[Immunohistochemical analysis of periprosthetic osteolysis in aseptic loosening of hip arthroplasty].

AIMS: The main complication in total hip arthroplasty is aseptic loosening. Wear-induced inflammatory processes lead to periprosthetic granulation tissue, which induces bone degradation due to aseptic osteolysis. At the site of bone degradation,the cell populations have not been further analysed so far. Therefore, the present study was designed to analyse bone degradation tissue in comparison to periprosthetic granulation tissue.

METHODS

Tissue specimens of 14 patients with failed modular cup components of cementless total hip arthroplasties were obtained during revision surgery. Immunohistochemistry was performed by using anti-CD 31 (endothelial cells),anti-CD 45 (granulocytes and lymphocytes) and anti-CD 68 antibodies (mononuclear phagocyte system, MPS). Fibroblasts and osteoblasts were immunohistochemically distinguished as CD 31/45/68-negative cells. Semiquantitative analyses,including a morphometric study, were then performed both in the bone degradation zone and in the periprosthetic granulation tissue.

RESULTS

At the site of bone degradation, the majority of cells belonged to MPS (73.6 +/- 3.31%),while fibroblasts were significantly less frequent (9.6 +/-1.67%). A distinct population of endothelial cells (7.75+/- 1.4%) as well as lymphoplasmacellular cells (5.75+/-2.35%) were observed. In addition,only a small amount of neutrophilic granulocytes (0.7 +/- 0.4 %) were detected. In the periprosthetic granulation tissue, findings were very similar to those of the bone degradation zone,with the exception of higher amounts of fibroblasts (15.69 +/- 2.74%).

CONCLUSIONS

This study confirms that, in aseptic hip arthroplasty loosening, the majority of cells detected at the site of bone degradation are of the MPS, which are predominantly involved in osteolytic processes. There is no pathologically significant difference between the cell population of periprosthetic granulation tissue and granulation tissue at the sites of bone degradation.