Glenohumeral Findings on Magnetic Resonance Imaging Correlate With Innings Pitched in Asymptomatic Pitchers

Abstract

Background: In recent years, there has been a documented increase in the number of professional baseball players on the disabled list and the total number of days on the disabled list. Pitchers account for the largest number of disabled list reports. Purpose: To examine the relationship between magnetic resonance imaging (MRI) findings in asymptomatic professional pitchers and subsequent time on the disabled list (DL). Study Design: Cohort study (Prognosis); Level of evidence, 2. Methods: A total of 21 asymptomatic professional pitchers from a single Major League Baseball (MLB) organization underwent preseason MRIs of their dominant shoulder from 2001 to 2010. Asymptomatic was defined as no related DL stays in the 2 seasons before the MRI. These studies were reevaluated by a fellowship-trained musculoskeletal radiologist who was blinded to patient name, injury history, and baseball history. A second investigator who was blinded to the MRI results collected demographic data, total career number of innings pitched, and any subsequent DL reports for each subject. Results: The mean age at the time of MRI was 29.04 years (range, 20-39 years). Eleven of 21 pitchers had a rotator cuff tear (RCT): 9 had an articular surface tear (AST), and 2 had a full-thickness rotator cuff tear (FTT). Ten had superior labral anterior posterior (SLAP) tears, and 13 had either anterior or posterior labral tears. There was a statistically significant relationship between the number of innings pitched and presence of an RCT (AST + FTT). The mean number of career innings pitched by those with an RCT was 1014 compared with a mean of 729 innings pitched in pitchers without an RCT ( P < .01). In addition, the number of career innings pitched was moderately correlated with presence of RCT ( r = 0.46) and presence of superior and anterior/posterior labral tears ( r = 0.43). There were no statistically significant findings between any single preseason MRI finding and subsequent time on the DL. Conclusion: The MRI findings in asymptomatic MLB pitchers do not appear to be related to near future placement on the DL. However, there was a significant difference in numbers of innings pitched between pitchers who had an RCT and those who did not and a moderate correlation between innings pitched and the presence of RCT as well as the presence of labral lesions. This finding supports the notion that RCT and labral injury in pitchers may result from repetitive overhead motion with subsequent strain on the rotator cuff tendons and glenoid labrum. Asymptomatic shoulder lesions in professional baseball pitchers appear to be more frequent than previously thought.