Changes in humeral torsion and shoulder rotation range of motion in high school baseball players over a 1-year period
Oyama S, Hibberd EE, Myers JB. Clin Biomech (Bristol, Avon). 2013 Feb 19. pii: S0268-0033(13)00015-6. doi: 10.1016/j.clinbiomech.2013.01.014. [Epub ahead of print]
Take Home Message: Over one year, high school baseball players had no bony changes (humeral retroversion) in their dominant arm’s humerus but had decreased shoulder internal rotation.
Unilateral overhead sports cause several bony and soft tissue adaptations on the dominant arm due to the large amounts of mechanical stress. However, it is unknown when bony adaptations (e.g., humeral retroversion) occur during skeletal development. Therefore, the authors examined the longitudinal change of humeral retroversion and glenohumeral range of motion in 138 high school baseball players between the start of 2 consecutive seasons. Participants also completed a history questionnaire indicating the number of years they participated in baseball. Players were excluded if they had a current injury or an injury within the past year. The authors used an ultrasound technique to measures humeral retroversion and standard procedures (inclinometer) to measure glenohumeral range of motion. The authors found that humeral retroversion did not change over a 1 year period regardless of the amount of years participating in baseball. Dominant arm internal rotation decreased over the 1 year period but was not affected by the amount of years participating in baseball. External rotation and total range of motion decreased bilaterally over the 1 year period among participants that only played baseball for 1 year prior.
This study found that bony adaptation of humeral retroversion may be complete prior to high school. This suggests that we need to examine younger adolescents to identify when this bony adaptation is occurring and how quickly it is occurs In addition, this study used a simple ultrasound method to measure humeral retroversion, which can be implemented clinically if a diagnostic ultrasound is present. The authors also found that dominant arm internal rotation decreased over the one year period. This is in agreement with a previous study that examined female high school overhead athletes. This may suggest that the deceleration stress caused during the throwing motion contributes to posterior shoulder soft tissue tightness. Previous research has linked decreases in internal rotation to shoulder injuries and internal impingement. Lastly, the authors found that external rotation and total range of motion to decreased bilaterally but only in players that only played the year prior. This is an interesting finding and may suggest that there is a soft tissue reaction to the new stress placed on the shoulder joint among players that just started to play. It would be interesting if this is only seen during the first year of participation and it resolves itself in time. Clinically, these results demonstrate the importance of examining players longitudinally. It suggests that if changes in range of motion are detected longitudinally in high school baseball players then the changes are indicative of soft tissue tightness and stretching should probably be implemented to reduce the risk of future shoulder injuries. Do you examine glenohumeral range of motion over the season in your overhead athletes? What information do you use to identify the players that need to be stretched?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Adaptations of Shoulder Joint Stiffness may Lead to Increased Muscle Efficiency and Neuromuscular Control