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Microstructural pathway of fracture in poly(methyl methacrylate) bone cement
L D Topoleski1, P Ducheyne, J M Cuckler
1Department of Bioengineering, University of Pennsylvania, Philadelphia 19104.
Biomaterials
|December 1, 1993
Summary
Understanding poly(methyl methacrylate) bone cement fracture is key to joint prosthesis longevity. Microcracks in the interbead matrix, not the beads, cause fatigue failure, suggesting targeted material improvements.
Area of Science:
- Biomaterials Science
- Orthopedic Engineering
- Polymer Chemistry
Background:
- Mechanical failure of poly(methyl methacrylate) (PMMA) bone cement contributes to total joint prosthesis failure.
- Understanding fracture resistance mechanisms is crucial for minimizing cement failure.
Purpose of the Study:
- To investigate the material characteristics controlling fracture resistance in PMMA bone cement.
- To analyze the distinct fracture mechanisms under fatigue and rapid crack propagation.
Main Methods:
- Gel permeation chromatography (GPC) to determine molecular weight (MW) distributions of polymer phases.
- Mechanical testing, scanning electron microscopy (SEM), and light microscopy to analyze fracture.
- Identification of four key phases: pre-polymerized beads, interbead matrix, BaSO4, and porosity.
Main Results:
- Fatigue crack propagation involves microcracks forming in the interbead matrix, distinct from rapid crack propagation.
- Rapid fracture shows craze formation on beads, absent in fatigue fracture surfaces.
- GPC analysis revealed increased MW in the interbead matrix compared to bead polymer, with bulk MW < 1 x 10(6).
Conclusions:
- Microcracks preferentially grow within the interbead matrix, likely due to BaSO4 presence, curing shrinkage, and differing polymerization processes.
- The higher molecular weight of the interbead matrix may influence crack propagation pathways.
- Findings provide insights into PMMA bone cement failure mechanisms, guiding future material design for enhanced prosthesis durability.