Internal impingement: findings on magnetic resonance imaging and arthroscopic evaluation.

PURPOSE The purpose of this study was to examine preoperative shoulder magnetic resonance imaging (MRI) and intraoperative arthroscopic findings in throwing athletes with a clinical diagnosis of internal impingement. TYPE OF STUDY Retrospective review. METHODS A retrospective review of the surgical indications for 769 shoulder arthroscopic procedures performed from 1997 to 2000 revealed 9 throwing athletes with a diagnosis of severe internal impingement. Each had failed treatment that included a minimum of 3 months of rehabilitation. Preoperative MRIs in all 9 were read by a fellowship-trained musculoskeletal radiologist blinded to the operative findings. Findings at arthroscopy were culled from the operative reports. RESULTS On both MRI and at arthroscopy, all 9 athletes had posterosuperior labral lesions, 1 had a humeral head articular cartilage lesion, and 1 had a SLAP lesion. Additional findings on MRI included humeral head edema, subchondral cystic changes, posterosuperior glenoid sclerosis, and rotator cuff tendonopathy predominantly in the infraspinatus. At arthroscopy, there were additional findings of articular-sided partial rotator cuff tears not shown on MRI. CONCLUSIONS Both MRI and arthroscopic findings described labral and humeral head articular cartilage lesions. These findings may be indicative of internal impingement in throwing athletes. LEVEL OF EVIDENCE Level III, diagnostic.