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Hydroxyapatite Whisker Reinforced Polyetherketoneketone Bone Ingrowth Scaffolds

Hydroxyapatite (HA) whisker reinforced polyetherketoneketone (PEKK) bone ingrowth scaffolds were prepared and characterized. High levels of porosity (75-90%) and HA whisker reinforcement (0-40 vol%) were attained using a powder processing approach to mix the HA whiskers, PEKK powder and a NaCl porogen, followed by compression molding at 350-375°C and particle leaching to remove the porogen. The scaffold architecture and microstructure exhibited characteristics known to be favorable for osteointegration. Scaffold porosity was interconnected with a mean pore size in the range 200-300 μm as measured by micro-computed tomography (micro-CT). HA whiskers were embedded within and exposed on the surface of scaffold struts, producing a micro-scale surface topography, shown by von Kossa staining and scanning electron microscopy (SEM).

Strontium-Containing Hydroxyapatite/Polyetheretherketone Composites

Strontium-containing hydroxyapatite/polyetheretherketone (Sr-HA/PEEK) composites were developed as alternative materials for load-bearing orthopaedic applications. The amount of strontium-containing hydroxyapatite (Sr-HA) incorporated into polyetheretherketone (PEEK) polymer matrix ranged from 15 to 30 vol% and the composites were successfully fabricated by compression molding technique. Strontium, in the form of strontium-containing hydroxyapatite (Sr-HA), was confirmed to enhance bioactivity in the PEEK composites.

Biomechanical Evaluation and Comparison of a PEEK Rod System to Traditional Ti Rod Fixation

PEEK lumbar fusion rods have recently become available for use in posterior lumbar fusion procedures. In this study, researchers from Jefferson and DePuy Spine performed biomechanical testing to evaluate PEEK rods in compressive bending and torsion. The rods were fabricated from an image-contrast grade of PEEK (6% BaSo4). Because of the flexibility of the PEEK rods, an angular displacement control variant of F1717 fatigue testing was performed in parallel with biomechanical studies in a cadaver model. PEEK rods provided comparable stability to titanium rods of equivalent diameter in cadaveric testing. Mechanical testing suggested that PEEK rods can withstand far beyond the angular displacements suggested by cadaveric testing and that of normal physiologic range of motion.

Load Sharing, Bone Screw Interaction and Stress in CFR-PEEK Lumbar Spine Constructs

The aim of this study is to develop a refined block fixation FE model to investigate the load sharing, bone screw interaction, and stresses and strains in a CFR PEEK lumbar spine construct. The results of this FE study indicate that for the Ti and CFR-PEEK screw, the disc expierences the least strain with the Ti rod and the greatest strain with the PEEK rod. Due to its enhanced mechanical strength, the CFR-PEEK rod sustained comparable loads compared with the Ti rod and experienced less deformation than the PEEK rod.

2009 SFB Workshop Invited Presentation: Incorporating Hydroxyapatite and Porosity in PEEK for Orthopaedic and Spine Applications

Ryan Roeder from the University of Notre Dame has reviewed the techniques of incorporating HA and porosity into PEEK for orthopedic and spinal applications. Bioactivity has been conferred to PEEK by the incorporation of calcium phosphate, typically hydroxyapatite (HA) but also Bioglass and tricalcium phosphate, as a coating or filler. Coatings have been applied directly using plasma spray or indirectly using surface treatment to induce apatite deposition in simulated body fluid. A larger number of investigations have studied the use of calcium phosphate fillers to reinforce PEEK. PEEK biomaterials offer a wide variety of opportunities for basic research and product development, which span across materials processing, nano- and microstructural characterization, surface engineering, mechanical behavior, implant design and osteointegration.

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