Simultaneous Bilateral Reconstruction of Chronic Achilles Tendon Rupture with Flexor Digitorum Longus Transfer and Turndown Flaps: A Case Report and Review of Literature

Background/Objectives: Bilateral Achilles tendon ruptures are exceptionally rare, accounting for <1% of Achilles injuries; chronic presentations are frequently linked to diagnostic delay in the acute phase. The aim of this paper is to describe a modified, single-stage bilateral reconstruction of neglected Achilles tendon ruptures using Flexor Digitorum Longus (FDL) transfer and turndown flaps. This study evaluates 12-month functional and radiological outcomes while comparing this surgical strategy with current literature. Methods: A 58-year-old man with rheumatoid arthritis on long-term corticosteroids presented 4 months after asynchronous bilateral Achilles ruptures with progressive weakness and gait limitation. Clinical examination and MRI confirmed chronic discontinuity with retracted stumps and interstump gaps of ~6.5–7.0 cm. Intervention: After pre-operative tapering of corticosteroids, a single-stage bilateral reconstruction was performed. Surgical intervention involved simultaneous bilateral reconstruction using flexor digitorum longus (FDL) transfer for one tendon and a combination of FDL and flexor hallucis longus (FHL) transfers for the other, with bilateral turndown flap augmentation. Decisions regarding tendon transfers were based on intraoperative findings, with the FDL selected for its larger caliber when the FHL was deemed insufficient. Results: Recovery was uneventful. At 6 months, the patient resumed full-time work and could perform repeated tiptoe rises. The AOFAS ankle-hindfoot score improved from 46 pre-operatively to 85. At 12 months, MRI demonstrated bilateral tendon continuity without re-rupture, with hypertrophy at the reconstructed stumps. Conclusions: In chronic, large-gap bilateral Achilles ruptures with systemic risk factors, single-stage reconstruction using FDL (with or without FHL) plus turndown augmentation is feasible and yields favorable functional recovery. Careful tensioning, secure calcaneal fixation, steroid optimization, and structured rehabilitation appear pivotal to outcomes. This case supports the applicability of this strategy in complex bilateral presentations.