Elbow injuries continue to be on the rise in baseball players, especially pitchers, yet little is known about the actual variables that influence these injuries.

While elbow varus torque is already linked to ulnar collateral ligament (UCL) injuries, the connection between certain pitching movements and elbow varus torque is unknown.

A recent study from Hospital for Special Surgery set out to find the relationship between elbow varus torque and the following variables: arm slot, arm speed and shoulder rotation. The prospective cohort study looked at 81 professional pitchers (either in the Major or Minor Leagues) who took 81,999 throws while wearing a Motus baseball sleeve.

These were a combination of throws that were evaluated in real settings such as structured long tosses and live game play, as opposed to in a laboratory like previous studies. This was the largest analysis of throwing biomechanics to date.

"Obtaining this comprehensive, individualized analysis of on–field throwing activity was made possible by technological advancements that give us the ability to accurately measure body motions outside the lab," said Joshua Dines, MD, sports medicine surgeon at HSS and primary investigator. "Capturing data during the pitchers’ normal activities provided us with robust, baseline biomechanical performance metrics."

The study found that arm slot, arm speed and shoulder rotation all have a significant relationship with elbow varus torque. There was a 1–nm increase in elbow varus torque associated with a 13 degree decrease in arm slot, 116% increase in arm speed and 8 degree increase in shoulder rotation.

Increased arm speed and shoulder rotation were found to be associated with increased elbow stress as well as decreased arm slot. Height and weight were also positively correlated with elbow varus torque.

"Now that we know these modifiable risk factors, we have a foundation to develop evidence–based rehabilitation programs. Additionally, these findings can be utilized to prevent injury and help to identify potential pitchers at risk," said David Altchek, MD, sports medicine surgeon at HSS.

HSS Clinical fellow Christopher Camp, MD, also was an author on the study.