Effect of hydroxyapatite concentration on high-modulus composite for biodegradable bone-fixation devices

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Polymer Science

Background:

• Over 3 million bone fractures occur annually in the US, with many requiring internal fixation.
• Current metal fixation devices cause stress shielding and metal ion leaching.
• There is a need for advanced biodegradable materials for bone fracture repair.

Purpose of the Study:

• To develop a biodegradable composite with high modulus and toughness for bone fixation.
• To address limitations of current metal implants like stress shielding and ion leaching.
• To create a material that mimics the mechanical properties of cortical bone.

Main Methods:

• Utilized long-fiber poly-l-lactic acid (PLLA) with a polycaprolactone (PCL) and hydroxyapatite (HA) nano-rod matrix.
• Fabricated composite samples via dip coating PLLA fibers in PCL/HA suspension and hot pressing.
• Conducted single fibril tensile tests and flexural mechanical testing.

Main Results:

• PLLA fibers exhibited a Young's modulus of 8.09 GPa.
• Synthesized HA nanorods had nanoscale dimensions with an aspect ratio > 6.
• Composite samples achieved a flexural modulus up to 9.2 GPa and flexural strength up to 187 MPa.
• The composite's mechanical properties fall within the range of cortical bone.
• Samples demonstrated toughness without catastrophic failure after testing.

Conclusions:

• The developed PLLA/PCL/HA composite shows promising mechanical properties for bone fixation applications.
• The material's properties align with cortical bone, suggesting it as a viable alternative to metal implants.
• The biodegradable nature and mechanical integrity indicate potential for improved bone healing and reduced complications.