Why does aseptic loosening occur and what is periprosthetic osteolysis?
Osteolysis around prosthetic joints causing loosening of the components is the most important long-term complication of total hip and knee surgery. It is reported that between 30% and 70% of prosthetic components (both cemented and cementless) have evidence of periprosthetic osteolysis at 10 years post arthroplasty as evidenced by a radiolucent line >2 to 3 mm in thickness around the prosthesis. It is caused by polyethylene particles or metal debris produced by wear at the articulating surfaces of the prosthesis. The particulate debris tracks down the side of the prosthesis where it is ingested by macrophages in the membrane lining the bone–cement or bone–implant interfaces. These macrophages produce prostaglandins and cytokines, such as interleukin-1 and tumor necrosis factor (TNF), which leads to osteoclast stimulation and endosteal bone resorption. Treatment has included bisphosphonates (downregulates macrophages and osteoclasts), indomethacin (decreases prostaglandin production), anti-TNF-α therapy, as well as revision surgery with bone grafting.