Synovial inflammation in patients with osteonecrosis of the femoral head

Abstract

Much of the work aimed at elucidating the pathogenesis of osteonecrosis (ON) of the femoral head has focused on bone blood supply, with little attention to the surrounding synovial tissue (ST). We hypothesized that patients with ON exhibit synovial inflammation. Using immunohistological techniques, we found that a large population of patients with ON had synovial inflammation. Moreover, a population of ON patients had inflamed ST without having an inflammatory disease co-morbidity. The inflammatory infiltrate in these patients comprised primarily CD4(+) T cells and CD68(+) macrophages, the latter of which expressed increased levels of cellular adhesion molecules. Our results suggest the presence of a previously unrecognized population of ON patients without a diagnosed inflammatory co-morbidity and a highly inflammed synovium consisting primarily of a macrophage and CD4(+) T-cell infiltrate.

Figure 1

A subset of patients with ON have an inflamed synovium without having an inflammatory disease co‐morbidity. n= number of patients. Values represent the mean ± SEM.

Figure 2

Representative photographs of CD3+ and CD68+ positive cells in OA, noninflammatory ON, and inflammatory ON ST. IgG treated controls are also shown for each group. Photographs were taken at 400×. Arrows indicate positive staining.

Figure 3

Macrophages from patients with ON and without other inflammatory co‐morbidities have an increased expression of adhesion molecules. (A) integrin αv expression, (B) ICAM‐1 expression. n= number of patients. Values represent the mean ± SEM.