Characterization of Hydroxyapatite Whisker Reinforced Composites and Scaffolds for Mechanical and Biological Function in Orthopaedic and Spinal Implants

Doctoral Dissertation

Abstract

The overall objective of this study was to investigate the mechanical and biological properties of HA whisker reinforced polyaryletherketone (PAEK) composites and scaffolds which are key to clinical translation for orthopedic and spinal implants. The fatigue behavior of polyetherketoneketone (PEKK) reinforced with 0, 20, and 40 vol% hydroxyapatite (HA) was investigated in four-point bending fatigue. The fatigue life decreased with increasing HA reinforcement. However, PEKK reinforced with 40 vol% HA whiskers exhibited a fatigue life greater than 2⋅106 cycles at 40 MPa. Moreover, HA whisker reinforcement resulted in decreased creep deformation and minimal modulus degradation.

The effects of the mold temperature and polyetheretherketone (PEEK) powder were investigated on the mechanical properties and crystallinity of HA whisker reinforced PEEK scaffolds prepared using compression molding and porogen leaching. The mechanical properties of the scaffolds increased while the PEEK crystallinity decreased, with increasing mold temperature and suggested an optimal mold temperature of 370-375å¡C for PEEK scaffolds comprising of 75% porosity and 20 vol% HA whisker reinforcement, regardless of the PEEK powder size.

The effects of the porogen morphology on the architecture, mechanical properties, and permeability of HA whisker reinforced PEEK scaffolds were investigated in 75 – 90% porous scaffolds. HA whisker reinforced PEEK scaffolds prepared with an ellipsoidal porogen exhibited a greater permeability than scaffolds prepared with a cubic porogen. The compressive modulus, yield strength, and yield strain were not affected by the porogen morphology.

The effects of HA reinforcement morphology and content was investigated on the behavior of primary osteoblasts on dense HA reinforced PEEK substrates in vitro. At day 7, the number of osteoblasts attached to PEEK substrate surfaces increased with increasing HA content and for HA whiskers compared to equiaxed HA powder reinforcement. This suggests that the HA reinforcement content morphology can promote cellular attachment and proliferation at early time points.

Attributes

Attribute NameValues
URN
  • etd-12062012-153723

Author Timothy Lee Conrad
Advisor Ryan Roeder
Contributor Diane Wagner, Committee Member
Contributor Ryan Roeder, Committee Chair
Contributor Glen Nieber, Committee Member
Contributor Paul McGinn, Committee Member
Degree Level Doctoral Dissertation
Degree Discipline Bioengineering
Degree Name PhD
Defense Date
  • 2012-10-23

Submission Date 2012-12-06
Country
  • United States of America

Subject
  • polyetheretherketone

  • bone mimetic

  • porogen morphology

  • interbody spinal fusion cage

  • hydroxyapatite

  • composite scaffold

Publisher
  • University of Notre Dame

Language
  • English

Record Visibility and Access Public
Content License
  • All rights reserved

Departments and Units

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