Study Sheds Light on Pitching Injuries

Pitching a baseball is an art form.

To athletic trainers and orthopedists, pitching is a feat of “biomechanics” — the windup, leg kick, delivery and follow-through that have enabled untold generations of baseball players to throw fastballs, curveballs and sliders past major league hitters for more than a century.

Pitching requires a complex, twisting motion that transfers energy from the feet through the legs, hips and torso to the arm — and finally to the ball. Enormous rotational forces impinge on the shoulder and elbow — forces that one sports medicine director at Johns Hopkins Medical Institutions in Baltimore, Md., likened to “trying to pull your arm off your body.”

“The shoulder wasn’t really designed to pitch a baseball,” Edward G. McFarland told The Washington Post. “If you throw long enough, you’re going to have shoulder problems. Look at why guys [have to] leave the major leagues. Some of them don’t have the talent, but others just wear out.”

Such frailty has baffled scientists for decades. Research has shown that injuries to professional and collegiate baseball players might be caused by years of overuse and repetitive motion; a study of U.S. college-aged men, for example, found that 15 percent of the athletes who had pitched in youth baseball suffered from pain, tenderness or limited motion that compromised their throwing ability.

Despite all the data, however, science has been unable to predict the susceptibility of wear and tear on a pitcher’s arm — until now. A study conducted by Image IQ and the Cleveland Clinic and funded by a grant from Major League Baseball has revealed fascinating new data on pitching injuries and shoulder anatomy that could help players and teams better assess a pitcher’s risk of injury. The study showed that professional baseball pitchers with lower degrees of dominant humeral torsion (the degree at which the humerus bone twists) are more prone to severe arm and shoulder injuries.

“We were excited to work with Cleveland Clinic to bring our approach to orthopedic image data analysis to bear on this study,” ImageIQ CEO Tim Kulbago said. “As pitchers must strike a delicate balance between mobility and functional stability, these research findings help us better understand the connection between shoulder range-of-motion and the level of injury suffered by professional baseball players, and how to predict and protect against the most severe arm and shoulder injuries.”

A group of Cleveland Clinic radiologists came up with the study idea in an attempt to better understand the physiological repercussions of long-term pitching. Cleveland-based ImageIQ used custom-tailored 3-D clinical image and motion analysis software to quantitatively measure joint anatomy differences in the shoulders of 25 professional pitchers from computed tomography (CT) image data provided by the Cleveland Clinic. The pitchers were followed for two years, and the study recorded the number of days missed from pitching activities as a measure of the severity and incidence of the players’ injuries. The study also found a trend relating lower side-to-side torsion differences with more severe upper extremity injuries.

Many professional pitchers start at a relatively young age, mainly in Little League,while they are still growing and developing. As a result, while they arestill growing and pitching, the head of their humerus boneremodels itself and basically grows in a different way because of pitching, so that it effectively is pre-rotatedback. “‘[The pitching arm] grows at an angle at which the bone has effectively reset itself to being in a cocked position,”Kulbago said.

Interestingly, the radiologists discovered that the pitchers who are the least likely to be injured are those whose humerus bones have remodeled themselves. To conduct the study (published in The American Journal of Sports Medicine), the radiologists conducted CT imaging on both the dominant and non-dominant humeri.

The CT images of the pitchers were studied and processed with Image IQ’s 3-D volume-rendering post-processing software program, which then was modified to digitally separate the bones and reconfigure them, enabling the researchers to see the effect of a pitch on the bones. Among the 11 pitchers injured during the study, five had shoulder injuries, seven suffered elbow injuries and two sustained finger trauma. Dominant humeral torsion was a statistically significant predictor of severe injuries (30 days) but not of milder injuries, the radiologists found.

Among injuredplayers, higher numbers of days missed because of injury were strongly correlated with lower degrees of dominanthumeral torsion, and smaller differences between dominantand non-dominant humeral torsions, the researchers noted.However, there was no significant association between the incidence of shoulder injury and minimum glenoid-tuberosity distance in the dominant or non-dominant shoulder or degree of dominant glenoid version.

“We found that simple measurements from standard image data sets were too limited to capture the complex interplay of 3-dimensional anatomic structures that are involved in sports injuries and other orthopedic pathologies, and we needed a more sophisticated approach,” said Dr. Joshua Polster, staff radiologist in the Department of Diagnostic Radiology within the Cleveland Clinic’s Imaging Institute and the study’s principal investigator. “This analysis produced meaningful and reliable data for sports medicine experts and professional athletes, and will hopefully help minimize pitching injuries in professional baseball.”

Researchers are hoping to conduct a larger study with a broader pitcher population to determine whether humeral torsion measurements could indeed determine risk injury assessment in pitchers.