ACAAI: Metal-Sensitive Patients May React to Orthopedic Implants

PHILADELPHIA, Nov. 12 -- When a patient with an orthopedic implant develops a rash or inflammatory symptoms, think metal allergy, suggested researchers here.

In one study reported at the American College of Allergy, Asthma & Immunology meeting here, researchers described a patient who had to have revision of his total knee arthroplasty, because he developed an allergic reaction to the cobalt in the implant.

In a second study, a small but significant fraction of patients receiving metal implants for pectus excavatum, or sunken chest, had allergic reactions to metal bars implanted into their chests.

The findings suggest that in patients with a history of atopy or suspected metal allergy, preoperative skin patch testing could identify patients who might develop reactions.

For these patients, a non-allergenic substitute, such as titanium, could be used, said the authors of both studies.

"Contact metal to allergy is common, occurring in 20% to 25% of the population, nickel sensitivity being the most well known and the most experienced," said Norman Koven, M.D., an allergist and asthma specialist in Philadelphia. "Fortunately, during and after a surgical procedure most of these patients don't react to the metal that's implanted, so the actual occurrence is low, but one needs to keep it in the back of one's mind."

Dr. Koven and colleagues reported the case of a 79-year-old artist who developed a progressive systemic delayed hypersensitivity reaction after receiving bilateral knee prostheses comprised of chromium, cobalt and nickel.

As a painter, the patient had been frequently exposed to cobalt blue pigment, commonly used in art paints. Two weeks after surgery, he developed bilateral sterile knee effusions with serpiginous eczemoid dermatitis over his swollen knees.

Four months after the surgery, the patient began to show systemic symptoms, include a 13-pound weight loss, fatigue, myalgia, anorexia and watery diarrhea.

A gastrointestinal workup proved negative, but patch tests were positive for cobalt sensitivity, and negative for chromium and nickel sensitivity. On arthrocentesis, his erythrocyte sedimentation rate and C-reactive protein levels were both indicative of inflammation, but his complete blood count, antinuclear antibody and rheumatoid factors tests were all normal.

Two additional arthrocenteses showed that the synovial fluid was sterile with evidence of inflammation.

The patient underwent revision arthroplasty nine months after the first procedure, and had the original implants swapped out for titanium alloy prostheses.

Histopathologic studies performed on the resected synovium showed proliferative synovitis with infiltration of lymphocytes, monocytes, and plasma cells-consistent with delayed hypersensitivity.

Following the removal of the cobalt-containing implants, the patient improved and has had no systemic gastrointestinal, dermal, or localized knee problems, Dr. Koven said.

"Following arthroplasty with metallic alloys, particles of metal can be detected for years in joint fluid, synovium, serum, and reticulo-endothelial system tissue," Dr. Koven and colleagues wrote in their poster presentation.

"Positive patch tests to cobalt were reported in 13 of a cohort of 35 patients with failed knee replacements. Two of the 13 experienced eczema over an inflamed knee similar to [the artist] but without systemic illness. We speculate [the artist] had prior occupational cobalt sensitization."

In the second study, Gregory D. Rushing, M.D., of Eastern Virginia Medical School in Norfolk, and colleagues, reported on metal sensitivity in patients who underwent the Nuss procedure, a widely used form or corrective surgery that involves the implantation of a steel bar under the sternum. Stainless steel is preferred, because titanium implants, used in the original form of the procedure, proved too soft in some cases.

The investigators performed a retrospective review of patients who underwent the procedure. Patients determined to have metal allergies were diagnosed either with skin-patch testing, or clinically based on the presence of rash, fever, elevated erythrocyte sedimentation rate, cultures, and pathology specimens.

The authors collected data on patient dermographics, allergies to jewelry, and history of atopy. They also looked at procedures in which a stainless steel bar was removed and replaced with a titanium bar.

They found that over an 18-year period, 862 patients underwent the Nuss procedure, and of these, 19 (2.2%) were diagnosed with metal allergy. The patients age was an average of 14.7 (range 9-23 years), and all but one were male.

Nine of the patients (56%) had a history of atopy, 10 (63%) were diagnosed when they presented with rash and erythema, one (6%) presented with granuloma, five (32%) with pleural effusion, and three (15%) were diagnosed as having sensitivity on preoperative screening.

In three patients stainless steel bars had to be removed because of allergic skin breakdown, and two of these patients required replacement titanium bars. All three of the patients had resolution of symptoms after removal of the stainless steel, the authors reported.

The three patients who had been diagnosed with stainless steel sensitivity pre-operatively received titanium bars instead at the time of surgery, without clinical events.

"Allergy symptoms often are misdiagnosed as infection, but require different treatment," the authors wrote. "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. Because the consequences of metal allergy may include the need to replace the bar, pediatric surgeons should be aware of this occurrence."