Joint-Preserving Reconstruction of a First Metatarsal Aneurysmal Bone Cyst Using Fibular Strut Autograft and Mini-Fragment-Assisted Dual Plate Fixation: A Case Report With Functional Outcome.

Background: Aneurysmal bone cyst (ABC) is a benign but locally aggressive osteolytic lesion that predominantly affects children and adolescents. Foot involvement is uncommon, with metatarsal lesions representing a rare subset. Reconstruction of the first metatarsal is particularly demanding due to its critical biomechanical role in forefoot load transmission and push-off during gait. Case Presentation: A 17-year-old male presented with right forefoot pain after trauma and was found to have a pathological fracture through an expansile lytic lesion of the first metatarsal. Initial conservative management was followed by clinical deterioration. Imaging revealed a 30 × 47 × 30 mm multiloculated lesion with fluid-fluid levels. Biopsy confirmed aneurysmal bone cyst. The patient underwent en bloc resection and reconstruction using an ipsilateral fibular strut autograft. Fixation was achieved using a joint-preserving dual plate construct assisted by a distal mini-fragment plate. Results: At 9 months, the patient demonstrated radiographic union, preservation of first-ray alignment, and no recurrence. Functional outcome improved significantly, with the AOFAS score increasing from 39% preoperatively to 90% postoperatively. Conclusion: Fibular strut graft reconstruction for metatarsal ABC is established in the literature. This case highlights a fixation refinement using mini-fragment-assisted dual plating to enhance distal fixation while preserving the first metatarsophalangeal joint. This technique may represent a viable option in selected cases.