Ask the Researcher
Stephen Thomas, PhD, ATC
Chronic Adaptations Leading to Overuse Shoulder Injuries
Baseball is a common and popular sport in the United States. More than 2.5 million children participate in some form of youth baseball and over 20,000 participate in collegiate baseball every year. Shoulder injuries have been on the rise in this population most likely due to the increased exposure and amount of throwing beginning at younger ages. Many of the injuries are due to overuse that causes a breakdown of the soft tissue structures. The most common of these soft tissue pathologies include rotator cuff tears, Superior Labrum Anterior to Posterior (SLAP) lesions and anterior instability. The repetitive nature of the overhead throwing motion has been linked with several anatomical and biomechanical tissue adaptations including altered glenohumeral range of motion, particularly GIRD (glenohumeral internal rotation deficit), altered scapular position and motion (dyskinesis), increased humeral retroversion, and a thickened posterior capsule. These changes are thought to represent various stages of maladaptation in the shoulder complex.
My research interest is in identifying and measuring the specific tissue adaptations that are occurring and accounting for the altered motion. I have done research with baseball players using new methodologies to measure many of these adaptations directly. Specifically, we have identified the presence of a hypertrophied posterior capsule on the throwing arm in collegiate baseball players that correlates with GIRD and scapular upward rotation. I believe that by narrowing in on the temporal progression of these adaptations we can develop prevention strategies at a young age to minimize the risk of many overuse injuries. I am also involved in basic science research using a rat model to study the effects of overuse activity on rotator cuff injury and healing. Specifically, we are examining the effect of overuse activity after a rotator cuff tear on the mechanical and biochemical properties of the uninjured structures of the shoulder joint.
This week I will be glad to answer questions about overuse shoulder injuries; including but not limited to risk factors for overuse injuries, methodology for measuring tissue adaptations, injury progression, and mechanical and biochemical alterations with overuse activity. I will try to answer your questions with objective responses and links to articles but some of these answers will represent my opinions on the available data and do not represent the opinions of SMR, the other collaborators to the blog, my research collaborators, or my medical institution.
I look forward to hearing from you and answering your questions.
Written by: Stephen Thomas
Reviewed by: Jeffery Driban