Proliferative cell response to loosening of total hip replacements: a cytofluorographic cell cycle analysis.

Monocyte/macrophages and fibroblasts are the major reactive cells in the periprosthetic connective tissue in a loose totally replaced hip. Monocyte/macrophages are bone-marrow-derived, hematogenous cells, whereas mesenchymal fibroblasts replenish by local proliferation. The cell-cycle-phase frequency distribution therefore reflects the local mitotic fibroblast response to the loose total hip replacement (THR) implant. In 13 patients who underwent revision of a loose THR implant, most of the local cells were in the resting G0/G1 phase (88.1 +/- 6.3%, mean +/- SD), whereas 8.6 +/- 3.7% were in the S phase of the cycle, and 3.4 +/- 2.9% had already reached the G2/M phase. The highest DNA values were recorded in an osteoarthritic patient undergoing revision 4 years after the primary uncemented THR, while the lowest values were observed in a rheumatoid arthritis patient with a loose cemented prosthesis 15 years after the primary operation. The results suggest that the local proliferative fibroblast response in general is uniform and does not seem to depend on the type of prosthesis or the use of cement. The responses in aggressive granulomatous-type loosening and the common type of loosening were similar.