Thursday, December 30, 2010

Metal Sensitivity (from Wikkipedia)

Although little is known about the short and long term pharmacodynamics and bioavailability of circulating metal degradation products in vivo, there have been many reports of immunologic type responses temporally associated with implantation of metal components. Individual case reports link hypersensitivity immune reactions with adverse performance of metallic clinical cardiovascular, orthopedic and plastic surgical and dental implants. [9]

By 2010 reports in the orthopaedic literature have increasingly cited the problem of early failure of metal on metal prostheses in a small percentage of patients.[10] Failures may relate to release of minute metallic particles or metal ions from wear of the implants, causing pain and disability severe enough to require revision surgery in 1–3% of patients.[11] Design deficits of some prosthetic models, especially with heat-treated alloys and a lack of special surgical experience accounts for most of the failures. Surgeons at leading medical centers such as the Mayo Clinic have reported reducing by 80 percent their use of metal-on-metal implants over the last year in favor of those made from other materials, like combinations of metal and plastic.[12] The cause of these failures remain controversial, and may include both design factors, technique factors, and factors related to patient immune responses (allergy type reactions).

In the United Kingdom the Medicines and Healthcare products Regulatory Agency commenced an annual monitoring regime for metal-on-metal hip replacement patients from May 2010.[13] Data which is shown in The Australian Orthopaedic Association's 2008 National Joint Replacement Registry, a record of nearly every hip implanted in that country over the previous 10 years, tracked 6,773 BHR (Birmingham Hip Resurfacing) Hips and found that less than one-third of one percent may have been revised due to the patient's reaction to the metal component.[14] Other similar metal-on-metal designs have not fared as well, where some reports show 76% to 100% of the people with these metal-on-metal implants and have aseptic implant failures requiring revision also have evidence of histological inflammation accompanied by extensive lymphocyte infiltrates, characteristic of delayed type hypersensitivity responses. [15] It is not clear to what extent this phenomenon negatively affects orthopedic patients. However for patients presenting with signs of an allergic reactions, evaluation for sensitivity should be conducted

Connie

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