Multiparametric 3-D analysis of bone and joint space width at the knee from weight bearing computed tomography.

Objective: Computed tomography (CT) can deliver multiple parameters relevant to osteoarthritis. In this study we demonstrate that a 3-D multiparametric approach at the weight bearing knee with cone beam CT is feasible, can include multiple parameters from across the joint space, and can reveal stronger relationships with disease status in combination. Design: 33 participants with knee weight bearing CT (WBCT) were analysed with joint space mapping and cortical bone mapping to deliver joint space width (JSW), subchondral bone plate thickness, endocortical thickness, and trabecular attenuation at both sides of the joint. All data were co-localised to the same canonical surface. Statistical parametric mapping (SPM) was applied in uni- and multivariate models to demonstrate significant dependence of parameters on Kellgren & Lawrence grade (KLG). Correlation between JSW and bony parameters and 2-week test-retest repeatability were also calculated. Results: SPM revealed that the central-to-posterior medial tibiofemoral joint space was significantly narrowed by up to 0.5 mm with significantly higher tibial trabecular attenuation up to 50 units for each increment in KLG as single features, and in a wider distribution when combined (p<0.05). These were also more strongly correlated with worsening KLG grade category. Test-retest repeatability was subvoxel (0.37 mm) for nearly all thickness parameters. Conclusions: 3-D JSW and tibial trabecular attenuation are repeatable and significantly dependent on radiographic disease severity at the weight bearing knee joint not just alone, but more strongly in combination. A quantitative multiparametric approach with WBCT may have potential for more sensitive investigation of disease progression in osteoarthritis.