Copyright information:Taken from "Anti-TNF-α therapy as a clinical intervention for periprosthetic osteolysis"Arthritis Research 2000;2(3):165-168.Published online 27 Mar 2000PMCID:PMC129996.Copyright © 2000 Current Science Ltd The radiograph demonstrates periprosthetic bone erosions along both the medial and lateral endosteal bone surfaces. The femoral head is eccentrically placed in a superior position in the acetabular cup, indicating polyethylene wear and the generation of particles. The bone in the osteolytic lesions is replaced by fibro-inflammatory tissue (arrow) consisting of a background of fibroblasts with a diffuse infiltrate of inflammatory cells (lymphocytes, plasma cells, and macrophages), which is most intense in the top left-hand quadrant of this micrograph. Released particles of wear debris accumulate in this tissue, which acts as a reservoir for them and thus enhances the progression of the bone loss and further loosening. This patient underwent a revision arthroplasty.