Does a Partial Rotator Cuff Tear Affect Pitching Ability? Results From an MRI Study

BACKGROUND: Numerous studies have examined changes in the athletic performance of baseball pitchers after rotator cuff surgery. However, only a few studies have evaluated changes in athletic performance caused by partial rotator cuff tears that are not treated surgically. PURPOSE: To examine the course of partial-thickness rotator cuff tears and its possible effect on the athletic performance of professional pitchers. STUDY DESIGN: Case series; Level of evidence, 4. METHOD: Of 191 professional pitchers who attended our clinic between January 2009 and October 2018, 52 individuals had partial-thickness tears with at least 2 years of follow-up magnetic resonance imaging (MRI) scans and were included in this study. All initial MRI examinations were performed when a season was finished or during the off-season for regular medical check-up purposes. Hence, any abnormal finding on MRI, which suggests damage to the rotator cuff tendon, was assumed to have occurred during the previous season. The mean follow-up MRI period was 40.8 months (range, 24.4-100.9 months). We defined the year before an athlete’s first MRI at our clinic as the year of damage, and we evaluated athletic performance during the season before the damage (pre-damage year 1), the season of the damage (damage year), and 1 and 2 seasons after the damage (post-damage years 1 and 2). We evaluated the changes in 5 statistical performance indicators: earned run average (ERA), fielding independent pitching (FIP), walks plus hits divided by innings pitched (WHIP), winning percentage (WPCT), and innings pitched (IP). RESULTS: The partial-thickness tears progressed in 39 of 52 (75%) patients. Of these 39 patients, 34 (87%) were grade 1 in severity and 5 (12.8%) were grade 2 or higher. The ERA of the pitchers did not increase significantly immediately after damage or at post-damage years 1 and 2. WPCT increased significantly compared with pre-damage year 1 (P < .001), and IP decreased significantly during the follow-up period (P < .001). Although no significant decrease in pitching ability was noted based on these 3 indices, significant increases were observed for FIP and WHIP. CONCLUSION: A partial-thickness rotator cuff tear does not have significant influence on the athletic performance of professional baseball pitchers in the short term based on conventional performance indicators. Our findings suggest that WHIP and IP decline significantly at 2 years after damage is noticed.