Unexplained Pseudotumor Formation in Ceramic-on-ceramic Hip Bearings: A Case Report.

Introduction: Adverse local tissue reactions (ALTRs) is a known complication post total hip arthroplasty (THA). ALTR is usually associated with cobalt chromium alloy joints with incidence rate of 36-61%. It has also been documented in mixed bearings such as metal on polyethylene. Although uncommon, pseudotumor formation has been reported in ceramic on ceramic (CoC) THA, suggesting that the ceramic debris is not entirely inert.

Case report: This case study relates the history of a 56-year-old man with ankylosing spondylitis who underwent bilateral THA using a CoC articulations. Initially asymptomatic for 4 years, he developed pain, swelling around the right hip, and his imaging showed extensive osteolysis with pseudotumor formation. His fine-needle aspiration cytology report was inconclusive, so he underwent stage 1 procedure that is removal of prosthesis and biopsy. His histopathology report confirmed pseudotumor formation with presence of fibrin, proliferating fibroblasts, hemosiderin-laden macrophages and lymphocytes. Since the patient was not keen on second stage revision arthroplasty, he was mobilized with heel and sole raise and walking aid.

Conclusion: Pseudotumor formation occurred without any damage to ceramic head and liner, without any malposition of components, with no impingement between components and normal metal ion levels in our case. This case report further strengthen existing literature about pseudotumor formation in CoC articulation. Further studies needed to know exact tribology and individual immune response for ceramic wear debris.