There are four leading classes of biomaterials used in implantable applications, including metals, ceramics, composites and polymers. The use of one material type over the other varies greatly based on a range of criteria, including functional use, performance requirements and cost.
When selecting a material for a critical application specific requirements must be met, including:
- Maintenance of physical and chemical properties over desired implantation time
- Lack of biologic responses when in contact / implanted
- Ability to be manufactured, reproduced and sterilized the same every time (to specification and regulation)
Implantable Polymer Types
Polymers are becoming increasing popular in implantable components due to ease of fabrication, range of properties and enhanced bio-stability and bio-compatibility. Implantable polymers are categorized based on anticipated duration in the body range from short-term (<30 days), bioresorbable, long-term (>30 days) to permanent.
Short-Term Implantable Polymers
Non-durable polymers are often implanted in the body for short-term treatment ( <30 days) or for procedural therapy. These materials include Thermoplastic Polyurethane (TPU), Polyamides (Nylon & PEBA) and Polyvinyl Chloride (PVC) for central venous (CVC), diagnostic (guiding), interventional (PTCA) and drainage catheters.
Bioresorbable polymers are metabolized by the human body after implantation and include polylactide (PLA), polyglycolide (PGA) and copolymers of PLA/PGA. These materials can be tailored to meet mechanical performance and resorption rates for non-structural drug delivery to resorbable screws and anchors.
Long-Term Implantable Polymers
Long-term implantable polymers include biodurable (non-resorbable) materials such as polyethylene for limited structural applications and polyketones (PEEK., PAEK) for spinal applications. Additional material options include polysulfones, polypropylene and polyurethane.