Abstract
Macroscopic synovitis of the glenohumeral joint is frequently seen during arthroscopy in patients with anterior instability. Interleukin‐1β is known to be expressed in inflamed tissue, to correlated with the magnitude of inflammation, and to affect articular cartilage in the joint. We hypothesized that chronic synovitis may occur in the glenohumeral joint in patients with anterior instability. The purpose of this study was to examine the expression of interleukin‐1β in the synovium of the glenohumeral joint with anterior instability and to discuss its clinicopathologic significance. Specimens of synovial tissue around the greater tuberosity in the subacromial synovium (as controls) and around the rotator interval in the glenohumeral synovium were obtained from 10 patients who had anterior instability without signs of subacromial impingement. Semiquantitative reverse transcriptase‐polymerase chain reaction was used to compare the levels of interleukin‐1β mRNA expression in the glenohumeral joint with those in the subacromial bursa. We also employed immunohistochemistry and in situ reverse transcriptase‐polymerase chain reaction to detect the cells producing interleukin‐1β protein and mRNA. The levels of interleukin‐1β mRNA expression were significantly higher in the glenohumeral joint than in the subacromial bursa (p < 0.01). Histology showed nonspecific inflammation in all 10 samples of glenohumeral synovium, whereas no inflammation was seen in seven of 10 samples of subacromial synovium. Immunohistochemistry identified interleukin‐1β protein in the vessels and inflammatory and synovial cells (from lining to sublining layers) in synovium of the glenohumeral joint, whereas immunoreactivity was negative in seven subacromial bursa. The remaining three synovial specimens of subacromial bursa, however, showed positive immunoreactivity that was unremarkable and confined around the vessels. In situ reverse transcriptase‐polymerase chain reaction was exclusively performed in the synovial specimens of the glenohumeral joint, which exhibited a positive reaction (in the same kinds of cells as seen with immunohistochemistry) in the lining and sublining layers and to a lesser extent in the stroma. Thus, our data confirmed the increased production of interleukin‐1β in the synovium of the glenohumeral joint in patients with anterior instability, suggesting the presence of chronic inflammation at the site. We conclude that this chronic synovitis may be partly associated with the development of dislocation arthropathy in the long term.