LOOSENING AND OSTEOLYSIS OF CEMENTED JOINT ARTHROPLASTIES - A BIOLOGIC SPECTRUM

The purpose of this study was to characterize the cell types (using im munohistochemistry) and cytokine expression (using in situ hybridizati on) of tissues surrounding well fixed and loose cemented prostheses un dergoing revision. Clinical and radiographic data were gathered prospe ctively for a series of cemented total joint replacements undergoing r evision. Three groups were identified: (1) loose implants with osteoly sis (10 specimens), (2) loose implants without osteolysis (11 specimen s), and (3) well fixed implants (7 specimens). At surgery, a specimen was harvested from the bone cement interface, Immunohistochemical stai ning was performed using monoclonal antibodies to identify macrophages and lymphocyte subgroups. Human antisense probes were selected to ide ntify the mRNA for specific cytokines using in situ hybridization. The percentage of positively staining cells was determined for each antib ody or probe using a grid counting technique. Tissues from loose cemen ted prostheses with osteolysis contained significantly greater numbers of macrophages and T lymphocytes compared with tissues from loose and well fixed cemented prostheses without osteolysis. The number of inte rleukin-1 and interleukin-6 positive cells was highest in specimens wi th osteolysis and lowest in specimens from well fixed prostheses. Thes e cytokines modulate the growth and differentiation of cells in the im mune system and the monocyte and macrophage system and mediate the rem odeling of bone and mesenchymal tissues. Specific cell populations and cytokine profiles appear to be involved in periprosthetic osteolysis; this information may be useful in planning strategies for prevention and treatment.