Stretching positions for the posterior capsule of the glenohumeral joint: strain measurement using cadaver specimens.

Background: Various stretches have been introduced for the posterior shoulder; however, little quantitative analysis to measure stretching of the posterior capsule has been performed. Hypothesis: The current shoulder stretching program is not sufficient to stretch the entire posterior capsule. Study Design: Controlled laboratory study. Methods: Using 8 fresh-frozen cadaver shoulders (average age, 82.4 years), 8 stretching positions for the posterior capsule were simulated by passive internal rotation. Stretching positions of 0 degrees, 30 degrees, 60 degrees, and 90 degrees of elevation in the scapular plane; 60 of flexion; 60 of abduction; 30 of extension; and 60 of flexion and horizontal adduction were adopted. Strain was measured in the upper, middle, and lower parts of the capsule. The measurement of strain was instituted from reference length. Results: With internal rotation, mean strain on the upper capsule was 3.02% at 0 degrees of elevation and 3.35% at 30 degrees of extension. Strain on the middle capsule at 0 and 30 elevation was 0.78% and 4.77%, respectively; on the lower capsule, it was 5.65% and 2.24% at 30 degrees and 60 degrees of elevation, respectively, and 2.88% at 30 degrees of extension. Increase in strains of the upper, middle, and lower capsule with internal rotation at 0 degrees, 30 degrees, and 60 degrees of elevation were statistically significant, respectively (P < .01). Other shoulder positions demonstrated no positive strain values. Conclusions: Based on the results of this cadaver study, large strains on the posterior capsule of the shoulder were obtained at a stretching position of 30 degrees of elevation in the scapular plane with internal rotation for the middle and lower capsule, while a stretching position of 30 degrees of extension with internal rotation was effective for the upper and lower capsule. Clinical Relevance: The current posterior capsule stretching program of the shoulder was not sufficient to stretch the entire posterior capsule.