Increased Rotatory Laxity after Anterolateral Ligament Lesion in Anterior Cruciate Ligament‐ (ACL‐) Deficient Knees: A Cadaveric Study with Noninvasive Inertial Sensors

The anterolateral ligament (ALL) has been suggested as an important secondary knee restrain on the dynamic laxity in anterior cruciate ligament‐ (ACL‐) deficient knees. Nevertheless, its kinematical contribution to the pivot‐shift (PS) phenomenon has not been clearly and objectively defined, and noninvasive sensor technology could give a crucial contribution in this direction. The aim of the present study was to quantify in vitro the PS phenomenon in order to investigate the differences between an ACL‐deficient knee and an ACL+ALL‐deficient knee. Ten fresh‐frozen paired human cadaveric knees (n = 20) were included in this controlled laboratory study. Intact, ACL‐deficient, and ACL+ALL‐deficient knees were subjected to a manual PS test quantified by a noninvasive triaxial accelerometer (KiRA, OrthoKey). Kinematic data (i.e., posterior acceleration of the tibial lateral compartment) were recorded and compared among the three statuses. Pairwise Student’s t‐test was used to compare the single groups (p < 0.05). Intact knees, ACL‐deficient knees, and ACL+ALL‐deficient knees showed an acceleration of 5.3 ± 2.1 m/s2, 6.3 ± 2.3 m/s2, and 7.8 ± 2.1 m/s2, respectively. Combined sectioning of ACL and ALL resulted in a statistically significant acceleration increase compared to both the intact state (p < 0.01) and the ACL‐deficient state (p < 0.01). The acceleration increase determined by isolated ACL resection compared to the intact state was not statistically significant (p > 0.05). The ALL sectioning increased the rotatory laxity during the PS after ACL sectioning as measured through a user‐friendly, noninvasive triaxial accelerometer.