Posterolateral anatomical reconstruction restored varus but not rotational stability: A biomechanical study with cadavers.

BACKGROUND AND AIM: Lesions to the posterolateral corner (PLC) of the knee are rarely isolated injuries, and they are potentially devastating, leading to progressive chondral injury, with important functional impairment. The objectives of this biomechanical study were to evaluate angular deformation with two loads and considering four flexion angles of the knee, varus and external rotation and in three situations of integrity, reconstruction and injury of posterolateral knee structures. METHODS: The posterolateral structures of 10 cadaveric knees were submitted to three biomechanical assays: in the "intact condition", "injured", and "reconstructed". The technique used for the reconstruction was the one proposed by LaPrade et al., but with autografts of hamstring tendons instead. A device was designed to apply loads of 2 and 5Nm, with zero, 30°, 60° and 90° of knee flexion, in varus or in external rotation, measuring angular deformation with photogoniometry. RESULTS: The anatomical reconstruction of the PLC proposed here did restore varus stability in all flexion angles (p<0.005), but not rotational stability. External rotation deformation at 90° was similar in all test conditions. In knee extension, external rotation was stabilized only at 2Nm. At 60°, external rotation was partially stabilized (p<0.05). CONCLUSIONS: The anatomical PLC reconstruction using hamstring tendons restored varus but not external rotational stability. CLINICAL RELEVANCE: The reconstruction of posterolateral corner injuries with autologous allografts is very important for regions were tissue banks are not available. This technique may be a first step to achieve this goal.

Importance of the different posterolateral knee static stabilizers: biomechanical study

PURPOSE: The purpose of this study was to evaluate the relative importance of the different static stabilizers of the posterolateral corner of the knee in cadavers. METHODS: Tests were performed with the application of a varus and external rotation force to the knee in extension at 30 and 60 degrees of flexion using 10 cadaver knees. The forces were applied initially to an intact knee and then repeated after a selective sectioning of the ligaments into the following: section of the lateral collateral ligament; section of the lateral collateral ligament and the popliteofibular complex; and section of the lateral collateral ligament, the popliteofibular complex and the posterolateral capsule. The parameters studied were the angular deformity and stiffness when the knees were submitted to a 15 Newton-meter varus torque and a 6 Newton-meter external tibial torque. Statistical analysis was performed using the ANOVA (Analysis of Variance) and Tukey's tests. RESULTS AND CONCLUSION: Our findings showed that the lateral collateral ligament was important in varus stability at 0, 30 and 60 degrees. The popliteofibular complex was the most important structure for external rotation stability at all angles of flexion and was also important for varus stability at 30 and 60 degrees. The posterolateral capsule was important for varus stability at 0 and 30 degrees and for external rotation stability in extension. Level of evidence: Level IV (cadaver study).