Ulnar collateral ligament (UCL) injuries of the elbow can be career-altering for athletes at all levels. First described in javelin throwers by Willie Waris in 1946 [1], UCL tears have recently achieved more attention due to an increased incidence in baseball players. An increase in games played and an increase in throwing velocity, among other risk factors, have increased the rate of UCL injuries and the need for surgical intervention at all levels in recent years [2-7].

Initial UCL repair reports demonstrated poor results [8,9]. Therefore, UCL reconstruction became the first-line surgical treatment for these injuries. First performed in 1974 and first described by Frank Jobe in 1986 [10], UCL repair has been modified on multiple occasions over time with the goals of decreasing ulnar nerve symptoms, decreasing graft re-rupture rates, maximizing positive outcomes, and returning the injured players to their sports [11]. While most modifications have achieved high return to sport rates [12-14], the main concern with UCL reconstruction is the long recovery period required before return to play. The average 12- to 16-month rehabilitation period after a UCL reconstruction results in considerable missed playing time that can extend up to two seasons.

To shorten the recovery process while still achieving high return to sport rates, UCL repair has been explored as a viable alternative surgical option. Indicated in patients with UCL avulsion tears and healthy ligament quality, recent advances in repair technique, specifically repair augmentation with an internal brace [15], have led to significantly better outcomes than those of initial repair reports [16-18]. Because of this, UCL repair is now considered to be a viable surgical treatment option for professional baseball players with UCL injuries. However, while recent reports of positive surgical repair outcomes are promising, the number of these reports is lacking. In this study, we sought to test the hypothesis that UCL repair is effective in returning professional baseball players to their pre-injury level of play. We tested the hypothesis by comparing advanced metrics before and after surgery with the goal of elucidating the effectiveness of UCL repair in returning professional baseball players to their pre-injury levels of play.

Approval for this study was obtained from the Institutional Review Board of Cedars Sinai (No. STUDY00002458). This study utilized a database with all identified patients; therefore, written informed consent was not required. Publicly available websites and resources were utilized to search for data on professional minor league baseball (MiLB) and major league baseball (MLB) players who underwent UCL repair from 2016 t0 2021. Active MiLB and MLB players undergoing primary UCL repair with an internal brace were included, regardless of position played. Amateur players or those undergoing revision UCL repair or UCL reconstruction were excluded. Access to Statcast’s advanced metric outcomes, specifically those for spin rate, predicated our study time frame choice, 2016 to 2021. These data were not available before 2015.

Data were collected from Statcast (https://baseballsavant.mlb.com/), Fangraph (https://www.fangraphs.com/) and Baseball Reference (https://www.baseball-reference.com/). For each player, demographic information was acquired. This information included date of birth, level of play, handedness, position played, date of surgery, and return to sport (RTS) at any level of playing. For pitchers, data collected included win-loss percentage, games played, innings pitched, walks plus hits per inning pitched (WHIP), exit velocity, pitch type breakdown, pitch type velocity, and pitch type spin rate. For positional players, batting and fielding data were collected. The batting data included number of at-bats, batting average, on-base percentage, slugging percentage, barrel percentage, exit velocity, and “sweet spot” attainment. Fielding data accrued included errors, fielding percentage, outs above average, arm strength, and catch percentage. Demographics were analyzed using descriptive statistics. Post-injury performance was compared to pre-injury combined performance using Mann-Whitney U-tests (IBM SPSS version 23 Statistics for Windows, IBM Corp.). For all analyses, statistical significance was set at P<0.05.

Treatment regimens for UCL injuries are an area of heightened recent interest, not only due to the increased incidence of these injuries but also because of the surgical treatment improvements made and the effect of these surgical treatments on players’ careers. UCL repair has garnered particular attention due to the potential for a shorter recovery period with high RTS rates [19]. Since 2015, Statcast has allowed for more precise analysis of advanced MLB player metrics. While not available for minor league players at this time, these statistics allow us to test new hypotheses related to UCL repair and post-surgical quality of play of MLB players. The main finding of our study is that professional pitchers undergoing UCL repair can RTS more quickly than those undergoing UCL reconstruction.

Despite common belief, undergoing Tommy John UCL reconstruction surgery does not improve performance compared to pre-injury levels [20]. The myth may have found basis in the declining performance sometimes experienced prior to debilitating injury. This is the reason we chose to average pre-injury performance over 2 years. For our limited sample, the pitchers improved in some performance aspects and declined in others, suggesting similar overall performance in the pre-injury years. We also chose to average performance in the 2 years before surgical intervention to account for mid-season injuries in addition to accounting for decline in performance secondary to a failing, but functional, UCL. We chose the first postoperative year for postoperative performance analysis to highlight immediate surgical results. However, merit could also have been gained in assessing longer-term performance effects.

Our finding that MiLB pitchers undergo UCL repair at a younger age than MLB pitchers has at least two possible explanations [5]. First, pitchers are usually younger in the minor leagues; the minor leagues are generally a learning ground for future MLB players. The second explanation is that UCL injury in younger MiLB pitchers prevents their development into MLB pitchers. This second explanation suggests that MLB pitchers are generally major injury-free during their professional maturation process.

Comparing our RTS times to those after UCL reconstruction is challenging due to the heterogeneity of competition levels and surgeon rehabilitation protocols in the relevant studies [21]. Camp et al. [5] noted that positional players RTS faster, but not at a higher rate, than pitchers after UCL reconstruction. We observed similar RTS rates at any level for MLB pitchers and positional players, a deviation from Camp et al.’s results [5]. While MiLB players took more time to RTS in our study, our RTS times for MLB pitchers were shorter than those in Gibson et al.’s UCL reconstruction study [22], 18.5 months. In addition, our RTS times for MLB position players were consistent with those reported for Jack et al.’s MLB position players [23], 336.9 days. Finally, both pitchers and positional players in our report had high RTS rates at any level, pointing to the success of UCL repair in returning baseball athletes to the sport. Some factors that may influence the longer time for RTS of MiLB players are decreased rehabilitation resources, decreased return opportunities, and presence of more extensive elbow pathology that may have limited their potential for advancement to the major leagues.

In our study, all six MiLB pitchers (100%) and one (20.0%) MLB pitcher returned to the sport at their pre-surgical competitive level of play. We anticipate that the MLB RTS rate will improve over time. This highlights the need to counsel pitchers not only on the RTS time but also the time required for return to pre-injury performance level. The lack of a statistically significant difference in RTS time between MiLB and MLB pitchers is consistent with Camp et al.’s study findings [5]. However, our data need to be interpreted with caution; the 8-month difference in RTS time we noted may have reached statistical significance with a larger sample size. Outcome differences between relief and starting pitchers would have been interesting to compare given the difference in pitch counts and elbow demands between the roles. Limited sample sizes of relief and starting pitchers precluded us from performing this assessment. In this study, 57.1% of MLB positional players returned to the sport at their pre-injury level of competition, a rate higher than the 20% of MLB pitchers. In Camp et al.’s study [5], positional players returned to the sport at a lower rate than pitchers.

The MLB hurlers in this study pitched in significantly fewer games and innings after surgery compared to the 2 years before surgery, but their ERAs and WHIPs were comparable over the time frame. We believe that the differences in games and innings pitched would become insignificant in a larger case series and would, therefore, bring our findings in line with Gibson et al.’s UCL reconstructive surgery results [22]. Our data also show no major differences in pitch type breakdown, pitch speed, or spin rate before and after UCL repair. These data are consistent with those for UCL reconstruction [24]. This emphasizes the relevance of Fleisig et al.’s report on variations in throwing mechanics, e.g., elbow extension, elbow velocity, and shoulder internal rotation, after UCL repair [25]. A study involving more pitchers is required to draw more definitive conclusions, but our results suggest that those pitchers undergoing UCL repair possess an ability to return to a pre-injury level of performance after UCL repair. This also suggests that these pitchers either overcome biomechanical changes and return to pre-injury biomechanics or that these differences do not correlate with changes in the performance metrics we measured. Similarities in post-surgery performance compared to pre-injury levels were demonstrated in both the batting and fielding metrics of our study’s positional players. Future studies are required to compare performance outcomes after UCL repair to those after UCL reconstruction. These data may then compliment the many studies noting biomechanical result similarities between the two procedures [26-28].

The limitations of this study are important to note. The most significant limitation is that the indications for each player’s requirement for UCL repair or reconstruction cannot be confirmed. Pre-operative symptoms and injury details, including chronicity, severity, and concomitant pathology, were not available for review. Therefore, the repair and subsequent postoperative performance might be more of a reflection of clinical decision-making than the effectiveness of UCL repair. The surgical technique used for each UCL repair was not available for review. The multiple available techniques for repair, including the use of anchors and internal braces or the exclusive use of sutures can introduce bias into the results. Limited numbers of cases in our cohort make many comparisons impossible, including those between MiLB and MLB players as well as between pitchers and positional players. Furthermore, the minor league 2020 season was cancelled due to the coronavirus pandemic, possibly affecting both return to play and possibly post-repair performance levels. Our outcome metrics analysis for players who participated in both the major and minor leagues may not have been completely satisfactory. The competition level differences suggest that metrics values should not just be averaged together in those cases. We attempted to minimize the confounding effects of these situations by only using the statistics from the league in which the player participated the most. Finally, the small sample size of players that have undergone UCL repair is a major limitation to the strength of our advanced metrics results. As more case results become available, future studies will experience improved statistical power; and stratification of results by demographic factors will be possible.

UCL repair can successfully restore performance of pitchers and positional players to pre-injury levels. Repair may be a feasible alternative to UCL reconstruction in a subset of UCL injuries and may provide a mechanism for return to maximal performance with minimal post-surgical recovery time.