Strain-controlled fatigue of acrylic bone cement

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Mechanical Engineering

Background:

• Acrylic bone cement is widely used in orthopedic surgery, particularly for joint replacements.
• Understanding the mechanical properties of bone cement under physiological conditions is crucial for implant longevity and patient safety.
• Previous research has focused on stress-based parameters, but the role of strain requires further investigation.

Purpose of the Study:

• To investigate the influence of strain versus stress on the monotonic tensile and fatigue failure of wet acrylic bone cement at body temperature.
• To analyze the effect of specimen porosity on the mechanical strength and fatigue life of bone cement.
• To evaluate the utility of Weibull analysis in characterizing bone cement's mechanical behavior for surgical applications.

Main Methods:

• Monotonic tensile and tension-compression fatigue tests were performed on wet acrylic bone cement specimens at 37°C.
• All tests were conducted under strain control at a consistent strain rate of 0.02/s.
• Weibull statistical analysis was applied to the tensile and fatigue test data.

Main Results:

• Monotonic fracture was more strongly governed by strain than by stress, as indicated by Weibull analysis.
• Fatigue failure (number of cycles to failure) was also more dependent on strain amplitude than stress amplitude.
• Specimen porosity distribution significantly influenced both the tensile and fatigue strengths of the bone cement.

Conclusions:

• Strain, rather than stress, is the dominant factor in acrylic bone cement's monotonic and fatigue failure under simulated physiological conditions.
• Porosity is a critical microstructural feature affecting bone cement's mechanical integrity.
• Weibull analysis of fatigue data shows promise for establishing design criteria for the clinical use of bone cement, potentially improving surgical outcomes.