When a baseball player pitches, about 1,000 pounds of pressure per square inch can be placed on a single ligament, the ulnar collateral ligament of the elbow joint. (Credit: North Charleston/Flickr)

Hips put baseball pitchers at risk for elbow injury

A limited range of motion in a baseball pitcher’s hips could be a risk factor in the injury known as pitcher’s elbow, new research shows.

“This could open up a whole new line of thought processes and research,” says Kevin W. Farmer, assistant professor of orthopaedics and rehabilitation at University of Florida. “We’re going to be able to ask: Is there an associated risk of injury down the road with limited hip range of motion, and can we minimize that risk by improving hip range of motion?”

Farmer presented his research at the meeting of the American Academy of Orthopaedic Surgeons.

When a pitcher throws, he begins by shifting weight on his feet. He then lifts one knee—the leg opposite his throwing arm—so his thigh is parallel with the ground. Simultaneously, he brings the ball behind his shoulder and begins the pitch, bringing his throwing hand over his shoulder at the same time his raised knee is coming down. That step forward helps power the pitch.

When a player pitches, much of the stress is focused on a single ligament: the ulnar collateral ligament of the elbow joint. About 1,000 pounds of pressure per square inch can be placed upon that ligament. The mechanics of the throw affect what researchers call the “elbow valgus torque.”

“Most studies have looked at shoulders and elbows. While very few studies have looked at lower extremities, some have done early work looking at range of motion, but no one has really correlated hips with the risk of injury to the elbow,” Farmer says.

To test how a pitcher’s hip range of motion affects the elbow, Farmer and colleagues tested the pitching style of seven college Division 1 athletes in a biomechanical throwing analysis. The analysis took place in a lab that has a pitching mound surrounded by high-speed cameras.

Angle, speed, and torque

The researchers placed motion-detecting markers on the pitchers’ joints. When the pitchers threw, the markers noted the mechanics of their motion and the high-speed cameras took visuals. The results were made into a computerized, 3D stick figure. The researchers then analyzed all angles, speed, and torques of the pitch, as well as how the different parts of the throw interacted with one another.

Certain aspects of the throwing cycle increase the risk of torquing that elbow ligament, says Farmer, such as the pitcher hyperextending his arm when he throws, whether his shoulder is too far back when he throws, or whether the pitcher is opening his body toward home plate too soon.

The researchers correlated the hip range of motion to what they already knew could risk injury, and found that the less range of motion pitchers had in their hips, the higher the risk to the pitchers’ arms. Pitchers unknowingly compensate for limited range of motion in their hips, which could place more torque on their elbows.

Pitchers with injured elbow ligaments often undergo a reconstructive surgery called the Tommy John surgery. “The fact is, some of these pitchers don’t get back to the level they were at before their injury,” Farmer says, but coaches and athletic trainers could easily help athletes improve hip flexibility.

Farmer will next follow pitchers over a period of time to determine whether there are changes in range of motion throughout their careers, and whether a stretching program can improve range of motion and reduce the risk of injury.

Source: University of Florida

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