the standard navigated position provides the best match to physiologic kinematics. One or more of the authors (AAA, AMJB) have received funding by Stryker (Europe). Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that tissue specimens were obtained in accordance with the laws of France.     

Motion of the femoral condyles in flexion and extension during a continuous lunge

Numerous studies have reported on in‐vivo posterior femoral condyle translations during various activities of the knee. However, no data has been reported on the knee motion during a continuous flexion‐extension cycle. Further, few studies have investigated the gender variations on the knee kinematics. This study quantitatively determined femoral condylar motion of 10 male and 10 female knees during a continuous weightbearing flexion‐extension cycle using two‐dimensional to three‐dimensional fluoroscopic tracking technique. The knees were CT‐scanned to create three‐dimensional models of the tibia and femur. Continuous images of each subject were taken using a single‐fluoroscopic imaging system. The knee kinematics were measured along the motion path using geometric center axis of the femur. The results indicated that statistical differences between the flexion and extension motions were only found in internal‐external tibial rotation and lateral femoral condylar motion at the middle range of flexion angles. At low flexion angles, male knees have greater external tibial rotation and more posteriorly positioned medial femoral condyle than females. The knee did not show a specific pivoting type of rotation with flexion. Axial rotation center varied from lateral to medial compartments of the knee. These data could provide useful information for understanding physiological motion of normal knees. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:591–597, 2015.     

The kinematics of fixed- and mobile-bearing total knee arthroplasty

The success of any total knee arthroplasty (TKA) is influenced by a complex interaction between component geometry and the surrounding soft tissues. The objective of this study was to investigate posterior femoral translation and tibial rotation in a single design posterior-stabilized TKA offering fixed- and mobile-bearing tibial components. Specifically, we examined whether mobile-bearing TKA restores normal knee translation and rotation better than fixed-bearing TKA design. Eleven human knee specimens retrieved postmortem were tested using a robotic system. The translation and rotation of the intact and reconstructed knees were compared. The data indicate that for all knees, posterior femoral translation occurs along the passive path and under muscle loading conditions. Furthermore, increasing flexion angle corresponded with increased internal tibial rotation. Femoral translation and tibial rotation for fixed- and mobile-bearing posterior-stabilized TKAs were similar despite component design variations. However, both arthroplasties only partially restored intact knee translation and rotation. The data presented here may serve as an aid in the development of a rationale for additional improvement in surgical techniques and prosthesis design, so that normal knee function may be restored.     

Intraoperative passive kinematics of osteoarthritic knees before and after total knee arthroplasty.

Total knee arthroplasty is a successful procedure to treat pain and functional disability due to osteoarthritis. However, precisely how a total knee arthroplasty changes the kinematics of an osteoarthritic knee is unknown. We used a surgical navigation system to measure normal passive kinematics from 7 embalmed cadaver lower extremities and in vivo intraoperative passive kinematics on 17 patients undergoing primary total knee arthroplasty to address two questions: How do the kinematics of knees with advanced osteoarthritis differ from normal knees?; and, Does posterior substituting total knee arthroplasty restore kinematics towards normal? Osteoarthritic knees displayed a decreased screw‐home motion and abnormal varus/valgus rotations between 10° and 90° of knee flexion when compared to normal knees. The anterior–posterior motion of the femur in osteoarthritic knees was not different than in normal knees. Following total knee arthroplasty, we found abnormal varus/valgus rotations in early flexion, a reduced screw‐home motion when compared to the osteoarthritic knees, and an abnormal anterior translation of the femur during the first 60° of flexion. Posterior substituting total knee arthroplasty does not appear to restore normal passive varus/valgus rotations or the screw motion and introduces an abnormal anterior translation of the femur during intraoperative evaluation. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1607–1614, 2006     

Simulation of total knee arthroplasty in 5° or 7° valgus: A study of gap imbalances and changes in limb and knee alignments from native

This study calculated the frequency of occurrence of gap imbalances between medial and lateral compartments at 0° flexion and within a compartment between 0° and 90° flexion, and changes in limb and knee alignment from native after computer simulation of total knee arthroplasty (TKA) with the knee set in 5° or 7° valgus at 0° flexion. TKA was simulated on 49 3D bone models of native limbs. At 0° flexion, the femoral component was set in 5° or 7° valgus from the anatomic axis of the femur, and the tibial component was set 0° to the tibial anatomic axis. At 90° flexion, internal‐external rotation of the femoral component was set perpendicular to the anteroposterior axis of the trochlear groove (Method 1), parallel to the transepicondylar axis (Method 2), 3° externally rotated to the posterior condylar axis (Method 3), and gap‐balanced to the tibial resection at 0° flexion (Method 4). For 5° and 7° valgus knees, the frequency of occurrence of TKAs (1) with ≥2 mm gap imbalance between compartments at 0° flexion was ≥49%, (2) with ≥2 mm gap imbalance within a compartment between 0° and 90° flexion ranged from 43–69% for Methods 1, 2, and 3, and (3) with ≥2° change in limb and knee alignment from native was ≥47%. Achieving balanced gaps between compartments at 0° flexion may often require soft tissue release. Unbalanced gaps within a compartment between 0° and 90° flexion represent a potential instability which is difficult to surgically correct. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2031–2039, 2017.

     

Influence of Component Rotation in Total Knee Arthroplasty on Tibiofemoral Kinematics—A Cadaveric Investigation

Background

Physiological tibiofemoral kinematics have been shown to be important for good knee function after total knee arthroplasty (TKA). The purpose of the present study was to investigate the influence of component rotation on tibiofemoral kinematics during knee flexion. We asked which axial component alignment best reconstructs physiological tibiofemoral kinematics and which combinations should be avoided.

In Vivo Knee Kinematics for a Cruciate Sacrificing Total Knee Arthroplasty Having Both a Symmetrical Femoral and Tibial Component

BackgroundEarly total knee arthroplasty (TKA) designs were symmetrical, but lead to complications due to over-constraint leading to loosening and poor flexion. Next-generation TKAs have been designed to include asymmetry, pertaining to the trochlear groove, femoral condylar shapes, and/or the tibial component. More recently, an advanced posterior cruciate sacrificing (PCS) TKA was designed to include both a symmetrical femoral component with a patented V-shaped trochlear groove and a symmetrical tibial component with an ultracongruent insert, in an attempt to reduce inventory costs. Because previous PCS TKA designs produced variable results, the objective of this study is to determine and evaluate the in vivo kinematics for subjects implanted with this symmetrical TKA.MethodsTwenty-one subjects, implanted with symmetrical PCS fixed-bearing TKA, were asked to perform a weight-bearing deep knee bend (DKB) while under fluoroscopic surveillance. A 3-dimensional to 2-dimensional registration technique was used to determine each subject’s anteroposterior translation of lateral and medial femoral condyles as well as tibiofemoral axial rotation and their weight-bearing knee flexion.ResultsDuring the DKB, the average active maximum weight-bearing flexion was 111.7° ± 13.3°. On average, from full extension to maximum knee flexion, subjects experienced −2.5 ± 2.0 mm of posterior femoral rollback of the lateral condyle and 2.5 ± 2.2 mm of medial condyle motion in the anterior direction. This medial condyle motion was consistent for the majority of the subjects, with the lateral condyle exhibiting rollback from 0° to 60° of flexion and then experienced an average anterior motion of 0.3 mm from 60° to 90° of knee flexion. On average, the subjects in this study experienced 6.6°± 3.3° of axial rotation, with most of the rotation occurring in early flexion, averaging 4.9°.ConclusionAlthough subjects in this study were implanted with a symmetrical PCS TKA, they did experience femoral rollback of the lateral condyle and a normal-like pattern of axial rotation, although less in magnitude than the normal knee. The normal axial rotation pattern occurred because the lateral condyle rolled in the posterior direction, while the medial condyle moved in the anterior direction. Interestingly, the magnitude of posterior femoral rollback and axial rotation for subjects in this study was similar in magnitude reported in previous studies pertaining to asymmetrical TKA designs. It is proposed that more patients be analyzed having this TKA implanted by other surgeons.     

Joint biomechanics and design of modern knee prostheses--time for revised thinking!

AIM AND METHOD: This review article summarises new knowledge about knee kinematics and induces a new discussion about the design of total knee arthroplasty (TKA) components. RESULTS: According to these new observations, knee flexion is not linked to femoral rollback but to a rotational movement between tibia and femur. The axis of this rotation is situated in the medial compartment of the knee when an intact anterior craciate ligament is present and not centrally through the tibial spines. In case of ACL insufficiency, such as that following TKA, the center of rotation shifts into the lateral compartment. Furthermore, the form of the posterior femoral condyle is not elliptical but round. CONCLUSION: Rotational movements between femoral component and tibial baseplate with the polyethylene-inlay have to be possible. One needs an asymmetric surface of the polyethylene-inlay, because different movements occur in the medial compartment than in the lateral compartment. The option to construct the posterior femoral condyle with a single radius allows a high congruency with the articulating inlay. The surgeon should let the new findings influence his choice of a TKA system. A closer analysis of modern prosthetic designs with either fixed or mobile bearings reveals that a few systems have already incorporated some of the new kinematic aspects of the knee.     

Dynamic activity dependence of in vivo normal knee kinematics

Dynamic knee kinematics were analyzed for normal knees in three activities, including two different types of maximum knee flexion. Continuous X‐ray images of kneel, squat, and stair climb motions were taken using a large flat panel detector. CT‐derived bone models were used for model registration‐based 3D kinematic measurement. Three‐dimensional joint kinematics and contact locations were determined using three methods: bone‐fixed coordinate systems, interrogation of CT‐based bone model surfaces, and interrogation of MR‐based articular cartilage model surfaces. The femur exhibited gradual external rotation throughout the flexion range. Tibiofemoral contact exhibited external rotation, with contact locations translating posterior while maintaining 15° to 20° external rotation from 20° to 80° of flexion. From 80° to maximum flexion, contact locations showed a medial pivot pattern. Kinematics based on bone‐fixed coordinate systems differed from kinematics based on interrogation of CT and MR surfaces. Knee kinematics varied significantly by activity, especially in deep flexion. No posterior subluxation occurred for either femoral condyle in maximum knee flexion. Normal knees accommodate a range of motions during various activities while maintaining geometric joint congruency. © Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:428–434, 2008     

In Vivo Kinematic Comparison of a Bicruciate Stabilized Total Knee Arthroplasty and the Normal Knee Using Fluoroscopy

Background

The bicruciate stabilized (BCS) total knee arthroplasty (TKA) features asymmetrical bearing geometry and dual substitution for the anterior cruciate ligament and posterior cruciate ligament (PCL). Previous TKA designs have not fully replicated normal knee motion, and they are characterized by lower magnitudes of overall rollback and axial rotation than the normal knee.

Kinematic Performance of Gradually Variable Radius Posterior-Stabilized Primary TKA During Various Activities: An In Vivo Study Using Fluoroscopy

BackgroundPosterior-stabilized total knee arthroplasty (TKA) with gradually variable radii (G-curve) femoral condylar geometry is now available. It is believed that a G-curve design would lead to more mid-flexion stability leading to reduced incidence of paradoxical anterior slide. The objective of this study was to assess the in vivo kinematics for subjects implanted with this type of TKA under various conditions of daily living.MethodsTibiofemoral kinematics of 35 patients having posterior-stabilized TKA with G-curve design were analyzed using fluoroscopy while performing three activities: weight-bearing deep knee bend, gait, and walking down a ramp. The subjects were assessed for range of motion, condylar translation, axial rotation, cam-spine engagement, and condylar lift-off.ResultsThe average weight-bearing flexion during deep knee bend was 111.4°. On average, the subjects exhibited 5.4 mm of posterior rollback of the lateral condyle and 2.0 mm of the medial condyle from full extension to maximum knee flexion. The femur consistently rotated externally with flexion, and the average axial rotation was 5.2°. Overall movement of the condyles during gait and ramp-down activity was small. No incidence of condylar lift-off was observed.ConclusionSubjects in this study experienced consistent magnitudes of posterior femoral rollback and external rotation of the femur with weight-bearing flexion. The variation is similar to that previously reported for normal knee where the lateral condyle moves consistently posterior compared to the medial condyle. Subjects experienced low overall mid-flexion paradoxical anterior sliding and no incidence of condylar lift-off leading to mid-flexion stability.     

全膝关节置换术后股胫关节运动学轨迹的数字化模型研究

 目的 通过透视技术结合数字化模型注册技术分析全膝关节置换术后股骨假体与胫骨垫片之间的相对运动和接触位置。方法 2007年7月至2008年6月,接受GENESISⅡ假体全膝关节置换术患者16例,均为女性;年龄56～76岁,平均66.4岁。随访48～60个月,平均(56±3)个月。采用膝关节学会评分(Knee Society Score,KSS)评价膝关节功能;采用循环透视方法获取影像学数据,对假体逆向数字建模,进行数字模型和影像学数据的匹配,重建膝关节的三维运动;测量股骨内、外髁接触位置的移动,计算胫骨内旋角度,测量股骨凸轮和胫骨立柱的接触时相和范围。结果 末次随访时KSS膝评分(93±5)分,功能评分(88±13)分,与术前比较差异有统计学意义。股骨内髁的移动范围(8.5±2.5) mm,外髁的移动范围(9.5±4.8) mm,胫骨内旋角度2.5°±8.4°。屈膝约30°～40°时凸轮和立柱发生接触,立柱后方的接触范围(8.0±1.8) mm。胫骨平台后倾角度越大,凸轮和立柱的接触越晚。结论 全膝关节置换术后股胫关节的运动学特征与正常膝关节不同,膝关节屈曲10°~30°时股骨内髁前移,屈曲大于40°后股骨内、外髁后移,胫骨平台后倾与凸轮和立柱的接触时相有相关性。     

Comparison of posterior-stabilized,cruciate-retaining,and medial-stabilized knee implant motion during gait

Accurate knowledge of knee joint motion is needed to evaluate the effects of implant design on functional performance and component wear. We conducted a randomized controlled trial to measure and compare 6-degree-of-freedom (6-DOF) kinematics and femoral condylar motion of posterior-stabilized (PS), cruciate-retaining (CR), and medial-stabilized (MS) knee implant designs for one cycle of walking. A mobile biplane X-ray imaging system was used to accurately measure 6-DOF tibiofemoral motion as patients implanted with PS (n = 23), CR (n = 25), or MS (n = 26) knees walked over ground at their self-selected speeds. Knee flexion angle did not differ significantly between the three designs. Relative movements of the femoral and tibial components were generally similar for PS and CR with significant differences observed only for anterior tibial drawer. Knee kinematic profiles measured for MS were appreciably different: external rotation and abduction of the tibia were increased while peak-to-peak anterior drawer was significantly reduced for MS compared with PS and CR. Anterior-posterior drawer and medial-lateral shift of the tibia were strongly coupled to internal-external rotation for MS, as was anterior-posterior translation of the contact center in the lateral compartment. MS exhibited the least amount of paradoxical anterior translation of the femur relative to the tibia during knee flexion. The joint center of rotation in the transverse plane was located in the lateral compartment for PS and CR and in the medial compartment for MS. Substantial differences were evident in 6-DOF knee kinematics between the healthy knee and all three prosthetic designs. Overall, knee kinematic profiles observed for MS resemble those of the healthy joint more closely than PS and CR.     

MRI analysis of in vivo meniscal and tibiofemoral kinematics in ACL-deficient and normal knees.

The objectives of this study were to analyze simultaneously meniscal and tibiofemoral kinematics in healthy volunteers and anterior cruciate ligament (ACL)-deficient patients under axial load-bearing conditions using magnetic resonance imaging (MRI). Ten healthy volunteers and eight ACL-deficient patients were examined with a high-field, closed MRI system. For each group, both knees were imaged at full extension and partial flexion ( approximately 45 degrees ) with a 125N compressive load applied to the foot. Anteroposterior and medial/lateral femoral and meniscal translations were analyzed following three-dimensional, landmark-matching registration. Interobserver and intraobserver reproducibilities were less than 0.8 mm for femoral translation for image processing and data analysis. The position of the femur relative to the tibia in the ACL-deficient knee was 2.6 mm posterior to that of the contralateral, normal knee at extension. During flexion from 0 degrees to 45 degrees , the femur in ACL-deficient knees translated 4.3 mm anteriorly, whereas no significant translation occurred in uninjured knees. The contact area centroid on the tibia in ACL-deficient knees at extension was posterior to that of uninjured knees. Consequently, significantly less posterior translation of the contact centroid occurred in the medial tibial condyle in ACL-deficient knees during flexion. Meniscal translation, however, was nearly the same in both groups. Axial load-bearing MRI is a noninvasive and reproducible method for evaluating tibiofemoral and meniscal kinematics. The results demonstrated that ACL deficiency led to significant changes in bone kinematics, but negligible changes in the movement of the menisci. These results help explain the increased risk of meniscal tears and osteoarthritis in chronic ACL deficient knees.     

Variations in medial‐lateral hamstring force and force ratio influence tibiofemoral kinematics

A change in hamstring strength and activation is typically seen after injuries or invasive surgeries such as anterior cruciate reconstruction or total knee replacement. While many studies have investigated the influence of isometric increases in hamstring load on knee joint kinematics, few have quantified the change in kinematics due to a variation in medial to lateral hamstring force ratio. This study examined the changes in knee joint kinematics on eight cadaveric knees during an open‐chain deep knee bend for six different loading configurations: five loaded hamstring configurations that varied the ratio of a total load of 175 N between the semimembranosus and biceps femoris and one with no loads on the hamstring. The anterior–posterior translation of the medial and lateral femoral condyles’ lowest points along proximal‐distal axis of the tibia, the axial rotation of the tibia, and the quadriceps load were measured at each flexion angle. Unloading the hamstring shifted the medial and lateral lowest points posteriorly and increased tibial internal rotation. The influence of unloading hamstrings on quadriceps load was small in early flexion and increased with knee flexion. The loading configuration with the highest lateral hamstrings force resulted in the most posterior translation of the medial lowest point, most anterior translation of the lateral lowest point, and the highest tibial external rotation of the five loading configurations. As the medial hamstring force ratio increased, the medial lowest point shifted anteriorly, the lateral lowest point shifted posteriorly, and the tibia rotated more internally. The results of this study, demonstrate that variation in medial‐lateral hamstrings force and force ratio influence tibiofemoral transverse kinematics and quadriceps loads required to extend the knee. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1707–1715, 2016.     

Posterior cruciate ligament removal contributes to abnormal knee motion during posterior stabilized total knee arthroplasty

Abnormal anterior translation of the femur on the tibia has been observed in mid flexion (20–60°) following posterior stabilized total knee arthroplasty. The underlying biomechanical causes of this abnormal motion remain unknown. The purpose of this study was to isolate the effects of posterior cruciate ligament removal on knee motion after total knee arthroplasty. We posed two questions: Does removing the posterior cruciate ligament introduce abnormal anterior femoral translation? Does implanting a posterior stabilized prosthesis change the kinematics from the cruciate deficient case? Using a navigation system, we measured passive knee kinematics of ten male osteoarthritic patients during surgery after initial exposure, after removing the anterior cruciate ligament, after removing the posterior cruciate ligament, and after implanting the prosthesis. Passively flexing and extending the knee, we calculated anterior femoral translation and the flexion angle at which femoral rollback began. Removing the posterior cruciate ligament doubled anterior translation (from 5.1 ± 4.3 mm to 10.4 ± 5.1 mm) and increased the flexion angle at which femoral rollback began (from 31.2 ± 9.6° to 49.3 ± 7.3°). Implanting the prosthesis increased the amount of anterior translation (to 16.1 ± 4.4 mm), and did not change the flexion angle at which femoral rollback began. Abnormal anterior translation was observed in low and mid flexion (0–60°) after removing the posterior cruciate ligament, and normal motion was not restored by the posterior stabilized prosthesis. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1494–1499, 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     

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