Sensitivity of cartilage mechanical behaviour to spatial variations in material properties

Area of Science:

• Biomechanics
• Biomaterials Science
• Orthopedics

Background:

• Articular cartilage exhibits spatially varying material properties influencing its mechanical behavior.
• Osteoarthritis (OA) involves complex changes in cartilage structure and mechanics.

Purpose of the Study:

• To develop a mathematical model of articular cartilage under confined compression, accounting for spatial property variations.
• To adapt the model for both healthy and osteoarthritic (OA) cartilage, identifying key mechanisms of mechanical response.

Main Methods:

• Developed a 1D confined compression model for normal and OA cartilage, incorporating spatial material property variations.
• Performed global sensitivity analysis on model parameters under static and dynamic loading conditions.

Main Results:

• Identified distinct dominant parameters for static vs. dynamic loading and healthy vs. OA cartilage.
• Predicted that OA-induced changes, like increased superficial zone permeability and reduced fixed charge, amplify sensitivity to stiffness alterations.
• Showed that superficial zone stiffness is particularly critical for cartilage deformation in OA.

Conclusions:

• Cartilage mechanical response is contingent on loading conditions and tissue health (normal vs. OA).
• Degenerative changes in superficial zone stiffness are amplified by other OA disease elements.
• This provides a mechanism-based explanation for the overlap in mechanical parameters between normal and OA cartilage.