Functional anatomy of the anterior cruciate ligament. Fibre bundle actions related to ligament replacements and injuries

TLDR

The study examined the fibre bundle anatomy of the anterior cruciate ligament. The authors measured bundle contributions to anterior subluxation resistance and length changes in flexion, extension, and tibial rotation through sequential transection experiments. Three functional bundles—anteromedial, intermediate, and posterolateral—were identified; none were isometric, with the posterolateral bundle stretched in extension and the anteromedial in flexion, correlating with greater stability and partial rupture risk, while tibial rotation had no significant effect, and the isometric point sought by some replacements lies anterior and superior to the intermediate bundle’s femoral origin.

Abstract

This work studied the fibre bundle anatomy of the anterior cruciate ligament. Three functional bundles--anteromedial, intermediate, and posterolateral--were identified in cadaver knees. Their contributions to resisting anterior subluxation in flexion and extension were found by repeated tests after sequential bundle transection. Changes of length in flexion and extension and in tibial rotation were measured. None of the fibres were isometric. The posterolateral bundle was stretched in extension and the anteromedial in flexion, which correlated with increased contributions to knee stability and the likelihood of partial ruptures in these positions. Tibial rotation had no significant effect. The fibre length changes suggested that the 'isometric point' aimed at by some ligament replacements lay anterior and superior to the femoral origin of the intermediate fibre bundle and towards the roof of the intercondylar notch.