Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka City, Fukuoka, 812-8582, Japan.
Department of Orthopaedic Surgery, Tokyo Women's Medical University, 8-1, Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
Knee Surg Sports Traumatol Arthrosc. 2019 May;27(5):1642-1650. doi: 10.1007/s00167-018-5276-9. Epub 2018 Nov 7.
To evaluate preoperative soft tissue balance for total knee arthroplasty (TKA), varus/valgus stress radiographs has been used in previous studies. While the joint line of femur and tibia is almost parallel in healthy and postoperative knees, osteoarthritis (OA) knees exhibit articular cartilage wear that causes the joint line tilting even in a non-stress condition. Therefore, the exact angle of the joint line might mislead to understand the joint laxity in OA knees. The purpose of this study was to evaluate soft tissue balance in varus OA knees using preoperative stress radiographs under three different constant loads, taking the articular cartilage wear into consideration.
One hundred and eighteen varus-deformed OA knees in 102 patients were investigated before primary TKA. Preoperative knee radiographs were obtained in the anteroposterior view with no stress (defined as the neutral condition) and with varus and valgus stresses (5, 10, and 15 kg) in extension. Two different types of joint line angle (JLA), the absolute JLA (an exact angle of joint line) and the relative JLA (the absolute JLA minus the JLA in the neutral condition), were compared for the same load with the paired t test.
The absolute JLA was 7.9 ± 1.2°/- 1.5 ± 2.2° under varus/valgus 15 kg stress, 6.7 ± 2.4°/- 0.3 ± 2.1° under varus/valgus 10 kg stress, and 4.7 ± 2.4°/1.1 ± 2.2° under varus/valgus 5 kg stress. Significant differences in the numerical values of the absolute JLA were observed between varus and valgus stresses for each load. The neutral JLA was 3.2 ± 2.0°. The relative JLA was 4.8 ± 2.1°/- 4.7 ± 1.8° under varus/valgus 15 kg stress, 3.5 ± 2.0°/- 3.5 ± 1.8° under varus/valgus 10 kg stress, and 1.5 ± 1.9°/- 2.1 ± 1.8° under varus/valgus 5 kg stress. No significant differences in the numerical values of the relative JLA were observed between varus and valgus stresses for each load.
Consideration of cartilage wear allowed knee laxity to be evaluated more precisely in this study than in previous reports. It was shown that medial soft tissue contracture did not always exist, even in varus OA knees. Regarding clinical relevance, surgeons should be aware that underestimating medial soft tissue laxity due to reliance on the absolute JLA might lead to excessive medial tissue release and result in postoperative instability and lower patient satisfaction.
IV.
在先前的研究中，已经使用外翻/内翻应力射线照相来评估全膝关节置换术（TKA）的术前软组织平衡。虽然在健康和术后膝关节中，股骨和胫骨的关节线几乎是平行的，但骨关节炎（OA）膝关节存在关节软骨磨损，即使在非应力状态下也会导致关节线倾斜。因此，关节线的确切角度可能会导致对 OA 膝关节关节松弛的误解。本研究的目的是在三种不同的恒定负荷下，考虑到软骨磨损，使用术前应力射线照相评估内翻性 OA 膝关节的软组织平衡。
102 例患者中的 118 例内翻畸形 OA 膝关节在初次 TKA 前接受了检查。在无应力（定义为中立状态）和外翻和内翻应力（5、10 和 15kg）下，获得膝关节前后位 X 线片。在相同的负荷下，使用配对 t 检验比较两种不同类型的关节线角（JLA），即绝对 JLA（关节线的确切角度）和相对 JLA（绝对 JLA 减去中立状态下的 JLA）。
在 15kg 外翻/内翻应力下，绝对 JLA 为 7.9±1.2°/-1.5±2.2°，在 10kg 外翻/内翻应力下为 6.7±2.4°/-0.3±2.1°，在 5kg 外翻/内翻应力下为 4.7±2.4°/1.1±2.2°。在每种负荷下，绝对 JLA 的数值在外翻和内翻之间存在显著差异。中立 JLA 为 3.2±2.0°。在 15kg 外翻/内翻应力下，相对 JLA 为 4.8±2.1°/-4.7±1.8°，在 10kg 外翻/内翻应力下为 3.5±2.0°/-3.5±1.8°，在 5kg 外翻/内翻应力下为 1.5±1.9°/-2.1±1.8°。在每种负荷下，相对 JLA 的数值在外翻和内翻之间没有显著差异。
与先前的报告相比，本研究考虑到软骨磨损，能够更精确地评估膝关节松弛度。结果表明，即使在内翻性 OA 膝关节中，内侧软组织挛缩也不一定存在。就临床相关性而言，外科医生应该意识到，由于依赖绝对 JLA，内侧软组织松弛度可能会被低估，这可能导致内侧组织过度松解，并导致术后不稳定和患者满意度降低。
IV。
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