External rotation, supraspinatus strength related to injury in baseball pitchers

KEYSTONE, Colo. — An investigation of professional baseball pitchers has revealed a significant association between external rotation strength, both seated and prone, and supraspinatus strength and injuries requiring surgical intervention.

“It has been theorized that an imbalance between the relatively strengthened internal rotators and relatively weakened external rotators can help damage the shoulder and elbow resulting in injury,” Ian Robert Byram, MD, said at the American Orthopaedic Society for Sports Medicine 2009 Annual Meeting, held here. “Supraspinatus weakness has been shown in professional pitchers, but so far there has been no prospective outcomes study of pitchers trying to link the strength variable and injury variable.”

In order to identify professional baseball pitchers who could be at risk for injury, Byram and colleagues collected data on 144 professional pitchers in the Colorado Rockies organization over the course of 5 years. Yearly strength measurements were taken in the preseason for each player, resulting in 207 distinct player data points.

“We checked these players in four activities: prone internal rotation, prone and seated external rotation, and supraspinatus,” he said. “A ratio was calculated for external to internatal rotation for each player at a given data point.”

The players were then followed throughout the baseball season, and all injuries were noted and classified as whether or not they required surgical intervention.

“We had 63 injuries in 50 players; 38 were treated nonsugically and 25 were treated surgically in 39 shoulders and 23 elbows and one lower-extremity sports hernia,” Byram said.

The researchers found that external rotation prone strength variable was significantly associated with injury requiring surgery, as was the seated external rotation strength variable, he said. The supraspinatus was also found to be significantly associated with injury requiring surgery.

“We hope this study has some applications in identifying at-risk players via preseason measurements and focusing rehabilitation efforts to those who are in a high-risk group,” he said. “A preseason strength program could be a way for us to prevent injury.”

Reference:
Byram IR, Bushnell BD, Dugger K, et al. Preseason shoulder strength measurements in professional baseball pitchers: Identifying players at risk for injury requiring surgery. Presented at the American Orthopaedic Society for Sports Medicine 2009 Annual Meeting. July 9-12, 2009. Keystone, Colo.