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Evaluation of absorbable poly(ortho esters) for use in surgical implants
A U Daniels1, K P Andriano, W P Smutz
1Orthopedic Bioengineering Laboratory, University of Utah School of Medicine, Salt Lake City.
Journal of Applied Biomaterials : an Official Journal of the Society for Biomaterials
|April 1, 1994
Summary
Poly(ortho esters) (POEs) offer a safer alternative to polyglycolides and polylactides for bone fixation devices. These hydrophobic polymers degrade slowly via surface hydrolysis, showing minimal inflammatory response and maintaining mechanical integrity.
Area of Science:
- Biomaterials Science
- Polymer Chemistry
- Medical Device Engineering
Background:
- Polyglycolides (PGA) and polylactides (PLA) bone fixation devices can cause adverse inflammatory responses due to acidic degradation products.
- There is a need for alternative biodegradable polymers with improved biocompatibility and predictable degradation profiles.
Purpose of the Study:
- To investigate poly(ortho esters) (POEs) as a potential alternative to PGA and PLA for bone fixation applications.
- To evaluate the degradation behavior, mechanical properties, and biocompatibility of POEs.
Main Methods:
- Degradation studies of hot-molded POE specimens in saline at varying pH.
- Mechanical testing of POE specimens under static and dynamic loading.
- Biocompatibility assessment using United States Pharmacopeia (USP) toxicity tests.
- Evaluation of solvent-cast POE films with different molecular weights.
Main Results:
- Hydrophobic POEs degrade via surface hydrolysis, producing nonacidic products initially.
- Hot-molded POE specimens retained significant stiffness and strength after 12 weeks in saline.
- Degradation was largely unaffected by pH changes but accelerated by mechanical loading.
- POE specimens demonstrated acute non-toxicity in USP implant tests.
- Higher molecular weight POE films showed stable mechanical properties over 31 days.
Conclusions:
- Poly(ortho esters) (POEs) exhibit favorable degradation characteristics and biocompatibility for bone fixation devices.
- Surface hydrolysis of POEs minimizes the release of acidic byproducts, reducing inflammatory responses.
- POE's mechanical properties remain stable, making them a promising alternative to bulk-hydrolyzing polyesters.