Biomechanical effect of posterolateral corner sectioning after ACL injury and reconstruction

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. 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 30A degrees and 90A degrees of flexion (AP30 and AP90) applying a 130 N load and IE at 30A degrees and 90A degrees of knee flexion with a 5 N load. Sectioning the ACL significantly increased the AP30 at 30A degrees and 90A degrees of knee flexion (p < 0.05). At 90A degrees of knee flexion, the resection of the LCL determined a significant increase in terms of AP laxity (p < 0.05). At 90A degrees 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 30A degrees and 90A degrees of knee flexion (p < 0.05). Isolated ACL reconstruction is able to control the AP laxity with a combined complete lesion of the PLC at 30A degrees 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.