February 21, 2012 — Patch tests to predict the likelihood of allergic contact dermatitis before the implantation of a prosthetic device are appropriate in cases in which the patient has a history of hypersensitivity to certain metal alloys, a retrospective study of 72 orthopedic surgery recipients suggests.
When patch tests are administered after implant surgery, however, to trace allergic complications such as chronic joint pain or cutaneous eruption, positive results are a less forceful signal to proceed with removal of the prosthesis, conclude Natasha Atanaskova Mesinkovska, MD, PhD, from the Department of Dermatology and the Department of Dermatology–Plastic Surgery Institute, Cleveland Clinic, Ohio, and colleagues in an article published online February 20 in the Archives of Dermatology.
The authors report that in each of 21 cases in which preoperative evidence of hypersensitivity resulted in procedural amendments, patient outcomes were successful. When metals hypersensitivity was confirmed with patch tests postoperatively, similarly favorable outcomes were observed in patients who elected to have their devices removed, whereas those who chose to leave a suspect prosthesis intact continued to experience symptoms.
However, investigators cautioned against placing too much emphasis on metals hypersensitivity when diagnosing allergic dermatitis postoperatively, given that the condition may also be stimulated by the plastics that simulate cartilage in some implants, or the cement used to anchor implants in bone.
Medical records were reviewed for patients who underwent patch testing in association with implantations of devices such as knee or hip arthroplasties, spinal implants, or Nuss bars at the Cleveland Clinic Department of Dermatology between January 1, 2003, and December 31, 2010. Thirty-one patients received patch tests before surgery, and 41 had tests administered after implantation, in an effort to diagnose complications. All those whose records were studied received patch testing by means of both standard screening, as stipulated by the North American Contact Dermatitis Group, and prosthesis trays.
Of the patients in the preoperative group, 68% (21/31) showed positive patch test hypersensitivity to at least 1 metal, with 15 patients (48%) reacting to more than 1 metal. Nickel was identified as the most problematic allergen in 52% of the patients, followed by palladium in 32% of patients. All who tested positive were more likely to have a documented history of metal alloy hypersensitivity from exposure to objects such as costume jewelry or belt buckles than those 10 patients in the group who did not test positive (70%; P = .03).
In each of the 21 cases in which positive patch tests motivated surgeons to opt for an allergen-free implant made from a zirconium oxide or titanium alloy, no subsequent contact dermatitis was observed.
The primary reason for patch testing in the postsurgical group was chronic pain at the surgical site, which was reported by 59% (24/41) of the patients. These patients also demonstrated localized or generalized dermatitis, localized pruritus, edema, and joint loosening. Along with metals hypersensitivity, causative factors such as infection or mechanical failure of the device were evaluated. Fewer positive patch tests (37%, or 15/41) were recorded for this group, and nickel, again, was found to be the most commonly identified allergen. Patients also demonstrated sensitivity to cobalt, palladium, chromium, and indium.
Symptoms disappeared in 6 of the 10 patients who received postoperative patch tests who had their suspect prosthetic devices removed. The remaining 4 patients continued to experience complications.
Investigators acknowledged the small sample size as a limitation of the study as well as the lack of a comparative group for whom the surgeons "disregarded the patch test results." In addition, in an accompanying editorial, Christen Mowad, MD, from the Geisinger Medical Center, Danville, Pennsylvania, noted that patch tests are performed not inside the body, but in a cutaneous tissue environment.
"Therefore, the testing might not recreate or elicit the same response as that of a metal within a joint space," he writes.
Moreover, Dr. Mowad continues, postoperative patch test results should always be evaluated within a thoroughly inclusive diagnostic context. "When postoperative patch test results are positive, did the joint problem cause the allergy? Did the allergy cause the joint problem? Are they related?"
Dr. Mowad suggests that a multidisciplinary prospective study of patch testing administered both before and after implant surgery be conducted, with comparisons made between patients receiving patch tests and patients for whom tests are not provided.
Two colleagues involved in the study reported extensive relationships with pharmaceutical companies and speaking bureaus, but none with direct financial relevance to the published work. The other authors and editorialists have disclosed no relevant financial relationships.
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