Rotator interval (RI) tears are classified into two types: contracted and unstable types. The present study was undertaken to elucidate the morphologic changes of RI tears in patients in their 2nd and 3rd decades, which are mainly involved in the latter type.
Eight patients with RI tears, whose other intr aarticular structural abnormality was excluded by shoulder arthroscopy, were evaluated. There were 6 males and 2 females, aged from 16 to 28 years. Five patients were overthrow athletes. An inferior instability was found in 6 shoulders. Specimens taken from the lesions were examined histologically and the findings were compared with those in 5autopsy cases of 41 to 50 years of age.
Synovial hyperemia and proliferation in RI regions were observed arthroscopically in all the patients.
Histologic sections from RI tears showed fibrin deposits on the synovial surface and proliferated small vessels in the synovial layer in all the patients, and those deep in the ligament in 1 patient. The number of inflammatory cells were quite limited and proliferation of the lining cells was almost negligible. The swelling and irregularity of the fibers of the capsule and ligaments in the RI region were evident. There were no thick collagen bundles in the sections.
These results suggest that in RI tears of young patients, irregularity of the fibers of the capsule and ligament occurred, followed by reactive changes in the synovium and deep layer of the ligament, without any thick collagen bundle formation. This phenomenon may be correlated to the absence of a contracture of the shoulder joint.