The measurement of subacromial contact pressure in patients with impingement syndrome.

This study presents the subacromial contact pressure findings in 25 patients who underwent an arthroscopic acromioplasty for impingement syndrome. All patients failed a course of conservative management before surgery. Patients were evaluated, both before and after acromioplasty, by examination, UCLA functional score, and radiographic assessment of acromial morphology. At the time of surgery, a 4 x 10 mm air-filled catheter was placed beneath the anterior aspect of the acromion under arthroscopic visualization. Subacromial contact pressures were recorded throughout an arc of shoulder motion. Mean pressure and standard deviation were derived from three trials. This protocol was performed on all patients and the results were statistically evaluated. The mean subacromial pressure before acromioplasty was 11.7, 35.6, 50.1, 51.1, and 57.4 mm Hg at abduction arcs of 0 degrees , 90 degrees , and 180 degrees, hyperabduction (forced passive limit of abduction), and cross-reach (arm adducted across the patient's chest with the shoulder internally rotated), respectively. The pressure after acromioplasty decreased to 1.6, 7.8, 15.9, 22.8, and 16.5 mm Hg, respectively. This decrease was significant in all positions (P = .016 at 0 degrees and <.001 in all other positions). At 90 degrees of abduction, pressure always decreased in internal rotation and increased in external rotation. Maximal contact pressure developed in either hyperabduction or cross-reach in all patients except two. Preoperative testing for the position of maximum impingement pain generally correlated with the position of maximum contact pressure.