Radiographic Predictors of Elbow Injury and Surgery in Major League Baseball Pitchers

摘要

Objectives: To evaluate predictive ability of asymptomatic screening MRI’s of Major League Baseball (MLB) pitchers and compare associated findings with future DL placement, pitching statistics, and elbow surgery. Methods: A total of 40 consecutive asymptomatic elbow MRI’s in MLB pitchers at a single organization were analyzed from 2005 - 2017. Asymptomatic MRI was defined as a screening MRI at time of contract signing having been performed at least 6 months prior to DL placement for any elbow-related injury. Publicly available DL data, career innings pitched, career games started, career pitch count, and career max velocity of pitch were obtained. A blinded investigator examined each MRI for pathological signals. Data was analyzed on players that were eventually placed on the DL compared to those with no DL placement. Results: 40 consecutive elbow MRIs of MLB players were reviewed. The average age of the injured cohort was 28.3 ± 3.2 years (16 players) and 28.8 ± 5.5 years (24 players) for the non-injured cohort. There was no statistical difference in age, handedness, height, weight, or pitching stats between the injured and non-injured cohorts. Abnormal radiographic signal intensity in the UCL (p<0.001) and humeral elevation of the UCL (p=0.01) were significantly associated with future DL placement. Those injured spent an average of 200.7 days and 191.7 days in the DL with signal in the UCL and those with humeral elevation of the UCL, respectively. Ulnar elevation/signal of the UCL (p=0.06), and posteromedial impingement (p=0.08) were approaching statistical significance. Of those injured 68.8% (11/16) underwent elbow surgery. Findings of ligament signal intensity (p<0.001), ulnar-sided UCL elevation (p=0.018), humeral-sided UCL elevation (p=0.002), and posteromedial impingement (p=0.042) were all significantly associated with future surgery. There was no significant correlation between injury and radiocapitellar or ulnohumeral chondral lesion, bone edema, loose bodies, or flexor-pronator mass muscle defect. The presence of a flexor-pronator mass muscle defect was associated with a significantly reduced number of innings pitched (53.7 ± 74.3 vs. 304.4 ± 305.5 innings, p=0.0317), games started (5 ± 7.1 vs. 40.1 ± 49.0 games, p=0.004), and pitch count (680.5 ± 919.9 vs. 40.1 ± 49.0 pitches, p=0.022). The presence of ligament signal (26.2 ± 37.1 vs. 51.7 ± 56.5 games, p=0.036) and ulnar elevation (6.3 ± 9.3 vs. 41.2 ± 9.3 games, p=0.003) was associated with significantly fewer games started. The presence of bone edema was associated with significantly decreased pitch count (1451.2 ± 1746.8 vs. 4128.0 ± 4718.0 pitches, p=0.023). There was no association between humeral UCL elevation, flexor-pronator mass tendon, or posteromedial impingement with innings pitched, games started, or pitch count. Conclusion: The heavy demand placed on the elbow joint in professional pitching produces degenerative changes visible on MRI prior to any symptoms, as demonstrated in previous studies. Specific degenerative changes in the UCL Ligament, particularly humeral sided elevation of the UCL, are significantly associated with future injury. Radiographic Findings on Elbow MRI as Related to Placement on Disabled List and Pitching Stats N (%): Injury vs. Non-Injury Relation to Injury (p) Relation to DL days (p) Relation to Future Surgery (p) Relation to inningsPitched (p) Relation to GamesStarted (p) Relation to Pitch Count (p) Relation to Max Pitching Velocity (p) Radiocapitellar Chondral Lesion Diffuse: 1 (6.25%)0 (0%) Focal: 2 (12.5%)3 (12.5%) None: 13 (81.3%)21 (87.5%) N.S. N.S. N.S. N.S. N.S. N.S. N.S. Ulnohumeral Chondral Lesion Diffuse: 0 (0%)0(0%) Focal: 1 (6.25%)0 (0%) None: 15 (93.8%)24 (100%) N.S. N.S. N.S. N.S. N.S. N.S. N.S. ArticularCartilage Bone Edema 3 (18.8%)3 (12.5%) 0.6678 0.5961 1 0.5661 0.9471 0.0227 0.0788 UCL Ligament Signal Heterogeneity/Hyperintensity 15 (93.8%)1 (4.2%) p < 0.001 N.S. p < 0.001 0.0563 0.1487 0.0357 0.8186 Ulnar-Sided Elevation/Signal 3 (18.8%)0 (0%) 0.06373 0.3591 0.0177 0.1010 0.0032 0.1829 0.8683 Humeral-Sided Elevation/Signal 9 (56.3%)3 (12.5%) 0.0103 0.7240 0.0018 0.7778 0.7134 0.2167 0.9052 Frank UCL Tear 0 (0%)0 (0%) N.S. N.S. N.S. N.S. N.S. N.S. N.S. Flexor-Pronator Mass Defect 1 (6.3%)1 (4.2%) 1 N.S. 1 0.0317 0.0035 0.0223 N.S. Flexor-Pronator Mass Tendon Signal 8 (50%)2 (29.2%) 0.2046 0.0261 1 0.8311 0.7951 0.9657 0.7875.