SYMPOSIA PAPER Published: 01 January 2000

Mechanical Evaluation of 70:30 Poly (L/DL-Lactide) Bone Screws After Degradation


Controlled in vitro degradation testing is typically used to complement animal trials in order to understand the material, design, and fabrication factors that affect in vivo resorption rates of bioabsorbable implants. Resorbable 1.5 mm craniofacial bone screws were injection molded from amorphous 70:30 poly (L/DL-lactide) granules. The screws were vacuum dried, bulk packed, and gamma sterilized. Some of the screws were fully immersed in 7.4 pH phosphate buffer solution. The solutions were maintained at 37°C during short term exposure periods that extended to 8 weeks. Non-exposed control samples were stored in sterilized packages until the testing commenced. Stability testing was performed with rigid polyurethane foam to evaluate whether this test material was satisfactory for use in phosphate buffer solution.

Screw pull-out strength was measured in accordance with ASTM F 1691. Shear strength before and after in vitro degradation was analyzed by determining the maximum applied force required to shear the screw shaft when mounted in a specialized test fixture.

Author Information

Disegi, JA
Synthes (USA) Technical Center, West Chester, PA
Dwyer, JW
Synthes (USA) Technical Center, West Chester, PA
Fairer, RE
Synthes (USA) Technical Center, West Chester, PA
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Developed by Committee: F04
Pages: 1–7
DOI: 10.1520/STP15296S
ISBN-EB: 978-0-8031-5444-5
ISBN-13: 978-0-8031-2870-5