Preparation and Characterization of Injectable Brushite Filled-Poly (Methyl Methacrylate) Bone Cement

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Materials Science

Background:

• Poly (methyl methacrylate) (PMMA) bone cements are standard in orthopedics but lack bioactivity.
• Previous attempts to add calcium phosphates (e.g., hydroxyapatite, brushite, tricalcium phosphates) to bone cements resulted in poor handling and mechanical properties.
• There is a need for bioactive bone cements with improved rheological properties and mechanical performance for enhanced osseointegration.

Purpose of the Study:

• To design and characterize a novel two-solution bone cement system incorporating brushite fillers.
• To evaluate the impact of brushite addition on the cement's rheological behavior, handling properties, void-filling capacity, and mechanical strength.
• To identify an optimal brushite concentration for a balance of injectability, viscosity, and load-bearing capability.

Main Methods:

• Preparation of two-solution bone cements with varying concentrations of brushite fillers.
• Rheological characterization, including complex viscosity and extrusion stress measurements.
• Assessment of handling properties, such as clumping tendency during injection.
• Evaluation of void-filling extent in bone analog specimens.
• Determination of compressive strength.

Main Results:

• Brushite addition did not alter the pseudoplastic behavior or handling properties of the cement.
• Extrusion stress was comparable to or lower than control PMMA cements across brushite concentrations.
• The brushite-filled cements effectively filled pre-formed voids in bone analog specimens.
• Compressive strength decreased with increasing brushite content, but remained adequate for load-bearing applications.
• A 40% mass concentration of brushite offered the best overall balance of properties.

Conclusions:

• Partially substituting PMMA with brushite in a two-solution cement system is a viable strategy to enhance bioactivity without compromising critical handling and mechanical properties.
• The developed brushite-modified cement demonstrates potential for applications requiring high injectability and viscosity, such as spinal fracture treatment and bone defect repair.
• This alternative cement formulation represents a promising advancement in the development of bioactive orthopedic materials.