KNEE B-SCORE SHAPE FROM COMPUTED TOMOGRAPHY IS ASSOCIATED WITH SUBCHONDRAL BONE ATTENUATION AND MARGINAL CORTICAL BONE THICKNESS

Change in shape of the distal femur demonstrated with MRI is an established biomarker for structural OA progression in clinical trials. This “B-score” has been ported across to CT with minimal bias, which brings the opportunity to include 3-D evaluation of periarticular bone distribution in shape analysis by combining statistical shape modelling (SSM) and cortical bone mapping (CBM). To look for significant relationships between 3-D knee shape and bone distribution with CT. This exploratory analysis was performed ancillary to the LOSEIT trial evaluating the efficacy of liraglutide in inducing and maintaining weight loss and pain relief in overweight patients with knee OA. After exclusions, 133 participants were included, 65 from the placebo group, 68 from the liraglutide group. All had baseline CT (140kV) and weight-bearing radiographs of both knees. Both knees were segmented from the CT data for CBM using Stradview followed by registration of canonical objects to femurs and tibias using wxRegSurf. SSM was performed on combined femur and tibia registrations using MATLAB 2024a. Index knee data were taken from each participant. Generalized estimating equation (GEE) analysis looked for associations of the first 10 shape modes with KLG controlling for age, sex and mass using Bonferroni correction. 3-D cortical thickness (CTh) and subcortical trabecular attenuation (TA) maps were transferred to the canonical objects. SPM analysis was performed using the MATLAB Surfstat toolbox to establish dependence of CTh and TA distribution on shape controlling for age, sex, mass and KLG. Study participants were 89 females and 44 males with mean +/- SD age of 59.6 +/- 9.2 yrs, mass 93.3 +/- 16.7 kg and an index knee breakdown of KLG1 = 19, KLG2 = 57, KLG3 = 57. GEE showed shape mode 2 (SM2) was the only mode significantly associated with KLG with an odds ratio of 1.43 (1.28-1.59 95% CI, P