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Orthopedic implants
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There are many types of orthopedic implants and each orthopedic implant is designed to correct the affected joint so that it withstands the associated movement and stress and to enhance mobility and decrease pain. Broadly speaking, orthopedic implants are available for the hip, knee, shoulder and elbow.

 

Total hip prostheses are made from metal alloy, which are stronger than pure metal, like titanium. The alloys used are:

 

Cobalt-chrome alloys, where the base metals are cobalt (> 34%) and chrome (>19%) mixed with smaller quantities of other metals, even nickel.

 

Titanium alloys, where the base metal is titanium, commonly used alloys contain (ca 4%) aluminium. These alloys are considered to be biocompatible.  They are the most flexible of all orthopaedic alloys.

 

Pure titanium may also be used in some implants where high strength is not required. It is used, for example, to make fibre metal, which is a layer of metal fibres bonded to the surface of an implant to allow the bone to grow into the implant, or cement to flow into the implant, for a better grip.

 

Stainless steel alloys, where the base metal is iron (> 58%), mixed with larger quantities of chrome and nickel and some other metals.

Oxiniumcan be a good alternative for metal-allergic people as it only contains niobium in addition to oxidised zirconium.

 

Nickel contamination
Several studies show that titanium alloys may contain traces of nickel as a result of the production process. This can trigger health problems in patients with nickel allergy, and it also means that a reaction may be falsely attributed to titanium itself. “Under certain circumstances, these small amounts may be sufficient to trigger allergic reactions in patients suffering from the corresponding allergies, such as a nickel, palladium or chrome allergy.”

 

Corrosion
All metallic alloys corrode and release metal ions into the body. The ions bind to proteins in the body and may trigger inflammation, such as allergy, autoimmunity and possibly cancer in susceptible patients.

 

Symptoms of implant allergy
As with dental implant allergy, symptoms to an orthopaedic implant may vary including skin rashes, general fatigue, pain, impaired wound and bone healing and in some cases implant loosening and failure. If you have experienced these symptoms after surgery you may want to consider testing for allergy.

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