A quantitative study of bone and soft tissues in cementless porous-coated acetabular components retrieved at autopsy

The authors examined 11 cementless acetabular components of one design retrieved at autopsy and made observations concerning tissue ingrowth and local tissue reaction, radiographic-histologic correlation, and the distribution of particulate wear debris. The cups were hemispherical in design with a commercially pure titanium fiber-metal porous coating. All of the prostheses were implanted with screws. The implants were in place for an average of 41 months (range, 5 weeks to 75 months). Ten of the cups had bone ingrowth, with the average volume fraction being 12.1 +/- 8.2%. There were no differences in the amount of bone ingrowth when the component was partitioned into nine anatomic regions. However, there was more bone adjacent to screw holes through which screws were inserted compared with empty screw holes. As the number of radiolucent zones increased on the clinical radiographs less bone ingrowth was observed histologically. The amount of metal debris in holes with screws and holes without screws was similar. In the longest term cases, polyethylene debris was noted within empty screw holes, but no granulomatous reactions or osteolytic processes were observed.