Allergy Testing in Patients Receiving Orthopedic Implants
Metal patch testing should be considered in patients who develop symptoms post implantation to rule out a metal allergy. Additionally, with the increase in frequency of joint replacements, it may be advantageous to perform preoperative patch testing for allergies. Preoperative metal patch testing should not only be performed in patients with a positive history of metal allergy, but also in patients with a negative history of metal allergy.
Studies indicate at least 5% of all patients with orthopedic implants can develop an implant-related allergic contact reaction. In addition, up to 21% of patients with preoperative metal sensitivity may develop a reaction upon re-exposure to the same metal.
Metal hypersensitivity develops secondary to repeated skin exposure to consumer products such as cosmetics, preservatives, jewelry, and leather goods. The three most common metals involved with contact reactions are nickel, cobalt and chromium. It is estimated that approximately 21% of the general population are sensitized to nickel and 8% are sensitized to cobalt, chromium or both.
Some patients develop a delayed allergic reaction after their knee and hip joint replacement, joint resurfacing, placement of plates or screws post bone fractures, spinal instrumentation or placement of a pectus bar.
Metal implant allergy symptoms may include:
- rash at the implant site
- total body rash
- joint loosening
- loss of joint function
These delayed implant allergy symptoms can begin within weeks or months after surgery and often can only be resolved by removal of implant.
Patch Testing for Allergies
Patch testing will help your physician identify any potential allergies to the metals which are present in your implant. If an allergy can be identified preoperatively then, if possible, this metal can be avoided.
There have been reports of patients who were negative on preoperative patch testing developing a new sensitivity postoperatively. There are no tests presently available to predict which patients will develop a new allergy.
How does Patch Testing work?
A panel of patches with many common allergens is placed in contact with the skin on the upper back and covered with adhesive. These patches are worn for 48 hours and removed in the office. Initial impressions are recorded. You will return for a final reading of the patches 5 – 7 days later. This last visit will help distinguish between irritant dermatitis (which is not a true allergic response) and contact dermatitis. Information on any positive responses will be provided so that these substances can be avoided.List of patch tests for joint replacements, joint resurfacing, spinal instrumentation, and pectus bar placement:
- Nickel Allergy Test
- Potassium Dichromate
- Chromium Chloride
- Copper Sulfate
- Molybdenum Chloride
- Manganese Chloride
- Zirconium (part of the bone cement)
- Titanium Allergy Test
- MMA (part of the bone cement)
- Gentamicin (cement infused with it)
- N,N-dimethylp-toluidine (DPT) (part of the bone cement)
- Benzoyl Peroxide (part of the bone cement)
Read more about patch testing