Material properties of articular cartilage in the rabbit tibial plateau

Abstract

The material properties of articular cartilage in the rabbit tibial plateau were determined using biphasic indentation creep tests. Cartilage specimens from matched-pair hind limbs of rabbits approximately 4 months of age and greater than 12 months of age were tested on two locations within each compartment using a custom built materials testing apparatus. A three-way ANOVA was used to determine the effect of leg, compartment, and test location on the material properties (aggregate modulus, permeability, and Poisson's ratio) and thickness of the cartilage for each set of specimens. While no differences were observed in cartilage properties between the left and right legs, differences between compartments were found in each set of specimens. For cartilage from the adolescent group, values for aggregate modulus were 40% less in the medial compartment compared to the lateral compartment, while values for permeability and thickness were greater in the medial compartment compared to the lateral compartment (57% and 30%, respectively). Values for Poisson's ratio were 19% less in the medial compartment compared to the lateral compartment. There was also a strong trend for thickness to differ between test locations. Similar findings were observed for cartilage from the mature group with values for permeability and thickness being greater in the medial compartment compared to the lateral compartment (66% and 34%, respectively). Values for Poisson's ratio were 22% less in the medial compartment compared to the lateral compartment.

Fig. 1

Materials testing system: (A) schematic of creep test setup, (B) Interchangeable positioning guide consisting of a translucent, collecting platform with a pinhole.

Fig. 2

Locations of testing sites on the tibial plateau.

Fig. 3

Force vs. displacement graph for needle probe test. The measured thickness was determined from the point of contact between the needle probe and cartilage surface (deviation from zero slope) until reaching the tidemark (inflection point before a rapid increase in load).

Fig. A1

The filtered data (+) is weighted towards the initiation of the test load. The unfiltered data is shown as a solid line (—).