[Isolated traumatic serratus anterior muscle palsy]

The serratus anterior, innervated by the long thoracic nerve, participates in shoulder abduction and elevation, stabilizing the scapula on the rib cage. Paralysis of the serratus anterior prohibits shoulder abduction and elevation beyond 90 degrees and elevation of the spinal border of the scapula. We report our experience with traumatic serratus anterior palsy.

Our series included 16 patients with traumatic unique injury to the long thoracic nerve. Mean age of the patients at the time of the accident was 27.6 years. Seven patients were not operated on due to total or partial spontaneous recovery. Scapulothoracic arthrodesis or scapulopexy was performed in nine patients.

For the non-operated patients, mean elevation was 125 degrees at diagnosis and 145 degrees at five years follow-up with a Constant score of 85 and muscle force reaching 83% (12 kg shoulder abduction) of the healthy side. Outcome was rated very good in 4 patients, and good, fair and poor in one each. For the operated patients, elevation was 95 degrees preoperatively and 104 degrees at last follow-up. At four years follow-up mean values were: elevation 104 degrees, Constant score 75, muscle force 72% (9 kg shoulder abduction) of the healthy side. An infection required a revision procedure in one patient who recovered successfully. Outcome was rated very good in six patients and good in three.

Several types of treatment have been proposed for serratus anterior palsy: non-operative care, muscle transfers mainly with pectoralis major flaps, and scapulothoracic arthrodesis. Most of the series on scapulothoracic arthrodesis have concerned fascioscapulohumeral dystrophy and cannot be compared with our patients. Data in the literature on muscle transfers, which could be considered as comparable with our trauma injuries, have demonstrated good results for shoulder motion but a limited effect on overall muscle force. In our series, scapulothoracic arthrodesis provided good results for muscle force, pain relief, and overall shoulder function, with shoulder motion being limited by the position of the arthrodesed scapula. We propose this type of treatment for serratus anterior palsy mainly for manual laborers.