Clinical Outcome of Isolated Endoscopic Flexor Hallucis Longus Transfer for Chronic Achilles Tendon Ruptures of Demanding Patients

BACKGROUND: Chronic rupture of the Achilles tendon, including neglected primary lesions and re-ruptures, remains a demanding clinical condition, particularly in active individuals. Endoscopic-assisted procedures with flexor hallucis longus tendon transfer have gained increasing popularity. This study aims to evaluate the clinical and functional outcomes of isolated endoscopic-assisted flexor hallucis longus tendon transfer in patients with high functional demands over an 11-year period. METHODS: This retrospective study included 35 patients (29 males, 6 females; mean age 48.3 ± 11.6 years) who underwent isolated endoscopic-assisted flexor hallucis longus tendon transfer for treatment of chronic rupture of the Achilles tendon between 2014 and 2024. Functional outcomes were assessed using the American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Score, the Achilles Tendon Total Rupture Score, and the single-leg heel-rise test. The mean follow-up was 20.0 ± 11.3 months. Rates of return to sports, running and work were evaluated. The Wilcoxon signed-rank test was used to compare pre and postoperative scores. The Spearman correlation coefficient was used to analyze the association between functional outcomes and both patient age and time from injury to surgery. RESULTS: Significant improvement was observed in functional scores: the American Orthopaedic Foot and Ankle Society score increased from a median of 49 to 97, and the Achilles Tendon Total Rupture Score from 18 to 95 (both P < .001). The heel-rise test was completed by 97.1% of patients. All previously active patients returned to sport, and 96.9% resumed work. Weak, nonsignificant negative correlations were observed between functional outcomes and both age and time to surgery. Three postoperative complications (8.6%) were observed. CONCLUSIONS: .