BIOMECHANICAL PROPERTIES OF HIP CARTILAGE IN EXPERIMENTAL ANIMAL-MODELS

The material properties of normal adult articular cartilage were deter mined in the femoral head and acetabulum of baboons, dogs, and bovines , and were compared with those of normal human hip cartilage, In situ creep and recovery indentation experiments were performed using an aut omated creep indentation apparatus, To curvefit the entire creep curve , a numerical algorithm based on biphasic finite element methods and n onlinear optimization was developed, This effort represents the first successful use of 100% of the creep indentation curve to obtain the me chanical properties of normal articular cartilage, The results show th at material properties of articular cartilage exhibit significant topo graphical variations in the femoral head and acetabulum, and between t hese two bone structures, Furthermore, significant differences exist i n the mechanical properties of hip cartilage among the 4 species, Spec ifically, in all species the smallest aggregate modulus is found in th e inferior aspect of the femoral head. Among all species, human hip ca rtilage is the stiffest in all test sites; bovine tissue is the softes t, Human tissue has the smallest Poisson's ratio and permeability in a ll test sites, The aggregate modulus of human hip cartilage is closely resembled by that of baboon hip cartilage, Anatomically, canine and b aboon hips exhibit similar characteristics to the human hip joint; the bovine hip joint is distinctly different, Based on this study's data, the baboon represents the most appropriate animal model of normal hum an hip articular cartilage.