Extensor indicis proprius transfer for the abducted small finger

PURPOSE: Persistent abduction of the small finger has usually been treated by transfer of the extensor digiti minimi muscle. However, anatomic variations of the extensor system may limit the potential for a successful extensor digiti minimi transfer. Therefore, we evaluated the outcomes of an alternative reconstruction method for the abducted small finger using an extensor indicis proprius (EIP) transfer. METHODS: We performed 8 EIP transfers in 8 patients with persistent, flexible abduction posturing of the small finger. The primary etiology of the deformity was incomplete motor reinnervation after surgeries for ulnar neuropathy in 6 patients, rupture of the third palmar interosseous musculotendinous unit in 1 patient, and intrinsic muscle fibrosis in 1 patient. The EIP was elongated by splitting the tendinous portion and was transferred to the distal and radial part of the extensor hood. Surgical outcomes were assessed by comparing preoperative and postoperative active adduction and abduction motion of the 2 ulnar digits. RESULTS: At the mean follow-up of 23 months, the average adduction angle improved from 19 degrees to 1 degrees postoperatively. In terms of active finger motion, 6 patients showed excellent results, 1 good, and 1 fair, without loss of flexion and extension. No patient had an extension lag or complained of functional deficits of the donor index finger. There was not adverse change to digital function or range of motion for the middle and ring fingers that are crossed by the EIP. CONCLUSIONS: Extensor indicis proprius transfer can be a reliable option for correction of abduction deformity of the small finger, maintaining active abduction and full flexion and extension. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.