EFFECT OF DOUBLE BUNDLE ACL RECONSTRUCTION ON TIBIAL INTERNAL ROTATION: AN “IN VIVO” CAOS STUDY

Abstract

Cadeveric studies showed that single bundle ACL reconstructions were successful in limiting anterior tibial translation but were insufficient to control a combined rotatory load of internal and valgus torque. One possible cause of these condition could be that current single bundle procedures cannot realistically reproduce the complex anatomy of the ACL, especially the different function of its anteromedial(AM)and posterolateral(PL)bundle. The hypothesis of our study is that the addition of the PL bundle to the AM bundle, in an “in vivo” double bundle computer assisted ACL reconstruction, is actually able to reduce the internal rotation of the tibia at 30° degrees of knee flexion. Computer assisted ACL reconstruction has been used because it could be very effective in evaluating the global performance of the reconstructed knee.

Ten consecutive doble bundle ACL reconstructions were performed in our Hospital using hamstrings graft and the 2.0OrthoPilot-B. Braun-Aesculap ACLnavigation system. The average age of patients was 27.8 years.

The double-looped semitendinosus tendon replicating the AM bundle was fixed first at 60° of knee flexion. Than the gracilis tendon replicating the PL bundle was fixed at 15° of knee flexion. Maximum manual A–P displacement at 30° of flexion, maximum internal and external rotation of the knee were evaluated using the navigation system before surgery and after single(A–M)and double (AM+PL)bundle reconstruction. Statystical anlisys was done using paired T-test.

Before ACL reconstruction mean manual maximum AP displacement was 17.2mm;mean manual maximum internal rotation was 19.8mm and mean manual maximum external rotation was 16.8mm. After AM bundle reconstruction mean manual maximum AP displacement was 6.1mm;mean manual maximum internal rotation was 17.0mm and mean manual maximum external rotation was 16.3mm. After AM+PL bundles reconstruction mean manual maximum AP displacement was 5.3mm;mean manual maximum internal rotation was 16.2mm and mean manual maximum external rotation was 14.6mm. There was no statistically significant difference in the tibial internal rotation at 30° after single bundle(AM)and double bundle(AM+PL)reconstruction.

In this study the effectiveness of the PL bundle in controlling the internal rotation of the tibia, responsible of rotational instability of the knee, was evaluated in “in vivo” ACL reconstruction. The navigator system allowed us to obtain “in vivo” the real and correct value of AP displacement and internal and external rotation of the tibia before and after reconstruction.

Our hypothesis that the addition of the PL bundle to the AM bundle is actually able to reduce the internal rotation of the tibia at 30° degrees of knee flexion, minimizing the pivot shift phenomenon, on the basis of our study has not been confirmed.