ENERGY ABSORBING ABILITY OF ARTICULAR-CARTILAGE DURING IMPACT

Samples (48) of 9 mm diameter articular cartilage and associated subchondral bone from the tibial plateau of human knee joints were mounted in methylmethacrylate cement and subjected to controlled impact velocities. The controlled velocities provided for the testing of 21 samples at a strain rate of 500 s-1 and 27 samples at a strain rate of 100 s-1. Data are presented on the energy absorption per unit volume of cartilage in relation to the associated stresses and strains. The data in each of the resultant 9 graphs are subjected to a least squares fit to the polynomial Y = a1X + a2X2. The relevant statistical data for each of the strain rates and for the combined data are presented. While the total energy absorption of the articular cartilage of the knee joint at ambulatory stresses of 0.8-6.3 N/mm2 is calculated to be no more than 0.13-3.65 J, it is suggested that the compliance of the cartilage of the knee joint together with the incongruity of the tibia and femur are essential features that should be considered in the design of total knee-replacement prostheses.