Glenohumeral motion in patients with rotator cuff tears: a comparison of asymptomatic and symptomatic shoulders.

The purpose of this study was to determine whether there was a relationship between altered scapular plane glenohumeral kinematics end shoulder pain. Subjects were divided into 3 groups: normal volunteers (n = 10), patients with symptomatic rotator cuff tears severe enough to warrant surgery (n = 10), and subjects with no symptoms who had tears documented on magnetic resonance imaging and normal examination (n = 10). Humeral kinematics were observed with a computer-enhanced modification of the Poppen and Walker technique. Scapular plane x-ray films were obtained at 0 degree, 30 degrees, 60 degrees, 90 degrees, 120 degrees, and 150 degrees of elevation. Measurements were made by 3 independent observers blinded to the diagnosis, and data interpretation was performed based on mean values for independent observers. Results showed a high degree of interobserver and intraobserver reliability (coefficients = 0.96 and 0.95, respectively). The symptomatic and asymptomatic groups showed progressive superior translation of the humeral head on the glenoid with increasing arm elevation. The normal group, in contrast, maintained a constant center of rotation along the geometric center of the glenoid. Symptomatic and asymptomatic rotator cuff tear groups showed superior head migration from 30 degrees to 150 degrees, which was significantly different from those seen in the normal group. No significant difference between the symptomatic and asymptomatic groups was demonstrated with the small numbers used in this study. The presence of a rotator cuff tear was associated in a disruption of normal glenohumeral kinematics in the scapular plane. Because significant superior migration of the humeral head was seen in both the asymptomatic and symptomatic rotator cuff groups, painless and normal shoulder motion is possible in the presence of abnormal glenohumeral kinematics. Abnormal glenohumeral kinematics alone was not an independent factor, which could explain the occurrence of symptoms.