Abstract
Background:
Elbow injuries cause significant disability for the throwing athlete. Scant data are available on the distribution and characteristics of these injuries in elite baseball players. No study exists that focuses solely on the epidemiological characteristics of elbow injuries in professional baseball players using a comprehensive injury surveillance system.
Hypothesis:
Professional baseball players have a high occurrence of elbow injuries influenced by factors including length of time playing, time period within the annual baseball season, and specific position played.
Study Design:
Descriptive epidemiological study.
Methods:
Data on elbow injuries occurring during the 2011-2014 seasons were collected from Major League Baseball’s Health Injury and Tracking System, a comprehensive injury surveillance system. Each specific type of elbow injury was evaluated with respect to overall injury rate, years as a professional player, mechanism of injury, treatment, average time lost, and return to play.
Results:
During the study period, 3185 elbow injuries (n = 430 Major League; n = 2755 Minor League) occurred. The mean number of days missed and percentage requiring surgery were similar between Major and Minor League players. Overall, 20.0% (650/3185) of the injuries required surgical treatment. Pitchers were the most likely to incur an elbow injury (40.0% of injured athletes were pitchers), were the most likely to require surgery (34.2% of injured pitchers required surgery), and had the greatest mean number of days missed when treated nonsurgically (33.2 days). Medial injuries composed 42.1% (1342/3185) of all elbow injuries. Of all elbow surgeries performed during the study period, the highest percentage involved ligaments (372/650; 57.2%).
Conclusion:
Elbow injuries are a considerable source of disability in professional baseball players. Pitchers are most likely to incur these injuries, are most likely to require surgery, and have the highest mean number of days missed when treated nonsurgically. The most common injuries involve the medial elbow, with ligament injuries most often requiring surgery. This study represents the only investigation to date using a comprehensive injury surveillance system to examine elbow injuries in professional baseball players. It provides a basis for injury prevention and treatment recommendations, establishes the most thorough framework for determining elbow injury risk, and focuses continued research on elbow injury prevention in the elite baseball player.
Keywords
Elbow injuries are prevalent in numerous sports, and several studies have described the diagnosis and treatment of these injuries.2,3,5,6,8,9,11,21,23,27-31 In the throwing athlete, elbow injuries are one of the most common causes of disability.9,12,16,21 The majority of available literature on elbow injuries in throwers is primarily retrospective, with some prospective evaluations of diagnosis and treatment of specific elbow injury types in heterogeneous populations.2,3,8,9,23,27-31
Few studies exist describing the epidemiological characteristics of baseball injuries. In high school baseball players, Collins and Comstock 11 evaluated the broad spectrum of musculoskeletal injuries over 2 seasons in a limited, sampled population. These authors noted elbow injuries as 7.2% of all scholastic or high school baseball injury types. At the collegiate level, data from the National Collegiate Athletic Association (NCAA) Injury Surveillance System noted that 6.9% of all reported game injuries were elbow-related. 16 Neither of these cohort studies documented player position, time of season when injury occurred, percentage of players requiring surgery, or time lost from play with respect to specific elbow injuries in the throwing athlete.
At the professional level, few epidemiological studies exist on elbow injuries, with notable limitations. Conte et al 12 reviewed the disability lists (DLs) of Major League Baseball (MLB) over an 11-year period with respect to all types of musculoskeletal injuries. Although the investigators did not focus specifically on any anatomic region, they noted that 22% of DL days involved the elbow. Posner et al 26 also reviewed MLB injury patterns using the DL, and as such their data were derived solely from web-based, public information. These authors found that over a 7-year period, elbow injuries represented 16.4% of all musculoskeletal injuries. Beyond these 2 studies, other existing studies of elbow injuries are predominantly case series on treatment of specific elbow injuries in overhead athletes. These studies include small, heterogeneous groups, are subject to potential selection bias, and do not provide enough epidemiological information to determine meaningful trends.2,8,9,31 No other data exist with respect to the epidemiological characteristics of elbow injuries specifically in elite baseball players, least of all at the professional level.12,26 The current study builds on those noted prior studies, including those by Posner et al and Conte et al that were based on the DL, by using a comprehensive injury surveillance system to generate a more granular view of injuries in comparison to the publically available data. Furthermore, this study is the first epidemiological study to specifically focus on elbow injuries in professional baseball players, while previous efforts studied all types of injuries with or without subset analysis on elbow injury.
The purpose of this study is to describe the specific characteristics of elbow injuries occurring in Major and Minor League Baseball players during the 2011-2014 seasons by using a comprehensive injury surveillance system developed by MLB. Understanding the characteristics of these injuries will provide important information with respect to elbow injury risk and will inform targeted prevention strategies.
Methods
Elbow injury data were collected for all Major and Minor League Baseball teams for the 2011-2014 seasons. MLB consists of 30 different ball clubs geographically spread across the United States and Canada, for a total of approximately 750 active players. There are 2 leagues, the National League and the American League, and each ball club plays 162 games scheduled over a 180- to 183-day regular season. Minor League Baseball consists of over 200 teams located across North and South America and the Caribbean, each of which is affiliated with a specific Major League parent ball club that contracts all players on all of their respective Minor League teams. The Minor Leagues consist of roughly 7500 players; approximately 6500 are actively playing at any given time due to several reasons: some are on the DL and others are on the restricted list or other inactive lists. Additionally, some Minor League–level seasons are shorter and do not start until June. Last, an influx of Minor League players occurs in late June and July when amateur players are signed and begin playing. Minor League teams are divided into different leagues (ie, AAA, AA, A, Rookie Ball) based on skill level and geographic location. The length of the Major League season extends from the beginning of April through the end of September. The standard Minor League schedule extends from the beginning of April until the first week of September. A low level of the Minor Leagues (Short Season) extends from mid-June through the first week of September.
Data Acquisition
All injuries were recorded in the MLB Health and Injury Tracking System (HITS). HITS is a centralized database containing the deidentified medical data from the player’s electronic medical record (EMR), which standardizes the tracking and transfer of all player medical records throughout the MLB.
The data extracted from the HITS system relate only to injuries that resulted in lost game time for a player and that occurred during spring training, regular season, or postseason play; off-season injuries were not included as they were not a result of baseball activities. Injuries are recorded in the database by each team’s certified athletic trainer if the physical complaint sustained by a player affects or limits participation in any aspect of baseball-related activity (eg, game, practice, warm-up, weight training). Injury events that were classified as “season ending” were not included in the analysis of days missed since many of these players may not have been cleared to play until the beginning of the following season, and hence calculation of their days missed would not accurately reflect time away from play in the same sense as it does for non-season-ending injuries. These injury events were excluded only when days missed were summarized but were included in all other analyses such as incidence, age, position, percentage requiring surgery, and reinjury. This is consistent with the reporting methods of other published epidemiological studies evaluating concussion, knee, hip, and hamstring injuries in professional baseball players.1,10,14,20 The data items for the analyzed injuries consist of basic information gathered at the time of injury, such as diagnosis, body region, activity, and location and date of injury. These study procedures were approved by the Johns Hopkins Bloomberg School of Public Health Institutional Review Board.
Defining Elbow Injury and Related Characteristics
For the purpose of data extraction, elbow injury was defined as a case having a body region variable identified as “elbow,” classified as work-related, not occurring in the off season, and with the specific elbow injury type as the primary diagnosis. All elbow injuries, acute and chronic, resulting in lost game time were extracted from the HITS system for Major and Minor League Baseball players during the 2011, 2012, 2013, and 2014 seasons.
Variables collected from HITS for each year of the study period included the following: level of play, position played at the time of injury (called “event position”), activity at time of injury, location on the field of injury, time of year, and surgical and nonsurgical treatment. The only exception is the event position variable that was added to the HITS system during the 2012 season, and so this is designated as “not classified” for the 2011 season.
Data Analysis
Data for the 2011-2014 seasons were aggregated, and results are presented for all players as well as separately for Major League players and Minor League players. Each specific injury type was described according to years of professional baseball, mechanism of injury, time of year (spring training, regular season, postseason), percentage of pitchers and position players, prior injury, average time lost with nonsurgical treatment, percentage requiring surgery, and percentage of pitchers and position players returning to preinjury level of play. Unless otherwise noted, the term frequency is used to denote the count or total number of elbow injuries in specified strata according to the aforementioned variables for the 2011-2014 seasons, as was done in other published epidemiological studies evaluating concussion and knee, hip, and hamstring injuries in professional baseball players.1,10,14,20
Time lost in this study represents the number of days from the injury event date to the medical clearance date (when the athlete was deemed able to play in any aspect of the game). This technique defines the occurrence of injury but does not accurately assess the severity of injury. Because of the importance of the days missed measure for professional baseball, both the mean and median are presented as was done in other published epidemiological studies evaluating concussion and knee, hip, and hamstring injuries in professional baseball players.1,10,14,20 Chi-square tests were used to test the hypothesis of equal proportions between the various categories of elbow injury characteristics, with statistical significance determined at the P = .05 level.
As in previous published epidemiological studies in professional baseball players,1,10,14,20 athlete exposures (AEs) were estimated and injury rates were calculated. To estimate exposure, we calculated the average number of players per team per game based on analysis of regular season game participation via box scores that are publicly available. This average number over a season, multiplied by the number of team games at each professional level of baseball, was used as an estimate of AEs to provide rates comparable with those of other injury surveillance systems. Injury rates were reported as injuries per 1000 AEs for those elbow injuries that occurred during the regular season. The number of regular season elbow injuries and the subsequent AE rates are based on injuries that were deemed work-related during the regular season. This includes injuries occurring during the course of a game as well as injuries sustained in game preparation. Due to the variations in spring training games and fluctuating rosters, accurate calculations of AEs could not be obtained; hence, exposure rates were not calculated for elbow injuries that occurred during spring training, consistent with other published epidemiological studies in professional baseball players.1,10,14,20 All data analysis was performed in the R statistical computing environment (R Core Team 2014).
Results
Overall Summary and Burden of Elbow Injuries
Table 1 presents a general summary of the characteristics of elbow injury in Major and Minor League Baseball players during the study period. A total of 3185 elbow injuries occurred from 2011 through 2014, with 430 (13%) occurring in the Major League and 2755 (86%) occurring in the Minor Leagues. The mean age of Major League players incurring an elbow injury was 28.5 years (range, 20.9-40.3 years), which was significantly older than the mean age of Minor Leaguers incurring an elbow injury (22.6 years; range, 16.2-41.2 years) (P < .05). No statistically significant difference was found between the Major and Minor League players for mean number of days missed, the percentage of players who required surgery after injury, and the percentage of players who reinjured their elbow.
General Summary of the Professional Baseball Elbow Injuries From Major and Minor League Players Over the 2011-2014 Seasons
Does not include season-ending injuries.
Percentage calculated within level of play.
Table 2 compares the burden of elbow injuries to all other injury types in professional baseball. Elbow injuries were the fourth most prevalent type of injury in both the Major and Minor Leagues, accounting for 7.8% and 9.8% of all injuries in each, respectively. Elbow injuries, however, accounted for the highest number of days missed of all musculoskeletal injuries for both Major and Minor Leagues (approximately 4 weeks) (results not shown).
Prevalence of the 10 Most Common Injuries by Body Part in Professional Baseball a
Freq, frequency; NA, not applicable.
For regular season games, it was estimated that 276,608 Major League and 1,197,738 Minor League AEs occurred over the course of the 4 seasons. The overall elbow injury rate across both Majors and Minors was 1.7 per 1000 AEs, based on the 287 and 2213 regular season elbow injuries in the Major and Minor Leagues, respectively. The rate of elbow injury was 1.8 times more likely in the Minors than in the Majors (P < .0001) (rate of 1.8 per 1000 AEs in the Minors and 1.0 per 1000 AEs in the Majors). Elbow injury rates were also stratified comparing rates for pitchers to rates for position players. Across both the Majors and Minors, the rate of elbow injury was 1.9 times more likely for pitchers than for position players (P < .0001) (rate of 2.6 per 1000 AEs for pitchers and 1.4 per 1000 AEs for position players across both leagues).
Characteristics, Diagnosis, and Surgery of Elbow Injuries
Table 3 displays the distribution of elbow injury by player event position with respect to percentage requiring surgery and mean number of days missed for nonsurgically treated injuries. These data show that more than one-third of all elbow injuries occurred in pitchers, the highest of all event positions with documented data during the study period (48.1% for Majors and 38.8% for Minors). “Location on the field” was most commonly noted as the pitcher’s mound and “mechanism of injury” was most commonly noncontact for Major Leaguers, Minor Leaguers, and combined leagues during the study period.
Frequency of Elbow Injury by Player Event Position for the 2011-2014 Seasons
Percentage calculated across event positions.
Percentage calculated with event position.
Mean days missed for nonsurgically treated injuries does not include season-ending injuries.
Mean days missed not presented (NP) due to no sample or small sample size.
Of all the positions, pitchers were the most likely to require surgery after an elbow injury (43.0% of Major Leaguers and 32.5% of Minor Leaguers). Of those professional baseball players incurring an elbow injury (Major, Minor, and combined) and treated nonsurgically, pitchers had the greatest number of days missed (Major, 34.2 days; Minor, 33.0 days; combined Major and Minor, 33.2 days). Days missed information was not summarized for the surgically treated elbow injuries since the majority of these were season-ending injuries and, as noted previously, accurate assessment of days missed is not available for these cases. This is consistent with other published epidemiological studies evaluating concussion and knee, hip, and hamstring injuries in professional baseball players.1,10,14,20
Table 4 presents the frequencies of specific elbow injury by Sport Medicine Diagnostic Coding System (SMDCS) and diagnoses subtypes (ligament, tendon, nerve, bone, and miscellaneous) for combined Major and Minor League players from 2011 through 2014. Of the 905 documented ligament injuries, injury to the ulnar collateral ligament (UCL) was most common (n = 768; 84.9%). Of the 562 documented tendon injuries, injury to the medial flexor-pronator mass was most common (n = 260; 46.3%). Of the 237 documented nerve injuries, injury to the ulnar nerve was the most common (n = 222; 93.7%). Of the 137 documented bone injuries, posteromedial impingement was most common (n = 92; 67.2%). Medial elbow injuries composed 42.1% (n = 1342/3185) of all elbow injuries documented in Major and Minor League players during the study period. Ligament injuries were the most common type of elbow injury noted in Major and Minor League players (n = 905/3185; 28.4%) resulting in the second highest number of average days missed for all types of elbow injuries across both leagues, a result that was also consistent within each league separately (results not shown). All injury types were also most common among pitchers.
Frequency of Specific Elbow Injury Diagnoses for Combined Major and Minor League Players From 2011 Through 2014 a
SMDCS, Sport Medicine Diagnostic Coding System.
Figure 1 displays the frequency of total elbow injuries with respect to time of baseball season (spring training, regular season, postseason) and month of year for the 4-year study period. Figure 2 displays elbow injury diagnoses subtypes with respect to time of baseball season for the 4-year study period. The greatest number of total elbow injuries and the highest number of each specific elbow diagnosis subtype was noted during the 6-month regular season followed by spring training and the postseason. With respect to specific month of the year, for Major League players the highest total number of elbow injuries (n = 93) and specifically the highest number of ligament injuries (n = 31) occurred in March. For Minor League players the highest total number of elbow injuries (n = 487) and specifically the highest number of ligament injuries (n = 142) occurred in July.
Frequency of total elbow injuries plotted by time of baseball season (spring training, regular season, postseason) and month of year for Major League (left) and Minor League (right) for the 2011-2014 seasons.
Frequency of elbow injury diagnosis subtypes (ligament, tendon, nerve, bone, miscellaneous) plotted by time of baseball season (spring training, regular season, postseason) and month of year for Major League (left) and Minor League (right) for the 2011-2014 seasons.
The percentages of specific elbow injury anatomic subtypes requiring surgery are presented in Table 5. When a specific elbow injury occurred, the percentage of that specific injury requiring surgery was noted. Bone injuries were the most likely to require surgery during the study period for Major Leaguers (64%), Minor Leaguers (59%), and leagues combined (60%). Fifty-three percent of Major Leaguers who incurred a ligament injury required surgery, whereas 39% of Minor Leaguers who incurred a ligament injury required surgery. Of all the elbow surgeries performed during the study period, the highest percentage involved the ligaments: 68 (58%) of the 118 Major League elbow surgeries, 304 (57%) of the 532 Minor League elbow surgeries, and 372 (57%) of the total leagues combined elbow surgeries.
Percentages of Specific Elbow Injury Diagnoses Subtypes Requiring Surgery for the 2011-2014 Seasons
Percentage calculated based on total requiring surgery within each diagnosis type.
Discussion
Elbow injuries represent one of the greatest causes of disability for the overhead or throwing athlete.9,12,16,21 Very limited data exist on the epidemiological characteristics of these injuries in baseball players.17,18 While data on high school 11 and collegiate 16 athletes provide some insight into elbow injuries at those levels, this information represents cohort studies that cannot be broadly applied to the professional baseball player. The professional baseball season is significantly longer; the professional baseball player often performs at a higher level; and the professional baseball player, particularly at the Major League level, has greater resources for diagnosis, treatment, and prevention of these elbow injuries.
The epidemiological data on elbow injuries at the professional level are also extremely limited. The available studies on professional baseball players12,26 are based on the DL for only a portion of the season or solely web-based sources. These studies focus on patterns with respect to general musculoskeletal injury and provide meaningful information on injury trends in MLB by analyzing DL data before the availability of MLB Injury Surveillance System data. Both noted an increasing injury burden among baseball players despite improvements in training and conditioning, injury diagnosis, and injury management. These studies did not, however, provide information on specific types of elbow injury with respect to such factors as player position, mechanism, timing, and treatment. The current study represents the first comprehensive review of elbow injuries using the MLB Injury Surveillance System for longitudinal tracking of medical histories in these athletes. It provides information regarding player position at time of injury, mechanism of injury, time of season for injury, percentage requiring surgery, and time lost from competition for elbow injuries. As such, this study provides a meaningful analysis of the distribution, correlates, and effects of these elbow injuries in this population. Furthermore, the study establishes a framework for determining elbow injury risk and provides a focus for future research on elbow injury prevention in the elite baseball player.
A general review of these injuries in professional baseball players identified a total of 3185 elbow injuries from the 2011-2014 seasons. Data extraction from the MLB Injury Surveillance System does not allow differentiation between acute, chronic, and acute-on-chronic injuries. And yet, although truly acute injuries do occur in baseball, very often there is a preceding insidious progression of chronic changes with elbow injuries in this population. Of the 3185 documented elbow injuries, 440 (13.5%) occurred in the Major Leagues, while 2755 (86.5%) occurred in the Minor Leagues. This is consistent with the far greater number of Minor League players from the different leagues (ie, AAA, AA, A, Rookie Ball). Although Major Leaguers incurring an elbow injury were an average of 5.9 years older than Minor Leaguers with elbow injury, this age difference did not play a role in the average number of days missed and percentage requiring surgery for Major and Minor League players. This may suggest that the diagnostic evaluation and treatment protocols are consistent throughout professional baseball, irrespective of specific level of play.
In Major League players, elbow injuries were the fourth most prevalent type of injury, behind upper leg (13.1%), shoulder (12.2%), and hand (9.1%). In Minor Leaguers, elbow injuries were also the fourth most prevalent type, behind shoulder (15.2%), upper leg (11.4%), and hand (10.3%). With respect to time missed after injury, however, elbow injuries represent the highest average number of days missed of all musculoskeletal injuries in Major League, Minor League, and combined leagues during the study period. This suggests that these injuries are a significant source of disability for baseball players given the importance of the upper extremity for the throwing mechanism and the lengthy rehabilitation required to return. This highlights the tremendous effect that elbow injuries have at a professional level with respect to time lost from play. Over the 4-year study period, however, elbow injuries were not found to increase in frequency. This is important in light of the heightened media scrutiny and perspective on elbow injuries in the professional baseball player.
The results of this study indicate that elbow injuries have the greatest effect on pitchers. In both the Major and Minor Leagues, pitchers had a significantly greater elbow injury rate than position players. Forty percent of all elbow injuries occurred in combined Major and Minor League pitchers, the highest of all “event positions” with documented data during the entire study period. Furthermore, this study indicates that pitchers are the most likely of all professional baseball players to require surgery after an elbow injury (Majors, 43.0%; Minors, 32.5%; combined, 34.2%). Of those players, Major and Minor, incurring an elbow injury and treated nonsurgically, pitchers required the highest number of days to return to play (Major, 34.2 days; Minor, 33.0 days; combined, 33.2 days). This prolonged time for return to play with treatment of elbow injuries in elite pitchers compared with position players may be due to the added time required to progress through the postinjury throwing program.
Specific Elbow Injury Subtype Review
A more detailed review of these epidemiological data indicates that with respect to specific diagnosis type, ligament injuries occurred most commonly over the study period (28.4%), followed by tendon injury (17.6%), nerve injury (7.4%), and bone injury (4.3%). The remainder of the documented elbow injuries comprised a variety of miscellaneous types (42.3%). This suggests the importance of elbow ligaments in playing elite baseball as well as the high stress experienced by those ligaments in this sport. Of all the documented ligament injuries in Major and Minor League players over the 4-season study period, the UCL was most commonly involved (84.9%). Of all the documented tendon injuries, the medial flexor-pronator tendon mass was most commonly injured (46.3%). Of all the documented nerve injuries, the ulnar nerve was most commonly involved (93.7%). Of all the documented bone injuries, posteromedial impingement was most common (67.2%). These medial elbow injuries (UCL, flexor-pronator tendon, ulnar nerve, and posteromedial impingement) composed 42.1% of all elbow injuries in professional baseball players during the study period. All of these injury types were the most common injury types noted in pitchers with the highest average number of days missed in pitchers. These data reinforce the concept that significant forces are generated along the medial elbow in elite throwing athletes, especially pitchers. Biomechanical studies have noted that these forces may exceed the tensile strengths of each of these structures individually.15,24,32 Fortunately, most often a balance exists between these structures that allows throwing activity to occur without injury. The previously established biomechanical significance of these medial structures and the high incidence of medial elbow injuries documented in this epidemiological review emphasize the importance of monitoring, strengthening, and conditioning these structures to prevent injury in professional baseball players, most specifically pitchers.
The specific time of the season in which elbow injuries occur in professional baseball players may provide insight into possible injury prevention techniques. Seasonal timing of injury has been evaluated for other sports-related injuries. 18 Factors proposed by these authors include lack of flexibility,4,33 core instability, 25 muscle weakness,7,13,19,25 and fatigue.22,34 These factors may all be present to varying degrees in elite-level baseball players throughout the year. The limited data evaluating seasonal timing of musculoskeletal injuries in professional baseball players indicate variable times for different anatomic injury types.1,10,12,14,20,26 Posner et al 26 noted the highest injury rate for general musculoskeletal injuries in MLB players during April. This study noted that the highest number of total elbow injuries and of each specific elbow diagnosis subtype occurred during the regular season. The MLB HITS system categorizes time of season into 3 periods: spring training, regular season, and postseason. The regular season includes 6 of the 9 months of baseball each year. This likely accounts for the highest incidence of elbow injuries noted in this time period. A more specific assessment by month, however, noted that Major Leaguers had the highest number of total elbow injuries and specifically the highest number of ligament and tendon injuries occur in March. This may have been due to the increased stress as spring training is ending and the regular season beginning, heightened effort by players on a Major League roster, and the continued conditioning of players who are still reacclimating from less vigorous off-season regimens. For Minor League players, the largest number of total injuries and all specific elbow injury subtypes occurred in July. This higher incidence for Minor Leaguers later in the season may reflect a combination of inexperience with the heightened level of play, fatigue, muscle weakness, progressive stiffness from prolonged effort, a push to advance to the Major League level by August/September, and an increased number of Minor League players from the June baseball draft. These data identifying late spring training (March) for Major League players and mid-to-late regular season (July) for Minor League players as high-risk time periods may help to focus and refine the chronological sequencing of possible elbow injury prevention techniques in professional baseball players.
In Major League and Minor League players, bone injuries, although occurring less frequently than ligament, tendon, and nerve injuries, were the most likely to require surgery when they did occur. In Major League players, when bone injury did occur, it was likely to require surgery 64.0% of the time. In Major Leaguers, ligament injuries required surgery 52.7% of the time. Overall, ligament injuries occurred most frequently, though, and so accounted for the most commonly performed procedure with respect to absolute volume. Of all the elbow surgeries performed during the 4-year study period, the highest percentage involved the ligaments. These data substantiate the current heightened focus on injuries to the ligaments of the elbow, specifically the UCL, in the elite, throwing athlete. This epidemiological study supports continued research on the diagnosis, nonsurgical and surgical treatments, rehabilitation, and, most important, preventive programs for UCL injury.
The strengths of this study include the following: (1) its review of prospectively collected data from the official MLB Injury Surveillance System rather than unofficial, Web-based documentation; (2) its focus solely on the characteristics of elbow injuries as opposed to more general groups of musculoskeletal injuries; (3) its use of data on all elbow injuries from an entire baseball cycle (spring training, regular season, and postseason) rather than only regular-season DL data; and (4) its use of an entire population of all levels of US professional baseball players (Major League and all levels of Minor Leagues) as opposed to just 1 level of professional baseball players as in prior studies. This research has several limitations. While this study fills an important gap in knowledge regarding elbow injuries to elite athletes, the data may not be generalizable to nonprofessional or recreational baseball players. Also, the HITS database classifies injuries in general categories, and its “miscellaneous” category may include injuries that would more precisely be included in the other categories of “ligament,” “tendon,” “nerve,” or “bone.” The HITS database also does not allow differentiation between acute, chronic, and acute-on-chronic injuries, which is important for these injuries. Furthermore, the HITS system provides precise data on time lost with injury, which correlates with injury occurrence but does not necessarily correlate with injury severity. Last, the MLB HITS database may include data variability due to collection from 30 different teams. This database does not currently allow correlation of preinjury and postinjury performance. Future studies using baseball specific performance metrics are necessary to evaluate the effect of these elbow injuries on return to play and return to prior performance level.
Conclusion
Elbow injuries are recognized as one of the greatest causes of disability for the throwing athlete. Limited data exist on the epidemiological characteristics of these injuries in professional baseball players. This study represents the first prospective detailed epidemiological review of elbow injuries in the professional baseball player using the MLB Injury Surveillance System.
This study indicates that elbow injuries occur most often in pitchers and while throwing. Pitchers are most likely to require surgery and have the highest mean number of days missed when treated nonsurgically. The most common injuries include the medial elbow, specifically UCL, flexor-pronator mass, ulnar nerve, and posteromedial impingement. The highest percentage of elbow surgeries performed at the professional level involve ligament injury. As such, this study serves as the largest, most thorough evaluation of the epidemiological characteristics of elbow injuries in this professional baseball player population. This study also confirms that these injuries occur with a concerning incidence and that they are influenced by a variety of factors including length of time playing, time period within the baseball competitive cycle, and specific position played. The findings of this study provide a framework for the medical providers for these athletes and a foundation for further research in prevention of elbow injuries in professional baseball players.
Footnotes
The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.