Evaluation of Apparent and Absolute Supraspinatus Strength in Patients with Shoulder Injury Using the Scapular Retraction Test

Abstract

Background Physical examination of patients with shoulder injury not involving actual rotator cuff tears frequently demonstrates decreased rotator cuff strength on manual muscle testing. This decrease has been attributed to supraspinatus muscle weakness, but it may be owing to alterations in scapular position. Hypothesis The position of stabilized scapular retraction, by minimizing proximal kinetic chain factors and providing a stable base of muscle origin, positively influences demonstrated supraspinatus strength. Study Design Controlled laboratory study. Methods Supraspinatus strength was tested in 20 injured patients and 10 healthy controls in both the empty-can arm position and a position of scapular retraction using a handheld dynamometer. Pain in both maneuvers was measured by use of a visual analog scale. Results Paired t tests indicated the scapular retraction position resulted in statistically significantly (P =. 001) higher supraspinatus strength values within both groups. There was no significant difference between the 2 positions in visual analog scale scores. Conclusion This study shows that demonstrated apparent supraspinatus weakness on clinical examination in symptomatic patients may be dependent on scapular position. The weakness may be owing to other factors besides supraspinatus muscle weakness, such as a lack of a stable base in the kinetic chain or scapula. Clinical Relevance The clinical examination that addresses scapular posture and includes scapular retraction will allow more accurate determination of absolute supraspinatus muscle strength and allow efficacious rehabilitation protocols to address the source of the demonstrated weakness.