Combined Use of EMG and Muscle Ultrasound for the Evaluation of Scapular Winging

Scapular winging occurs as an abnormal protrusion of the scapula due to nerve injury, muscle weakness, bone, or joint pathology. The main muscular stabilizers of the scapula include the serratus anterior, trapezius, rhomboid major and minor, levator scapulae, and pectoralis minor. Needle electromyography (EMG) has historically been used as one of the primary diagnostic tests for evaluating this finding. However, sampling of these muscles can be technically difficult and carries risks for complications. Muscle ultrasound (MUS) can also reliably identify abnormalities in the muscles involved in scapular stabilization while offering the benefit of rapid side-to-side comparison and improved patient comfort. This study aims to highlight the concordance of ultrasound and EMG findings using our published MUS protocol in patients with scapular winging.

A retrospective analysis was performed of 13 patients who presented to an electrodiagnostic (EDX) laboratory with the referral diagnosis of "scapular winging" or "scapular dyskinesis." All patients underwent MUS testing of scapular muscles according to a previously published protocol followed by EMG of muscles deemed relevant by the clinician.

Seven patients were found to have a neurogenic cause of their scapular winging and in those patients, all had both EMG and MUS abnormalities. MUS was found to have a sensitivity of 87.5%, specificity of 95.7%, and individual muscle concordance with EMG of 90.6%.

There is high concordance between EMG and MUS in patients with scapular winging. This combined with potential advantages of the MUS modality supports their concurrent use in patients with scapular winging.