In Vitro characterization of low modulus linoleic acid coated strontium-substituted hydroxyapatite containing PMMA...

Current PMMA bone cements used in spinal procedures have high stiffness, which can increase fracture risk in adjacent vertebrae. Traditional porous PMMA variants face issues with particle wear and mechanical degradation. Prior research has shown that high modulus PMMA increases vertebral stiffness, but porous alternatives suffer from performance limitations. This gap motivated a new approach to reduce cement stiffness without compromising strength. No prior work had resolved how to lower modulus while maintaining compressive properties. It was already known that hydroxyapatite can influence cement behavior, but its combination with linoleic acid had not been tested. This study introduces a novel method using strontium-substituted hydroxyapatite and linoleic acid to address these limitations. The aim is to develop a material with reduced stiffness suitable for clinical use in vertebroplasty.

This research aimed to evaluate a new PMMA bone cement formulation using linoleic acid-coated strontium-substituted hydroxyapatite nanoparticles. The specific problem is the high stiffness of conventional PMMA, which increases fracture risk in adjacent vertebrae. The motivation is to create a cement with lower modulus while maintaining mechanical strength. The study focused on how Sr5-HA and linoleic acid affect compressive properties and biocompatibility. Researchers tested compressive strength, modulus, hydrophobicity, injectability, and bioactivity. The goal was to determine if this combination could reduce stiffness without sacrificing performance. This approach could improve outcomes in vertebroplasty procedures. The findings may guide future cement design for spinal applications.

The study used Sr5-HA nanoparticles coated with linoleic acid as a filler in PMMA cement. Linoleic acid was also added as a plasticizer to reduce modulus. Researchers measured compressive strength (UCS) and modulus (Ec) at various filler and acid concentrations. They tested hydrophobicity, injectability, and in vitro bioactivity. Pre-osteoblast cell attachment was assessed using MC3T3-E1 cells. The cement was evaluated at 20 wt% Sr5-HA and 15 v/v linoleic acid. Mechanical properties were compared to standard PMMA. The experimental setup included a controlled incubation period of seven days. Results were analyzed for statistical significance and biological relevance.

At 20 wt% Sr5-HA, UCS decreased from 63 ± 2 MPa to 58 ± 2 MPa, and modulus dropped from 2142 ± 129 MPa to 1785 ± 64 MPa. Adding 15 v/v linoleic acid further reduced UCS to 49 ± 2 MPa and modulus to 774 ± 70 MPa. These values suggest a significant stiffness reduction with minimal strength loss. After seven days, cell attachment on 20 wt% Sr5-HA was 3.73 ± 0.01 x 10⁴, higher than PMMA’s 1.83 ± 0.04 x 10⁴. The linoleic acid addition further reduced cell attachment to 2.27 ± 0.02 x 10⁴. Hydrophobicity and injectability remained within acceptable ranges. These results indicate that the combination of Sr5-HA and linoleic acid effectively lowers modulus. The cement maintains sufficient mechanical strength for clinical use.

The combination of Sr5-HA and linoleic acid in PMMA significantly reduces modulus without major strength loss. This approach may improve vertebroplasty outcomes by lowering fracture risk in adjacent vertebrae. The study shows that 20 wt% Sr5-HA and 15 v/v linoleic acid are effective in stiffness reduction. Cell attachment was higher on Sr5-HA cement than on standard PMMA. These findings suggest the material has potential for clinical use. The researchers propose that this formulation could address current limitations in PMMA bone cements. The results support further investigation into the material’s performance in vivo. This study provides a foundation for developing low-modulus bone cements for spinal procedures.