Symptomatic progression of asymptomatic rotator cuff tears: a prospective study of clinical and sonographic variables

Abstract

Background: The purposes of this study were to identify changes in tear dimensions, shoulder function, and glenohumeral kinematics when an asymptomatic rotator cuff tear becomes painful and to identify characteristics of individuals who develop pain compared with those who remain asymptomatic.

Methods: A cohort of 195 subjects with an asymptomatic rotator cuff tear was prospectively monitored for pain development and examined annually for changes in various parameters such as tear size, fatty degeneration of the rotator cuff muscle, glenohumeral kinematics, and shoulder function. Forty-four subjects were found to have developed new pain, and the parameters before and after pain development were compared. The forty-four subjects were then compared with a group of fifty-five subjects who remained asymptomatic over a two-year period.

Results: With pain development, the size of a full-thickness rotator cuff tear increased significantly, with 18% of the full-thickness tears showing an increase of >5 mm, and 40% of the partial-thickness tears had progressed to a full-thickness tear. In comparison with the assessments made before the onset of pain, the American Shoulder and Elbow Surgeons scores for shoulder function were significantly decreased and all measures of shoulder range of motion were decreased except for external rotation at 90° of abduction. There was an increase in compensatory scapulothoracic motion in relation to the glenohumeral motion during early shoulder abduction with pain development. No significant changes were found in external rotation strength or muscular fatty degeneration. Compared with the subjects who remained asymptomatic, the subjects who developed pain were found to have significantly larger tears at the time of initial enrollment.

Conclusions: Pain development in shoulders with an asymptomatic rotator cuff tear is associated with an increase in tear size. Larger tears are more likely to develop pain in the short term than are smaller tears. Further research is warranted to investigate the role of prophylactic treatment of asymptomatic shoulders to avoid the development of pain and loss of shoulder function.

Fig. 1

Radiographic measurement of glenohumeral kinematics. The geometric center of the humeral head (C) was located first with a so-called best-fit circle positioned over the humeral head outline. The superior and inferior rims of the glenoid were then marked to demarcate the glenoid line. The glenoid center point (G) was then located automatically by the software. The vertical distance from the geometric center of the humeral head to the glenoid center was measured for superior humeral head migration. The angle formed by the line drawn along the long axis of the humerus (H) and the glenoid line (S) was measured to calculate the glenohumeral angle. The glenoid line (S) was compared with the vertical axis of the body (B) to calculate the scapulothoracic angle. A reference bar (R) with a known length (5 cm) was always included in radiographs to adjust for magnification differences.

Fig. 2

The position of the humeral head in relation to the glenoid showed a gradual superior translation with shoulder abduction at both Visit 1 and Visit 2. However, there were no significant differences between visits at any of the abduction angles.