Structural and biochemical evaluation of the elbow capsule after trauma

Abstract

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.

Figure 1

(a) Control specimen viewed by ordinary light and (b) polarizing light. (c) Contracture specimen viewed by ordinary light and (d) polarizing light. Note the well-organized bundles of collagen fibers with intervening fibroblasts in the control specimens versus the collagen disorganization in the contracture specimens (40x).

Figure 2

A 100x magnification of one of the five contracture specimens displaying lymphocyte infiltration as can be seen in the center of the field.

Figure 3

Percentage of control and contracture specimens displaying more than 30% of the cells and/or matrix within all sections for MMP-1, MMP-2, MMP-3 and TIMP-2. For each of the MMPs, there was significantly greater staining in the contracture specimens compared to the controls (p<0.05). Although the TIMP-2 specimens showed no difference in the overall level of staining between the two groups, the capsules specimens showed TIMP-2 staining primarily in the blood vessels and synovium.

Figure 4

Examples of control (a,c,e) and contracture (b,d,f) specimens displaying more than 30% of the cells and/or matrix within all sections for MMP-1 (a,b), MMP-2 (c,d), and MMP-3 (e,f). The contracture specimens displayed distinctively more staining than the controls for each cytokine.

Figure 5

TIMP-2 staining in control (a) and contracture (b) specimens. Staining was dispersed throughout the tissue in the control tissues, but was limited to the blood vessels and synovial membrane in the contracted capsules.

Figure 6

Staining for collagen type III in control (a) and contracture (b) specimens. Staining was greater in every control specimens as compared to every contracture specimen. Time of surgical excision of contracture from identifiable related trauma had no relationship to level of collagen type III staining.