Ultrasonographic and radiographic findings of polyethylene component displacement with severe metallosis and metal-induced synovitis following total knee arthroplasty.

Aseptic loosening and wear is second to only infection as the most common cause of arthroplasty failure. Degeneration of the polyethylene and metal arthroplasty components can lead to metallosis, which can cause a combination of direct cytotoxic effects and an inflammatory response within the synovial and periarticular tissues. This can result in bone resorption and secondary arthroplasty component loosening as well as a metal containing joint effusion and metal-induced synovitis. Little literature exists as to the ultrasonographic findings of metal-induced synovitis and polyethylene component displacement. As the use of musculoskeletal ultrasound significantly increases, being aware of these findings is important. The most important ultrasonographic findings include differentiating a joint effusion from synovitis utilizing dynamic compression, identifying areas of echogenic shadowing related to metal deposition and visualizing displaced arthroplasty components. The following is a case report that demonstrates the ultrasonographic imaging findings of metallosis, metal-induced synovitis and polyethylene component displacement. We will also demonstrate the ultrasound-guided aspiration findings as well as radiographic and gross pathologic correlations.