Effect of Posture on Acromiohumeral Distance With Arm Elevation in Subjects With and Without Rotator Cuff Disease Using Ultrasonography

摘要

Objectives: To examine the effects of posture on subacromial (SA) space with arm elevation in patients with rotator cuff disease (RCD) and healthy subjects. Background: Poor posture has been linked to altered scapular mechanics, theorized to lead to excessive SA space narrowing. However, no study has examined the direct effects of posture on SA space using ultrasonography. We hypothesize that when compared to a neutral posture, upright posture will increase SA space and slouched posture will decrease SA space. Methods: Subjects with painful RCD (n=31) and healthy (n=29) shoulders participated. SA space was measured on ultrasound generated images using the acromiohumeral distance (AHD), which is the shortest distance between acromion and the humerus. Two trials each were collected in three postures of normal, slouched and upright posture with the arm at two angles of rest (0° elevation) and 45° abduction. Results: Two RMANOVAs for each arm angle compared the AHD across postures and groups. There was no interaction between group and posture, and no significant main effect of group for AHD. Groups were collapsed for further analysis. There was a significant main effect of posture on AHD at the 45° abduction (p = 0.0002); AHD increased significantly from normal (AHD= 8.63mm) to upright (AHD= 9.76mm) posture. Conclusion: The effect of posture on SA space is minimal; only upright posture increasing AHD over normal posture by 1.13mm, at 45° abduction position. Research is needed to determine the effects of posture on shoulder pain and posture interventions.