Patch testing may prove useful pre- and postimplant surgery

According to Dr. Taylor, who is a consultant dermatologist, department of dermatology, Dermatology-Plastic Surgery Institute, Cleveland Clinic, patch testing may also be indicated in patients with postimplant complications such as a rash, pain or loosening, especially if the surgeon is anticipating replacing the device. He spoke at the 54th Annual Meeting of the Noah Worcester Dermatological Society.

“It is uncommon for patients who receive metal implants to develop a hypersensitivity reaction to the prosthetic device chosen, which may first become evident in the form of an allergic contact dermatitis that develops in the patient soon after the surgical procedure. In patients with putative reactions to metal implants, patch testing can be a very useful method to identify potential allergy to the metal device used,” Dr. Taylor says.

Considering complications

In a recent retrospective medical chart review study, Dr. Taylor and colleagues assessed the effect of patch testing on surgical decision making and outcomes in patients evaluated for suspected metal hypersensitivity related to implants in bones or joints. The study included 72 patients who underwent patch testing for allergic contact dermatitis related to orthopedic implants received.

Patients were divided into two main groups in respect to the timing of their patch testing, namely, preimplantation (31 patients) and postimplantation (41 patients). Dr. Taylor reviewed the surgeon’s preoperative choice of metal implant alloy compared with patch testing results, as well as the presence of hypersensitivity complications related to the metal implant after the surgery.

The clinical history of sensitivity to metals was a predictor of positive patch tests to metals in both groups, results showed. In all preimplantation cases, Dr. Taylor said that positive patch test results to a metal influenced the decision making process of the surgeon in terms of the type of implant used. Patients with metal sensitivity who received an allergen-free implant had surgical outcomes free of hypersensitivity complications. In postimplantation patients who were patch test positive to a metal in their implant, the removal of the device lead to resolution of associated symptoms.

“Patch testing is not routinely performed or indicated in those patients set to receive a prosthetic device unless the physician or patient raises the question. However, the screening tool can help avoid allergic contact dermatitis in the predisposed patient, as well as other signs of implant rejection including localized pain and loosening of the implant. Based on the preop patch test results, the physician could fine-tune the choice of implant used, wherever possible,” Dr. Taylor says.

Nickel allergies

According to Dr. Taylor, more than 1 million lower-extremity total joint replacements are performed yearly in the United States, and this number is expected to rise. Most of the implants used are metal alloys and are typically made of two or more components, the most common of which is nickel due to its strength and durability.

However, Dr. Taylor says nickel is the leading cause of contact dermatitis associated with metals, affecting up to 19 percent of the population evaluated with patch testing.

As with any device, a metal implant would be contraindicated if the patient has a proven allergy to any of its ingredients. However, Dr. Taylor says that though there are literally hundreds of different metal implants available consisting of different metal alloys of varying percentages, the alternatives are often limited in terms of the willingness of surgeons to use a different product.

In patients who are nickel sensitive, an implant that contains less or no nickel could be used in orthopedic cases such as those made of titanium or oxinium. From an allergy standpoint, titanium is widely considered as the ideal metal alloy in prosthetic implants, Dr. Taylor says, but this is less so from an orthopedic standpoint in terms of the alloy’s wear and functionality.

“These alternative implants have different metallurgical properties and different orthopedic and functional capabilities. Surgeons have to be comfortable with the device that they are using, and it is often not that easy to simply switch to an alternative device, as each device has a particular benefit and ‘strength’ in a given surgical case,” Dr. Taylor says.

No guarantee

Fortunately, most patients will tolerate the implant that they receive, even though patch testing proves them to be allergic to a metal in their implant alloy, Dr. Taylor says. The degree of hypersensitivity reaction in these patients very much depends on the amount of the corrosion that occurs in the release of the metal, if the metal is bound or mixed with other metal alloys, and what percentage of the metal is contained in a given implant.

“A positive patch test does not necessarily predict or guarantee that a patient will have a reaction to a metal prosthesis when it is implanted. In many cases, however, the test can help direct the physician to possibly choose an alternative implant preoperatively or postoperatively with similar functional attributes,” Dr. Taylor says.

Replacement considerations

The decision to replace a metal implant that is suspected of causing allergic contact dermatitis depends on the severity of symptoms. A positive patch test alone is clearly no reason to remove a device, especially if it is functioning well, Dr. Taylor says, and many cases of allergic contact dermatitis can be managed with topical therapy.

Postoperative testing

According to Dr. Taylor, an allergic reaction to a metal implant in a knee or hip joint is often not the cause of a rash seen in the area; instead, the symptoms could be due to an insidious subclinical infection. Here, he says the patient may require aspiration of the joint and systemic antibiotics to clear the symptoms.

The main reasons for performing patch testing postoperatively are symptoms of pain or loosening of the implant, or in cases where the surgeon is considering replacing the device for better functional outcomes, Dr. Taylor says.

“More and more patients are being sent for evaluation of allergy to metals before and after surgery,” he says. “Though patch testing has a role, there is no clear-cut solution of what to do with positive patch tests to a given metal alloy contained in the implant. The decision whether or not 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.”  DT

Disclosures: Dr. Taylor reports no relevant financial interests.