BIOMECHANICAL COMPARISON OF ONE OR TWO-STRAND HAMSTRING RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT

Abstract

Purpose: The anterior cruciate ligament (ACL) is composed of two strands, the anteromedial (AM) and the posterolateral (PL). Each strand has a distinct biomechanical role. The classical techniques for reconstruction of the ACL using a one-strand graft cannot replace the AM strand of the ligament. Control of knee laxity after graft reconstruction with a single strand cannot restore physiological laxity.

Material and methods: This study was performed on 16 matched cadaver knees randomised for reconstruction technique. Anterior tibial dislocation was measured with the Rolimeter arthrometer using manual traction on the intact knee, after section of the ACL, and after arthroscopic reconstruction of the ACL using a 2-strand or 4-strand hamstring method at 20°, 60°, and 90° flexion. Changes in the length of each reconstructed strand were measured.

Results: For the 16 intact knees, anterior laxity was measured at 20°, 60° and 90°. After section of the ACL, laxity increased significantly at all angles studied. Statistical parametric and non-parametric tests demonstrated a significant difference between laxity after ACL section and after ACL reconstruction (one-strand) at 20°, 60° and 90° flexion. There was a significant difference between intact ACL and reconstructed ACL at 20° flexion, the residual laxity was greater after one-strand reconstruction. Conversely, at 60° and 90°, there was no difference in anterior displacement of the tibia for intact and reconstructed ACL. There was a statistically significant improvement in laxity between sectioned and reconstructed (two-strand) ACL at 20°, 60° and 90° but no difference in anterior dislocation between the intact ACL and the reconstructed ACL at 2°, 60°, and 90° flexion.

Conclusion: Two-strand reconstruction of the ACL provides laxity comparable with that of the intact ACL at 20°, 60°, and 90° flexion while one-strand reconstruction only re-establishes physiological laxity at 60° and 90°.