Niki Yasuo, Sassa Tomoki, Nagai Katsuya, Harato Kengo, Kobayashi Shu, Yamashita Taro
Department of Orthopaedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
Knee Surg Sports Traumatol Arthrosc. 2017 Nov;25(11):3452-3458. doi: 10.1007/s00167-017-4459-0. Epub 2017 Feb 21.
The flexion-extension axis (FEA) of the femur is substantially changed after mechanically aligned total knee arthroplasty (TKA) due to a discrepancy in bone cut thickness between the posterior and distal femoral regions. This study assessed the bony gap changes and FEA displacement caused by this problem in osteoarthritis patients.
The study enrolled 60 knees from 60 patients for whom primary TKA was planned due to medial knee osteoarthritis. All patients underwent computed tomography, and 3-dimensional (3D) bone models were reconstructed on 3D-planning software. Bone cuts of the distal femur and proximal tibia were simulated to be perpendicular to each mechanical axis. Bony gap change was computed as the difference in bone cut thickness between medial and lateral compartments. Each femoral condyle was assessed for potential FEA displacement, as the difference in bone cut thickness between posterior and distal femoral regions.
The mean magnitude of bony gap discrepancy necessary for mediolateral balancing was 1.6 ± 3.3 mm (range -7 to 8.2 mm) at 0° extension and -0.2 ± 2.6 mm (range -6.4 to 4.3 mm) at 90° flexion. At least 2 mm of bony gap discrepancy at 0° extension and 90° flexion was found in 40 patients (67%) and 26 patients (43%), respectively. In terms of femoral bone cut, posterior bone cut thickness was significantly larger than distal bone cut thickness in the medial compartment (p < 0.001). Bony gap discrepancy between distal and posterior regions of the femoral condyle was ≥2 mm in 28 patients (47%).
This study focused on two flaws of mechanically aligned TKA in OA patients. Substantial numbers of patients inevitably required >2 mm of medial collateral ligament release at 0° extension and showed a bone cut discrepancy between distal and posterior regions, carrying a risk of FEA displacement and subsequent unnatural knee motions during knee extension and flexion. Level of evidence IV.
由于股骨后髁与远端区域截骨厚度存在差异，机械对线全膝关节置换术（TKA）后股骨的屈伸轴（FEA）会发生显著变化。本研究评估了骨关节炎患者中该问题导致的骨间隙变化和FEA位移。
本研究纳入了60例因膝关节内侧骨关节炎计划行初次TKA的患者的60个膝关节。所有患者均接受了计算机断层扫描，并在三维（3D）规划软件上重建了3D骨模型。模拟股骨远端和胫骨近端的截骨垂直于各自的机械轴。骨间隙变化计算为内侧和外侧间室截骨厚度的差值。评估每个股骨髁潜在的FEA位移，即股骨后髁与远端区域截骨厚度的差值。
伸直0°时，内外侧平衡所需的平均骨间隙差异幅度为1.6±3.3mm（范围-7至8.2mm），屈曲90°时为-0.2±2.6mm（范围-6.4至4.3mm）。分别有40例患者（67%）和26例患者（43%）在伸直0°和屈曲90°时存在至少2mm的骨间隙差异。在股骨截骨方面，内侧间室后髁截骨厚度显著大于远端截骨厚度（p<0.001）。28例患者（47%）股骨髁远端与后髁区域的骨间隙差异≥2mm。
本研究关注了骨关节炎患者机械对线TKA的两个缺陷。大量患者在伸直0°时不可避免地需要>2mm的内侧副韧带松解，并且在远端和后髁区域存在截骨差异，存在FEA位移以及膝关节屈伸过程中后续不自然膝关节运动的风险。证据等级IV。
