Medial pectoral nerve transfer

Abstract

Dr. Wellons and his colleagues6 report convincing evidence that medial pectoral nerve (MCN) to musculocutaneous nerve (MCN) transfer can improve elbow flexion in infants with birth brachial plexus injury.6 They performed the MPN transfer procedure in a relatively large number of patients and achieved excellent surgical outcomes. Their results corroborate those previously reported by Blaauw and Sloof4 and make a strong case for MPN as a donor nerve that can be used in brachial plexus reconstruction for birth injury. The present report will serve as a valuable reference for many years. I commend the authors for their significant contribution to the treatment of birth-related brachial plexus injury. Some aspects of their report and the use of this particular MPN transfer in infants warrant discussion. As the authors indicate, infants with C8–T1 injury would not be candidates for the nerve transfer procedure because the MPN receives output from C8–T1 nerve roots. Potential candidates are infants with C5–6 or C5–7 injury. In these infants, surgical treatment should be aimed to maximize improvement of both shoulder and elbow function and should be undertaken before 12 months of age. Patients with persistent limited shoulder abduction, arm external rotation, and elbow extension/flexion suffer from life-long disabilities, and they develop fixed shoulder and elbow joint deformities that cannot be corrected. Unless infants show shoulder abduction greater than 90°, the limited shoulder abduction in infancy will lead to worsening shoulder abduction due to increased shoulder adductor contractures. These patients cannot carry out arm movements that require concomitant shoulder movement. Orthopedic procedures for the fixed deformities coupled with muscle weakness do not restore full shoulder and elbow function. For example, rotational osteotomy at a later age can reposition the arm in more external rotation but does not increase the total arc of motion of the arm. Fixed elbow flexion deformities cannot be fully corrected with surgeries. Shoulder subluxation/dislocation and resulting late shoulder deformities cannot be prevented in many patients. Thus, one should not rely on palliative orthopedic procedures later in childhood. Instead, one should employ a broad brachial plexus reconstruction before the patient reaches 12 months of age. When planning a type of brachial plexus reconstruction for C5–6 or C5–7 injury, one should remember favorable surgical outcome of resection of neuroma and nerve grafts, sometimes combined with C-4–suprascular nerve neurotization. Gilbert and colleagues5 reported shoulder abduction of more than 90° in 81% of 241 infants with C5–6 repairs and 76% of 81 infants with C5–7 repairs. Such good improvements were also observed in elbow flexion and extension. We have reported similar outcomes.1 In contrast, the MPN transfer improves only elbow flexion but does not help improve elbow extension and shoulder function. If infants older than 6 months cannot flex their elbow against gravity but can abduct their shoulder more than 90°, the MPN transfer would be a good option. However, I have not seen persistent weakness confined to the biceps in our patients, nor am I aware of reports of such cases in 345 347