Abstract
Introduction
Osteoarthritis continues to be a major cause of pain and disability. The pathological processes leading to the end-stage of joint degeneration remain poorly understood. Advances in radiological imaging have the potential to improve understanding of the structural and functional changes observed in OA. The aim of this study was to describe the microarchitecture of the femoral head in osteoarthritis.
Methods
Twenty osteoarthritic femoral heads underwent micro-computed tomography scanning at 30µm. Four parameters of micro-architecture and structure were determined: bone volume ratio (BV:TV), trabecular thickness, structural model index and degree of anisotropy. The femoral head was divided into 27 cubic volumes of interest. Analysis of variance (ANOVA) was used to assess differences between regions. Cystic and sclerotic changes were assessed qualitatively.
Results
There was marked heterogeneity in the density and architecture throughout the head. The greatest density and trabecular thickness was found in a central core that extended from the medial calcar to the physeal scar (ANOVA p< 0.001). This region also correlated with the greatest degree of anisotropy (DA=2.4, p< 0.001), plate-like trabeculae (SMI=−0.22, p< 0.001). All osteophytes exhibited a radially orientated trabecular pattern, in close relation to the superior and inferior nutrient foramina in the region of the physeal scar. Cartilage eburnation was associated with loss of the normal subchondral structure of radially-orientated trabeculae and replacement by thickened lamellar bone.
Discussion
This study demonstrated marked structural heterogeneity at the 30 µm resultion and the micro-architectural changes associated osteophytes, cysts and sclerosis. The elucidation of the osseous microstructure can clarify the interaction between geometry and function in OA. Further work is necessary to relate this to underlying pathogenic process to determine the temporal sequence of microarchitectural changes.
