Partial-thickness Rotator Cuff Tear Itself Did Not Cause Shoulder Pain Or Muscle Weakness In Baseball Players

OBJECTIVES: Rotator cuff tears are common shoulder injuries in baseball players. In some severe tears (i.e. through more than 50% of the cuff’s thickness), conservative treatment does not work well, and surgical treatment is sometimes chosen in an effort to ensure return to play. In contrast, some partial thickness rotator cuff tears do not cause shoulder symptoms, even during throwing motion. The objective of this study was to assess whether partial thickness rotator cuff tears cause shoulder pain and muscle weakness in baseball players. METHODS: We studied 87 university baseball players (age: 19.5±0.8 years; baseball career: 11.5±1.6 years). Rotator cuff tendons were ultrasonographically examined (Fig 1), then divided into 4 groups; (1) no tear, (2) supraspinatus tendon tear, (3) infraspinatus tendon tear, (4) both supraspinatus and infraspinatus tendons tear. Current shoulder pain and shoulder muscle strength (Dominant/Non-dominant) in abduction, external rotation, and internal rotation were compared using Chi square test and t-test. RESULTS: Forty-one (47%) players were diagnosed with articular-sided partial-thickness rotator cuff tears using ultrasonography. Nineteen tears were in the supraspinatus, 13 in the infraspinatus, and 9 in both the supraspinatus and the infraspinatus. Tear depth was 4.6±2.3 mm in the supraspinatus and 6.2±3.6 mm in the infraspinatus. There was no significant difference in rate of shoulder pain (p=0.96) and muscle strength among four groups (p=0.15 - 0.70). CONCLUSION: In this study, articular-sided partial-thickness rotator cuff tears did not cause shoulder pain and muscle weakness in university baseball players. Most of articular-sided partial-thickness rotator cuff tears are tears of the superior capsule but not the rotator cuff tendons, because the superior capsule is attached in the articular half of the greater tuberosity. Therefore, most so-called articular-sided partial-thickness rotator cuff tears may not be pathological tendon tear.