Bioresorbable High-Strength HA/PLLA Composites for Internal Fracture Fixation

Area of Science:

• Biomaterials Science
• Materials Engineering
• Orthopedic Surgery

Background:

• Internal fixation plates are crucial in fracture treatment.
• Current hydroxyapatite/poly(L-lactide) (HA/PLLA) composites have inadequate mechanical properties for clinical use.
• The pressure-induced flow (PIF) technique offers a potential solution to enhance composite performance.

Purpose of the Study:

• To improve the mechanical properties of HA/PLLA composites using the PIF technique.
• To evaluate the suitability of PIF-processed HA/PLLA composites as internal fixation plates.

Main Methods:

• HA/PLLA composites were processed using the pressure-induced flow (PIF) technique under optimal conditions (140 °C, 250 MPa).
• Mechanical properties including flexural strength, tensile strength, and notched Izod impact strength were measured.
• Crystallinity, crystal orientation, and glass transition temperature were analyzed.
• In vitro degradation studies were conducted over 2 months.

Main Results:

• PIF processing significantly enhanced HA/PLLA composites, achieving a flexural strength of 199.2 MPa, comparable to human cortical bone.
• Tensile strength reached 84.2 MPa and notched Izod impact strength was 16.7 kJ/m².
• PIF processing led to multi-level stacked crystal layers, increasing crystallinity (53.1%), crystal orientation (81.6%), and glass transition temperature (78.8 °C).
• After 2 months of degradation, composites retained substantial flexural strength (135.3 MPa).

Conclusions:

• The PIF technique effectively enhances the mechanical properties of HA/PLLA composites.
• The improved HA/PLLA composites demonstrate potential for use as internal fixation plates in orthopedic surgery.
• The enhanced material properties address current clinical limitations in fracture treatment.