Anatomic double-bundle versus single-bundle ACL reconstruction: a comparative biomechanical study in rabbits

Thirty New Zealand white rabbits underwent anterior cruciate ligament (ACL) reconstruction in their right knees; 15 animals underwent a double-bundle anatomic ACL reconstruction using the medial third of the patellar tendon and the semitendinosus tendon. Additionally, 15 animals underwent ACL reconstruction, using a single-bundle semitendinosus tendon autograft. The knees of both groups were evaluated with a device similar to the KT1000 arthrometer onto which a dial indicator was attached (Mitutoyo dial indicator 2050) in 30A degrees and 90A degrees of flexion, preoperatively, after ACL resection and 3 months postoperatively. Statistical analysis of the results revealed that for 90A degrees of knee flexion, the mean estimated anterior shift for the double-bundle technique was 1.92 mm lesser than that of the single-bundle technique (P = 0.006). For 30A degrees of knee flexion, the mean anterior shift was again lesser than that of the single-bundle technique by 0.66 mm, but this difference was not statistically significant. The described double-bundle ACL reconstruction technique resulted in a more stable knee as far as the anterior tibial shift was concerned as compared to a single-bundle ACL reconstruction. This animal model may be potentially useful in the future for the study of other parameters influencing the outcome of the double-bundle ACL reconstruction.