Bone Bruise Patterns After Noncontact Anterior Cruciate Ligament Tears Differ Between Alpine Skiers and Pivoting Sports Athletes

Background: Concomitant injuries after an anterior cruciate ligament (ACL) tear differ between sports, which may be related to divergent loading patterns. Bone bruises (BBs) can provide insight into the biomechanical injury mechanism. Purpose/Hypothesis: The purpose of this study was to compare BB patterns and concomitant injuries after noncontact ACL tears between pivoting sports athletes and alpine skiers. It was hypothesized that pivoting sports athletes would have a higher prevalence and depth of BBs and a higher prevalence of concomitant injuries. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 446 consecutive patients with ACL injuries between December 2016 and November 2020 were retrospectively analyzed. Patients with contact injuries, an injury mechanism other than alpine skiing or pivoting sports, missing magnetic resonance imaging, failed previous nonoperative treatment, open physes, or incomplete ACL tears were excluded. Magnetic resonance imaging was used to classify BB location and depth as well as concomitant meniscal and collateral ligament injuries. There were 2 groups (alpine skiers vs pivoting sports athletes) that were propensity score matched for age, body mass index, and sex. Chi-square and Mann-Whitney U tests were used to detect differences, with significance set at P < .05. The Fleiss kappa (κ) was used to assess observer agreement. Results: Propensity score matching of 122 included patients resulted in 27 patients per group. Pivoting sports athletes showed a higher prevalence of BBs in the lateral femoral condyle than alpine skiers (85.2% vs 51.9%, respectively; P = .008). No significant differences were found for BB prevalence in other anatomic locations, BB depth, and concomitant meniscal and collateral ligament injuries. Post hoc power analysis showed a power of 75%. Observer agreement was almost perfect for BB prevalence (κ = 0.95-1.00), substantial for BB depth (κ = 0.68-0.75), and substantial to almost perfect for concomitant injuries (κ = 0.64-0.94). Conclusion: The prevalence of BBs in the lateral femoral condyle was higher in pivoting sports athletes than in alpine skiers after acute noncontact ACL tears. This suggests that ACL injuries in pivoting sports are associated with higher lateral compression forces in a pivot-shift mechanism, whereas anterior tibial translation and tibial rotation may be the predominant loading pattern in alpine skiing.