HISTOLOGY OF POROUS-COATED ACETABULAR COMPONENTS - 25 CEMENTLESS CUPSRETRIEVED AFTER ARTHROPLASTY

25 hemispherical acetabular components retrieved from patients who had a total hip arthroplasty (THA) were studied histologically. All of th e components had titanium fiber metal porous coatings and were implant ed with adjuvant screw fixation, 18 in primary THA and 7 in revision T HA. None of the cups had been removed because of infection or failure of fixation. The components had been in place an average of 30 (1-140) weeks. 18 cups had bone ingrowth into the porous coating. Up to one t hird of the available void space within the porous coating was occupie d by bone, while the maximal proportion of the area of the bone-implan t interface with bone ingrowth was over 80 percent. Bone ingrowth was more often observed at the dome and in the vicinity of sites of screw fixation than elsewhere. Peripherally, bone ingrowth was less consiste nt, and in isolated areas fibrocartilage and mineralized fibrocartilag e were occasionally observed. The longer-term cases had more bone ingr owth than the shorter-term cases. Apparent metallic debris was observe d within histiocytes adjacent to screw holes, and the amount of this m aterial increased with duration of implantation.