Allergy Tests Needed Before New Knee or Hip (MedPageToday)
Preoperative skin patch testing for metal allergy influenced treatment planning in two-thirds of a small cohort of patients scheduled to receive metal-containing prosthetic devices, a retrospective chart review showed.
All 21 patients with positive tests received allergen-free prostheses and had no complications associated with hypersensitivity.
Post-implantation patch testing led to prosthesis removal in 10 additional patients, and six had resolution of hypersensitivity-associated symptoms.
“The findings of this study support a role for patch testing in patients with a clinical history of metal hypersensitivity before prosthetic device implantation,” Natasha Atanaskova Mesinkovska, MD, PhD, of the Cleveland Clinic, and co-authors wrote in an article published online in Archives of Dermatology.
“The decision of whether to remove an implanted device after positive patch test results should be made on a case-by-case basis, as decided by the surgeon and patient,” they said.
The author of an accompanying editorial cautioned that “the patch test is a cutaneous test that does not recreate the environment in which the metal resides.”
“Therefore, the testing might not recreate or elicit the same response as that of a metal within a joint space, for example,” wrote Christen M. Mowad, MD, of Geisinger Medical Center in Danville, Pa.
More than one million Americans receive lower-extremity joint prostheses each year, and the number will likely continue to increase with the population’s age. Most of these prostheses consist of a mix of metal alloys.
The issue of preimplantation patch testing presents a conundrum for physicians. The prevalence of contact allergy to metal is relatively high, but hypersensitivity-associated complications occur in about 0.1% of patients who receive metal prostheses, the authors wrote.
Patch tests offer a means to identify patients at potentially increased risk of a hypersensitivity reaction to a metal implant, but the extent to which the results might influence surgeons’ decision making has remained unclear.
Mesinkovska and colleagues searched medical records for patients who had skin patch tests for contact allergy associated with orthopedic implants from 2003 to 2010. They identified 72 patients, 31 of whom had preoperative tests and 41 who had postoperative tests.
The authors reported that 21 patients tested preoperatively had positive results, most often reflecting allergy to nickel (52%), palladium (32%), gold (23%), and cobalt (19%). Several patients had allergy to more than one metal.
In all 21 cases, the surgeon altered the original treatment plan and used an allergen-free implant. None of the patients had complications that could be attributed to hypersensitivity.
In the postoperative group, pain at the site of implant was the most common reason for skin patch testing (24 of 41). Fifteen patients had positive tests, and eight of the 15 had a history of metal hypersensitivity (versus five of the 26 patients who had negative tests, P=0.03).
The metals most often associated with positive skin patch tests were nickel, cobalt, palladium, and chromium. No patient exhibited sensitivity to gold.
Ten of the 15 patients with positive postoperative tests had reactions to a metal in their implant. Seven of the 10 reported a history of hypersensitivity, and all seven reacted to nickel.
Six of the 10 patients underwent implant revision, and all had symptom alleviation. The remaining four patients continued to have symptoms related to the implant.
The authors acknowledged the study limitations, such as its retrospective nature, relatively small sample size, and the lack of a comparative group in which the surgeons disregarded the patch test results.
“The study confirms the need for surgeons and dermatologists to work together and establish guidelines with a goal to identify patients who would benefit from revisions of previously implanted metal,” the authors wrote.
Mowad agreed, pointing out that “the dermatologist who patch tests must set realistic expectations for the patient and referring physician alike.”
The authors argued that “patch testing remains a standard for evaluating patients with suspected metal allergy. However, it may not always result in a diagnosis. We acknowledge the lack of agreement on which specific allergens, especially which metal salts, should be used for patch testing when devising the prosthesis trays.”