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