Atrofia infraespinosos

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Infraspinatus Muscle Atrophy in Professional Baseball Players
Craig Anthony Cummins,*† MD, Terry M. Messer,‡ MD, and Michael F. Schafer,§ MD From †Lake Cook Orthopedic Associates, Barrington, Illinois, the ‡Department of Orthopaedics, University of North Carolina, and the §Department of Orthopaedic Surgery, Northwestern University Medical School

Background: Infraspinatusmuscle atrophy has been observed in athletes who stress their upper extremities in an overhead fashion. The majority of such case reports have been in volleyball players, with far fewer cases reported in baseball players. Hypothesis: Infraspinatus muscle atrophy occurs to a notable degree in professional baseball players. Study Design: Retrospective cohort study. Methods: At the end of the 1999baseball season, data were collected from all Major League Baseball teams in regards to players affected with infraspinatus muscle atrophy. Results: Twelve of the 1491 major league professional baseball players were identified as having appreciable infraspinatus muscle atrophy. There was an increased prevalence of the muscle atrophy in professional pitchers (10 of 494, 4%) compared to positionplayers (2 of 997, 0.2%) (P < 0.001). Among affected pitchers, the atrophy was identified more frequently in starting pitchers (8 of 10) compared to relief pitchers (2 of 10) (P = 0.036), pitchers who had played for more years at the major league level (8.7 ± 4.9 versus 5.2 ± 4.0) (P = 0.017), and pitchers who had thrown for more innings at the major league level (971.4 ± 784.4 versus 485.0 ± 594.6) (P< 0.001). Conclusion: Infraspinatus atrophy was identified in 4.4% of major league starting pitchers and occurred in those pitchers who pitched for more years and innings during their major league career. Keywords: suprascapular nerve; baseball; infraspinatus muscle; muscle atrophy; spinoglenoid notch

Infraspinatus muscle atrophy has been observed in athletes who place significant andrepetitive stresses across their shoulders.1,2,4,6,7,9–16 The muscle wasting of the infraspinatus muscle is typically secondary to an injury to the suprascapular nerve at the spinoglenoid notch. Injury to the nerve at this location is distal to its innervation of the supraspinatus muscle, and therefore patients develop isolated atrophy and weakness of the infraspinatus muscle1,2,4–12,15–17 (Fig. 1).Despite the marked atrophy of this muscle, the diagnosis is often made incidentally as patients are typically pain free with apparent normal shoulder function. The genesis of this investigation is the result of taking care of a minor league baseball player with infraspinatus muscle atrophy and a distal suprascapular neuropathy.4 Suprascapular neuropathy with isolated infraspinatus

muscle atrophy hasbeen reported in a wide variety of athletes who stress their shoulders in an overhead fashion. However, the vast majority of case reports have been in volleyball players6,7,9,13,16,17 with fewer cases having been reported in baseball players.2,4,8,12,15 It has been hypothesized that the unique requirements of the shoulder that occur while striking a volleyball place the suprascapular nerve atparticular risk for this injury.3,13,14,16 Unfortunately, there has been no scientific evaluation of other athletes who stress their shoulder in an overhead fashion to determine if indeed this injury is relatively unique among volleyball players. The null hypothesis of this investigation is that infraspinatus muscle atrophy does not occur to any notable degree in professional baseball players.MATERIALS AND METHODS
* Address correspondence and reprint requests to Craig Anthony Cummins, MD, Lake Cook Orthopedic Associates, 27401 West Highway 22, Suite 125, Barrington, IL 60010. The American Journal of Sports Medicine, Vol. 32, No. 1 DOI: 10.1177/0363546503260731 © 2004 American Orthopaedic Society for Sports Medicine

One month prior to the end of the 1999 Major League Baseball season,...