Summary
In assessing risk of first-time, noncontact ACL injury, lateral tibial cartilage slope measurements should be considered in conjunction with AP laxity- and strength-related factors.
Abstract
Authors:
Carl Imhauser, Jacob Zeitlin, Mark Fontana, Michael Parides, Thomas Wickiewicz, Andrew Pearle, Bruce Beynnon, Danyal Nawabi
Introduction
Univariable analyses of knee geometry, anteroposterior (AP) laxity, and muscular strength have revealed associations with risk of first-time, noncontact ACL injury in females. However, multivariable analyses assessing the risk associated with combinations of these factors have been limited. As a result, it is unclear how these factors act interdependently to exacerbate or attenuate risk of injury. The purpose of this study was to characterize the risk of first-time, noncontact ACL injury associated with pairwise combinations of factors related to tibial slope, AP laxity, and strength.
Methods
First-time, noncontact ACL injury events were identified as they occurred in 61 female high school and collegiate athletes over a four-year period. Simultaneously, 61 sex- and age-matched control subjects, with no history of lower extremity injury, were selected from the same team. Magnetic resonance imaging (MRI) was acquired bilaterally, and articular geometries were obtained. From the MRI data, measurements of lateral posterior slope in the region of the middle articular cartilage and in the region of the posterior articular cartilage (covered by the posterior horn of the lateral meniscus) were measured using on objective method. On contralateral, uninjured case and control knees, AP knee translation was measured using a KT-2000 arthrometer, knee flexion strength was measured with a Biodex System 2, and hip ab/adduction strength was measured using a fixated, isometric dynamometer. Pairwise interaction effects, were inspected with partial dependence plots, which describe the (potentially nonlinear) shape of those associations, and odds ratios were determined.
Results
Two pairwise interaction effects were identified: lateral middle cartilage slope with hip adduction strength and lateral posterior cartilage slope with AP translation. The first revealed that the increase in risk associated with increasing middle tibial cartilage slope was larger in athletes with decreased hip adduction strength. The second revealed that the increase in risk associated with increasing posterior tibial cartilage slope was larger in athletes with increased AP translation.
Conclusions
The risk associated with increased middle cartilage slope may be reduced in athletes with greater hip adduction strength. This could be explained by an increase in femoral stability with stronger muscular forces. Moreover, clinicians should pay close attention to patients presenting with increased AP translation and greater posterior cartilage slope, as these features interacted to exacerbate risk of injury in our cohort. In assessing risk of first-time, noncontact ACL injury, lateral tibial cartilage slope measurements should be considered in conjunction with laxity- and strength-related factors.