Knee Morphology After Secondary Ipsilateral ACL Injury Compared to Those that Have Not Reinjured

Abstract

Modifiable and non-modifiable risk factors have been identified for primary anterior cruciate ligament (ACL) injury, however less research is available examining risk factors for a second ACL rupture. Identifying whether bony morphological factors are different (or more exaggerated) among those that experience a secondary ACL injury is critical to understanding if non-modifiable risk factors are associated with re-injury. PURPOSE: To identify if bony morphology is different among those that experience a secondary ACL re-injury as compared to ACL individuals that do not. METHODS: 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±4.0yrs), the primary clinical magnetic resonance imaging 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 re-injury (ACLx1, n=14, 8f/6m, 18.7±4.0yrs). 10 healthy controls were also enrolled (5m/5f, 20.8±3.9yrs) for the purposes of comparing our 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) were compared between all ACL participants (combined ACLx1 and ACLx2 groups) and controls using independent t-tests and across groups (ACLx1, ACLx2, controls) using one-way ANOVAs. RESULTS: All ACL reconstructed patients had a steeper LPTS than controls (6.5±2.7deg vs. 3.9±3.7deg, d=0.87, 95% CI 0.11-1.60, P=0.023), however no difference in LPTS was found between ACLx1 and ACLx2 (6.8±3.2deg vs. 6.3±2.4deg, P>0.05). 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>0.05). CONCLUSION: Compared to healthy individuals, a steeper LPTS is a common bony abnormality among all ACL injured participants. Individuals that go onto 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 re-injury.