Large well-defined soft tissue mass surrounding the right hip joint is most compatible with particle disease. It results in smooth erosion of the acetabulum and right pubic rami. This mass is effacing the common femoral vein. 

Particle disease is a potential complication post hip replacement. All prostheses produce particles. Usually the particles produced by an implant are eliminated by the immune system and a balance exists between their production and elimination. When the particle load production exceeds the immune system’s elimination capacity, the decompensation process begins ¹. The tiny prosthetic particles stimulate periprosthetic cells to express pro-inflammatory/pro-osteoclastic cytokines and other substances that ultimately result in increased accumulation/activity/survival of osteoclasts, and inhibit the osteogenic activity of osteoblasts ². Thus osteoresorption predominates over osteogenesis leading to bone defects.