Supraspinatus tear—a mechanical outlet impingement lesion?

Abstract

Background The etiology of degenerative supraspinatus tendon (SSP) tear is still subject to discussion. Objectives Our objective was to correlate clinical, radiological, and intraoperative signs of mechanical outlet impingement in patients with degenerative SSP tears. Materials and methods This prospective study included 100 patients with degenerative SSP tears that required surgery. Preoperatively, clinical impingement signs and radiological parameters (critical shoulder angle [CSA], acromion type according to Bigliani, acromion index [AI]) were recorded. Intraoperatively, the extent of the rupture and grinding marks on the bottom of the acromion were assessed. Results Of the 100 patients, 59 had clinical impingement signs preoperatively; 90 patients had at least one positive radiological sign (CSA > 35°, AI > 0.67, acromion type II or III). In 23 patients a partial tear, in 55 patients a full thickness tear, and in 22 patients an additional infraspinatus tendon tear were found. In 10 cases no grinding marks at the bottom of the acromion during arthroscopy were found. In 75 cases moderate grinding marks and in 15 cases severe marks with bare bone at the bottom of the acromion were found. There was no statistically significant correlation between preoperative impingement signs and arthroscopic grinding marks (p = 0.83) or between clinical signs and radiological parameters (p = 0.44). There was no significant correlation between extent of the rupture, extent of grinding marks or radiological impingement parameters (p = 0.16; p = 0.26). Conclusion We could not verify a correlation between clinical and radiological impingement sign and arthroscopic impingement parameters. Based on our study, degenerative SSP tear cannot be characterized as the result of a mechanical outlet impingement.