Reconstruction of lateral pinch in an isolated paralysis of the first dorsal interosseous muscle - A new surgical technique.

Lack of function of the first interosseous muscle (FDI) might be responsible for insufficient stabilisation of the index finger during lateral pinch, and may induce disability in hand function. The first cause of FDI palsy is ulnar nerve palsy. We describe a new tendon transfer to reanimate the FDI muscle, using the extensor indicis proprius tendon. The tendon is sectioned at its distal insertion and rerouted in the first extensor tendon compartment. We report one case of isolated first interosseous muscle palsy secondary to direct trauma. Preoperatively, the patient complained of a severe lack of strength during key pinch with an ulnarly deviated index finger. Thirty months postoperatively, the patient recovered active abduction of the index finger and lateral pinch was measured at 5.5kg (54N). Compared to the original Bunnell transfer our technique restores the native moment arm of the FDI muscle and does not require a tendon graft.