Assessing Functional Outcomes and Complications After Turndown Flap With Flexor Hallucis Longus Augmentation in Chronic Achilles Tendon Ruptures

Introduction: Chronic Achilles tendon rupture (CATR) presents a therapeutic challenge due to tendon retraction, degeneration, and muscle atrophy that typically occur beyond four weeks after injury, complicating delayed repair. To address the resultant tendon defect and restore functional continuity, several reconstructive strategies have been described, including turndown flap augmentation and flexor hallucis longus (FHL) tendon transfer. Objective: This study evaluated functional outcomes and complications following combined turndown flap augmentation and FHL tendon transfer for CATR. Methodology: This retrospective study included eight patients with CATR who underwent turndown flap augmentation combined with FHL tendon transfer between March 2018 and December 2024. Chronic rupture was confirmed clinically and radiographically. Functional outcomes were assessed using the Foot and Ankle Ability Measure (FAAM) and the Achilles Tendon Rupture Score (ATRS) preoperatively and at follow-up. Complications, operative time, and postoperative outcomes were recorded and analyzed. Results: Eight patients (mean age, 53 ± 13.3 years; males, 5 (62.5%); females, 3 (37.5%)) were included. Four of the patients (50%) had a sedentary lifestyle, while another four (50%) were active in sports. Three patients (37.5%) had diabetes mellitus, while five (62.5%) had no comorbidities. A history of previous tendinitis was found in two patients (25.0%). Intraoperatively, tendinitis with calcification was found in four patients (50%). The mean tendon gap was 5.25 ± 1.58 cm, and the mean length of the distal stump from the tendo-Achilles insertion was 1.75 cm. The mean operative time was 122 ± 20 minutes. Reconstruction was performed at a median of 4 months after injury, with a mean follow-up of 13 months (range, 6-36 months). Significant functional improvement was observed. FAAM Activities of Daily Living scores improved from 49.6% ± 14.9% preoperatively to 83.5% ± 16.6% postoperatively (P = 0.0005), and FAAM Sports scores improved from 22.3% ± 13.1% to 71.5% ± 29.9% (P = 0.0002). ATRS improved from 31.4% ± 16.9% to 82.5% ± 12.8% (P < 0.001). All patients were able to perform a single-limb heel rise. Complications were limited, with one case each of wound dehiscence (12.5%), transient neuropraxia (12.5%), and complex regional pain syndrome (12.5%). No neurovascular injury or tendon re-rupture occurred. Conclusions: Turndown flap augmentation combined with FHL tendon transfer provides significant functional improvement with acceptable complications in the treatment of CATR. This technique represents a reliable option for the reconstruction of large tendon defects in delayed presentations.