New-generation metal-on-metal bearings made from cobalt-chromium alloys for use in total hip arthroplasty are now being utilized worldwide. A hypersensitivity reaction to a metal-on-metal bearing is a rare but reported complication and is thought to be a novel mode of failure of these implants1,2. These reactions were initially observed in patients with first-generation bearings and are now being reported in association with the second-generation metal-on-metal bearings currently in use3-5. Characteristic histological changes in the periprosthetic tissues obtained during revision surgical procedures in these patients have suggested the development of an immunological response2,6.
Reports have suggested that the possibility of such a reaction should be considered when a patient presents with persistent, or the early reappearance of, preoperative pain symptoms, including a marked joint effusion, and the development of early osteolysis or radiolucent lines in the absence of infection2,7. Fever and elevated serum levels of inflammatory markers have routinely been reported to not occur in these patients.
We describe two patients with failure of metal-on-metal implants who presented with signs that mimicked a deep-seated hip infection. To our knowledge, this has not been reported previously. Although the two cases were similar in terms of the clinical presentation, each ultimately represented a different pathological condition and etiology.
The patients were informed that data concerning the case would be submitted for publication, and they consented.
Case 1. A fifty-three-year-old man presented to our emergency department because of bilateral hip pain and episodes of low-grade fever three years after a bilateral metal-on-metal total hip arthroplasty. A Pinnacle acetabular component with a cobalt-chromium metal bearing surface (DePuy Orthopaedics, Warsaw, Indiana) had been implanted bilaterally. The pain had been present since the surgery, and the patient had never stopped …
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