Metal allergy complicates orthopedic implant

Nov 20 (HealthCentersOnline) - Infection is the usual suspect when patients develop inflammation or rash after an orthopedic implant, but the problem could be an allergy to metal, researchers report.

Physicians presented two studies on the topic this month at the annual scientific conference of the American College of Allergy, Asthma & Immunology:

Researchers at Eastern Virginia Medical School conducted an 18-year review of patients who had undergone a Nuss procedure, in which a curved metal bar is implanted beneath the breastbone (sternum). Nuss procedures are performed to correct a sunken chest (pectus excavatum), which can be a birth defect or result from conditions such as severe scoliosis.
Stainless steel is typically used in a Nuss procedure because titanium is not always strong enough. However, the researchers found that 19 of the 862 young patients in their study had a metal allergy. Three patients required removal of their steel bars because of allergic skin breakdown, and two of these had titanium bars inserted instead.

Three other patients had been found before their surgery to be sensitive to stainless steel. Their original implant was of titanium, and none of them developed problems.

"Allergy symptoms often are misdiagnosed as infection, but require different treatment. If a history of metal allergy or atopy is suggested preoperatively, the patient should be tested for metal allergy and if positive, a titanium bar used," the researchers wrote.
Researchers in Philadelphia described the case of a 79-year-old man who underwent a joint replacement (arthroplasty) in both knees, a common treatment for severe osteoarthritis. Two weeks later his knees swelled and developed an eczema-like rash. Four months later his symptoms included fatigue, muscle pain and weight loss.
Skin patch testing showed a sensitivity to cobalt. An analysis of synovial (joint) fluid revealed inflammation. The patient underwent another operation in which his cobalt-containing implants were traded for titanium ones.

Up to one-fourth of the population has an allergy to metal, most commonly to nickel, the Philadelphia researchers reported. Like the authors from Eastern Virginia Medical School, they suggested using titanium or other nonallergenic implants with these patients, who could be identified before surgery with allergy tests.