The use of bioabsorbable polymers in the manufacture of implants for soft tissue fixation has been clinically accepted for many years.
Bioabsorbable versus Metal
Bioabsorbable implants have many advantages over metal implants, including:
Bioabsorbable polymers are a special class of plastic materials that allow the material to serve a function, and then gradually break down, metabolise and be eliminated from the body.
It is imperative to match the degradation time with the initial period during which the material must function.
The ideal bioabsorbable material will provide appropriate strength while degrading in a predictable fashion without adverse reactions occurring in the body throughout the healing process. Specific Bioabsorbable Polymers
There are three main types of bioabsorbable polymers used in orthopedics:
Copolymers
Bioabsorbable polymers are often blended into a copolymer to maximise initial strength and increase the rate of absorption. Typical blends are:
Self-Reinforced PLA
There are many ways of manufacturing bioabsorbable polymers, including compression moulding, casting, injection moulding and extrusion.
An extruded bar is heated until soft and pulled through a dye in a controlled manner. This aligns the polymer chains in the direction of pulling and also entangles them to form the Self-Reinforced polymer.
This Self-Reinforced polymer has high initial strength that reduces premature fracture during implant insertion. It also allows the implant to maintain holding power throughout the healing process.
As with all bioabsorbable implants, they biologically resorb over time, allowing the load to transfer to the bone after primary bone healing and eventually completely disappear through safe biological resorption