The Energy-Absorbing Function of Cancellous Bone and Its Influence on the Loosening of Artificial Joints

Abstract

Deformation behavior of trabecular architecture (cancellous structure) was visualized using an ultrahigh-speed video recording camera during both static and impact compression tests of subchondral cancellous bone at nominal strain rates from 0.008 to 25 s−1. The mechanical energy-absorbing mechanisms of cancellous bone could be roughly classified into two types: viscoelastic hysteresis and release of elastic energy from microfractures of the trabeculae. The energy-absorbing ability of degenerated cancellous bone was approximately 50% that of normal bone. The osteoarthritic process results in a change in the cancellous structures such that a pronounced fabric direction is not evident. In the case of normal cancellous bone, the structural stiffness of the bone was maintained by each trabecula functioning as a long column in the cancellous structure. It was confirmed visually that, for the in vitro case, aseptic loosening of the prosthesis was caused by a decrease in the cancellous bone stock or reduction in the energy-absorbing abihty of the joints. Thus, the energy-absorbing properties of subchondral cancellous bone were dependent on the morphology and deformability of the cancellous structure.