AM bundle controls the anterior-posterior and rotational stability to a greater extent than the PL bundle - a cadaver study.

BACKGROUND: The purpose of this study was to evaluate the influence of both bundles of the anterior cruciate ligament (ACL) on knee stability, anterior-posterior translation (APT) and internal (IR) and external (ER) rotation in cadaveric knees using a computer navigation system.

METHODS: The APT, IR, and ER of the knees were recorded in the intact condition, the anterolateral bundle (AM) or the posterolateral bundle (PL) deficit condition and in the ACL-deficient condition. The KT-1000 arthrometer was used for APT evaluation. The measurement of rotational movements was done using a rollimeter. All tests were performed at 30°, 60° and 90° of flexion.

RESULTS: At 30° of flexion: In the intact knee APT was 5.8mm, IR 12.1°, ER 10.1°. After the AM was cut, the APT increased to 9.1mm, IR to 13.9° and ER to 12.6°. After the PL was cut, the APT was 6.4mm, IR 13.1° and ER 10.6°. After the AM and PL were cut, the APT was 10.8mm, IR 15.7° and the ER was 12.9° on average.

CONCLUSIONS: The AM has a greater impact on the APT than the PL in all knee joint flexion angles. The PL does not resist the rotational stability more than the AM. The rotational stability is better controlled by both bundles of ACL as compared to one bundle of the ACL.

CLINICAL RELEVANCE: This study acknowledges the fact that the both bundles of the ACL are importants for AP and rotational stability of the knee joint.