PURPOSE Previous cadaver studies showed that the additional bone cuts in the distal and posterior femur and joint line elevation resulted in laxity at mid-flexion after total knee arthroplasty (TKA). However, these results are not always applicable to TKA candidates because the related studies used cadaver knees with no osteoarthritis. It was hypothesized that the joint line elevation results in mid-flexion laxity after TKA in patients with knee osteoarthritis. The purpose of this study was to analyze the relationship between joint line elevation and mid-flexion laxity in patients with knee osteoarthritis. METHODS 30 knees with varus osteoarthritis undergoing TKA were evaluated. Two femoral trial component models were prepared: (1) normal model with a thickness of the distal and posterior femoral components of 9 mm, and (2) 2-mm joint line elevation model with a thickness of the distal and posterior femoral components of 9 - 2 = 7 mm. This 2-mm joint line elevation model simulated an additional bone cut in the distal and posterior femur, and joint line elevation, without an additional bone cut. The femoral trial component models were set before implantation and measured the joint gap kinematics using a tensor device through the full knee range of motion. RESULTS The differences in joint gap change from 30° to 90° were not statistically significant between the two models. However, the joint line elevation model decreased the joint gap laxity at 120° (p = 0.02) and at 145° (p = 0.01). CONCLUSIONS This study showed that a 2-mm joint line elevation was not associated with mid-flexion laxity in patients with varus osteoarthritis in the knee. The results of this study differed from the results in previous cadaver studies. LEVEL OF EVIDENCE Therapeutic study, level II, prospective comparative study.

中文翻译：

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全膝关节置换术后内翻性骨关节炎患者的关节线抬高与中屈松弛不相关。

目的先前的尸体研究表明，在全膝关节置换术（TKA）后，股骨远端和后股骨的额外切割以及关节线抬高导致屈曲中期松弛。但是，这些结果并不总是适用于TKA候选人，因为相关研究使用了无骨关节炎的尸体膝盖。假设膝关节骨关节炎患者在TKA后关节线抬高会导致中屈松弛。这项研究的目的是分析膝关节骨关节炎患者的关节线抬高与中屈松弛度之间的关系。方法对30例膝内翻性骨关节炎行TKA的患者进行评估。准备了两种股骨试验组件模型：（1）股骨远端和后部组件厚度为9 mm的正常模型，（2）2毫米关节线高程模型，股骨远端和后部组件的厚度为9-2 = 7毫米。这个2毫米的关节线高程模型模拟了股骨远端和后部的额外骨切开以及关节线高程，而没有额外的骨切开。在植入前设置股骨试验组件模型，并在整个膝关节运动范围内使用张量设备测量关节间隙运动学。结果在两个模型之间，关节间隙从30°到90°的变化差异均无统计学意义。但是，关节线高程模型降低了120°（p = 0.02）和145°（p = 0.01）时的关节间隙松弛度。结论该研究表明，膝关节内翻性骨关节炎患者2mm关节线抬高与中屈松弛不相关。这项研究的结果与以前的尸体研究结果不同。证据级别治疗研究，II级，前瞻性比较研究。