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Long-term biostability of polyacetal (Delrin) implants
H A McKellop1, H L Milligan, T Röstlund
1J. Vernon Luck Orthopaedic Research Center, Orthopaedic Hospital, Los Angeles, CA 90007, USA.
The Journal of Heart Valve Disease
|August 1, 1996
Summary
Polyacetal homopolymer (Delrin) used in medical implants shows no signs of degradation after long-term in vivo use. This suggests Delrin maintains its wear resistance, ensuring reliable performance for devices like heart valves and hip replacements.
Area of Science:
- Biomaterials Science
- Polymer Engineering
- Medical Device Technology
Background:
- Polyacetal homopolymer (Delrin) has been utilized in medical implants, including heart valve occluders and total hip replacements, for over 20 years.
- These implants are subjected to mechanical stress and wear, raising concerns about long-term performance and potential degradation.
Purpose of the Study:
- To investigate the molecular integrity of Delrin components after extended in vivo use in human implants.
- To compare the properties of retrieved Delrin implants with non-implanted controls and assess the impact of mechanical loading and biological exposure.
Main Methods:
- Analysis of retrieved Delrin heart valve occluders and hip prostheses.
- Comparison with non-implanted control components using infrared spectroscopy, dilute solution viscosity, and gel permeation chromatography.
- Evaluation of mechanically loaded versus non-loaded regions within implants.
Main Results:
- No systematic degradation was observed in Delrin components after long-term in vivo implantation.
- Molecular properties remained consistent between retrieved implants and control samples.
- No significant differences were found between loaded and non-loaded regions, suggesting uniform stability.
Conclusions:
- Long-term exposure to biological fluids and cyclic loading does not appear to cause systematic degradation of Delrin in medical implants.
- The findings indicate that Delrin maintains its resistance to wear, supporting its continued use in demanding orthopedic and cardiovascular applications.