Anterolateral rotatory instability of the knee: anatomy, biomechanics, and related reconstructions

Abstract

There are several different factors, why an anterior cruciate ligament (ACL) graft may fail. One reason is missed peripheral injuries, especially on the anterolateral side of the knee, which may be responsible for different grades of instability after ACL rupture. Thus, the aim of this thesis was to investigate the role of the anterolateral structures in restraining knee instability and provide a surgical rationale for extra-articular lateral reconstruction.

A cutting study was performed using a six degree of freedom robotic setup. The anterolateral structures were subsequently transected in ACL-intact and ACL deficient knees and the drop in force was analysed. The iliotibial tract was the primary restraint to internal tibial rotation in 30°, 60°, and 90° knee flexion. The ACL presented the main contribution in full extension.

In high-grade anterolateral rotatory instability (ALRI), an ACL reconstruction and an additional extra-articular lateral reconstruction may control this instability better than an isolated ACL reconstruction. Furthermore, it will share the load with the intra-articular graft and therefore prevent re-rupture. Cadaveric knees were tested in a muscle loading rig and the length changes of the native anterolateral structures and several extra-articular reconstructions were measured using a suture and a linear variable displacement transducer (LVDT). The Lemaire and the MacIntosh reconstruction, which were guided deep to the lateral collateral ligament (LCL) had preferable length change pattern, being tight in extension and slacken in flexion.

The iliotibial tract was the primary restraint to internal tibial rotation and an injury should be expected in high-grade ALRI. Regarding length change pattern of lateral extra-articular reconstructions a Lemaire or MacIntosh reconstruction, guided deep to the LCL should be used.