The use of tungsten as a chronically implanted material

Area of Science:

• Biomaterials Science
• Corrosion Engineering
• Medical Implant Technology

Background:

• Tungsten is historically used in medical implants due to its density and strength.
• Chronic implant materials require long-term corrosion resistance in physiological environments.
• Tungsten's inertness is often assumed but is challenged by its behavior in vivo.

Purpose of the Study:

• To review the suitability of tungsten as a chronically implanted material.
• To evaluate tungsten's corrosion resistance and potential toxicity in the human body.
• To recommend alternative materials for medical implant applications.

Main Methods:

• Literature review of tungsten's properties and implant history.
• Analysis of tungsten's corrosion thermodynamics and chemical dissolution pathways in physiological conditions.
• Examination of reported implant failures and toxicity studies.

Main Results:

• Tungsten corrodes in body fluids, dissolving into soluble hexavalent tungstate (W6+).
• Corrosion is accelerated by reactive oxygen species produced by the immune system.
• Numerous implant failures due to tungsten dissolution have been documented, with elevated blood tungstate levels observed.

Conclusions:

• Tungsten is not suitable for chronic implantation due to its susceptibility to corrosion.
• The dissolution of tungsten can lead to the release of potentially toxic tungstate ions.
• Alternative biomaterials should be considered for long-term medical implant applications.