Original Research

The Epidemiology of Hip and Groin Injuries in Professional Baseball Players

Am J Orthop. 2016 March;45(3):168-175

Injuries of the hip and groin among professional baseball players can result in a significant number of disabled list days. The epidemiology of these injuries has not been delineated. The purpose of this study is to describe the incidence, mechanism, type, and rehabilitation course of hip and groin injuries among Major League Baseball (MLB) and Minor League Baseball (MiLB) players.

The MLB injury database for hip and groin injuries from 2011-2014 was analyzed. Occurrence of injuries was assessed based on level of play, field location, activity during which the injury occurred, mechanism of injury, and days missed. The treatment was recorded as nonoperative or surgical. The subsequent rehabilitation and return to play were recorded. Chi-square tests were used to test the hypothesis of equal proportions between the various categories of hip and groin characteristics. From 2011-2014, 1823 hip and groin injuries occurred among MLB and MiLB players, which accounted for approximately 5% of all injuries. Of these, 1514 (83%) occurred among MiLB players and 309 (17%) among MLB players; 96% of injuries were extra-articular. Among all players, a noncontact mechanism during defensive fielding was the most common activity causing injury (74%), and infielders experienced the most hip and groin injuries (34%). The majority of extra-articular injuries were treated nonoperatively (96.2%), resulting in an average of 12 days missed. Intra-articular pathology more commonly required surgery, and resulted in an average of 123 days missed. Hip and groin injuries can be debilitating and result in a significant number of days missed. Intra-articular pathology and athletic pubalgia were usually treated surgically, while the majority of extra-articular hip injuries were treated successfully with nonoperative modalities. Correct diagnosis and appropriate treatment can lead to a high rate of return to play for professional baseball players with injuries to the hip and groin.

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Injuries around the hip and groin occurring in professional baseball players can present as muscle strains, avulsions, contusions, hip subluxations or dislocations, femoroacetabular impingement (FAI) causing labral tears or chondral defects, and athletic pubalgia.^1-9 Several recent articles have reported on the epidemiology of musculoskeletal injuries in Major League Baseball (MLB) players^4,8,10 but with little attention to injuries to the hip and groin, likely because prior studies show only a 6.3% overall incidence for these injuries, much less than the more commonly discussed shoulder or elbow injuries.⁸ Despite the lower proportion of hip and groin injuries overall, these injuries lead to a relatively long period of disability for the players and often have a high rate of recurrence.^4,8,9

The important contribution of hip mechanics and the surrounding muscular function in the kinetic chain during overhead athletic activities, such as a tennis serve or throwing, has recently been discussed.^11,12 In sports requiring overhead activities, trunk rotation is a key component to generating force, and hip internal and external rotation is necessary for this trunk rotation to occur.^12,13 Alterations in hip morphology causing constrained motion, as seen in FAI, may predispose an overhead throwing athlete to intra-articular injury such as labral tears or chondral injuries, or to a compensatory movement pattern causing an extra-articular soft tissue injury about the hip.¹² Decreased hip range of motion may also lead to increased forces across the upper extremity during the throwing motion, which puts the shoulder and elbow at increased risk of injury.¹²

Increased awareness of hip and groin injuries, advances in diagnostic imaging, and an understanding of the relationship between the throwing motion in baseball and hip mechanics have improved our ability to appropriately identify and treat athletes with injuries of the hip and groin. Several studies on hip and groin injuries in elite athletes treated both operatively and nonoperatively have reported a high rate of return to sport.^3,7,14-19 A systematic review on return to sport following hip arthroscopy for intra-articular pathology associated with FAI showed a 95% return to sport rate and a 92% rate of return to pre-injury level of play in a subgroup of professional athletes in 9 studies.²⁰

Despite the large body of literature on upper extremity injuries, there is no study specifically focusing on the epidemiology of hip and groin injuries in MLB or Minor League Baseball (MiLB) players. The incidence of all injuries in professional baseball players has steadily increased over the last 2 decades,⁸ and the reported incidence of hip and groin injuries will likely increase as well. The current incidence of this injury, the positions most at risk, the mechanism of injury, and the time to return to sport are important to understand given the large number of players who participate in baseball not only at a professional level, but also at an amateur level, where this information may also be applicable. This information could improve our efforts at prevention and rehabilitation of these injuries, and can guide efforts to counsel and train players at high risk of a hip or groin injury. To address this gap in the literature, the purpose of this study was to describe the epidemiology of hip and groin injuries in MLB and MiLB players from 2011 to 2014.

Materials and Methods

Population and Sample

US MLB is comprised of the major and minor leagues. The major leagues are divided into 30 clubs, with 25 active players, for a total of 750 active players. Each club has a 40-man roster consisting of 25 active players and up to 15 additional players who are either not active or optioned to the minor leagues. The minor leagues are comprised of a network of over 200 clubs that are each affiliated with a major league club, and organized by geography and level of play. The minor leagues consist of roughly 7500 players, of whom about 6500 are actively playing at any given time. The entire population of players in the MLB who sustained a hip or groin injury over the study period was eligible for this study.

Data

The MLB’s Health and Injury Tracking System (HITS) is a centralized database that contains the de-identified medical data from the electronic medical record (EMR) system. Data on all injuries are entered into the EMR by each team’s certified athletic trainer. An injury is defined as any physical complaint sustained by a player that affects or limits participation in any aspect of baseball-related activity (eg, game, practice, warm-up, conditioning, weight training). The data extracted from HITS only relates 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. Injury events that were classified as “season-ending” were not included in the analysis of assessing days missed because many of these players may not have been cleared to play until the beginning of the following season. For each injury, data were collected on the diagnosis, body part, activity, location, and date of injury.