Side-to-side differences in anterior cruciate ligament volume in healthy control subjects

Examination of anterior cruciate ligament (ACL) anatomy is of great interest both in studying injury mechanisms and surgical reconstruction. However, after a typical acute ACL rupture it is not possible to measure the dimensions of the ACL itself due to concomitant or subsequent degeneration of the remaining ligamentous tissue. The contralateral ACL may be an appropriate surrogate for measuring anatomical dimensions, but it remains unknown whether side-to-side differences preclude using the contralateral as a valid surrogate for the ruptured ACL. This study examined whether the ACL volume is significantly different between the left and right knees of uninjured subjects. ACL volumes were calculated for the left and right sides of 28 individuals using a previously validated MRI-based method. The mean ACL volume was not significantly different (p=0.2331) between the two sides in this population. Side-to-side ACL volume was also well correlated (correlation=0.91, p<0.0001). The results of this study show that the volume of the contralateral ACL is a valid surrogate measure for a missing ACL on the injured side. This non-invasive, in vivo technique for measuring ACL volume may prove useful in future large-scale comprehensive studies of potential risk factors for ACL rupture, in quantifying potential loading effects on ACL size as a prophylactic measure against ACL rupture, and in the use of ACL volume as a screening tool for assessing risk of injury.