Exploring allergic reactions to medical implants

I am occasionally asked by patients who are having pain and have had a surgery where an implant was utilized if they could be allergic to the implant used in surgery.

Surgeons across a wide variety of fields — orthopedic, cardiothoracic, neurosurgical and dentistry — utilize plates, screws, pins, sutures, stents and other devices to repair bone and joints.

In orthopedics, allergic or hypersensitivity reactions to various implants poses a significant diagnostic challenge. In essence, hypersensitivity reactions become a diagnosis of exclusion for physicians. In other words, an orthopedic surgeon has to first exclude the more likely causes of continued pain or swelling around an implant such as infection, instability, implant loosening or tendinitis before considering hypersensitivity associated with an implant.

There is currently no consensus on skin or blood testing for an allergic reaction to an implant. When this issue arises, physicians may ask patients if they have had past skin reactions to metal (such as inexpensive jewelry causing skin redness and itchiness). Approximately 10 percent of the population exhibits some form of skin reaction to metal.

Nickel is by far the most common metal that patients can be sensitive to. The metals cobalt and chromium, which are often utilized in joint replacement components, have also been found to be allergens. Titanium is considered to be relatively biologically inert. Females are found to be four times more likely to develop a sensitivity to the metal nickel compared to males. This is thought to be due to the fact that women tend to wear more jewelry than men, and this repeated exposure can lead to the development of an allergy to certain metals due to chronic exposure.

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No Recommended Test

Previous implantation of a joint replacement may lead to increased hypersensitivity to the metals in the replacement parts. However, there does appear to be a genetic predisposition for metal allergies, with some people just being more susceptible than others.

Patients with hypersensitivity to an implant may have a skin reaction or dermatitis overlying the area where the implant is located. There may be persistent pain and swelling in this area. However, there are much more common causes of persistent pain and swelling around an implant such as infection or implant loosening or a tendinitis and these sources have to be first considered and eliminated as possibilities before considering that the implant is an allergen, which is less common.

Currently, there is no widely accepted or recommended test for the clinical determination of implant hypersensitivity. However, I do recommend patients who are going to have surgery let their surgeons know if they routinely have skin reactions to metal (such as jewelry) or other allergen triggers.

Dr. Rick Cunningham is a knee and shoulder sports medicine specialist with Vail-Summit Orthopaedics. He is a physician for the US Ski Team. Visit his website at http://www.VailKnee.com. For more information about Vail-Summit Orthopaedics, visit http://www.VSOrtho.com.