Long-term compressive creep deformation and damage in acrylic bone cements

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Materials Science

Background:

• Acrylic bone cements are widely used in orthopedic surgery for fixation.
• Understanding their long-term mechanical behavior, particularly creep, is crucial for patient outcomes.
• In vivo conditions present unique challenges, including sustained loading and physiological environments.

Purpose of the Study:

• To evaluate the compressive creep behavior of commercially available acrylic bone cements.
• To compare the creep resistance of different bone cement formulations.
• To develop and validate a model for predicting creep strain in bone cements.

Main Methods:

• Compressive creep tests were conducted on five acrylic bone cements.
• Tests simulated in vivo loading conditions.
• An empirical creep model (epsilon = a exp(b sigma)tn) was applied and validated.

Main Results:

• Measured creep strains were substantial, often surpassing elastic strains.
• Significant variability in creep response was observed across different cements.
• A carbon-reinforced cement demonstrated markedly higher creep resistance.
• The empirical model predicted creep strains with approximately 10% accuracy.

Conclusions:

• Acrylic bone cements exhibit significant time-dependent deformation under simulated in vivo loading.
• Material composition, particularly carbon reinforcement, greatly influences creep resistance.
• Microscopic analysis indicated cracking as a potential factor in time-dependent failure.
• The developed empirical model offers a reliable tool for predicting bone cement creep.