Artificial composite bone as a model of human trabecular bone: the implant-bone interface

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Tribology

Background:

• Artificial bone (Sawbones) is widely used in implant testing for consistency.
• Friction coefficients are crucial for load transfer in uncemented implants.
• Limited data exists comparing friction between human and artificial bone under varying conditions.

Purpose of the Study:

• To compare static and dynamic friction coefficients between artificial and human trabecular bone.
• To evaluate the influence of titanium surface finish, lubrication (wet/dry), and normal stress on friction.
• To assess the suitability of artificial bone in pre-clinical implant load transfer studies.

Main Methods:

• Tested static and dynamic friction coefficients of four titanium surfaces (polished, Al2O3 blasted, plasma sprayed, beaded) on artificial bone (Sawbones) and human trabecular bone.
• Varied normal interface stress (0.25, 0.5, 1.0 MPa) under dry and wet conditions.
• Analyzed friction coefficients using statistical significance (alpha<0.05).

Main Results:

• Friction coefficients were generally lower for artificial bone compared to human bone.
• Dry polished artificial bone surfaces showed significantly lower static friction (20% of human bone).
• Dry beaded artificial bone surfaces showed 42-61% of human bone static friction.
• Dynamic friction differences were less pronounced.
• Normal stress and wet/dry conditions had significant but non-systematic effects.

Conclusions:

• Artificial bone models may not accurately replicate friction characteristics of human bone, particularly for specific surface finishes.
• Pre-clinical implant testing relying on interface load transfer is sensitive to artificial bone's surface properties and lubrication.
• Results suggest caution when extrapolating findings from artificial bone to in vivo scenarios regarding load transfer and mechanical integrity.