We reported that there was no relation between night pain and the arthroscopic findings in shoulders with rotator cuff tears (JOA,2002). Further, we reported that pressure was significantly increased in the shoulders with night pain compared to that in shoulders of patients who had not experienced night pain, and was significantly increased in shoulders with night pain in the position in which night pain appeared (JSS,2002). The aim of this study was to compare the preoperative and postoperative pressures on the subacromial bursa and to investigate the relation between night pain and the subacromial bural pressure. The pressure on the subacromial bursa of six shoulders (five male, one female, average age 58 years old) with rotator cuff tears were preoperatively and postoperatively measured. In all shoulders, night pain disappeared postoperatively. The pressure was measured on average 19.6 days before operation and on average 7.5 (5-12) months after operation. The size of rotator cuff tears was medium in 3 and large in 3 shoulders. The procedure for the rotator cuff tears was arthroscopic rotator cuff repair in 1 and mini open method in 5 shoulders. Pressure was measured by using a fiber optic transducer-tipped catheter system in the standing position, the supine position and the lateral decubitus position. Postoperative pressure was significantly decreased compared to preoperative pressure. The pressure(preoperative→postoperative)was (15.8→5.6 mmHg) in the standing position, (48.1→13.0mmHg)in the supine position and(54.9→36.9 mmHg)in the lateral decubitus position. We believed that this increase in pressure on the subacromial bursa may be the cause of night pain.
