HISTOLOGICAL AND MORPHOMETRIC STUDIES ON FEMURS WITH STABLE HIP PROSTHESES - AN AUTOPSY STUDY WITH SPECIAL REGARD TO THE FACTORS LEADING TO LATE LOOSENING OF PROSTHESES

To gain insight into the tissue reactions leading to non-infectious loosening 25 autopsy specimens of femurs with well-fixed cemented femoral components of hip prostheses were analysed histomorphologically and morphometrically. The implant duration ranged from one month to 15 years. With the exception of some focal bone-cement contacts bone and cement were separated by a fibrohistiocytic soft tissue membrane. This membrane contained wear particles predominantly of the bone cement mantle and - less abundant - of the polyethylene cups. The amount of wear particles as well as histiocytes and necroses within the membrane statistically significantly increased with advancing time in situ. The cancellous bone adjacent to the soft tissue membrane often revealed a mainly histiocytic infiltration too, accompanied by bone remodeling in this area. The histiocytic inflammatory reaction at the bone cement interface, which is mainly caused by the accumulation of wear particles is considered to be of major importance for the non infectious late loosening of cemented prostheses.