Triangular Osteotomies for Y-shaped Metacarpal Synostosis.

Metacarpal synostosis is a rare congenital hand anomaly characterized by abnormal fusion between adjacent metacarpals. Although most commonly involving the fourth and fifth metacarpals, atypical fusion patterns may occur. We report a rare case of Y-shaped synostosis between the third and fourth metacarpals in a 17-year-old man and describe surgical correction using 3 triangular osteotomies. Realignment and stabilization were achieved with mini plates and screws. At 1-year follow-up, correction of angular deformity and digital shortening was maintained, with satisfactory functional and cosmetic outcomes. Triangular osteotomies provide a practical and reproducible technique for selected cases of Y-shaped metacarpal synostosis.