Dynamic mechanical behavior of PMMA based bone cements in wet environment

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Materials Science

Background:

• Bone cements are crucial for orthopedic prostheses, interfacing bone with metal implants.
• Understanding their mechanical and viscoelastic properties is vital for implant longevity and patient outcomes.
• Variations in cement conditioning can significantly impact performance.

Purpose of the Study:

• To investigate the mechanical and viscoelastic properties of three commercial bone cements: Braxel, Simplex-P, and CMW1-G.
• To evaluate the influence of specimen conditioning (water uptake, heat treatment) on these properties.
• To determine the suitability of these bone cements as interlayers between bone and metal implants.

Main Methods:

• Mechanical testing using stress relaxation and dynamic mechanical analysis (DMA).
• Three-point bending method (ASTM D790) employed for loading geometry.
• Tests conducted in a water chamber with temperature sweeps (17-57°C) and across four frequency decades.

Main Results:

• Viscoelastic properties are highly sensitive to specimen conditioning, including water uptake and heat treatment.
• The mechanical properties of the tested bone cements are intermediate between cancellous bone and implant metals.
• Dynamic mechanical analysis revealed an increased damping factor (tan delta) at body temperature, indicating enhanced shock absorption capabilities, particularly at higher loading frequencies.

Conclusions:

• Bone cements exhibit viscoelastic properties influenced by conditioning, necessitating standardized preparation protocols.
• Their intermediate mechanical profile effectively mitigates stress concentrations at the bone-implant interface.
• The tested bone cements demonstrate valuable shock-absorbing characteristics at physiological temperatures, enhancing implant performance.