膝关节前交叉韧带损伤后III°轴移的形成机理研究

The pivot-shift test is one of the important phenomenons to evaluate the degree of knee joint instability following anterior cruciate ligament (ACL) injury, which can be categorized into three grades: grade I (glide), grade II (clunk), and grade III (locked subluxation). Recently, some studies have shown that patients with grade III pivot-shift usually present with residual laxity after ACL reconstruction, which indicates unsatisfied long-term clinical outcomes. Therefore, it is imperative to regard the grade III pivot-shift as a “special type” of ACL injury. Until now, as the real mechanism of grade III pivot-shift has not been clarified, the optimal treatment algorithm cannot be determined. We hypothesize that the grade III pivot-shift phenomenon has a different mechanism from grade I and grade II, which is resulted from a subset injury pattern of ACL associated with lateral structures of knee joints. In this study, we use computer-assisted navigation system to evaluate the kinematic biomechanical effect of knee joint. First, cadaveric knees are used to simulate the ACL injury model. The lateral structures including lateral meniscus, iliotibial band, and anterolateral ligament are randomly sectioned. The navigation system is then used to evaluate their effects on producing the pivot-shift phenomenon. Meanwhile, different reconstruction protocols are also performed to evaluate their influences on eliminating the pivot-shift phenomenon. Based on the results of our study, we hope to further clarify the real mechanism of grade III pivot-shift phenomenon, and to provide a better way of improving the treatment algorithm of ACL reconstruction in the future.

轴移现象是ACL损伤后膝关节不稳定程度的重要临床观察指标，根据轻-重的顺序分为I°（滑动）、II°（跳动）、III°（锁定半脱位）。III°轴移属重度不稳定，术后常存较高松弛率和失效率，与I°和II°不同，可视为一种“特殊类型”的ACL损伤。轴移现象的发生机理一直被归结为单纯ACL损伤，即“单一机制”，但近期研究表明：单纯切断ACL，并不导致III°轴移，只有联合切断其他结构才会出现。故研究假说：III°轴移的发生机理应为“多重机制”，是ACL与一个或多个膝关节外侧结构共同损伤的结果。本研究采用尸体切断试验，利用计算机辅助导航进行生物力学评估。塑造ACL损伤模型，按不同顺序切断外侧半月板、髂胫束及膝前外侧韧带。通过轴移变化和生物力学指标确定III°轴移的形成机制，并对受损结构进行修复，观察轴移的改善，进一步验证假说。本研究旨在探索III°轴移的发生机理，制定针对性治疗，提高ACL手术疗效。

本研究按照项目计划书完成了相应的研究工作。研究过程中，首先采用尸体切断试验的方法，塑造前交叉韧带（Anterior cruciate ligament, ACL）损伤模型，然后按照不同顺序分别切断膝关节外侧半月板以及膝前外侧韧带，在此基础上对损伤的结构按照不同顺序逐一修复。每次操作后，均行轴移试验，并利用导航系统测量轴移过程中胫骨外侧平台相对股骨外髁的前向位移及内旋角度。结果发现：单纯切断ACL后，胫骨前向位移及内旋角度有显著性增加，但并不能造成III度轴移现象。继续切断外侧半月板或膝关节前外侧韧带后，胫骨前向位移及内旋角度会进一步显著增加，最终导致III度轴移现象的发生。在此基础上，单独重建ACL，随能够显著减少胫骨前向位移及内旋角度，但与完整的膝关节尸体标本相比仍存在显著差异，且轴移现象并不能完全消除，唯有将切断的外侧半月板或膝关节前外侧韧带修复后，胫骨前向位移及内旋角度才能恢复至正常状态，此时轴移现象才能完全消除。由此得出本研究的结论：1、III度轴移现象的发生机理应为“多重机制“，是ACL与一个或多个膝关节外侧结构共同损伤的结果；2、当发生III度轴移时，单纯重建ACL并不能完全消除轴移现象，只有将受损的膝关节外侧结构同时修复后，才能消除。本研究阐明了ACL损伤后III度轴移现象的发生机理，并为临床工作中III度轴移现象的诊疗提供了依据。