Flexor Hallucis Longus Preservation vs. Harvest in Fibula Free Flap Surgery: Functional Recovery and Gait Outcomes at 12 Months.

Abstract

The flexor hallucis longus (FHL) is often manipulated during free fibula flap (FFF) harvest. While its resection facilitates exposure, the impact on long-term donor-limb function remains unclear. This prospective cohort study compared 12-month functional outcomes between patients undergoing FFF harvest with intentional FHL preservation (n = 46) and those requiring FHL resection (n = 33). A standardized rehabilitation protocol was implemented. Outcomes were assessed via patient-reported measures (AOFAS-AH, FFI), objective clinical tests (manual muscle testing, single-leg heel rise, 6-min walk, single-leg stance), and instrumented 3D gait analysis at preoperative, 3-, 6-, and 12-month timepoints. The FHL-harvested group demonstrated significant early deficits in great toe strength, gait propulsion (peak plantarflexion moment and power), walking endurance, balance, and patient-reported function compared to the FHL-preserved group (all p < 0.05 at 3 months). However, by 12 months postoperatively, all measured functional parameters, including kinetic gait metrics and patient-reported scores, recovered to levels statistically indistinguishable from the FHL-preserved group (all p > 0.05). Donor-site complication rates were equivalent between groups (6.5% vs. 6.1%, p = 1.000). While FHL resection during FFF harvest is associated with significant transient functional impairment, structured rehabilitation facilitates substantial neuromuscular adaptation. By 12 months, patients achieve functional recovery comparable to those with an intact FHL, suggesting that FHL harvest is a viable option with manageable functional morbidity when surgically necessary for optimal flap dissection.