Comparative Outcomes of Isolated vs Augmented FHL Tendon Transfer for Chronic Achilles Tendon Ruptures: A Systematic Review

Research Type: Level 5 - Case report, Expert opinion, Personal observation Introduction/Purpose: Chronic Achilles tendon ruptures are challenging to manage, often requiring surgical intervention to restore function and alleviate pain. The flexor hallucis longus (FHL) tendon transfer has emerged as a viable solution for augmenting repair in neglected cases of Achilles tendon rupture. This procedure can be performed either as an isolated transfer or as an augmentation to a primary tendon repair. However, the outcomes of these two approaches remain uncertain, with variations in patient outcomes. This study aims to compare the clinical outcomes, return to activity, and re-rupture rates between isolated FHL tendon transfer and FHL augmentation for the management of chronic Achilles tendon ruptures. Methods: A systematic review was conducted in January 2025, utilizing multiple databases, including PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library, to identify clinical studies that assessed the outcomes of isolated versus augmented FHL tendon transfer for chronic Achilles tendon ruptures. Studies were selected based on their inclusion of clinical outcomes, patient demographics, return to activities, and complication rates. Data were extracted and analyzed to provide a comparative evaluation of the two techniques, focusing on key outcome measures such as the Visual Analog Scale (VAS) for pain, American Orthopaedic Foot and Ankle Society (AOFAS) scores, Achilles Tendon Rupture Score (ATRS), and re-rupture rates. Results: We included 40 studies, involving 819 patients (522 in the augmented cohort, 305 in the isolated cohort). The mean age was 50.9 years (augmented) and 53.3 years (isolated), with mean follow-up of 33.8 and 20.19 months, respectively. The mean time between injury and surgery was 141.6 days (augmented) and 131.9 days (isolated). Postoperative outcomes showed a significant improvement in both cohorts, with the augmented group achieving a mean VAS score of 1.06 (preop: 4.8), AOFAS score of 91.9 (preop: 60.6), and ATRS of 88.13. In the isolated group, VAS improved to 0.3 (preop: 4.26), AOFAS to 91.6 (preop: 51.09), and ATRS to 81.36. The mean return to activities was 24.3 weeks (augmented) and 21.3 weeks (isolated). Re-rupture rates were below 1% in both cohorts. Conclusion: Both procedures yielded favorable clinical outcomes, with significant improvements in pain, function, and activity levels. The augmented group showed a slightly higher ATRS and lower complication rates, although the differences between groups were minimal. Both techniques had low re-rupture rates, indicating their reliability in treating chronic Achilles ruptures. While both approaches provide effective treatment, the isolated FHL transfer may offer a less invasive option with comparable outcomes to the augmented technique and a slightly faster return to activities. Future studies with higher-quality evidence and longer follow-up are needed to definitively determine the optimal approach for chronic Achilles tendon rupture repair.