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Ultrasound for measuring infraspinatus cross-sectional area allows for large-scale studies in overhead athletes
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PHILADELPHIA — The results of the first study to use ultrasound imaging to measure infraspinatus cross-sectional area were presented here, at the National Athletic Trainers’ Association 2010 Annual Meeting & Clinical Symposia.
“Currently MRI is the commonly used method to measure muscle cross-sectional area and water content; the problem, however, is that it is expensive and not portable,” Sakiko Oyama said during her presentation.
Several advantages
Oyama told Orthopedics Today that decreased radiation dosage is among the key advantages of the ultrasound method. Additionally, large-scale, longitudinal studies, which would have been impossible using MRI, can now be performed using ultrasound to measure infraspinatus cross-sectional area in overhead athletes.
Joe Myers, PhD, ATC, co-author of the study, told Orthopedics Today that the ultrasound method will also allow physicians and trainers to determine when the etiologies that are seen in collegiate and professional pitchers are occurring. “Are they occurring as part of youth participation, during maturation? We could never answer those questions because of safety issues,” he said.
Implications for injury
With their study, Oyama and colleagues aimed to evaluate the changes in infraspinatus cross-sectional area and shoulder range of motion (ROM) before, immediately after and 24 hours after repetitive eccentric external rotator contractions.
She reported that infraspinatus cross-sectional area increased immediately after exercise and remained elevated from the baseline at the 24-hour follow-up. Internal-rotation ROM and horizontal-adduction ROM were significantly decreased at 24-hour follow-up, compared to baseline and immediately after exercise.
“We think that it is important to continually look at this phenomenon, which probably has implications for the development of upper extremity injuries; however, the results of this study cannot be directly extrapolated to the responses after pitching,” Oyama said, noting that future studies are needed to investigate the course of recovery of the posterior shoulder muscles and the associated biomechanical changes following pitching.
Reference:
- Oyama S. Changes in infraspinatus cross-sectional area and shoulder range of motion with eccentric shoulder external rotator fatigue: application to thrower’s shoulder. Presented at the National Athletic Trainers’ Association 2010 Annual Meeting & Clinical Symposia. June 22-25, 2010. Philadelphia.