Laird Harrison

April 01, 2015

LAS VEGAS — Young baseball players who are tall, throw fast, or play for more than one team are more likely to be injured, according to the results of a new study.

Youth baseball leagues should have lower pitch-count limits for fast throwers, Peter Chalmers, MD, a resident at Rush University Medical Center in Chicago, said here at the American Academy of Orthopaedic Surgeons 2015 Annual Meeting.

"Our current pitch limits have no accounting for velocity," Dr Chalmers told Medscape Medical News. Those two elements should be considered together on a sliding scale, "so if you throw 90 mile/h, your pitch-count limit may be lower than if you throw 70 mile/h," he explained.

Because young baseball players can injure their arms pitching, the Baseball Medical and Safety Advisory Committee in the United States recommends limiting the number of pitches thrown per week.

Previous cross-sectional studies have also identified breaking pitches as a risk factor. However, motion studies have not shown high shoulder or elbow torque in such instances, Dr Chalmers said.

He and his colleagues wondered whether other factors, such as pitch velocity, are more likely to contribute to injury.

They used dual orthogonal high-speed video analysis to record the speed of pitches thrown by 420 youth pitchers. A pitching-related injury was reported by 31% of the cohort, and current shoulder or elbow pain was reported by 30%. In addition, 12% reported receiving physical therapy.

On multivariate logistic regression analysis, the only risk factors that were significant were height (= .009), pitch velocity (= .006), and pitching for more than one team (= .019).

If you throw 90 mile/h, your pitch-count limit may be lower than if you throw 70 mile/h.

For every 10-inch increase in height, a pitcher was 20% more likely to be injured. For every 10 mile/h increase in velocity, a pitcher was 12% more likely to be injured. And playing for more than one team increased the risk for injury by 22%.

Using these three variables, the researchers found they could predict 77% of injuries. "The value of this study is to connect those factors directly to injury," Dr Chalmers explained.

All these variables are linked, he pointed out. The arm acts as a lever, and longer arms, usually found on taller pitchers, can generate more force during a pitch. Taller pitchers can also generate more force through their strides.

This increased force strains the ulnar collateral ligament and the shoulder joint capsule.

Repetitive Strain Injuries

Pitchers who throw faster are more successful, so they are asked to pitch more often and to play for more teams, increasing the number of pitches they throw and increasing the repetitive strain on their arms.

"To fully prevent injury, age-based velocity limits could be considered," the researchers suggest. But Dr Chalmers said he doesn't think that idea will fly. "It would be kind of anti-American of me to suggest that we alter the game of baseball," he said.

However, he continued, current efforts to prevent injury don't seem to be working. "Since the advent of pitch counts, the injury rate has not gone down."

In a separate study presented at the meeting, researchers from the University of Florida in Gainesville found that 53% of the caregivers of youth pitchers are not aware of current pitch-count limits or other guidelines for preventing injury in pitchers.

In addition to limiting pitch counts, Baseball Medical and Safety Advisory Committee guidelines state that "youth pitchers should avoid throwing breaking pitches." Dr Chalmers and his team found that throwing breaking pitches is associated with injury, but he said he doesn't think breaking pitches cause the injuries.

"In actuality, faster pitching was the cause of both the breaking pitches and the injuries," he said. "People who throw fast are targeted by coaches who say, 'You can throw 90 mile/h, let's teach you to throw some sliders now'."

Researchers looking at professional pitchers have seen a similar association between velocity and injury, said Bert Mandelbaum, MD, director of research for Major League Baseball.

"As you get faster pitching, you're at greater risk," he told Medscape Medical News. In professional baseball, "the inflection point is around 92 mile/h."

Dr Mandelbaum said that as researchers learn more about the association between pitch counts, intervals between games, and pitching speed, there will likely come a time when pitchers who can throw that fast get relieved more often. "I think the whole sport is going to have to adjust," he said.

Dr Chalmers and Dr Mandelbaum have disclosed no relevant financial relationships.

American Academy of Orthopaedic Surgeons (AAOS) 2015 Annual Meeting: Paper 361, presented March 25, 2015; paper 078, presented March 24, 2015.


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