Internal Impingement of the Shoulder in Flexion
Authors: Kim & McFarland
References: Presented at AAOS 2003
Abstract
Background: Contact of the rotator cuff to the superior glenoid with the arm in flexion has been described and postulated to be a source of rotator cuff disease. This study was conducted to determine the prevalence of internal impingement in flexion (IIF) in patients with a variety of diseases and to investigate its clinical significance. Methods: A consecutive case series of 376 patients who were undergoing arthroscopy of the shoulder were prospectively entered into this study. In arthroscopy, intraarticular lesions were evaluated and the presence of contact of the rotator cuff to the superior glenoid and the degree of flexion making the contact were noted. Statistical analysis was performed with two dependent variables defined: the presence of IIF and the flexion degree making IIF. Results: Of the 376 patients, 277 (74%) had IIF and 99 (26%) did not have IIF. There were no statistically significant differences in the prevalence of IIF according to the primary diagnoses. The presence of IIF was associated with Type II SLAP lesions and the presence of internal impingement of the rotator cuff to the superior glenoid in abduction external rotation. There was a significant relationship between rotator cuff disease and decreasing angle of contact for IIF. Conclusion: This study demonstrates that IIF is common in a cohort of patients undergoing shoulder surgery, with an overall prevalence of 74%. This study suggests that IIF may contribute the development of Type II SLAP lesions and rotator cuff disease. (241 words)