Isolated glenohumeral range of motion, excluding side-to-side difference in humeral retroversion, in asymptomatic high-school baseball players

Abstract

Glenohumeral range of motion is correlated with shoulder capsular condition and is thus considered to be predictive of shoulder pathology. However, in throwing athletes, a side-to-side difference in humeral retroversion makes it difficult to evaluate capsular condition on the basis of glenohumeral range of motion measured by using the conventional technique. The purpose of this study was to measure isolated glenohumeral rotation, excluding side-to-side differences in humeral retroversion, in asymptomatic high-school baseball players. A total of 195 high-school baseball players (52 pitchers and 143 position players; median age, 16years) and 20 high-school non-throwing athletes (median age, 16years) without any shoulder symptoms were enroled in this study. Glenohumeral external and internal rotations were measured by using both a conventional technique and our ultrasound-assisted technique. This technique, neutral rotation, was standardized on the basis of the ultrasonographically visualized location of the bicipital groove to exclude side-to-side differences in humeral retroversion from the calculated rotation angle. Intra- and inter-observer agreements of rotational measurements were evaluated by using intra-class correlation coefficients (ICCs). Isolated glenohumeral rotation measurements, excluding side-to-side differences in humeral retroversion, demonstrated excellent intra-observer (ICC>0.89) and inter-observer (ICC>0.78) agreements. Isolated glenohumeral internal rotation was significantly less in the dominant shoulder than in the non-dominant shoulder in asymptomatic baseball players (P<0.001). Isolated glenohumeral external rotation in baseball players was significantly greater than in non-throwing athletes (P<0.05). In the baseball players, humeral torsion in the dominant shoulder was significantly greater than that in the non-dominant shoulder (P<0.001), indicating that the retroversion angle was greater in dominant shoulders than in non-dominant shoulders. Isolated glenohumeral external and internal rotations can be measured with high intra- and inter-observer reliability with the exclusion of side-to-side differences in humeral retroversion. Capsular and muscular changes in the throwing shoulder may be better evaluated by using our ultrasound-assisted technique. Cross-sectional study, Level III.