Examination of Knee Morphology After Secondary Ipsilateral ACL Injury Compared With Those That Have Not Been Reinjured: A Preliminary Study

Abstract

Modifiable and nonmodifiable risk factors have been identified for sustaining a primary anterior cruciate ligament (ACL) injury; however, less research is available examining risk factors for a second injury. Identifying whether bony morphological factors are different (or more exaggerated) among those that experience a secondary ACL injury is critical to understanding if nonmodifiable risk factors are associated with a second injury. To determine if bony morphology is different among those that experience a secondary ACL reinjury as compared with those that do not. Case-control. University laboratory. ACL participants were tracked after return to play following primary reconstruction, and if individuals experienced a second ipsilateral injury (ACLx2; n = 14, 8f/6m, 17.9 ± 4.0y), the primary clinical MRI was analyzed for bony morphological risk factors. ACLx2 participants were matched to individuals (sex, age, height, graft, gender, and activity level) that had undergone reconstruction but did not experience reinjury (ACLx1, n = 14, 8f/6m, 18.7 ± 4.0y). Ten controls were also enrolled (5m/5f, 20.8 ± 3.9y) for the purposes of comparing the authors' ACL data against healthy knees. Lateral and medial posterior tibial slopes (LPTS, MPTS), notch shape index (NSI), and medial tibial plateau depth of concavity (MDC). All ACL-reconstructed patients (combined ACLx1 and ACLx2 group) had a steeper LPTS than controls (d = 0.87, 95% CI 0.11-1.60, P = .023); however, no difference in LPTS was found between ACLx1 and ACLx2 (P > .05). No differences in MPTS, NSI, and MDC were found between all ACL participants (combined ACLx2 and ACLx1) and controls or between ACLx1 and ACLx2 (P > .05). Compared to healthy individuals, a steeper LPTS is a common bony abnormality in all ACL-injured participants. Individuals that go on to experience a second ipsilateral ACL injury do not have more exaggerated bony morphology than those that do not suggesting that differences in modifiable risk factors at return to play may contribute to reinjury.