External Rotation as a Result of Suprascapular Nerve Neurotization in Obstetric Brachial Plexus Lesions

Abstract

Obstetric brachial plexus lesions may cause lifelong limitations of upper limb function. Nerve repair is widely advocated in infants who do not show spontaneous recovery. Typically, the suprascapular nerve (SSN) is involved in the lesion. Neurotization of the SSN routinely is performed, aiming at reinnervation of the infraspinatus muscle to restore external rotation. The results after SSN neurotization have not, as yet, been studied in detail; therefore, this study was undertaken. Of special interest was the comparison of two commonly applied SSN neurotization procedures: nerve grafting from C5 versus nerve transfer of the accessory nerve. Infants with obstetric brachial plexus lesions after nerve grafting of C5 to the SSN (n = 65) or nerve transfer of the accessory nerve to the SSN (n = 21) were selected for retrospective analysis after a mean follow-up period of 3 years. Outcome was expressed in degrees of true glenohumeral external rotation. This was defined as the angle between the position of the 90 degrees (actively or passively) flexed elbow resting against the abdomen and the position of the flexed elbow after external rotation with the upper arm held in adduction by the investigator. This movement can be executed only by infraspinatus muscle contraction. In addition, functional external rotation was evaluated by testing the ability to reach the mouth and the back of the head. Only 17 (20%) of the 86 patients reached more than 20 degrees of external rotation, whereas 35 (41%) were unable to perform true external rotation. There was no statistically significant difference between nerve grafting from C5 and extraplexal nerve transfer using the accessory nerve. Functional scores showed that 88% can reach the mouth and that 75% can reach the head. The restoration of a fair range of true glenohumeral external rotation after neurotization of the SSN in infants with obstetric brachial plexus lesions, whether by grafting from C5 or by nerve transfer of the accessory nerve, is disappointingly low. However, it seems that compensatory techniques contribute to effectuate a considerable range of movement.