Tendon-bone interface becomes matured with the perforating fiber and the cells striding over the bone area. We suggest that both “perforating fiber” and “cell stride” could play a crucial role in regeneration after rotator cuff repair. To obtain a successful outcome after rotator cuff repair, repaired tendon requires to be anchored biologically to the bone. However, it is well known that the histological structure of the repaired tendon-bone insertion is totally different from the normal insertion. This morphological alteration may contribute to biological instability after surgical repair. To address these issues, it is fundamental to clarify the difference of the structure between the normal and the repaired insertion in detail. Surprisingly, few studies on the tendon-bone insertion using electron microscopy has been performed so far, since the insertion area is solid (bone/cartilage) and extremely limited for the analysis. Recently, a new scanning electron microscopical method (FIB/SEM tomography) has been developed, making it possible to analyze the wider area with the higher resolution and reconstruct 3D ultrastructures. The purpose of this study was to analyze the ultrastructure of the repaired supraspinatus tendon-bone insertion in rat using FIB/SEM tomography.Summary Statement
Introduction
Synovitis in the subacromial bursa (SAB) and the gle-nohumeral joint (GHJ) is often seen in rotator cuff diseases. In order to clarify its significance, following studies were conducted. The mRNA expression levels of IL-1B, sIL-1ra and icIL-1ra and the amount of substance P in the SAB synovium were correlated with the degree of shoulder pain. The cytokine-mRNAs in the GHJ synovium expressed more significantly in full-thickness tears (perforating tears) than in non-perforating tears. Biochemical markers (MMP-1, MMP-3) in the GHJ fluid were significantly higher in massive cuff tears than in smaller tears. These findings suggest the possibility that SAB and GHJ synovitis in rotator cuff diseases are associated with shoulder pain and the development of glenohumeral arthropathy, respectively.
