Objective:This study aimed to explore the correlation between the insufficient coverage of lateral trochlear bone resection and the various alignment parameters of the lower extremities in kinematically aligned total knee arthroplasty(KA-TKA).Methods:Forty-eight patients (54 knees) who underwent KA-TKA surgery at Beijing Chaoyang Hospital from May 2018 to July 2020 were retrospectively investigated. The patients comprised 12 males and 36 females who were aged 69±6.7 years (range: 57-85 years). Twenty-three patients (23 knees) underwent surgery using patient-specific instruments, and conventional instruments with caliper and other special tools were used in 25 patients (31 knees). The hip-knee-ankle (HKA) angle, the mechanical distal femoral lateral angle (mLDFA), the joint line convergence angle (JLCA), the medial proximal tibial angle (MPTA), and the transepicondylar axis angle (TEAA) were obtained through full-length weight-bearing X-ray, CT, or intraoperative measurement and used as independent variables. The exposed resection bone surface data at the middle (MIDcover) and inferior (INFcover) levels of the patients' lateral femoral trochlear were recorded through CT or intraoperative caliper measurements and used as dependent variables. Spearman correlation and linear regression analyses were conducted.Results:Among the 54 knees, 37 (87%) had varying degrees of lateral trochlear resection coverage insufficiency, with MIDcover and INFcover being 2.8 mm (2.6 mm) and 2.3 mm (2.5 mm) [ M( QR)], respectively. MIDcover and INFcover had a significant negative correlation with mLDFA, and the correlation coefficients were -0.839 and -0.691 (all P values<0.05), respectively; they were also significantly negatively correlated with HKA, and the correlation coefficients were -0.574 and -0.585 (all P values<0.05), respectively. The insufficient coverages were not significantly correlated to TEAA and MPTA. Linear regression analysis showed that MPTA had a great impact on MIDcover and INFcover, with regression coefficients of -0.703 ( R2=0.708) and -0.473 ( R2=0.489), respectively. Conclusions:When performing KA-TKA using conventional prostheses, insufficient coverage of the lateral trochlear resection surface is common. The greater the valgus of the distal femoral joint line is, the more insufficient the coverage of the lateral trochlear bone resection is.

目的 通过建立自动化流程对膝关节假体股胫接触面积的影响因素进行分析,总结设计参数对接触面积的影响规律,并找到最大接触应力和接触面积之间的关系.方法 在Isight中建立参数化有限元模型,包括几何模型自动变参、自动化有限元前处理和有限元运算3个组件,实现自动化流程,提取接触面积进行统计学分析.结果 有限元模型用Tekscan应力分布系统进行验证.当股骨、胫骨矢状面半径逐渐接近时,接触面积最大为295 mm2.股骨矢状面半径对接触面积是正效应,而胫骨矢状面半径是负效应.最大接触应力和接触面积近似呈线性负相关.结论 通过分析股胫矢状面半径对接触面积和接触应力的影响规律,为临床降低衬垫磨损提供设计依据.

ISO 14243 is the governing standard for wear testing of knee prostheses, but there is controversy over the correct direction of anterior-posterior (AP) displacement and loading and the correct direction of tibial rotation (TR) angles and torque. This study aimed to analyze how altering the direction of AP and TR affected wear on the tibial insert. Modifications to the conditions specified in ISO 14243-1 and ISO 14243-3 were also proposed. As such, five loading conditions were applied to FEA models of a knee prosthesis: (1) Modified ISO 14243-3 with positive AP displacement and TR angle, (2) ISO 14243-3:2004 with negative AP displacement and positive TR angle, (3) ISO 14243-3:2014 with positive AP displacement and negative TR angle, (4) Modified ISO 14243-1 with positive AP load and TR torque, and (5) ISO 14243-1:2009 with negative AP load and positive TR torque. This study found that changing the input directions for AP and TR according to ISO 14243-1 and 14243-3 had an influence on the wear rate and wear contours on the tibial insert model. However, the extent of wear varies depending on the design features of the tibial insert and shape of the input curves. For displacement control according to ISO 14243-3, changing the direction of AP displacement had a marked influence on the wear rate (272.77%), but changing the direction of TR angle had a much lower impact (2.17%). For load control according to ISO 14243-1, reversing the AP load (ISO 14243-1:2009) only increased the wear rate by 6.73% in comparison to the modified ISO 14243-1 conditions. The clinical relevance of this study is that the results demonstrate that tibial wear is affected by the direction of application of AP and TR. Incorrect application of the loading conditions during the design stage may lead to an ineffective preclinical evaluation and could subsequently influence implant longevity in clinical use.

PurposeSingle radius knee implants were introduced to reduce the level of paradoxical anterior femoral translation (AFT) during mid-flexion after total knee arthroplasty. Findings from clinical and experiment studies are inconsistent, which may be due to the different loading conditions and articular conformities of the knee implants studied. The aim of this study is to analyze how variations in these two factors affect the mid-flexion stability of a single radius knee prosthesis.MethodsSix daily activities (walking, stair ascent, stair descent, sit-to-stand, pivot turn and crossover turn), and three articular conformity ratios (low, moderate and high) were considered. The resulting AFTs from the 18 finite element models were analyzed.ResultsFor low conformity knees, the worst case activity (the greatest AFT) was sit-to-stand with an AFT of 6.2mm, while for the moderate conformity the worst case was crossover turn and pivot turn. For high conformity, all activities produced a relatively small AFT ranging from 0mm to 1.8mm, which more closely resembles natural knee motion. In addition, no AFT was recorded during stair ascent for all three conformities (low, moderate, high).ConclusionsThis study demonstrated that the amount of AFT is highly dependent on the activity being undertaken and the articular conformity of the knee prosthesis, and the worst case activity depends on the knee conformity. The clinical relevance of this study is that it offers valuable information towards the design of improved knee prostheses and selection of knee implants for clinical use.Level of evidenceII.

Excellent clinical and kinematical performance is commonly reported after medial pivot knee arthroplasty. However, there is conflicting evidence as to whether the posterior cruciate ligament should be retained. This study simulated how the posterior cruciate ligament, post-cam mechanism and medial tibial insert morphology may affect postoperative kinematics.