Total hip arthroplasty is a common surgical procedure that has brought restoration of function to many patients suffering from joint diseases. Commonly used materials in prosthetic implants include metal, ultra-high molecular weight polyethylene and methyl methacrylate.1 Over time, use of artificial joint replacements results in accumulation of prosthesis-associated wear debris in the synovium, bone marrow spaces or periprosthetic soft tissue, stimulating a local biologic response to the foreign material.2 Macrophages recruited to the site phagocytose the debris and release cytokines and other inflammatory mediators, eventually resulting in osteoclastic bone resorption and implant loosening.3

The histologic appearance of wear debris varies by material. Metallic debris is often found in histiocytes as small 1-3 μm, weakly birefringent black metal fragments.1 High-density polyethylene can be found in histiocytes and giant cells as strongly birefringent fibers, best seen under polarization and 10-20 μm in length.1 Methyl methacrylate, on the other hand, normally gets dissolved during tissue processing, leaving empty spaces in its wake.1