O-39 High resolution ultrasound of scapula alata – A prospective case control study

Abstract

Scapulae alatae (SA) is a rare but also underreported disorder caused by neuromuscular disturbance in the scapulothoracic stabilizer muscles. The study is a single-blinded, prospective, controlled multi-center-study. We recruited 27 patients and 41 healthy-subjects. A standardized clinical examination was performed, electrodiagnostic-tests(EDx) were performed according to the department’s guidelines, and a Siemens ACUSON S1000 device with a high-frequency linear array transducer (18L6HD) used. The serratus anterior (SAM), trapezius and rhomboid muscles and the long thoracic (LTN), dorsal scapular, and accessory nerves were scanned bilaterally at predefined standardized sites. Muscle-thickness and nerve-diameter were measured. A reliability study in ten subjects was performed. Twenty patients showed a medial winging, seven patients showed a lateral winging and one patient had a lateral winging on the static examination but a medial winging on the dynamic examination. EDx were normal in 11 (40%) out of 27 patients. In patients with medial winging, the ratio of muscle thickness of SAM between the symptomatic side and the asymptomatic side differed significantly from the ratio in healthy-subjects: upper SAM (p-value: 0.007), lower SAM (p-value: 0.003), but no difference found for middle SAM (p-value: 0.051). Comparing difference in LTN diameter between the symptomatic and asymptomatic side in the patients with the difference between sides in the healthy-subjects, we found significant difference in two of three scanning-sites in the neck. The diagnosis of SA patients can be difficult and EDx are often normal. Our study shows that ultrasound of the neck/ shoulder may be used as a supplement in the diagnostic work-up.