Long-term performance of a low-modulus acrylic cement in a simulated physiological environment

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Materials Engineering

Background:

• Adjacent fractures after vertebroplasty are linked to the mismatch in elastic modulus between vertebral bone and conventional bone cement.
• This mechanical disparity can necessitate revision surgeries to address new fractures in adjacent vertebrae.

Purpose of the Study:

• To investigate a novel vertebroplasty bone cement formulated with gelatin to better match the mechanical properties of vertebral bone.
• To evaluate the impact of gelatin incorporation on the mechanical performance and durability of acrylic bone cement.

Main Methods:

• Quasi-static compression tests were performed on the bone cement.
• Dynamic mechanical analysis (DMA) was utilized to assess material properties.
• Fatigue tests were conducted to evaluate the cement's performance under cyclic loading.
• Immersion studies in phosphate-buffered saline (PBS) at 37°C were carried out to simulate physiological conditions.

Main Results:

• Compression testing revealed a 33% decrease in elastic modulus after 6 months of immersion in PBS at 37°C.
• Dynamic mechanical analysis confirmed the reduction in elastic modulus and indicated that gelatin and immersion affect the relaxation behavior of the polymethyl methacrylate (PMMA) matrix.
• Fatigue testing demonstrated a characteristic life of at least 24,600 cycles at 7 MPa, both with and without gelatin.
• While compression showed reduced mechanical performance, other tests indicated that gelatin did not significantly compromise the overall properties.

Conclusions:

• The modified bone cement with gelatin exhibits a reduced elastic modulus, addressing the issue of mechanical mismatch with vertebral bone.
• Despite a decrease in elastic modulus, the bone cement retains adequate mechanical integrity for stabilizing vertebrae.
• Gelatin incorporation offers a promising strategy to improve the clinical outcomes of vertebroplasty by minimizing stress shielding and adjacent fractures.