Foster, LLC compounds functionality into polymers for permanently implantable applications. Foster, LLC’s expertise in the implantable material segment is un-matched in the industry and is a is an example of expertise and experience that has been built up over many years. Our polymer expertise in this segment covers durable and non-durable solutions.
Foster, LLC’s market participation regards medical “implantable” materials is indicative of our commitment to providing extreme polymer capability, infrastructure, and polymer/processing expertise found no place else in the polymer industry.
Implantable applications are demanding in terms of polymer requirements. This being the case, it is imperative that the application be thoroughly considered before making a choice as to which material will be chosen for the specific application.
Polymer requirements to be considered include:
Mechanical Properties | Biocompatibility |
Yield Strength | Sterilization Method |
Elastic Modulus | Heat Resistance |
Corrosion Resistance | Chemical resistance |
Fatigue Resistance | In-The-Body Environment |
Chemical Structure | Molecular Weight |
Chemical Composition | Molecular Weight Distribution |
Amorphous/Crystalline | Hydrophobicity/Hydrophilicity |
In addition to the above polymer-related requirements, in-body factors, part geometry, as well as processes that affect biodegradation are also critical considerations:
Ph | Variation of Diffusion Coefficient |
Enzymes | Annealing |
Microorganisms | Sterilization Process |
Oxidation | Storage History |
Radiation | Drying |
Site of the Implantation | Part Shape & Design |
Mechanism of Hydrolysis | Presence of Additives |
Processing Conditions | Mechanical Stresses |
Water |
In addition to compounded implantable solutions, our Foster SCS distribution business also features permanently implantable polymers and functional additives including:
• Thermoplastic polyurethane (TPU)
• Polypropylene (PP)
• Silicones
• Beta TCP (osteoconductivity)
• Bismuth subcarbonate (radiopacity)
• PEKK
Foster SCS Website:
https://www.fosterscs.com/
Foster offers clean-room compounding for implantable material applications. This capability includes:
- Class 7 (10,000) clean room
- 27mm twin screw extruder
- 18mm twin screw extruder (R & D)
- Loss-in-weight-feeders
- Pelletization (customizable)
- Air & water cooling
- Non-clean room processing area for R & D runs
Development Services:
Foster also offers developmental services as implants and drug delivery systems are the most highly regulated products in the medical market. Effective product development that can be validated and scaled to production is essential. We offer a complete range of services throughout the product life cycle including:
- Formulation & Material Selection
- Feasibility – Small Batch Production
- Process Development
- Scale-Up
- Validation – Process & Test Methods
- Production – Implement Manufacturing Protocols
In addition, Foster offers our Medical Plastics Innovation Center for customers that need/want an operational platform to develop their applications from start to finish. Our Innovation provides customers with the following capability:
- R & D lots to production scale up
- Formulation development
- Feasibility – small batch production
- Process development
- GMP trials
- Color
- Validation
- Injection molding
- Finished property testing
- Direct extrusion forms and shapes
- Rods
- Fiber
- Tubing
- Film
- Pellets
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.
Documentation
Implantable Polymer Brochure
Durable & Non-Durable Materials and Functionality
Durable material solutions
- Polyether ketones (PEKK, PEEK, etc.)
- Sulfones
- Thermoplastic Polyurethane (TPU)
- Polypropylene (PP)
- Silicones
- The above among others
Ketone Based Polymers:
Ketone based (PEKK, PEEK) are used extensively for implantable devices. PEEK is a highly crystalline polymer while PEKK is less crystalline (more amorphous) while maintaining the excellent physical properties inherent in ketone-based materials. Ketones have bone-like modulus which makes them a good choice for bone-screws and the like. Other applications include spinal implants, trauma fixation, and dental implants.
Both are excellent choices for implantable devices as they exhibit high temperature resistance, with excellent strength/stiffness, chemical resistance, and toughness. Because of its “tunable” crystallization rate, PEKK is an excellent choice for customizable 3D printed implantable applications.
Sulfones:
Just starting to be used in implantable applications. Physical properties are not quite at the level of ketone-based polymers but are still excellent for many implantable devices. Commonly used for the outer shell of implantable catheter ports.
Thermoplastic Polyurethanes (TPU):
Thermoplastic polyurethane has a long positive history in medical devices and are used in implantable applications where there is a need for an elastomeric/flexible material, or a material that withstands flexure well. Their customization options enable them to be used in a wide variety of applications as they are considered to be a balance between rigid and elastomeric materials.
TPU’s are used in vascular grafts, artificial hearts, spinal implants, as well as for construction of knee and hip implants, among others.
Polypropylene:
Polypropylene is used extensively in fabric based implantable applications (surgical meshes). It is also used is suture applications. It is also used in vascular grafts and artificial ligaments.
Silicones:
Silicones are another material that has a long positive history in medical devices and is used extensively in implantable devices. It is flexible and durable and has good chemical stability and temperature resistance. Common applications include pacemaker insulation, intraocular lenses, shunts, among others.
Non-Durable Solutions
Non-durable (bioabsorbable materials) solutions include:
- Polylactides (PLA)
- Polyglycolides (PGA)
- Poly(lactide-coglycolides) (PLGA)
- Polycaprolactone (PCL)
- Alloys of the above
Bioabsorbable polymers are plastic materials that break down in the human body and are fully and safely absorbed after a finite amount of time. They are predominantly used for implantable medical devices and come in homopolymer and copolymer chemical configurations. They are a very versatile polymer platform as the ability to blend the materials above allows for a wide variety of material property adjustability.
Features of bioabsorbable materials:
Synthetic polymers | Absorbed Into The Body and Metabolized |
Hydrolytically Unstable | Easily Processed Via Common Techniques |
Biocompatible | Sterilizable With Gamma & EtO |
Wide Range of Physical Properties | Programmable Properties |
Wide Range of Degradation Characteristics | Wide Range of Functionalization |
Polylactides:
Highly crystalline, high modulus materials with a slow rate of absorption (over two years).
Polyglycolides:
Highly crystalline materials that absorbs in the body quickly (6-12 months). High modulus and used a lot in sutures.
Poly(lactic-co-glycolic acid):
Copolymer with properties dependent on the ration of lactide to glycolide. Amorphous to fully crystalline properties that are dependent on the block structure. Very good solubility with degradation dependent on copolymer ratio.
Polycaprolactone:
Low melting point materials with a slow degradation rate that is often used as an additive to improve processing characteristics and end use properties. Commonly used in dental applications and drug encapsulation.
Bioabsorbable material length of time in the body:
