Effect of Posterior Capsule Tightness and Humeral Retroversion on 5 Glenohumeral Joint Range of Motion Measurements: A Cadaveric Study

Altered glenohumeral joint range of motion can be caused by increased humeral retroversion (HR) and/or posterior capsule tightness (PCT). To make informed clinical decisions, it is vital to understand how HR and PCT alterations, individually and in combination, affect joint range of motion measurements. To evaluate the effect of experimental tissue alterations on clinical range of motion measures. Controlled laboratory study. Five clinical measurements were quantified in 8 fresh-frozen cadavers under 4 experimentally created conditions: baseline (no alterations), HR condition (20° increase in HR by transecting the bone), PCT condition (20% decrease in length via thermal energy), and PCT + HR combined. Clinical measurements included bicipital forearm angle, low flexion, glenohumeral internal and external rotation, and horizontal adduction. All measurements were taken by the same blinded tester. Separate 1-factor repeated measures analyses of variance were used to evaluate the effect of the alterations on each clinical measurement. There was a significant main effect of condition for bicipital forearm angle (P = .02, F = 4.03), low flexion (P = .02, F = 3.86), internal rotation (P = .03, F = 3.65), and external rotation (P < .001, F = 15.15) but not for horizontal adduction (P = .29, F = 1.33). The HR condition resulted in a decreased bicipital forearm angle of 16.1° and 15.8° as compared with the PCT and PCT + HR conditions, respectively. When compared with baseline, the PCT + HR condition decreased the low flexion test by 13.5°, and the HR condition decreased internal rotation range of motion by 14.2°. All conditions increased external rotation when compared with baseline. Greater measurement changes were noted in both HR conditions, suggesting that bony alterations influence motion to a greater extent than posterior capsule alterations. Clinicians should be aware that humeral retroversion will influence the measurement of posterior shoulder tightness