The purpose is to evaluate and report the results that treated with open reduction and internal fixation in delayed diagnosed fracture and dislocation of the hamatometacarpal joint.

We evaluated 12 cases that had been treated with open reduction and internal fixation in delayed diagnosed fracture and dislocation of the hamatometacarpal joint. The mean interval between injury and operation was 34 days (21~60 days), the mean age of 12 cases was 28.1 years old, and mean follow-up period was 18 months. The computer tomography was done in all cases and the fracture and dislocation types were classified by Cain's classification. For the evaluation of results, pain scale, grasping power, range of motion of wrist and metacarpophalangeal joint were analyzed preoperatively and at final follow up, and the arthritic change of the hamatometacarpal joint was also checked.

According to Cain's classification, type Ia was one case, type Ib was two, type II was six, and type III was three. The pain scale was improved from 7.75 preoperatively to 0.92 at last follow up. The mean grasping power was improved up to 97.5% of normal. The preoperative range of motion of the wrist joint measured to be 60 degrees in extension and 70 degrees in flexion; the final range of motion indicated to be 75 degrees in extension and 80 degrees in flexion. The preoperative range of motion of the metacarpophalangeal joint measured to be 0 degrees in extension and 70 degrees in flexion; the final range of motion indicated to be 0 degrees in extension and 85 degrees in flexion. Carpometacarpal arthritis was developed in two cases.

The open reduction and internal fixation is considered as one of good treatment option in the delayed diagnosed hamatometacarpal fracture and dislocation.