TEENAGE BASEBALL PITCHERS AT RISK FOR PERMANENT SHOULDER INJURY
Young baseball
pitchers who throw more than 100 pitches per week are at risk for a newly
identified overuse injury that can impede normal shoulder development and lead
to additional problems, including rotator cuff tears, according to a new study
published online in the journal Radiology
The injury, termed
acromial apophysiolysis by the researchers, is characterized by incomplete
fusion and tenderness at the acromion. The acromion, which forms the bone at
the top or roof of the shoulder, typically develops from four individual bones
into one bone during the teenage years.
"We kept seeing
this injury over and over again in young athletes who come to the hospital at
the end of the baseball season with shoulder pain and edema at the acromion on
MRI, but no other imaging findings," said Johannes B. Roedl, M.D., a
radiologist in the musculoskeletal division at Thomas Jefferson University
Hospital in Philadelphia.
To investigate the
unexplained pain, Dr. Roedl and a team of researchers conducted a retrospective
study of 2,372 consecutive patients between the ages of 15 and 25 who underwent
magnetic resonance imaging (MRI) for shoulder pain between 1998 and 2012. The
majority of the patients, which included both males and females, were baseball
pitchers.
"Among high
school athletes, pitching is the most common reason for shoulder pain,"
Dr. Roedl said.
Sixty-one of the
patients, (2.6 percent) had pain at the top of the shoulder and an incomplete
fusion of the acromion but no other findings. The patients were then age and
sex-matched to patients who did not have the condition to form a control group.
Pitching history was
available for 106 of the 122 patients included in the study. Through
statistical analysis, the researchers found that throwing more than 100 pitches
per week was a substantial risk factor for developing acromial apophysiolysis.
Among the patients with this overuse injury, 40 percent threw more than 100 pitches
per week, 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.
All 61 injured
patients took a three-month rest from pitching. One patient underwent surgery
while the remaining 60 patients were treated conservatively with non-steroidal
pain medication.
Follow-up MRI or
X-ray imaging studies conducted a minimum of two years later after the patients
turned 25 were available for 29 of the 61 injured patients and for 23 of the 61
controls. Follow-up imaging revealed that 25 of the 29 patients (86 percent)
with the overuse injury showed incomplete fusion of the acromion, compared to
only 1 of the 23 (4 percent) controls.
"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.
Twenty-one of the 29
patients with the overuse injury continued pitching after the rest period, and
all 21 showed incomplete bone fusion at the acromion. Rotator cuff tears were
also significantly more common among this group than in the control group (68
percent versus 29 percent, respectively). The severity of the rotator cuff
tears was also significantly higher in the overuse injury group compared to the
control group.
"This overuse
injury can lead to potentially long-term, irreversible consequences including
rotator cuff tears later in life," Dr. Roedl said.
Dr. Roedl and his
colleagues suggest teenage and young adult pitchers limit the number of pitches
thrown in a week to 100. The American Sports Medicine Institute currently
recommends that baseball pitchers between 15 and 18 years of age play no more
than two games per week with 50 pitches per game.
"Pitching
places incredible stress on the shoulder," Dr. Roedl said. "It's
important to keep training in the moderate range and not to overdo it."
Dr. Roedl pointed
out that many successful professional baseball pitchers played various
positions, and even other sports, as young athletes and thereby avoided overuse
shoulder injuries.
"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."
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