A small percentage of patients may have an allergy to certain metals. This is usually a nickel sensitivity that makes wearing jewelry containing nickel troublesome due to the skin rash it can create. The Chrome Cobalt implants have a trace amount of Nickel in them in addition to the chromium and cobalt metals. This type of sensitivity can rarely cause an allergic type of reaction to the prosthetic implant. While it is estimated that 10 percent of the population has some metal sensitivity, implant-related reactions are estimated to be one in several thousand patients and have been more commonly observed after knee replacements.
While there is no easy test to assess patients metal sensitivity, there are several options currently available to help patients with known severe metal allergies. In the hip, titanium implants are often used and pose no risk to the patient. The ball and socket can also be made of ceramic or oxinium materials which impart no allergic response. In the knees, alternatives to chrome cobalt femoral implants include Oxinium, coated titanium, or ceramic (investigational) implants. Because of the expense of these devices and the lack of long-term studies, they are reserved for patients with well-documented metal allergies to the chrome cobalt alloy.