Andrew Gregory, MD, Gary Waslewski, MD, Glenn Fleisig, PhD, Jason Oliveri, MPH, James Andrews, MD
Purpose:
To identify any relationship between skeletal maturity (measured as bone age,
presence of elbow ossification centers and medial epicondyle development) and
injury (measured as post-game arm pain) in youth pitchers.
Methods:
In 1999 ASMI completed the Youth Baseball Pitching Study for USA Baseball. One
hundred and eighteen out of the five hundred pitchers involved in the original
study also had x-rays taken of their pitching elbow and left hand prior to the
beginning of the season. From the hand and wrist films a bone age was determined
by Gary Waslewski using standards from the Gruelich and Pyle Atlas. From the
pitching elbow films three variables were determined: the latest of the six
secondary ossification centers to appear, the development of the medial epicondyle,
and any unusual findings. For the entire season following a pitching appearance
the players were interviewed regarding any elbow or shoulder pain. Of the one
hundred and eighteen players x-rayed sixty-eight had completed pain scores at
the end of the season. A Pearson's Chi Squared analysis was run on all data
comparisons.
Results:
The average age of the pitchers was twelve and the range was nine to fourteen.
Except for eleven year olds, elbow and shoulder pain ranged from 10 to 36 percent
without a statistical trend. All six of the pitchers who were eleven years old
had shoulder pain. The average bone age was twelve and a half with a range of
eight to fifteen. Elbow pain ranged from 10 to 44% while shoulder pain was 0
to 60%, both with a peak at twelve years old.
The bone age was a mean of half a year ahead of chronological age with a range
of three years ahead to three years behind. Twice as many pitchers with advanced
bone age had elbow (37%) and shoulder (42%) pain as compared with those with
delayed bone age (both 17%).
Most of the pitchers (60%) had all the secondary ossification centers present,
40% lacked the lateral epicondyle, 20% lacked it and the olcranon, 10% also
lacked the trochlea, and only 2% also lacked the medial epicondyle. There were
no players without the radial head or capitellum. The incidence of elbow pain
ranged from 0 to 31% while shoulder pain was 0 to 46% & both peaked in players
lacking their lateral epicondyle. None of the players lacking their trochlear
ossification center had pain.
Most of the players had a fusing or fused medial epicondyle (60%), 23% had a full size epicondyle without evidence of fusion and 12% had a newly formed epicondyle. Again only two percent of players lacked their medial epicondyle. Of these the incidence of elbow pain was 0 to 30% while shoulder was 0 to 48%. The incidence of both seemed to drop off somewhat after complete fusion to the humerus.
There were sixteen players (14%) with unusual elbow x-ray findings. Five had a patent olecranon fossa, five had a bipartite olecranon, four had a UCL ossicle, one had a ligament of Struthers and one had a fragmented medial epicondyle. Three out of the four players with a UCL ossicle had elbow pain and none of the others did.
Conclusions:
There was no statistically significant correlation between any of our skeletal
maturation indices and elbow or shoulder pain. The high incidence of elbow pain
in eleven year old pitchers is thought to be erroneous based on data from the
previous study. Although not statistically significant, there does appear to
be a trend that pitchers with advanced bone age get more shoulder and elbow
pain. If bone age correlates with pubertal changes then it makes sense that
the pitchers with precocious puberty would get more arm pain since they can
generate more force. Also statistically significant is the correlation with
ossicle formation in the UCL and elbow pain. We realize that using arm pain
as our outcome limits our conclusions because it may not necessarily correlate
well with injury.