Orthopaedic Clinic CTO, University of Florence, Largo Palagi 1, 50139, Florence, Italy.
J Orthop Surg Res. 2022 Jun 3;17(1):299. doi: 10.1186/s13018-022-03184-4.
Knee varus alignment represents a notorious cause of knee osteoarthritis. It can be caused by tibial deformity, combined tibial-femoral deformity and/or ligament imbalance. Understanding malalignment is crucial in total knee arthroplasty to restore frontal plane neutral mechanical axis. The aim of this study was to determine which factor contributes the most to varus osteoarthritic knee and its related surgical implications in performing a total knee arthroplasty.
We retrospectively evaluated 140 patients operated for total knee arthroplasty due to a varus knee. Full-leg hip to ankle preoperative X-rays were taken. Radiological parameters recorded were: mechanical axis deviation, hip-knee-ankle, anatomical-mechanical angle, medial neck shaft angle, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), lateral proximal femoral angle, lateral distal tibial angle (LDTA), femoral bowing, and length of tibia and femur. We also determined ideals tibial and femoral cuts in mm according to mechanical alignment technique. A R2 was calculated based on the linear regression between the predicted values and the observed data.
The greatest contributor to arthritic varus (R = 0.444) was MPTA. Minor contributors were mLDFA (R = 0.076), JLCA (R = 0.1554), LDTA (R = 0.065), and femoral bowing (R = 0.049). We recorded an average of 7.6 mm in lateral tibial cut thickness to restore neutral alignment.
The radiological major contributor to osteoarthritic varus knee alignment is related to proximal tibia deformity. As a surgical consequence, during performing total knee arthroplasty, the majority of the correction should therefore be made on tibial cut.
膝内翻对线是膝关节骨关节炎的一个众所周知的病因。它可由胫骨畸形、胫骨-股骨联合畸形和/或韧带失衡引起。在全膝关节置换术中，理解对线不良对于恢复额状面中立机械轴至关重要。本研究旨在确定导致内翻性骨关节炎膝的主要因素及其在进行全膝关节置换术中的相关手术意义。
我们回顾性评估了 140 例因内翻膝行全膝关节置换术的患者。术前拍摄了下肢髋踝全长 X 线片。记录的影像学参数包括：机械轴偏差、髋膝踝角、解剖-机械角、内侧颈干角、机械外侧股骨远端角（mLDFA）、内侧胫骨近端角（MPTA）、关节线会聚角（JLCA）、外侧股骨近端角、外侧胫骨远端角（LDTA）、股骨弯曲、胫骨和股骨长度。我们还根据机械对线技术确定了理想的胫骨和股骨截骨厚度（mm）。根据线性回归，计算了预测值与观察值之间的 R²。
导致关节炎性内翻的最大因素（R²=0.444）是 MPTA。次要因素是 mLDFA（R²=0.076）、JLCA（R²=0.1554）、LDTA（R²=0.065）和股骨弯曲（R²=0.049）。我们记录到平均需要 7.6mm 的外侧胫骨截骨厚度来恢复中立对线。
导致骨性关节炎内翻膝对线不良的主要影像学因素与胫骨近端畸形有关。因此，在进行全膝关节置换术时，作为手术后果，大部分矫正应在胫骨截骨上进行。
