Comparison of human and animal femoral head chondral properties and geometries.

Investigations into tissue-preserving orthopaedic treatments should consider the tribology of articular cartilage; where simulations using animal joints are a predominant choice. However, very few studies have investigated the differences between human and animal cartilage. The aim of the present study was to characterise the differences in geometry and mechanical properties of human, porcine, bovine and ovine articular cartilage. Creep indentation was performed on osteochondral plugs taken from the superior region of femoral heads of all these species. Cartilage thickness was measured via the resistive force change of a needle descending through cartilage and bone. A biphasic finite element model was used to derive equilibrium elastic modulus and permeability. Results showed that human cartilage was significantly thicker than all other species tested. A positive correlation was found between femoral head diameter and cartilage thickness when comparing between species of quadrupeds. Human cartilage had the largest equilibrium elastic modulus, which was significant when comparing against porcine and bovine. However, porcine cartilage had significantly lower permeability. Significant differences in geometry and mechanical properties of articular cartilage were found between all species tested. It is necessary to consider these variations when choosing animal tissue to represent human.