Foster Corporation specializes in custom blending and forming of highly regulated materials, including long-term implantable and bioresorbable polymers. These materials are formulated and processed in a dedicated cGMP cleanroom environment using precise hot melt extrusion. In terms of processing, twin screw extruders offer several advantages for these materials such as easy material feeding, high kneading / dispersing capacities and short transit time. Screw elements, screw rotation and screw speeds can be custom designed for the formulation being produced.
Implantable Polymer Types
Implantable polymers can be categorized based on anticipated duration in the body and range from short-term (<30 days), bioresorbable, long-term (>30 days) to permanent.
Long-Term Implantable Polymers – Long-term implantable polymers include biodurable (non-resorbable) materials such as polyethylene for limited structural applications and polyketones (PEEK) for spinal applications.
Bioresorbable Polymers – 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.
Implantable Polymer Additives
Implantable polymers can be enhanced to improve application performance with biomedical additives that provide visibility under x-ray or stimulate bone growth.
Bone Mineral – Phase pure β Tricalcium phosphate (TCP) is an osteoconductive and biocompatible additive that can be melt blended with bioresorbable polymers, such as PLA for the stimulation of bone growth. Alternatively, hydroxyapatite (HA) may also be blended with bioresorbable polymers (PLLA) for biphasic applications including interference screws used in anterior cruciate ligament (ACL) reconstruction.
Radiopaque Fillers – Polymers are inherently transparent to x-ray imaging and require specific additives to achieve visibility. Radiopaque filler selection depends on end application and intended implantation time. For more information, please refer to Radiopaque Compounds.