The Effect of Sequential Tearing of the Anterior Cruciate and Anterolateral Ligament on Anterior Translation and the Pivot-Shift Phenomenon: A Cadaveric Study Using Navigation.

ABSTRACT

PURPOSE: To evaluate the effect of progressive lesions of the anterior cruciate ligament (ACL) and anterolateral ligament (ALL) on anterior tibial translation (ATT) as evaluated through the Lachman test and internal tibial rotation (ITR) during a dynamic pivot-shift test in a cadaveric model. METHODS: A total of 7 specimens were tested using a navigation system (2.2 OrthoPilot ACL navigation system). The anterior stability of the knee was measured through the Lachman test and dynamic rotational stability was measured through the pivot-shift test in 3 different conditions intact knee; ACL-deficient knee; and finally, ACL- and ALL-deficient knee. The resulting measurements from the navigation system recorded the real-time changes in both translation and internal rotation during the Lachman and pivot-shift maneuvers. RESULTS: Mean ATT was 7.57 ± 0.53 mm in the intact knee, 14 ± 2.44 mm in the ACL-deficient knee, and 14 ± 2.44 mm in the ACL- and ALL-deficient knee. Mean ITR during the pivot-shift test was 10.14° ± 2.26° in the intact knee, 12.14° ± 2.19° in the ACL-deficient knee, and 18.86° ± 2.73° in the ACL- and ALL-deficient knee. There was a statistically significant difference in static ATT between the intact and ACL-deficient knees (P = .039) but no difference through the addition of an ALL lesion (P = .068). For dynamic rotational control testing, there was no significant difference in ATT between groups but a significant difference in ITR was found (F = 25.17, P = .00034). CONCLUSIONS: During the pivot-shift test, a combined lesion of the ACL and ALL has a significant effect on ITR whereas an isolated lesion of the ACL has no effect on either ATT or ITR. During the Lachman test, an isolated lesion of the ACL has a significant effect on ATT but an additional lesion of the ALL does not affect ATT. CLINICAL RELEVANCE Dynamic rotational control as tested by the pivot-shift test is greatly influenced by a combined lesion of the ACL and ALL. In clinical cases of a pivot shift, addressing the anterolateral structures may be considered.