Anterior Cruciate Ligament Injury with PLRI

Injuries to the posterolateral corner(PLC) structures can result in posterolateral rotatory instability (PLRI) of the knee, which is a pathological instability caused by posterolateral tibial subluxation when an external rotational force is applied to the knee joint. However, the diagnosis of PLC injury can be easily missed, unless there is a high level of clinical suspicion for possible injury to this region, so routine assessment of PLRI is necessary to make the correct diagnosis. The presence of PLRI was assessed by physical examination using the posterolateral drawer test and the dial test and by palpation of subluxation of the posterior tibial condyle by placing four small fingers on the posterolateral aspect of the popliteal fossa. Markolf et al. measured the force on a simulated intact ACL with and without the posterolateral knee structures and found that cutting the posterolateral structures increased the force on the ACL during varus loading. LaPrade et al. examined the force on ACL grafts in cadaver knees in which the posterolateral structure had been selectively cut and found that grade III posterolateral injuries were associated with significantly increased force on ACL grafts. In addition, untreated posterolateral injuries were associated with graft failure in ACL and PCL reconstructions, highlighting the clinical importance of treating posterolateral injuries when other ligament injuries are present. More recently, anatomical reconstructions of the PLC have been shown to provide the best results when compared to other surgical techniques for the treatment of in the treatment of chronic posterolateral instability. However, a cadaveric biomechanical study by Apsingi et al. showed that anatomical PLC reconstruction did not outperform the single fibular sling technique. The varus bony malalignment and varus thrust gait should be corrected prior to surgical reconstruction of severe lateral and posterolateral ligament deficiencies. In chronic ACL defects, varus malalignment, medial meniscus loss, and partial to complete ACL insufficiency, a valgus tibial osteotomy should be performed first to avoid overloading the lateral capsular structures to be reconstructed. Therefore, patients with suspected PLC injury should be carefully monitored for limb alignment using full-length weight-bearing radiographs and changes in gait.