Bilateral Congenitally Absent Trapezius Musculature and Anomalous Scapuloclavicular Accessory Muscle: A Case Report.

CASE: An otherwise healthy 10-year-old boy presented with severe bilateral shoulder dysfunction because of lateral scapular winging. He underwent bilateral modified Eden-Lange tendon transfers, resulting in near-normal restoration of shoulder range of motion at the 1-year follow-up. Intraoperatively, he was found to have bilateral absent trapezial muscles and an anomalous scapuloclavicular muscle spanning from the superomedial scapula to the posterolateral clavicle.

CONCLUSION: This case represents the only known report of bilateral absent trapezius muscles without involvement of other trunk musculature or congenital abnormalities. In addition, the patient exhibited a previously unidentified anomalous muscle.