Prognosis Analysis of Service Time and Performance in Major League Baseball Players after Ulnar Collateral Ligament Reconstruction
Date Issued
2015
Date
2015
Author(s)
Jhuo, Long-Hong
Abstract
Background Ulnar collateral ligament reconstruction (UCLR) is the mainly medical treatment for arms ligament injury in American Major League Baseall (MLB). The cases of UCLR slightly increased between 1974 and 2000. After 2000s, UCLR rapidly increased to about 10 to 20 cases annually. Particuarly in 2012, the performed cases dramatcially increasd to 36 cases. Therefore, the recent literatures have payed increased attention in studying the UCLR in the sport journals. Objectives Prior literatures focued on the performance of pitcher before and after UCLR for 1 to 3 years, but did not analyze what prognosis factors may affect the the performance after UCLR based on the service time after returning the MLB. Therefore, the aim of this thesis was to establish a long-term prognsistic model for the service time after UCLR, and use this model to predict the dynamic post-UCLR performance of these elite players. Methods We selected 276 major league baseball players’ record with performing UCLR between September 25, 1974 and June 30, 2014 from public data in Baseball-reference (http://www.baseball-reference.com) and Baseball Prospectus (http://www.baseballprospectus.com). All the selected players were followed up to April 28, 2015.We define a time response variable, called ‘service time after UCLR’, as to the numbers of days from players’return dates to MLB after UCLR until the date of retirement from MLB. This service time was used to stand for the performance of a player. In addition, beause some players are still active in the collected data, survival analysis was applied to solve such a right-censored problem. Result. In the totally 276 players’record, there were 236 players(85.1%) who had successfully returned in MLB after UCLR, and the medium service time after UCLR was 1,675 days/4.59 years (95%CI：1163-1588 days/2.94-4.35 years). In the univariate analyses, the players with age≥ 28 years old had significantly shorter service days (P<0.0001), and the other significant prognosis factors induced shorter service time included longer (≥4.7years) MLB experience before UCLR (P=0.0003), lower (≤26.5) BMI (P=0.0085), pitchers vs. players with other positions (P=0.0159), the second vs. first UCLR (P=0.0063) and other players vs. all-star players (P=0.0494). The Kaplan-Meier method was used to estimate the probabilities of playing in MLB at the days after returning in MLB with repsect to different prognosis factors. In the multivariate analysis, we use Cox-regression model and backward stepwise method to select the prognosis factors in the model.We found that the players with age≥28 years old had significantly higher hazard (P=0.0070), and the other significant prognosis factors induced higher hazard included longer (≥4.7years) MLB experience before UCLR (P=0.0319), lower (≤26.5) BMI (P=0.0054), pitchers vs. players with other positions (P=0.0055), American Leagues vs. National Leagues (P=0.0437) and other players vs. all-star players (P=0.0020). Conclusion We adopt the survival analysis to identify the significant prognostic factors related to the risk of leaving MLB because the issue of the incomplete post-UCLR service times can be tackled. We found the player with the younger, shorter MLB experience before UCLR, higher BMI, with other positions than pitcher and National League all-star players are most likey to have a longer post-UCLR service times in MLB.
Subjects
Major League Baseball
Prognsis factors
Service time
Survival analysis
Ulnar collateral ligament reconstruction
Type
thesis
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