Lateral Transfer of the Flexor Digitorum Longus for Peroneal Tendinopathy

Background: Few studies have reported midterm outcomes after single-stage flexor digitorum longus (FDL) tendon transfer to the lateral foot for irreparable rupture of the peroneal tendons. Methods: Over a 7-year period (2008-2015), 25 consecutive patients underwent transfer of the FDL to the fifth metatarsal for irreparable peroneal tendon tears. Of these, 15 patients were available for inclusion with a mean follow-up of 53.7 ± 23.3 months, mean age at surgery of 48.4 years, and mean body mass index (BMI) of 29.8 kg/m². Patients completed the pain visual analog scale (VAS), Foot Function Index (FFI), Short Musculoskeletal Function Assessment (SMFA), and Foot and Ankle Ability Measure (FAAM) and participated in range of motion, peak force, and peak power testing. Results: All 15 patients were satisfied with their surgery and reported a reduction in their pain level with a decreased VAS of 5.6 ± 2.5. The mean FFI was 12.8 ± 9.2, the SMFA Function Index was 12.4 ± 8, and the mean SMFA Bothersome Index was 11.5 ± 11. The mean FAAM was 86.4 ± 9.7. Patients had on average 58% less eversion and 28% less inversion compared with the nonoperative side. Isometric peak torque and isotonic peak velocity were 38.4% and 28.8% less compared with the contralateral side, respectively. The average power in the operative limb was diminished by 56% compared with the nonoperative limb. Conclusion: In this small case series with midterm follow-up, FDL transfer to the lateral foot for significant, irreparable peroneal tendinopathy was an effective and durable treatment option. Level of Evidence: Level IV, retrospective case series.