Background: Partial-thickness rotator cuff tears are common shoulder injuries in baseball players. For some tears, the symptoms can be relieved through physical therapy or debridement without rotator cuff repair.
Purpose: To assess whether partial-thickness rotator cuff tear by itself causes shoulder pain and muscle weakness in baseball players.
Study design: Cross-sectional study; Level of evidence, 3.
Methods: We studied 87 university baseball players (age, 19.5 ± 0.8 years; baseball career, 11.5 ± 1.6 years). All data were obtained during a full-participation annual medical check in 1 team. Rotator cuff tendons were examined ultrasonographically and allocated to 4 groups: (1) no tear, (2) supraspinatus tendon tear, (3) infraspinatus tendon tear, and (4) both supraspinatus and infraspinatus tendon tears. Current shoulder pain and shoulder muscle strength (dominant/nondominant) in abduction, external rotation, and internal rotation were compared by using chi-square and t tests. All players could play baseball with or without shoulder pain in this study.
Results: Of the 87 players, 41 (47%) had articular-sided partial-thickness rotator cuff tears diagnosed on ultrasonography; the remaining 46 athletes were tear-free. Of the 41 affected patients, 19 had tears in the supraspinatus, 13 in the infraspinatus, and 9 in both the supraspinatus and infraspinatus tendons. Tear depth (mean ± SD) was 4.6 ± 2.3 mm in the supraspinatus and 6.2 ± 3.6 mm in the infraspinatus. Neither the rate of shoulder pain nor muscle strength differed significantly among the 4 groups (P = .96 and P = .15-.70, respectively).
Conclusion: Articular-sided partial-thickness rotator cuff tear-by itself-did not cause shoulder pain and muscle weakness in university baseball players. Most so-called articular-sided partial-thickness rotator cuff tears may not be pathologic tendon tears.
Keywords: baseball; rotator cuff; shoulder capsule; superior; tear.