Inflammatory pseudotumor associated with femoral nerve palsy following metal-on-metal resurfacing of the hip

Metal-on-metal resurfacing arthroplasty of the hip has been used increasingly in Europe over the last ten years for the treatment of osteoarthritis of the hip in younger (<65 years of age), active patients. In 2005, 6,153 procedures were performed in England and Wales1. Marketing of the Birmingham hip replacement for resurfacing arthroplasty was approved by the United States Food and Drug Administration in May 2006. Metal-on-metal resurfacing of the hip is known to be associated with elevated concentrations of metal ions within the hip joint and systemically, but, to our knowledge as of this writing, no adverse effects of this process have been identified. However, the United Kingdom Medicines and Healthcare Products Regulatory Agency (MHRA) issued an alert in June 2007 about the Ultima metal-on-metal bearing total hip arthroplasty prosthesis (DePuy International, Leeds, United Kingdom) following reports of the need for early revision due to periprosthetic soft-tissue necrosis2. The bearing in question was a cobalt-chromium-molybdenum alloy similar to that used in the Birmingham hip replacement. We report the development of an ipsilateral mass associated with markedly elevated intralesional cobalt and chromium levels and a femoral nerve palsy in a patient who underwent a Birmingham metal-on-metal resurfacing arthroplasty of the hip one year previously. Our patient was informed that data concerning the case would be submitted for publication, and she consented.