Metacarpal Synostosis: Treatment With a Longitudinal Osteotomy and Bone Graft Substitute Interposition

PurposeTo describe a case series of congenital metacarpal synostosis treated with longitudinal osteotomy and bone graft substitute interposition.MethodsWe retrospectively reviewed charts of all patients with metacarpal synostosis treated with a longitudinal osteotomy and bone graft substitute interposition at 2 institutions. Radiographic and clinical appearances were analyzed at initial diagnosis, intraoperatively, and at last follow-up.ResultsA total of 10 patients (14 hands) met the inclusion criteria. Six patients (8 hands) demonstrated ring-little finger metacarpal synostosis and 4 patients (6 hands) had a middle-ring finger metacarpal synostosis. The median age at operation was 5 years (range, 2–16 y). Follow-up ranged from 1 to 14 years (average, 3 y). Associated hand anomalies included polydactyly, symbrachydactyly, and clinodactyly. Before surgery, the little finger proximal phalanx was angulated away from the middle finger metacarpal on average 46° (range, 26°–60°), and the angulation between the middle and the ring fingers averaged 43° (range, 26°–50°). Postoperative correction at 1 year was statistically significant for both ring-little finger metacarpal synostosis, average 23° (range, 10°–30°), and middle-ring finger metacarpal synostosis, average 16° (range, 5°–44°). Recurrence of digital abduction was evident in 2 patients who had middle-ring finger metacarpal synostosis.ConclusionsMetacarpal synostosis is an uncommon congenital hand anomaly characterized by the coalescence of 2 adjacent metacarpals. In the most common form, the ring and little finger metacarpals are associated with abduction of the small finger in an awkward position. Use of the described technique is safe and effective, yet concerns remain regarding mild persistent angulation and risk of recurrence.Clinical relevanceCongenital metacarpal synostosis may be effectively treated with a longitudinal osteotomy, realignment of component metacarpals, and interposition of bone graft substitute. When the procedure is performed at a young age, we recommend follow-up until skeletal maturity to identify recurrence of the deformity.Type of study/level of evidenceTherapeutic IV.