Isolated ring-little finger metacarpal synostosis: a new classification system and treatment strategy.

PURPOSE: To devise a comprehensive classification system for isolated ring-little finger metacarpal synostosis that offers a clear guide to specific treatment for each variation of the deformity.

METHODS

Based on the experience of 13 cases (20 hands) of isolated ring-little finger metacarpal synostosis, we devised a classification system that takes into account 2 key pathological features of this malformation: the fourth-fifth intermetacarpal angle and the severity of hypoplasia of the fifth ray. In our classification, all patients were divided into 3 types, according to the fourth-fifth intermetacarpal angle, and each type was further subdivided into 2 subtypes according to the length of the fifth ray.

RESULTS

All 20 hands could be classified according to our classification, including 2 hands of type A (both A1), 10 hands of type B (9 B1; 1 B2), and 8 hands of type C (7 C1; 1 C2). Patients of different classification types received different treatments according to our proposed classification-related guidelines. It was also possible to classify all the cases found in literature according to this scheme.

CONCLUSIONS

Our classification for ring-little finger metacarpal synostosis is simple and easy to remember. It is applicable to all possible variations of the congenital anomaly and can guide treatment for the whole spectrum of the deformity.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.