Teenage Baseball Players at Increased Risk for Permanent Shoulder Injury

First Posted: Oct 14, 2014 04:20 AM EDT

Teenage baseball pitchers throwing more than 100 pitches a week suffer an increased risk of permanent shoulder injury, states a new study.

In the latest retrospective study, researchers at the University Hospital in Philadelphia looked at 2,372 consecutive patients aged between 15 and 25 years who underwent magnetic resonance imaging (MRI) for shoulder pain between 1998 and 2012. Majority of the patients, which included both males and females, were baseball pitchers.

It was observed that the young baseball pitchers who throw more than 10 pitches per week suffer an increased risk of a newly identified injury called acromia apophysiolysis. This injury - characterized by incomplete fusion and tenderness at the acromion - can hinder the development of normal shoulder and trigger additional problems that include rotator cuff tears. The acromion, which forms the bone at the top of the roof of the shoulder, develops mostly from four individual bones into one during the teen years.

On studying the patients, it was seen that 61 patients had pain at the top of the shoulder and an incomplete fusion of the acromion. They then compared them to age and sex-matched control group patients who had no such condition.

The researchers had pitching details for 106 of the 122 patients. Based on statistical analysis, they observed that throwing over 100 pitches a week led to a substantial risk factor for developing acromial apophsiolysis. Among those with overuse injury, 40 percent threw more than 100 pitches per week as compared to 8 percent in the control group.

"We believe that as a result of overuse, edema develops and the acromion bone does not fuse normally," Dr. Roedl explained.

Among 61 injured who took three-month rest from pitching, one underwent surgery and the rest were treated with treated with non-steroidal pain medication.

Two years later, a follow up MRI or X-ray imaging was done when the patients turned 25. The data was available for 29 patients out of 61 injured and 23 out of 61 controls. The follow up showed that 25 out of 29 with the overuse of the injury had incomplete fusion of the acromion.

"The occurrence of acromial apophysiolysis before the age of 25 was a significant risk factor for bone fusion failure at the acromion and rotator cuff tears after age 25," Dr. Roedl said.

Out of 29 patients with overuse of the injury, 21 of them continued pitching even after a rest period and all of these 21 had incomplete bone fusion at the acromion. When compared to the control group, this group experienced more of rotator cut offs and the severity of this was higher in overuse injury group.

"More and more kids are entering sports earlier in life and are overtraining," he said. "Baseball players who pitch too much are at risk of developing a stress response and overuse injury to the acromion. It is important to limit stress to the growing bones to allow them to develop normally."

The finding was documented in the journal Radiology.

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