Revision ACL Reconstruction - A retrospective failure analysis with a mean follow up of 35 months

AIMS AND OBJECTIVES: While patients following primary anterior cruciate ligament (ACL) surgery show satisfying results, the outcome after revision ACL reconstruction (ACLR) seems to be less favourable. The purpose of this study was to evaluate the outcome of patients after revision ACLR. We hypothesize that peripheral knee instabilities and further concomitant lesions are risk factors for failure of revision ACLR. Furthermore, we hypothesize that peripheral stabilisation will reduce the risk of failure. MATERIALS AND METHODS: Between 2013 and 2016, 111 patients with revision ACLR (revision surgery after primary ACL reconstruction) were included in the retrospective study. All patients were clinically examined with a minimum of 2 years after revision surgery (mean 35 months) and identified as “failed revision ACLR” (side-to-side difference greater than 5mm and/or pivot-shift grade 2/3) and “stable revision ACLR”. Multiple logistic regression modeling was used to evaluate whether certain predisposing factors were associated with increased odds of failure of the revision ACLR. RESULTS: Failure after revision ACLR occurred in 14.5% (n=16) of the cases. Preoperative medial knee instability (n=36) was associated with failure of revision ACLR, thus patients had a 17 times greater risk of failure when medial knee instability was diagnosed preoperatively. Also, the risk of failure was reduced when patients had peripheral medial (n=24) and/ or antero-lateral stabilisation (n=51). Increased posterior tibial slope (PTS, n=11 greater than 12°) and high-grade anterior knee laxity (side-to-side-difference greater than 5 mm and/or pivot-shift grade 3, n=41) were associated with failed revision ACLR. Furthermore, patients had a 9 times greater risk of failure when they were obese (BMI greater than 30 kg/m2, n=30). Also, postoperative functional scores in comparison to preoperative scores were shown to be significantly higher (Lysholm 85±27 vs. 51±31.9, p=0.024; Tegner 6.5± 1.3 vs. 4± 2.6, p=0.015). CONCLUSION: Results following revision anterior cruciate ligament reconstruction (ACLR) are less favourable than primary ACLR. Peripheral medial knee instability, high-grade anterior knee laxity, increased PTS and high BMI are risk factors for failure in revision ACLR while additional medial and/or antero-lateral stabilisation reduces the risk of failure.