Modified Unipolar Latissimus Transfer to Restore Elbow Flexion in Musculocutaneous Nerve Palsy

Abstract

L oss of elbow flexion can be disabling and have a significant impact on daily function. It occurs as a result of an injury to the brachial plexus, the musculocutaneous nerve, or occasionally direct damage to the biceps and brachialis muscles. The most common mechanisms include obstetric injury, iatrogenic injury, trauma, infection, and congenital disorders such as arthrogryposis. In the setting of isolated an musculocutaneous nerve palsy, restoration of elbow flexion power and excursion without loss of upper extremity function is of paramount importance for patient functional status. Surgical techniques to correct loss of elbow flexion are either nerve repairs/transfers or muscle transfers. Nerve repair with or without grafting, nerve transfers, or a combination of the 2 are commonly used in the treatment of traumatic brachial plexus injuries. Seddon used an ulnar nerve graft to connect the third and fourth intercostal nerves to the musculocutaneous nerve.1 Other well described nerve transfer donors include an ulnar nerve fascicle (Oberlin transfer) and/or a median nerve fascicle, intercostal nerves, and the phrenic nerve.2 However, when > 18 months have elapsed since injury, muscle atrophy makes nerve repairs or transfers ineffective, necessitating a muscle transfer. In addition, nerve transfers may provide limb excursion but with diminished power. For muscle transfers, one must consider the size, force vector, strength, and donor site morbidity of the transferred muscle. A variety of muscle transfers have been described for elbow flexion, including free gracilis transfer, pectoralis major transfer, pronator-flexor transfer (Steindler flexorplasty), triceps transfer, rectus femoris transfer and bipolar latissimus dorsi transfer. Pectoralis major transfer creates a nonphysiological vector with weaker and shorter elbow excursion. Triceps transfers naturally limit elbow extension after surgery. Latissimus transfer for restoration of elbow flexion or extension was first reported in 1956 by Hovnanian3; he proposed a unipolar technique that freed the latissimus from its origins in the trunk. The latissimus dorsi transfer has the advantage of maintaining its neurovascular pedicle after transfer, obviating the need for neurotization. Since the insertion of the latissimus on the proximal humerus is in close proximity to the biceps origin, an ipsilateral unipolar transfer with maintained proximal attachment may result in ideal biomechanics. Here, we describe our novel modification of the original unipolar latissimus dorsi transfer technique.3 Our technique encompasses 3 key concepts. The first addresses the critical distal anastomosis of the latissimus to the biceps tendon. Our weaving technique maintains desired rest-length tension and creates a robust repair that is less likely to fail. Second, tubularization of the latissimus muscle improves flexion strength by aligning the pull vector of muscle fibers linearly in the plane of flexion. Tubularization also improves cosmesis by more closely resembling the native biceps (now atrophied). Last, a skin paddle allows for a tension-free wound closure and promotes healing while acting as an indicator for underlying muscle viability. We believe this combination of techniques provides enhanced functional outcomes for patients undergoing this procedure by restoring strength, power, and joint excursion without compromise of upper limb functionality.