Mixed-mode failure strength of implant-cement interface specimens with varying surface roughness

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Mechanical Engineering

Background:

• Aseptic loosening at the implant-cement interface is a primary failure mode in joint arthroplasty.
• Traditional testing methods do not fully replicate complex in-vivo functional loading conditions.

Purpose of the Study:

• To determine the strength of the implant-cement interface under mixed-mode tensile and shear loading.
• To investigate the influence of interface roughness on interface strength.
• To develop an interface failure criterion for numerical modeling.

Main Methods:

• Interface specimens with varying roughness (R(a) from 0.89 to 2.76 μm) were tested under mixed-mode loading.
• Polynomial regression was used to model interface strength as a function of loading angle and roughness.
• An interface failure criterion was derived from experimental data.

Main Results:

• Interface strength increased with roughness, ranging from 0.40-1.95 MPa (low roughness) to 4.90-9.90 MPa (high roughness).
• Pure shear strength was substantially higher than pure tension strength.
• A second-order interpolation function accurately described the relationship between strength, loading angle, and roughness (R²=0.85).

Conclusions:

• Interface roughness is a critical factor influencing implant-cement bond strength under complex loading.
• The derived failure criterion and predictive model can enhance numerical simulations of aseptic loosening.
• Findings provide valuable data for designing more robust implant fixation strategies.