Scapular dysfunction in throwers with pathologic internal impingement

Case control group study.

To compare scapular position and orientation between baseball players with and without pathologic internal impingement.

Scapular dysfunction has been implicated as a contributor to throwing-related pathologic internal impingement of the shoulder due to its role in increasing the contact between the greater tuberosity and posterior-superior glenoid, thereby impinging the posterior rotator cuff tendon(s) and labrum. However, to date, no definitive data demonstrate this scapular dysfunction in throwing athletes. The purpose of this study was to assess, in a controlled laboratory environment, whether scapular position and orientation would be different in throwing athletes diagnosed with pathologic internal impingement than in a control group of throwing athletes.

Eleven throwing athletes diagnosed with pathologic internal impingement, using both clinical examination and a magnetic resonance arthrogram, were demographically matched with a control group of 11 throwers with no history of upper extremity injury. An electromagnetic tracking device was used to measure scapular internal/external rotation, anterior/posterior tilt, upward/downward rotation, sternoclavicular protraction/retraction, and elevation/depression during humeral elevation within the scapular plane. Comparisons were made between groups with analysis of variance models (P<.05).

The individuals in the pathologic internal impingement group demonstrated statistically significant increased sternoclavicular elevation when elevating their humerus from 30 degrees to 120 degrees (P = .002) and from 60 degrees to 120 degrees (P = .003), compared to the control group. Furthermore, these patients also had increased posterior scapular tilt position (P = .016). No statistically significant differences were present in any other scapular variables measured.

Based on the results of this study, throwing athletes diagnosed with pathologic internal impingement present with statistically significant increases in sternoclavicular elevation and scapular posterior tilt position during humeral elevation in the scapular plane.