Background: Medial ulnar collateral ligament reconstruction surgery (UCLR) is a common surgical procedure performed on elite level baseball players. Physical signs and symptoms of ulnar collateral ligament (UCL) injuries requiring UCLR along with treatment have been clearly defined, however, an exact etiology of UCL injuries and methods of preventing UCLR surgery remain unclear. Objective: Systematically review and qualitatively provide an in-depth summary of recent literature about the relationships between changes in advanced pitching metrics for potential warning signs of UCL injury prior to requiring UCLR. Methods: We searched two electronic databases (PubMed, Scopus) from inception to October 2021 using a keyword search. Data extracted included author and year of publication, study design, sample size, study location, and primary outcome variables. Articles that met inclusion criteria were then evaluated using a modified Downs and Black criteria. Results: The key word search returned 51 articles of which a total of seven articles were included in the review. For the papers that met the inclusion criteria, four noted changes to velocity as potential an indicator for UCLR surgery, two identified lateralization of arm angles as an indicator of UCLR surgery, and one reported change to spin rates of specific pitches as an indicator for UCLR surgery. Conclusions: The results of this review show that changes in certain advanced pitching metrics such as spin rate, velocity, and lateralization of arm angles could be potential indicators of UCL damage. Further evaluation is needed to continue to improve our understanding of how these trends could be used as predictors of UCLR.

本研究以資料包絡分析法來衡量職業球員的績效表現，球員在簽訂複數年合約前後與績效表現之關聯性，來探討球員是否有合約週期的現象，進而再探究球員處於合約年的比率多寡，是否會對球隊的勝率造成影響。 　　本研究以2002年球季結束後至2008年球季開始前，這段期間曾與球團簽訂複數年合約的美國大聯盟球員為研究對象。實證結果顯示投手在簽訂複數年合約前一年，純粹技術效率有明顯增加，野手部分則顯示在簽約前兩年整體技術效率呈現顯著增加。研究結果顯示支持合約週期理論，即球員在合約年之前會刻意增加表現，以便爭取較佳之合約。另外，以2009年各球隊的勝場數為研究對象，實證結果顯示，當球隊中有較多投手處於複數年合約的第一年，則球隊的勝場數顯著較少。 / This research applies Data envelopment analysis to examine the performance of Major League Baseball (MLB) players before and after signing multi-year contracts. The research also aims to explore the claim of contract cycle theory by investigating whether contract status has an influence on wining ratio of a team. The sample includes players who signed multi-year contracts between end of season 2002 and prior season 2008. The result illustrates that pitchers’pure technical efficiency increase significantly before signing the contract and fielders’total technical efficiency increase significantly 2 years before the contract signing. The results support the contract cycle theory that players show a tendency to improve their performance prior to signing a contract in order to earn a better contract. In addition, the teams with more players who are in their first year of multi-year contract have a significantly less number of wining ratio.