Metallosis Following Total Hip Arthroplasty: A Case Report

Total hip arthroplasty (THA) is a common procedure for treating hip osteoarthritis but carries potential complications, including implant loosening and wear. Metallosis is a rare complication caused by metal debris from prosthetic components, particularly in metal-on-metal implants, leading to adverse local tissue reactions such as osteolysis, soft-tissue necrosis, and pseudotumor formation.

A 45-year-old male presented with progressive right hip pain, difficulty walking, and shortening of the affected limb following trauma. He had undergone right total hip arthroplasty 10 years previously. On evaluation of the patient, the systemic parameters were under normal limits. The radiographs showed proximal and medial migration of the metal femoral head, giving an impression of subluxation of the metal femoral head. The patient was planned for a revision THA suspecting an osteolysis. Intraoperatively, blackish pigmentation of the surrounding soft tissue was noted along with hypertrophy of the capsule. The metal femoral head was intact and eroded into the polyethylene liner and acetabular cup. This showed that extensive Metallosis secondary to catastrophic polyethylene liner wear and acetabular shell failure could have caused the failure of the previous surgery, contrary to the earlier expected osteolysis as the causative phenomenon. This diagnosis was confirmed by the histopathological examination of the tissues slides obtained intraoperatively via biopsy of the stained tissues. Post-surgery, the patient regained his function, and remained pain-free with stable implants at the follow-up.

Metallosis must be a diagnosis kept in mind in cases where the patient presents with problems post-THA particularly when radiographs demonstrate eccentric femoral head migration, polyethylene wear, osteolysis, or component failure. Although initially asymptomatic, the presence of metal ions in the tissue and blood can cause soft-tissue damage locally and systemically as well. Thus, early diagnosis and planning can help in the proper management and are crucial to limit progressive soft-tissue destruction, bone loss, and potential deleterious effects caused by metal ions in the body. .