Presentation
Past history right total hip replacement.
Patient Data
Destructive lesion involving the right hemipelvis at the level of the total hip replacement. This is associated with a large soft tissue mass. This is an aggressive lesion and is most likely a metastatic deposit. Solitary plasmacytoma can give a similar radiological appearance. CT is recommended.
Right total hip replacement. There is a large lobulated well-defined soft tissue mass measuring 9.2 x 13.5 cm encompassing the right femoral head and neck and extending anteriorly and posteriorly to the hip joint within the iliopsoas bursa. The soft tissue mass also extends medially, smoothly eroding through the acetabulum and inferior and superior pubic rami. The acetabular cup is medially displaced with only a slither of bone overlying the cup. Callus formation at the site of the previous right acetabular fracture.
The iliac vessels on the right are abutted by the mass and the vein is compressed.
Case Discussion
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.
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