Shoulder injuries are associated with tightness of posterior shoulder tissues. Posterior shoulder tightness is currently evaluated by using two measures of shoulder joint range of motion, internal rotation with the shoulder abducted to 90°, or horizontal adduction with the shoulder flexed to 90°. The range of motion in these measurements is influenced by tightness in the posterior capsule and/or posterior muscles, and is also impacted by the magnitude of humeral torsion. The inability to identify the specific structure responsible for range of motion loss using these measurements affects the planning and outcome of conservative treatments aimed at regaining range of motion. The aim of this project was to evaluate current and potential measurements of posterior shoulder tightness so that separate measurements of glenohumeral joint posterior capsule and posterior muscles can be identified. Another aim was to evaluate the validity of palpation of bicipital tuberosities for measuring humeral torsion.
To evaluate the effects of glenohumeral joint (GHJ) posterior capsule contracture on range of motion, a cadaver study was conducted. The purpose of the study was to identify a range of motion measurement sensitive to changes in the GHJ posterior capsule length. Repeated measures of shoulder ROM across four posterior shoulder tightness measurements were performed before and after experimental capsular contracture.
Maximum reductions in the range of motion were observed in measurements that combined shoulder flexion and internal rotation.
To evaluate the effects of posterior muscle extensibility on the range of motion, an in-vivo study was conducted. Repeated measures of shoulder range of motion across four posterior shoulder tightness measurements were performed before, immediately after, at 24 hours, and at 48 hours after repeated eccentric exercises of Infraspinatus and Teres minor. To verify the effect of eccentric exercise, Infraspinatus and Teres minor hardness were also measured at the same time as the range of motion measurements. Maximum reduction in the range of motion was observed in a measurement that combined shoulder extension and internal rotation. Infraspinatus hardness was observed to increase immediately after repeated eccentric exercise.
To evaluate the validity of using palpation of bicipital tuberosities for measuring humeral torsion, an in-vivo study was conducted. The bicipital-forearm angle, an indirect measure of humeral torsion, was measured using palpation of bicipital tuberosities and real-time ultrasound imaging. Agreement among the two methods was excellent with the intraclass correlation coefficient = 0.92.
The findings of these studies taken together suggest using a progressive approach to test posterior shoulder tightness. The first step should be the comparison of humeral torsion between the dominant and non- dominant shoulders. If between shoulder range of motion differences are greater than between shoulder humeral torsion differences, posterior capsule and muscle should then be evaluated. The posterior capsule may be best evaluated in a position of shoulder joint flexion and internal rotation, while for evaluating posterior muscles a position of shoulder joint extension may be used.