Transfer of the Pronator Quadratus Motor Branch for Wrist Extension Reconstruction in Brachial Plexus Palsy

Background: In extended upper-type lesions of the brachial plexus, nerve transfers and root grafting have improved the results of shoulder and elbow reconstruction. However, wrist extension reconstruction has received little attention. Methods: In 20 cadaveric upper limbs, we dissected the anterior interosseous nerve and extensor carpi radialis brevis motor branch. Four patients with upper-type lesions of the brachial plexus with paralysis of wrist and finger extension were operated on within 10 months of trauma and followed up for 12 months after surgery. The terminal division of the anterior interosseous nerve, which innervates the pronator quadratus muscle, was transferred to the extensor carpi radialis brevis, and the distal stump was connected to a motor fascicle of the median nerve (n = 2) or to the distal branch of the flexor superficialis of the index finger (n = 2). Results: The anterior interosseous nerve and extensor carpi radialis brevis had similar diameters (roughly 1 mm). The number of myelinated fibers in the nerve averaged 670, whereas the number in the extensor carpi radialis brevis averaged 183. The length of the nerve was approximately 80 mm, allowing for direct transfer to the extensor carpi radialis brevis with redundant length. At last evaluation, pronation scored M4 according to the Medical Research Council grading system. All patients recovered active wrist extension, scoring M4 with full, independent motor control. Conclusion: In C5 to C8 root injuries of the brachial plexus, transfer of the motor branch of the pronator quadratus to the extensor carpi radialis brevis can restore active wrist extension, and pronation is preserved. (Plast. Reconstr. Surg. 130: 1269, 2012.)