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Prevalence of Ulnar Collateral Ligament
Surgery in Professional Baseball Players
Stan A. Conte,
*
y
PT, DPT, ATC, Glenn S. Fleisig,
z
PhD, Joshua S. Dines,
§
MD,
Kevin E. Wilk,
z||
PT, DPT, Kyle T. Aune,
z
MPH, Nancy Patterson-Flynn,
y
MS, ATC,
and Neal ElAttrache,
y{
MD
Investigation performed at the Los Angeles Dodgers, Los Angeles, California, USA
Background: While the high rate of ulnar collateral ligament (UCL) injuries in professional baseball is widely discussed in the
media and medical literature, the actual prevalence of UCL reconstruction has not been documented.
Hypothesis: The prevalence of UCL reconstruction will be higher among pitchers than nonpitchers, and Major League Baseball
(MLB) pitchers will have a higher prevalence than will minor league pitchers.
Study Design: Descriptive epidemiology study.
Methods: An online questionnaire was distributed to all 30 MLB organizations. Certified athletic trainers from each team admin-
istered the questionnaire to all players in the organization, including major league players and 6 levels of minor league players.
Demographic data were compared between major and minor league players. Continuous variables (age, years of professional
baseball, country of origin, etc) were compared with Student ttests (P\.05). Categorical variables (level, position, etc) were com-
pared using chi-square analysis (P\.05).
Results: A total of 5088 professional baseball players (722 major league and 4366 minor league) participated in the survey. Pitch-
ers represented 53% of all players, and 497 players reported at least 1 UCL reconstruction, demonstrating a prevalence rate of
10% (497 of 5088). Pitchers reported a significantly higher prevalence of UCL reconstruction (16%; 437 of 2706) than nonpitchers
(3%; 60 of 2382; P\.001). Among major league pitchers, 25% (96 of 382) had a history of UCL reconstruction, while minor league
pitchers showed a 15% (341 of 2324) prevalence (P\.001). Major league pitchers were also significantly older (28.8 63.9 years)
than minor league pitchers (22.8 63.0; P\.001). The majority of major leaguers (86%) had their UCL reconstruction as profes-
sional pitchers, whereas the majority of minor league pitchers (61%) underwent their UCL reconstruction during high school and
college (P\.001). The rates of UCL revision, prior elbow surgery, prior shoulder surgery, and types of UCL graft were similar
between the major league and minor league pitchers. No difference in prevalence was shown between pitchers born in the United
States versus Latin American countries.
Conclusion: Pitchers have a high prevalence of UCL reconstruction in professional baseball, with 25% of major league pitchers
and 15% of minor league pitchers having a history of the surgery.
Keywords: UCL; ulnar collateral ligament revision; Tommy John surgery; pitchers; Major League Baseball
Throwing elbow injuries are common at all levels of baseball,
andrecentreportssuggestthattheseinjuriesmayevenbe
on the rise.
4,11,14
Studies utilizing the Major League Baseball
(MLB) disabled list have shown that elbow injuries represent
between 16% and 22% of all MLB injuries.
5,19
These injuries
havebeenshowntoresultinanaverageof4451lostdaysper
MLB season.
5
Ulnar collateral ligament (UCL) injuries are
a common problem in the throwing athlete and account for
a large percentage of days lost because of elbow injury. By
far, baseball exhibits the highest incidence of UCL injuries
requiring surgical reconstruction.
4,12
Throwing is particu-
larly stressful on the UCL, placing large amounts of valgus
torque across the medial elbow.
3,8,10,11,18
This opening stress
of the medial elbow peaks near the instant of maximum
shoulder external rotation and the arm’s acceleration phase
of throwing.
3,8,10,11,18
This stress appears to be the greatest
in professional baseball pitchers.
11,13
Numerous studies have documented successful out-
comes in both the short term and the long term after
UCL reconstruction in baseball players and other athletes,
with return-to-play rates approaching as high as
90%.
2,4,6,7,9,14,15,17
A recent study by Makhni et al
17
*
Address correspondence to Stan A. Conte, PT, DPT, ATC, Los
Angeles Dodgers, 1000 Elysian Park, Los Angeles, CA 90045, USA (email:
scontept@aol.com).
y
Los Angeles Dodgers Baseball Organization, Los Angeles, California,
USA.
z
American Sports Medicine Institute, Birmingham, Alabama, USA.
§
Hospital for Special Surgery, New York, New York, USA.
||
Champion Sports Medicine, Birmingham, Alabama, USA.
{
Kerlan-Jobe Orthopaedic Clinic, Los Angeles, California, USA.
The authors declared that they have no conflicts of interest in the
authorship and publication of this contribution.
The American Journal of Sports Medicine, Vol. 43, No. 7
DOI: 10.1177/0363546515580792
Ó2015 The Author(s)
5-in-5
1764
reported that among MLB players, performance declines
after UCL reconstruction similar to the typical decline
over time of a cohort of age-matched healthy pitchers.
Pitchers with a history of UCL reconstruction also exhibit
an increased risk of future time on the disabled list for
elbow injury. Controversy exists among baseball players,
baseball organizations, the medical community, mass
media, and the general public about the actual prevalence
of UCL reconstruction in baseball, how the numbers have
increased in recent years, why so many players (particularly
pitchers) are injuring their elbows and tearing their UCLs,
and whether pitchers are too anxious to have a UCL recon-
struction. Surprisingly, the prevalence of UCL reconstruc-
tive surgery in baseball has not been documented.
Therefore, the purpose of this study was to document the
prevalence of UCL reconstructions in professional baseball
players. It was hypothesized that the prevalence would be
much higher among pitchers when compared with nonpitch-
ers. Data were also analyzed with respect to playing level,
age, and country of origin. These findings can improve our
understanding of UCL injuries in professional baseball,
including the subgroups particularly affected, as well as
serve as a baseline to assess whether the prevalence of
UCL reconstructions decreases or increases in the future.
METHODS
This study was conducted after it was reviewed and
approved by MLB and the Major League Baseball Players
Association. An online questionnaire for minor league
players not on the 40-man roster was distributed to all
30 MLB organizations during July and August of the
2012 baseball season. A similar online questionnaire was
also sent to all 30 MLB organizations in April and May
of 2013 for the players on the 40-man roster. Certified ath-
letic trainers from each team administered the question-
naire to all players in the organization, including the
major league players and 6 levels of minor league players:
AAA, AA, High A, Low A, High Rookie, and Low Rookie.
The questionnaire consisted of 8 to 26 questions based on
whether the player had no history of UCL reconstruction
(8 questions), a single UCL reconstruction (20 questions),
or multiple UCL reconstructions (26 questions). Two ver-
sions of the questionnaire were available per the player’s
preferred language, English or Spanish. For inclusion in
the study analysis, players were required to answer all
applicable questions pertinent to their subgroup.
Statistical analyses were performed with JMP 10 (SAS
Institute Inc). Demographic data were compared between
major league and minor league players. Preliminary anal-
ysis confirmed that pitchers were much more likely to have
undergone previous UCL reconstruction (P\.001), and for
this reason UCL reconstruction prevalence was further
analyzed among only pitchers. Variables were also com-
pared between major league and minor league pitchers.
Continuous variables (age, years of professional baseball,
etc) were compared with Student ttests (P\.05). All cat-
egorical variables (level, position, etc) were compared
using a chi-square analysis (P\.05).
RESULTS
Demographics of the participants in this investigation are
shown in Table 1. There were 5088 professional baseball
players, including 722 major league players and 4366
minor league players. An estimated 5700 players were
offered to complete the survey, thus resulting in an 89%
response rate. The minor league population consisted of
643 AAA, 673 AA, 1739 A, and 1311 Rookie players. The
major league players were significantly older and had
more professional baseball experience than did the minor
league players. Pitchers represented 53% of all players.
The majority of players were from the United States
(US), with a significant minority of players from the
Dominican Republic and Venezuela.
Among the 5088 respondents, 497 had undergone at
least 1 UCL reconstruction. Thus, the prevalence of profes-
sional baseball players including pitchers and position
players who had UCL surgery was 10% (497 of 5088).
The prevalence of UCL reconstruction was much higher
in pitchers (16%) than in nonpitchers (3%). Among pitch-
ers, the prevalence of UCL reconstruction was higher in
major league pitchers, older pitchers, and current relief
pitchers (Table 2). There was no difference in prevalence
between left- and right-handed pitchers nor between US-
born and international pitchers. When the subgroups of
international pitchers born in the Dominican Republic or
all Latin American countries were compared with pitchers
from the US, there was still no difference in UCL recon-
struction prevalence.
As shown in Table 3, there were several differences
between the major league and minor league pitchers with
a history of UCL reconstruction. The major league pitchers
were significantly older (P\.001) with more years of pro-
fessional baseball experience. The average age for first
UCL reconstruction was also higher in major league
TABLE 1
Demographics of All Players
a
Major League
Players
(n = 722)
Minor League
Players
(n = 4366) P
Age, y 28.8 63.9 22.8 63.0 \.001
Professional baseball, y 8.8 64.0 3.9 62.9 \.001
Current age, y \.001
\21 \1 (3) 20 (858)
21-25 18 (128) 65 (2858)
26-30 54 (387) 13 (548)
31-35 22 (157) 2 (86)
.35 7 (47) 0 (16)
Position .87
Pitcher 53 (382) 53 (2324)
Nonpitcher 47 (340) 47 (2042)
Country of origin .14
United States 73 (526) 71 (3119)
Dominican Republic 10 (72) 13 (533)
Venezuela 8 (57) 7 (286)
Other 9 (67) 9 (407)
a
Values are presented as mean 6SD or % (n).
Vol. 43, No. 7, 2015 Prevalence of UCL Surgery in Professional Baseball 1765
pitchers. The majority of major leaguers (86%) had their
UCL reconstruction as professional pitchers, whereas the
majority of minor league pitchers (61%) underwent their
UCL reconstruction during high school. The rates of UCL
revision, prior elbow surgery, prior shoulder surgery, and
types of UCL graft were similar between the major league
and minor league pitchers. Ulnar nerve transposition was
performed in a majority of pitchers who underwent UCL
reconstruction (71%). Other commonly performed concom-
itant procedures were bone spur removal (33% of all pitch-
ers) and loose body removal (14%).
The outcome results portion of the questionnaire for
pitchers who underwent UCL reconstruction are shown
in Table 4. All players in the UCL reconstruction group
were asked about their perception regarding their current
throwing velocity. Because previous studies suggested that
it takes 12 to 18 months for players to return to their pre-
vious levels of play after UCL reconstruction, responses
were excluded for this question among players who had
undergone their primary UCL reconstruction during the
past 12 months. When asked, ‘‘If you had to, would you
have Tommy John surgery again?’’ 72% of the players in
the UCL reconstruction group responded that they would,
17% said that they would not, and 11% were unsure. Minor
league pitchers were more likely than major league pitch-
ers to have self-reported higher throwing velocity after
their surgery but were less likely to state that they would
undergo UCL reconstruction again.
DISCUSSION
Despite an increasing body of literature being written on
the topic of UCL reconstructions in baseball players, there
has not been a study documenting the prevalence of UCL
reconstructive surgery among professional baseball play-
ers. Single-center studies have done an excellent job in
reporting their follow-up findings, with Cain et al
4
report-
ing on the largest number of athletes after UCL recon-
struction to date.
2,4,6,7,16,17
However, even the Cain et al
study did not elucidate the number of players in profes-
sional baseball who had undergone reconstruction of their
UCLs. In the current investigation, the overall prevalence
of UCL reconstruction among professional baseball players
was 10%. Not surprisingly, the majority of the UCL surger-
ies (88%) were performed on pitchers. In analyzing only
pitchers, 16% had UCL reconstruction surgery. During
the time of this study, the prevalence was 14% (161 of
1176) among starting pitchers and 18% (276 of 1530)
among relief pitchers. These group percentages were sur-
prisingly similar given that there is so much debate over
which type of pitcher is at higher risk to incur a tear of
his UCL. Although the prevalence of UCL reconstruction
was higher among active relief pitchers when compared
with active starting pitchers, 51% (220 of 433) of the pitch-
ers with a history of UCL reconstruction were starters at
the time of injury. Sixty-one current relief pitchers were
starting pitchers at the time that they sustained their
UCL injuries, while only 1 current starting pitcher was
a relief pitcher at the time of his UCL injury.
Whereas the overall prevalence of UCL reconstructions
among pitchers was 16%, the rates were higher among
major league pitchers and among older pitchers. Since
major leaguers were older in general, a worthwhile ques-
tion is whether the higher prevalence among major league
TABLE 2
Prevalence of Ulnar Collateral Ligament
Reconstruction Among Pitchers
Prevalence, % (n) P
Current level \.001
Major league 25 (96 of 382)
Minor league 15 (341 of 2324)
Current age, y \.001
21-25 14 (235 of 1698)
26-30 27 (132 of 484)
31-35 36 (39 of 108)
Current role .002
Starting pitcher 14 (161 of 1176)
Relief pitcher 18 (276 of 1530)
Throwing hand .26
Right-handed 17 (328 of 1969)
Left-handed 15 (109 of 737)
Country of origin
United States 16 (322 of 2007)
Not United States 16 (115 of 699) .81
a
Latin America 16 (91 of 577) .87
a
Dominican Republic 16 (54 of 343) .89
a
a
Pvalue based on comparison with ‘‘United States.’’
Figure 1. Prevalence of ulnar collateral ligament (UCL)
reconstruction for various age groups and levels. The height
of each column represents the prevalence of UCL recon-
struction among pitchers in each league within each age
group, and the width of each column is representative of
the total number of pitchers in each league within each age
group. UCL prevalence increased with age group (21-25 vs
26-30 vs 31-35 years), with no interaction between levels
(major vs minor leagues) within each age group.
1766 Conte et al The American Journal of Sports Medicine
pitchers can be attributed solely to age. Figure 1 shows
UCL prevalence for various age groups of major and minor
league pitchers. A Cochran-Mantel-Haenszel stratification
by age group (21-25 vs 26-30 vs 31-35 years) of UCL recon-
struction prevalence revealed no significant differences
between major and minor league pitchers (P= .55). How-
ever, the question of age and UCL injury certainly requires
further examination.
A topic receiving attention in the media is the appar-
ently increasing number of younger athletes requiring
UCL reconstruction. Much of this media commentary is
based on the work of Fleisig and Andrews,
11
who reported
a significant increase in UCL reconstruction surgery in
youth baseball players during the past 15 years. In the cur-
rent investigation, the overall prevalence of UCL recon-
structions in baseball players younger than 20 years was
5%. When we look at the minor league players in isolation
(which is statistically a younger aged population), the cur-
rent study demonstrated that 30% of minor league players
underwent UCL reconstruction before the age of 20 years
(including one who was 14 and one who was 15 years
old), echoing the results of Fleisig and Andrews. While
TABLE 3
Comparison of Major and Minor League Pitchers With a History of UCL Reconstruction
a
Major League Pitchers Minor League Pitchers P
Current age, y 28.7 63.8 22.8 62.7 \.001
Professional experience, y 8.4 64.0 3.8 62.7 \.001
At time of first UCL reconstruction
Age, y 24.0 64.1 21.0 62.8 \.001
Level \.001
High school 6 (6 of 96) 61 (205 of 338)
College 7 (7 of 96) 30 (103 of 338)
Professional 86 (83 of 96) 9 (30 of 338)
Position .064
Starting pitcher 59 (57 of 96) 48 (163 of 337)
Relief pitcher 41 (39 of 96) 52 (174 of 337)
No. of UCL reconstructions .71
1 97 (93 of 96) 98 (333 of 341)
2 3 (3 of 96) 2 (8 of 341)
Graft (first UCL reconstruction) .60
Forearm–throwing arm 59 (55 of 94) 60 (198 of 330)
Forearm–nonthrowing arm 14 (13 of 94) 13 (44 of 330)
Leg 27 (25 of 94) 22 (74 of 330)
Other/don’t know 1 (1 of 94) 4 (14 of 330)
Surgery before first UCL reconstruction
Elbow 11 (11 of 96) 7 (25 of 338) .21
Shoulder 9 (8 of 94) 4 (15 of 335) .13
a
Values are presented as mean 6SD or % (n). UCL, ulnar collateral ligament.
TABLE 4
Outcomes for Pitchers With UCL Reconstruction
a
Major League Pitchers Minor League Pitchers P
Surgery since primary UCL reconstruction
Shoulder 11 (10 of 94) 5 (17 of 335) .057
Elbow 9 (9 of 96) 11 (36 of 335) .85
Current velocity vs that before primary UCL reconstruction .004
Faster 26 (20 of 77) 46 (111 of 239)
Same 1 (1 of 77) 1 (3 of 239)
Slower 51 (39 of 77) 42 (101 of 239)
Don’t know 22 (17 of 77) 10 (24 of 239)
If had to, would have UCL reconstruction again
b
.047
Yes 86 (65 of 76) 72 (171 of 239)
No 9 (7 of 76) 16 (39 of 239)
Don’t know 5 (4 of 76) 12 (29 of 239)
a
Values are presented as % (n). UCL, ulnar collateral ligament.
b
Includes only responses from players with primary UCL reconstruction at least 12 months before survey.
Vol. 43, No. 7, 2015 Prevalence of UCL Surgery in Professional Baseball 1767
this highlights the fact that UCL reconstructive surgeries
are being done on younger patients, it also indicates that
the surgery is often successful enough to allow these ath-
letes to excel to the highest level of baseball even after
a major surgical reconstruction. To this point, Osbahr
et al
18
evaluated the outcomes after UCL reconstruction
in competitive baseball players at a minimum 10-year fol-
low-up. They found that 83% of athletes (90% of pitchers)
were able to return to baseball in \1 year and that after
surgery, the average baseball career was 3.6 years. More
to our point, professional baseball players returned for lon-
ger than college or high school athletes. What remains
unknown is how many teenage baseball players undergo
UCL reconstruction and are subsequently unable to reach
the level of professional participation or even return to their
prior levels of function. A large multisite prospective study
would be needed to determine the long-term clinical out-
comes of UCL reconstruction in teenage athletes.
Another issue that is frequently discussed in the media
is whether UCL reconstruction is a problem preferentially
affecting US-born athletes.
20
Despite news articles stating
this to be the case, the results of the current study clearly
show this to be false and that the prevalence of UCL recon-
struction is equal between US and Latin American players.
One difference that was noted to be statistically significant
(P\.001) was that there was a much larger percentage of
Dominican Republic pitchers who underwent their first
UCL reconstruction at the professional level when com-
pared with pitchers from the US (96% vs 56%). However,
there was no difference between the average ages of the
first UCL reconstructive surgery between these 2 groups
(21 years of age). This was also true when pitchers from
all Latin American countries were compared with the
pitchers from the US.
When a pitcher returns to throwing after shoulder sur-
gery, there is often concern about potential elbow injury
owing to altered throwing mechanics and incomplete reha-
bilitation. This survey indicated that only 9% of the UCL
reconstruction group had any previous elbow surgery and
only 5% had previous shoulder surgery. Given the limita-
tions of the study, we do not have details regarding any
prior surgeries. However, the players who had undergone
previous surgeries represent a very small number of the
study population, so on the basis of these data, it appears
that previous elbow or shoulder surgery is not a significant
risk factor for subsequent UCL reconstruction.
Of the players who had a UCL reconstruction, 10% had
an additional elbow procedure later in their careers, and
only 6% underwent a shoulder surgery. These are encour-
agingly low values that represent a minimal risk of addi-
tional injury after a return to throwing after UCL
reconstruction. Cain et al
4
reported that 7% of their
patients with UCL reconstruction underwent a subsequent
elbow procedure, with the most common one being the
removal of an olecranon osteophyte. They also reported
a 3% incidence of a shoulder surgery after the UCL recon-
struction. The most likely reason for these findings can be
attributed to adequate and complete rehabilitation after
UCL reconstruction. While our study looked at the risk of
future surgery after UCL reconstruction, it is important
to note that this underestimates the risk of future injury
after UCL reconstruction. The study by Makhni et al
17
revealed that 57% of pitchers undergoing UCL reconstruc-
tion returned to the disabled list after surgery because of
injury to their throwing arms.
A major concern regarding players undergoing UCL
reconstruction is whether their performance will be
reduced after the surgery. Along these lines, Makhni
et al
17
reviewed 147 cases of MLB pitchers who underwent
UCL reconstruction and returned to MLB. Eighty percent
returned to pitch at least 1 MLB game. However, only 67%
returned to their prior levels of competition, and even more
discouraging was the fact that 57% returned to the dis-
abled list after the surgery because of injury to their throw-
ing arms. Additionally, in contrast to other reports,
performance declined after surgery.
17
In our current survey, we did query about throwing
velocity. Admittedly, this was based solely on the athlete’s
own perception, which may be inaccurate. We included
the results because physicians treating these athletes are
often asked if the athlete will throw harder after surgery,
and a significant proportion of athletes and coaches believe
that performance is enhanced by the procedure.
1
In fact,
41% of the players who underwent UCL reconstruction
reported throwing faster after surgery, while 44% reported
throwing slower after surgery. However, this study does
not include players who were unable to return to profes-
sional baseball after UCL reconstruction. If this group of
players were to be included, it is likely that the percentage
(41%) of respondents reporting that they were able to throw
faster after UCL reconstruction would be lower.
There exist several limitations to this study. It is vital to
recognize that this study reported the prevalence, not the
incidence, of UCL reconstruction in professional baseball.
Professional baseball players who had UCL reconstruction
but are no longer in professional baseball were not
included. Results from this study—particularly, the out-
comes reported in Table 4—could be different if players
who did not return and stay in professional baseball were
included. A prospective longitudinal study is needed to quan-
tify the incidence of UCL injuries and outcomes after all UCL
reconstructions. Furthermore, the prevalence of UCL recon-
struction was determined by self-report, which may have
introduced misclassification bias. Ideally, we would have
compared participants’ responses with their medical records.
Unfortunately, this was not possible. It is our belief, however,
that because Tommy John surgery is so common among
baseball players and requires such a long, unique rehabilita-
tion protocol, professional baseball players’ recollections of
what elbow surgery they underwent are unlikely to be too
disparate from their medical records. Players were given
the option of an English or Spanish version of the question-
naire, and a small number of players in the study were
from countries that did not speak either language fluently.
The survey was administered by the given player’s certified
athletic trainer, who was able to ensure understanding and
completion of every question. Players who were not able to
understand or complete every question were excluded.
Clearly, the strength of this study is that it reported on
a homogeneous group of .5000 professional baseball players,
1768 Conte et al The American Journal of Sports Medicine
with an estimated 89% of eligible players completing the sur-
vey. A perceived increased frequency of UCL reconstruction
in professional baseball has drawn much attention from
the medical community, press media, and general public,
but the current study is the first to report the true prevalence
of UCL reconstruction in professional baseball. Since any
past prevalence is unknown, a historical rise in UCL recon-
struction rates cannot be confirmed. However, this study
showed a current prevalence of 16% among professional
pitchers and 3% among nonpitchers. These numbers provide
a perspective of the effect that UCL reconstructions have on
professional baseball today and so can serve as a baseline for
assessing future increases or decreases in UCL surgery
rates.
ACKNOWLEDGMENT
The authors thank K. C. Cord for her assistance in the sur-
vey design, as well as Major League Baseball and the ath-
letic trainers of the Professional Baseball Athletic Trainers
Society for the collection of the data. A special thanks to
Michael Weiner, executive director of the Major League
Baseball Players Association. Without the advice and sup-
port of the late Dr Lewis Yocum, this article would not
have been possible.
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Vol. 43, No. 7, 2015 Prevalence of UCL Surgery in Professional Baseball 1769
