Retroversion of the humerus in the throwing shoulder of college baseball pitchers.
BACKGROUND
Increased external rotation and decreased internal rotation have been noted to occur progressively in the throwing shoulder of baseball pitchers.


OBJECTIVE
Proximal remodeling of the humerus contributes to the rotational asymmetry between shoulders in pitchers.


METHODS
Descriptive anatomic study.


METHODS
Both shoulders of 19 male college baseball pitchers were evaluated and retroversion of the humerus calculated by using the technique of Söderlund et al. Measurements were taken of passive glenohumeral external rotation at 0 degrees and 90 degrees of abduction and internal rotation at 90 degrees of abduction under a 3.5-kg load. Subjects completed a questionnaire on the amount and duration of overhead throwing performed during the ages 8 through 16 years.


RESULTS
All of the subjects had greater external rotation at 0 degrees and 90 degrees of abduction, decreased internal rotation at 90 degrees of abduction, and greater retroversion of the humerus in their dominant compared with nondominant shoulders. A significant difference was found between dominant and nondominant external rotation at 0 degrees and 90 degrees of abduction, internal rotation at 90 degrees of abduction, and retroversion of the humerus. In the dominant arm, there was a significant correlation between retroversion of the humerus and external rotation at 0 degrees and 90 degrees of abduction. There was also a significant correlation between the side-to-side difference in retroversion of the humerus compared with the side-to-side difference in external rotation at 90 degrees of abduction.


CONCLUSIONS
Rotational changes in the throwing shoulder are due to bony as well as soft tissue adaptations.
Osbahr
Daryl C
DC
Coach Michael W. Krzyzewski Human Performance Research Laboratory, Division of Orthopaedic Surgery, Section of Sports Medicine, Duke University Medical Center, Durham, North Carolina, USA.
Cannon
David L
DL
Speer
Kevin P
KP
D000293:Adolescent; D000328:Adult; D001484:Baseball / Q000502:physiology*; D001696:Biomechanical Phenomena; D016723:Bone Remodeling / Q000502:physiology; D006801:Humans; D006811:Humerus / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008297:Male; D011859:Radiography; D016059:Range of Motion, Articular; D012016:Reference Values; D012399:Rotation; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D014495:Universities