Transosseous Flexor Hallucis Longus Tendon Transfer for Large Achilles Tendon Defects: Surgery Technique and Outcome.

Background: Operative management of chronic Achilles tendinopathy with large defects can be surgically challenging. Concerns exist regarding transosseous transfer of the flexor hallucis longus (FHL) tendon because of the shortened lever arm of flexion and weakening of the big toe. The aim of this study was to demonstrate the 2-year outcome of transosseous FHL transfer for the treatment of large Achilles tendon defects.

Methods: We retrospectively analyzed 28 patients who underwent FHL transfer. The extent of the defect was measured with magnetic resonance imaging. Outcome parameters were the German Foot Function Index (FFI-D) evaluated at baseline and 6, 12, and 24 months postoperatively, the University of California-Los Angeles (UCLA) activity scale, 2 questions about patient satisfaction, reports on complications, or plantar flexion weakness of the great toe.

Results: Mean FFI-D scores of pain and disability improved from 37.2 and 52.3, respectively, at baseline to 6.9 and 15.0, respectively, 24 months postsurgery. (P < .001). At 24 months, 57% of patients were very satisfied and 25% were satisfied with the current symptoms related to their Achilles tendon. All patients noted a relevant improvement at the 2 year follow-up; 1 patient noted weakness of big toe flexion without relevant functional limitation. Complications occurred in 3 patients in the initial postoperative course (2 with delayed wound healing, and 1 with severe perifocal wound necrosis); all resolved completely.

Conclusion: We found transosseous FHL transfer using the long, open harvest method and additional bridging of large Achilles defects to be a successful treatment. The majority of patients experienced a significant improvement in both function and pain level and were satisfied with the outcome. Flexion weakness of the big toe does not appear to be a clinically relevant issue after this treatment for chronic Achilles tendinopathy.