Metal Allergy

Most common sensitizers are: nickel, cobalt, and chromium
Incidence of sensitivity: Chromium=0.2%, nickel=1.3%, and cobalt=1.8% (Swiontkowski MF, J Orthop Trauma 2001; 15: 86-89).
Stainless steel and cobalt-chromium alloys contain the above sensitizers, especially Nickel.
Titanium and titanium alloys generally do not contain the above sensitizers.
People with a history of allergies to cobalt, chromium or nickel generally are not sensitive to titanium or its common alloys. (Ti-6AL-4V)
Metal allergy may affect 10-15% of the population (Hallab N, JBJS 2001;83A:428). Prevalence may be increasing (Thyssen JP, Contact Dermatitis 2007;57:287).

Testing

Patients with a potential metal sensitivity should be seen by a dermatologist or allergist for testing prior to any orthopedic implant. (Mesinkovska AN, MD, Arch Dermatol. Published online February 20, 2012)
Dermatologist generally use testing kits such as, T.R.U.E Test Patch Test for testing. (www.truetest.com or www.allerderm.com, 800-365-6868)
Patients with metal sensitivity or a nickel allergy may report nonspecific deep generalized pain over the implant.

Metal Allergy TKA

Patients with metal allergy should be treated with a modular titanium or all poly tibial component and an oxidized zirconium femoral component. Titanium has a propensity for metallosis and is not suitable for the articulating portions of the components. (Laskin RS, CORR 2003;416:191).

Metal Allergy THA

Press-fit titanium stem, ceramic (alumina) head, and cementless titanium cup.
Titanium femoral heads are susceptibility to abrasive wear. Cemeted titanium stems transmit greater stresses to the cement column and are not recommended. Titanium is less stiff than cobalt-chrome (and stainless steel).

References