No clinical differences between outside-in and all-inside techniques in medial meniscus repair: emphasizing Minimal Clinically Important Difference (MCID) -based outcomes

Abstract

Background While the all-inside (AI) technique is widely preferred for its simplicity and efficiency, the outside-in (OI) method is less commonly used. Despite both techniques being effective, direct comparisons of their functional outcomes are limited. This study aims to compare the clinical efficacy of OI and AI repair techniques for zone-3 and zone-4 medial meniscus tears, emphasizing outcomes based on the Minimal Clinically Important Difference (MCID).We hypothesized that there would be no significant difference in outcomes between the two techniques. Methods A retrospective cohort study was conducted on 93 patients (mean age: 37.6 +/- 11.8 years) with isolated zone-3 or zone-4 medial meniscus tears treated between 2020 and 2023. Patients were divided into two groups: OI (n = 63) and AI (n = 30), with all surgeries performed by two experienced orthopedic surgeons. Clinical outcomes were assessed using the International Knee Documentation Committee (IKDC) score, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Tegner-Lysholm Knee Scoring Scale (TLKS) at a minimum follow-up of 6 months. The MCID was calculated using the 0.5 standard deviation method. Statistical analyses included ANCOVA to adjust for age-related differences, with significance set at p < 0.05. Results Both OI and AI techniques resulted in significant improvements in IKDC, KOOS, and TLKS scores, surpassing MCID thresholds for all measures (p < 0.001). No significant differences were observed between the two groups in terms of functional outcomes (p > 0.05). The OI group utilized significantly fewer sutures (median: 1 [1-4] vs. 2 [1-7]; p < 0.001) and had a higher, though not statistically significant, complication rate (11% vs. 0%; p = 0.092). All complications were observed in the OI group, including saphenous nerve palsy and septic arthritis. Conclusion Both outside-in and all-inside techniques offer comparable clinical improvements in the repair of zone-3 and zone-4 medial meniscus tears, achieving success defined by MCID thresholds. The outside-in group used fewer sutures and exhibited a slightly higher complication rate, although this difference was not statistically significant. These findings support similar clinical outcomes for both techniques and may help guide surgical decision-making based on individual cases and surgeon experience.