Structural and biochemical evaluation of the elbow capsule after trauma

This study evaluates the structural and biochemical alterations of the elbow capsule after trauma through microscopy and immunohistochemistry. We compared capsules from 37 patients undergoing surgery for elbow contracture with normal capsules from 7 donors. Contracture capsules were significantly thicker than control capsules (P < .05) and exhibited extensive disorganization of collagen fiber bundle arrangement. Levels of specific cytokines involved in connective tissue turnover were measured. The results showed that the levels of cytokines matrix metalloproteinase (MMP) 1, MMP-2, and MMP-3 were greater as compared with control capsules (P < .05). This was associated with collagen disorganization, fibroblast infiltration, and in some specimens, lymphocytic infiltration in the capsular tissue. In contracture specimens, there was a localization of tissue inhibitor of matrix metalloproteinase 2 staining only in the vicinity of the synovial membrane and in blood vessels. Immunohistochemistry for type III collagen showed a greater presence in the control capsules compared with contracture capsules. This study demonstrates pathologic thickening, disorganization of the collagen fiber arrangement, and involvement of cytokines in the pathology of post-traumatic contracture of the elbow.