Biomechanical Function of Anterior Cruciate Ligament Remnants: Quantitative Measurement With a 3-Dimensional Electromagnetic Measurement System

Abstract

To evaluate quantitatively the biomechanical function of anterior cruciate ligament (ACL) remnants in patients with ACL injuries. Anterior tibial translation (ATT) with KT-1000 and during the Lachman test with an electromagnetic measurement system (EMS) and tibial acceleration during the pivot shift test with EMS were measured. A total of 121 unilateral ACL injuries were examined. ACL remnants were morphologically classified as being attached to the posterior cruciate ligament (PCL group), to the roof of the intercondylar notch (RIN group), to the lateral wall of the intercondylar notch (LWIN group), or as having no substantial remnants (NONE group). Partial ACL tears were excluded. ATT was measured using KT-1000. ATT during the Lachman test and tibial acceleration during the pivot shift test were measured using EMS. ACL remnant patterns were as follows: PCL group, 27 knees; RIN group, 34 knees; LWIN group, 27 knees; and NONE group, 33 knees. The ATT side-to-side difference in LWIN group (3.4 ± 0.7mm) by KT-1000 was significantly smaller than the RIN (5.7 ± 1.0mm) and NONE groups (5.9 ± 1.0mm)(P < .05). The ATT side-to-side difference during the Lachman test was significantly smaller in the LWIN group (5.3 ± 1.2mm) than the PCL (8.6 ± 1.4mm), RIN (8.5 ± 1.2mm), and NONE groups (7.6 ± 1.0mm)(P < .05). Tibial accelerations were 2.0 ± 0.4, 1.7 ± 0.2, 1.9 ± 0.2, and 1.8 ± 0.3m/s(2) in the PCL, RIN, LWIN, and NONE groups, respectively. There were no significant differences among groups. ACL remnants attached to the lateral wall of the intercondylar notch partially contributed to anterior-posterior stability but did not contribute to dynamic knee stability. These findings suggest that ACL remnants attached to nonanatomic insertion sites do not contribute significantly to knee stabilization. Level III, diagnostic study of nonconsecutive patients.