PERIPHERAL-TO-CENTRAL TRABECULAR BONE TEXTURE IS ASSOCIATED WITH STRUCTURAL PROGRESSION OF KNEE OSTEOARTHRITIS:...

Bone morphology is increasingly recognized as important in the pathogenesis and progression of OA. Previous studies have shown that medial subchondral trabecular bone texture (TBT) predicts OA progression. However, the predictive validity of peripheral-to-central medial TBT regions as a structural imaging biomarker for radiographic knee OA progression is not clear.

To investigate the predictive validity of longitudinal changes in TBT across peripheral-to-central medial subchondral regions assessed using directional fractal dimensions METHODS: We used data from the MOST (Multicenter Osteoarthritis Study), right knees from the Birmingham, Alabama clinical site at baseline and 60-month follow-up (n = 726). Regions of interest (ROIs) were defined with anatomical landmarks to ensure consistent size and position (Figure 1). Three regions were placed immediately beneath the medial tibial cortical plate, extending from the peripheral medial edge (ROI 1) towards the intermediate (ROI 2) and central medial tibia (ROI 3). For each region, fractal dimensions (FD) along the horizontal (FD_H), vertical (FD_V) and roughest (FD_Sta) directions were calculated. Higher FD values indicate rougher bone texture (i.e., more complex and irregular bone architecture), and the highest value defines FD along the roughest direction. TBT assessments were performed at baseline and 60 months. Knees that remained KL 0/1 at 60-months served as the control group. Comparisons were performed between the control group (n = 474) and knees that progressed from KL 2 to 3 (n = 50), KL 2 to 4 (n = 9), or KL 3 to 4 (n = 56). Differences in mean 60-month FD values between the progression and control groups were assessed using linear regression, adjusted for baseline FD values. Comparisons were based on estimated marginal means with Dunnett adjustment for multiple comparisons.

Results are summarized in Table 1. Vertical FD showed the strongest and most consistent differences between progressor and control knees across ROIs. FD_Sta and FD_V were significantly lower in knees progressing from KL 3 to 4 across all regions, and from KL 2 to 4 in ROI 1 and ROI 2. For KL 2 to 3 progression, FD_V in ROI 2 and ROI 3 and FD_Sta in ROI 3 differed significantly, whereas FD_H was significant only for KL 3 to 4 progression.

The risk of radiographic progression to advanced OA was associated with lower medial trabecular bone texture complexity, with the vertical direction showing the strongest and most consistent differences across all regions. These findings suggest that region-specific directional fractal bone texture analysis may serve as a potential structural imaging biomarker for identifying knees at risk of radiographic OA progression.