Comparative outcomes of different achilles stump management after flexor hallucis longus tendon transfer

Various surgical techniques for reconstruction of chronic Achilles tendinosis have been developed, including free semitendinosus tendon autograft and allograft for larger Achilles tendon defects. Flexor hallucis longus (FHL) transfer has emerged as an effective treatment option for patients with insertional Achilles tendinopathy (IAT). During FHL transfer, FHL tendon is harvested at its distal part and rerouted to augment or replace the diseased portion of the Achilles tendon, providing improved structural integrity and function, but the necessity of reattachment of the Achilles stump in FHL transfer remains controversial. Patients who underwent FHL transfer surgery for IAT between 2013 and 2022 were enrolled in this retrospective study. Evaluating parameters included clinical evaluations, complications, a satisfaction questionnaire, preoperative and postoperative visual analog scale (VAS) as well as outcomes scores including American Orthopaedic Foot and Ankle Society (AOFAS), Achilles Tendon Total Rupture Score (ATRS), Foot Function Index (FFI). Furthermore, active range of motion (AROM) and torque of strength in both plantarflexion(PF) and dorsiflexion(DF) for both healthy and operated ankles of all patients were measured. The follow-up time was more than 12 months for all patients. A total of twenty-nine patients, with a median age of 63.0 years old and an average follow-up time of 28.1 months were enrolled. Thirteen patients were assigned to the Non-attached group and sixteen patients were assigned to the Reattached group. The functional outcomes such as AOFAS, ATRS, FFI, and VAS scores, as well as ankle strength in both groups were significantly improved after surgeries. However, no significant differences between groups in preoperative and postoperative VAS scores and functional outcomes were found. AROM and ankle torque were comparable, except for less plantarflexion torque loss at 30°/sec in the reattached group (p = 0.046). All evaluating parameters significantly improved without notable complications in patients after FHL transfer surgery whether with or without reattachment. There were no significant differences in the improvement of most parameters among subgroups. While reattachment of the Achilles tendon stump to the FHL transfer for IAT may not be crucial for superior outcomes, the torque improvement seen in the reattached group indicates possible advantages that require additional investigation.