BACKGROUND: Ankle and hindfoot fusion in the presence of large bony defects represents a challenging problem. The purpose of this study was to evaluate outcomes of patients who underwent ankle-hindfoot fusions with impaction bone grafting (IBG) with morselized femoral head allograft to fill large bony void defects. METHODS: This was a 3-center, retrospective review of a consecutive series of 49 patients undergoing ankle or hindfoot fusions with femoral head IBG for filling large bony defects. Union was assessed clinically and radiologically with radiography or computed tomography. Graft stability/collapse was identified on radiographs as loss of graft height across the fusion interface. Indications included 35 failed total ankle arthroplasty, talar osteonecrosis and collapse (7 patients), failed ankle fusion (4 patients), trauma with bone loss or fracture nonunion (1 patients), and other (2 patients). Tibiotalocalcaneal (TTC) fusion was performed in 36 (73%) patients and ankle (TT) fusion in 13 (27%). RESULTS: Mean age was 59.3 (19-78) years. Mean follow-up was 22.9 ± 8.3 months. Eighteen percent were smokers. Mean depth of the bone defect was 35.2 ±8.7 mm, and mean volume of the defect was 62.2 ±5.8 cm CONCLUSION: Impaction of morselized femoral head allograft can fill large bony voids around the ankle or hindfoot during fusion, with rapid graft incorporation and no graft collapse despite early loading. This technique offers satisfactory and comparable union outcomes without limb shortening or expensive custom 3D-printed metal cages.