Glenohumeral Arthritis Impairs Shoulder Mobility and Promotes Dynamic Compensatory Strategies During Overhead Reach.

Abstract

Glenohumeral arthritis (GHA) decreases shoulder range of motion, yet the extent of glenohumeral motion loss and accompanying whole-body compensations are not well quantified. Eighty-six patients with GHA completed an overhead reach task using both symptomatic and asymptomatic shoulders in a motion-tracking laboratory. Range of motion and peak angles of symptomatic to asymptomatic contralateral shoulders were compared. The symptomatic shoulder demonstrated 38° less flexion (84° symptomatic vs 122° asymptomatic, p <0.001), 4° less abduction (25° vs 29°, p <0.001), and 22° less internal rotation (21° vs 43°, p <0.001) compared to the asymptomatic shoulder. Patients compensated for these deficits via greater lumbar extension (6° vs 5°, p <0.01), greater lumbar rotation (9° vs 3°, p <0.001), contralateral pelvic rotation (6° vs 2°, p <0.001), reduced cervical flexion (9° vs 18°, p<0.001) with altered lateral bending (7° vs 11°, p<0.001), and greater elbow flexion (26° vs 4°, p 0.001). GHA is associated with substantial loss of shoulder motion during an overhead reach task that mimics daily activities, which leads to compensatory increases in cervical, lumbar, pelvic, and elbow kinematics. GHA is associated with decreased shoulder motion that results in an increase in compensatory spine motion during daily tasks. This increased compensatory spine motion may place the spine at increased risk for long term pathology.