Scapular Dyskinesis And Thoracic Paraspinal Muscle Thickness: A Relationship Study

Investigations into the pathogenesis of scapular dyskinesis (SD) have largely focused on the activity and strength of superficial periscapular muscles. However, research exploring the relationship between scapular dyskinesis and regional factors of the thoracic spine, particularly muscle thickness both superficially and deeply, remains limited. PURPOSE: To explore the relationship between the scapular dyskinesis and the thickness of thoracic paraspinal muscles. METHODS: A total of 60 male university students aged 18-27 years, who reported a habit of working at a desk and engaging in regular exercise, were recruited for this study. Participants were divided into two groups according to the classification system proposed by Uhl: the SD group (n = 50) and the non-SD group (n = 10). Supersonic imaging was used to measure the thickness of the middle trapezius, lower trapezius, rhomboid major, and deep thoracic paraspinal muscles in prone and standing position, respectively. RESULTS: The thickness of the bilateral lower trapezius and deep thoracic paraspinal muscles, measured in the prone position, and the left middle trapezius and right deep thoracic paraspinal muscles, measured in the standing position, were significantly smaller in the SD group compared with the non-SD group (P < 0.05). For each 1-mm increase in the thickness of the left lower trapezius measured in the prone position, the incidence of scapular dyskinesis decreased by 45.8% (95% CI: 5.0%-69.1%). Similarly, for each 1-mm increase in the thickness of the left middle trapezius measured in the standing position, the incidence of scapular dyskinesis decreased by 31.5% (95% CI: 1.8%-52.2%). CONCLUSIONS: Subjects with scapular dyskinesis exhibited thinner middle trapezius and deep thoracic paraspinal muscles. Increasing the thickness of the middle and lower trapezius muscles may be beneficial in preventing scapular dyskinesis.