Department of Mechanical Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ, UK.
Department of Orthopaedic Surgery, Newcastle Freeman University Hospital, Newcastle, UK.
Knee Surg Sports Traumatol Arthrosc. 2021 Feb;29(2):659-667. doi: 10.1007/s00167-020-05995-6. Epub 2020 Apr 22.
Revision constrained-condylar total knee arthroplasty (CCK-TKA) is often used to provide additional mechanical constraint after failure of a primary TKA. However, it is unknown how much this translates to a reliance on soft-tissue support. The aim of this study was therefore to compare the laxity of a native knee to the CCK-TKA implanted state and quantify how medial soft-tissues stabilise the knee following CCK-TKA.
Ten intact cadaveric knees were tested in a robotic system at 0°, 30°, 60° and 90° flexion with ± 90 N anterior-posterior force, ± 8 Nm varus-valgus and ± 5 Nm internal-external torques. A fixed-bearing CCK-TKA was implanted and the laxity tests were repeated with the soft tissues intact and after sequential cutting. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were sequentially transected and the percentage contributions of each structure to restraining the applied loads were calculated.
Implanting a CCK-TKA did not alter anterior-posterior laxity from that of the original native knee, but it significantly decreased internal-external and varus-valgus rotational laxity (p < 0.05). Post CCK-TKA, the sMCL restrained 34% of the tibial displacing load in anterior drawer, 16% in internal rotation, 17% in external rotation and 53% in valgus, across the flexion angles tested. The dMCL restrained 11% of the valgus rotation moment.
With a fully-competent sMCL in-vitro, a fixed-bearing CCK-TKA knee provided more rotational constraint than the native knee. The robotic test data showed that both the soft-tissues and the semi-constrained implant restrained rotational knee laxity. Therefore, in clinical practice, a fixed-bearing CCK-TKA knee could be indicated for use in a knee with lax, less-competent medial soft tissues.
Controlled laboratory study.
在初次全膝关节置换术（TKA）失败后，常采用修正型限制型髁假体全膝关节置换术（CCK-TKA）来提供额外的机械限制。但目前尚不清楚这在多大程度上依赖于软组织的支撑。因此，本研究旨在比较正常膝关节与植入 CCK-TKA 后的膝关节松弛度，并定量评估 CCK-TKA 后内侧软组织对膝关节的稳定性。
在机器人系统中对 10 个完整的尸体膝关节进行测试，在 0°、30°、60°和 90°的屈曲角度下，施加±90 N 的前后向力、±8 Nm 的内外翻扭矩和±5 Nm 的内收外展扭矩。植入固定轴承 CCK-TKA 后，在保留软组织的情况下和依次切断软组织后重复松弛度测试。依次切断深层和浅层内侧副韧带（dMCL、sMCL）和后内侧囊（PMC），并计算每个结构对限制施加负荷的贡献百分比。
植入 CCK-TKA 不会改变原始自然膝关节的前后松弛度，但会显著降低内外旋转和内外翻旋转松弛度（p<0.05）。在 CCK-TKA 后，sMCL 在前方抽屉中限制了胫骨移位负荷的 34%，在内部旋转中限制了 16%，在外部旋转中限制了 17%，在外翻中限制了 53%，在测试的所有屈曲角度下。dMCL 限制了 11%的外翻旋转力矩。
在体外具有完全功能的 sMCL 的情况下，固定轴承 CCK-TKA 膝关节提供的旋转约束比自然膝关节更多。机器人测试数据表明，软组织和半约束植入物都限制了膝关节的旋转松弛度。因此，在临床实践中，对于内侧软组织松弛、功能不全的膝关节，可考虑使用固定轴承 CCK-TKA 膝关节。
对照实验室研究。
