Biomechanical effect of posterolateral corner sectioning after ACL injury and reconstruction.

Purpose: Posterolateral corner structures functionally interact with the ACL. The aim of this study was to investigate the capability of an isolated ACL reconstruction control laxity parameters in a knee with combined ACL and PLC and the increase in terms of laxity produced by the resection of the PC in an ACL-deficient knee.

Method: An in vitro cadaveric study was performed on seven knees. The joints were analysed in the following conditions: intact, after ACL resection, after popliteus complex resection, after ACL reconstruction and after LCL. Testing laxity parameters were recorded with an intra-operative navigation system and defined as: AP displacement at 30° and 90° of flexion (AP30 and AP90) applying a 130 N load and IE at 30° and 90° of knee flexion with a 5 N load.

Results: Sectioning the ACL significantly increased the AP30 at 30° and 90° of knee flexion (p < 0.05). At 90° of knee flexion, the resection of the LCL determined a significant increase in terms of AP laxity (p < 0.05). At 90° has been found a significant difference for the IE laxity (p < 0.05) after PC resection. Sectioning the LCL produced a significant increase in IE laxity at 30° and 90° of knee flexion (p < 0.05).

Conclusion: Isolated ACL reconstruction is able to control the AP laxity with a combined complete lesion of the PLC at 30° of knee flexion, but not at higher angle of knee flexion. Considering the IE rotations, the reconstruction was not sufficient not even to control a partial lesion of the PLC. These findings suggest that additional surgical procedures should be considerate even when facing combined PLC lesion.