Microarchitectural Adaptations of Primary Osteoarthrotic Subchondral Bone

Abstract

Interest in the concept of bone quality has increased recently, with new imaging techniques and computer modeling abilities capable of assessing bone microarchitecture and bone strength. These novel imaging methods have enabled a detailed and versatile quantification of three-dimensional microarchitecture of bone tissue. Osteoarthrosis (OA) has an unclear pathogenesis and is one of the commonest agerelated degenerative joint disease. Little is known about microarchitectural changes in human early OA. Difficulty in obtaining cartilage-bone samples for research in human OA has stimulated the development of animal models. In this chapter, an intensive investigation of the subchondral microarchitectural adaptations of human early OA and primary guinea pig OA is presented. Human early OA subchondral cancellous bone was shown to be significantly thicker and markedly plate-like, but weaker in mechanical properties. The increased trabecular thickness and density but relatively decreased connectivity indicated a mechanism of early-stage OA bone remodeling: a process of filling trabecular remodeling cavities. This process led to a progressive change of trabeculae from rod-like to more plate-like, opposite to that of normal aging. Guinea pig OA subchondral plate was shown to have a markedly increased volume fraction and thickness prior to OA initiation. Subchondral cancellous bone displayed a significant decreased volume fraction in the early stage, but increased volume fraction and trabecular thickness with age, and changing from a rod-like to typical plate-like structure with advancing OA. Subchondral cortical bone had an increased cross-sectional area in severe stage OA. This suggested that a significant microarchitectural adaptation followed by bone matrix density changes resulted in changed mechanical properties and hence decreased bone quality.