Shoulder injuries in baseball players may be avoided with a new 3-D motion tracking system, suggests a new study from the Loyola University Medical Center.

The motion sensing system is called the Xbus Kit, and requires only a portable computer and several wearable motion tracking devices. While other motion tracking systems require heavy equipment like cameras, the Xbus system can be used on the field outdoors.

According to the researchers, baseball pitchers are prone to shoulder injuries after the rhythm of their throwing arm muscles deteriorates from overuse. The "scapula-humeral rhythm" in a strong pitcher is well-coordinated- the humerus, or upper armbone, moves in sync with the scapula, or shoulder blade. With constant use, however, the surrounding muscles tire and the rhythm becomes irregular, setting pitchers up for injuries.

The Xbus Kit places motion trackers on a baseball pitcher's sternum, scapula, humerus, and forearm in order to detect subtle changes in the scapulo-humeral rhythm that can be easily missed by even the most vigilant coach. Each motion tracker records dynamic movement data from 3D accelerometers, gyroscopes, and magnetometers that is synthesized by a computer algorithm in order to assess risk for shoulder injuries.

Researchers tested the system on 13 college baseball pitchers in the Chicago area over three repetitive arm-movement sessions: before and after 60 successive pitches, and then 24 hours later.

The results showed that only two pitchers maintained strong scapulo-humeral rhythms, while eight deteriorated immediately after the repetitive pitching session but recovered at least somewhat by the next day.

The three remaining pitchers, however, had deteriorated rhythms that lasted into the next day, identifying them as at higher risk for shoulder injuries.

The scapulo-humeral rhythm is assessed by the Xbus motion-tracking system in terms of coordination between the movements of the scapula and humerus, which meet at the shoulder joint. [Musculoskeletal Surgery]

The 3D motion tracking system is useful in assessing baseball pitchers' predisposition to shoulder injuries, say the researchers, and can help increase players' performance on the field by identifying when they need to rest.

Sports medicine surgeon Dr. Pietro Tonino, a study coauthor, said in a news release that at-risk players identified by the Xbus system might prevent injuries with muscle-building exercises and physical therapy.

Tonino says that "even the most successful surgery and rehabilitation cannot completely restore a shoulder to the full function the player had before the injury." As a result, "the best strategy is to prevent injuries, and the motion tracking system can help in that effort."

According to the news release, the researches plan to test the Xbus system on Little League pitchers.

The study was published last week in the journal Musculoskeletal Surgery.