Department of Mechanical Engineering, and Musculoskeletal Surgery Group, Imperial College London, London SW7 2AZ, UK.
Knee Surg Sports Traumatol Arthrosc. 2012 Apr;20(4):613-20. doi: 10.1007/s00167-011-1864-7. Epub 2012 Jan 26.
This paper reviews the functional anatomy of the anterior cruciate ligament (ACL), which has a parallel array of collagen fascicles that have usually been divided into two 'fibre bundles': anteromedial (AM) and posterolateral (PL), according to their tibial attachment sites. The PL bundle has shorter fibres, and so it is subjected to greater tensile strains than the AM bundle when the whole ACL is stretched; its oblique orientation in the coronal plane imbues it with greater ability to resist tibial rotation than the more vertical AM fibre bundle. Most studies have found that the AM bundle is close to isometric when the knee flexes, while the PL bundle slackens approximately 6 mm. There is little evidence of significant fibre bundle elongation in response to tibial rotation. Selective bundle cutting studies have been performed, allowing both the bundle tensions and their contributions to resisting tibial anterior translation and tibial rotation to be calculated. These show that the function of the PL bundle was dominant near knee extension in some studies, particularly when resisting anterior drawer and that its contribution reduced rapidly with knee flexion through 30 degrees. There has been little study of the contributions of the fibre bundles in control of tibial internal-external rotation or the pivot shift: one study found that the AM bundle had larger tensions than the PL bundle during a simulated pivot shift, but another study found that cutting the PL bundle allowed a larger increase in coupled tibial anterior translation than cutting the AM bundle. It was concluded that the AM bundle is most important for resisting tibial anterior drawer-the primary function of the ACL-while the PL bundle is tight near knee extension, when it has a role in control of tibial rotational laxity. There is a clear need for further study of dynamic knee instability, to gain better understanding of how best to reconstruct the ACL and associated tissues.
本文回顾了前交叉韧带（ACL）的功能解剖结构，ACL 的胶原纤维束呈平行排列，通常根据其胫骨附着部位分为两个“纤维束”：前内束（AM）和后外束（PL）。PL 束的纤维较短，因此当整个 ACL 被拉伸时，它比 AM 束承受更大的拉伸应变；其在冠状面上的倾斜方向使其具有比更垂直的 AM 纤维束更大的抵抗胫骨旋转的能力。大多数研究发现，当膝关节弯曲时，AM 束接近等长，而 PL 束松弛约 6 毫米。几乎没有证据表明纤维束在响应胫骨旋转时有明显的伸长。已经进行了选择性束切割研究，允许计算束张力及其对抵抗胫骨前向移位和胫骨旋转的贡献。这些研究表明，在一些研究中，PL 束在膝关节伸展附近的功能占主导地位，特别是在抵抗前抽屉时，其贡献随着膝关节弯曲通过 30 度迅速降低。关于纤维束在控制胫骨内-外旋转或枢轴移位中的贡献的研究很少：一项研究发现，在模拟枢轴移位期间，AM 束的张力大于 PL 束，而另一项研究发现，与切割 AM 束相比，切割 PL 束允许更大的耦合胫骨前向移位增加。结论是，AM 束在抵抗胫骨前抽屉方面最为重要——ACL 的主要功能——而 PL 束在膝关节伸展附近时较为紧张，此时它在控制胫骨旋转松弛方面发挥作用。显然需要进一步研究动态膝关节不稳定，以更好地了解如何最好地重建 ACL 和相关组织。
