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Predicting Tibial Subchondral Bone Stiffness in Osteoarthritis

By AnalyzeDirect Staff, last updated March 17, 2016

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OsteoarthritisOsteoarthritis is a progressive degenerative joint disorder seen especially among older people that mostly affects cartilage, the tissue that covers the ends of bones forming a joint. Healthy cartilage allows bones to glide over one another and absorbs energy from the shock of physical movement. In osteoarthritis, cartilage breaks and wears away, allowing the bones under it to rub against each other. This causes pain, swelling, and loss of motion of the joint which, over time, may lose its normal shape.

Although osteoarthritis has long been viewed as a primary disorder of articular cartilage, the role of subchondral bone in the progression of this disorder is attracting increasing attention. In fact, structural stiffness of subchondral bone has been shown to aggravate cartilage shear stresses, contributing therefore to the pathogenesis of osteoarthritis.

To better understand subchondral bone alterations in this condition, scientists from the University of Saskatchewan, Canada, combined in situ macro-indentation testing and quantitative computed tomography (QCT). From QCT-scans of 13 proximal tibial compartments, Analyze software was used to segment the bony region from surrounding materials and extract the outer surface of each sample. CT grayscale intensity values were then converted to bone mineral density (BMD) values. The team then used different combinations of density-modulus equations (E-BMD) to derive local subchondral bone structural stiffness from BMD. Finally, they compared the results of the equations with the values obtained from in situ macro-indentation testing, a technique that combines compressive indentation with iterative milling to characterize subchondral bone stiffness.

The group was able to find two combinations of E-BMD equations that led to lower differences between predicted and experimentally measured stiffness. Although further investigation is warranted in order to improve density-stiffness relationship, findings from this study offer insight into a novel, non-invasive method that can be used to monitor subchondral bone alterations in subjects with osteoarthritis.

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