371 MRI-BASED CARTILAGE THICKNESS LOSS AND JOINT SPACE NARROWING IN AN OAI CORE PROGRESSION SAMPLE, AND THEIR RELATIONSHIP WITH AGE, SEX, AND BMI

Abstract

Purpose: Recent evidence suggests that peri-articular bone changes are integral to knee osteoarthritis (OA) pathophysiology. Peri-articular trabecular morphology changes have been associated with radiographic knee OA severity and may identify individuals at risk for knee OA progression. However, it is unclear how patient characteristics are associated with peri-articular trabecular morphology in knees with OA. The purpose of this study was to evaluate the association between patient characteristics and trabecular morphology in knees with OA. Methods: The sample comprised a convenience sample of 337 participants in the Osteoarthritis Initiative (OAI) progression cohort who at the 30or 36-month OAI visit had 3-tesla magnetic resonance imaging that included coronal 3D Fast Imaging with Steady State Precession (FISP) trabecular morphometry sequences. We used a trabecular morphometry program with a modified algorithm (calcDCN, University of CaliforniaSan Francisco) to evaluate 4 peri-articular trabecular morphology measures: bone volume fraction (BVF), trabecular number (tb.n), spacing (tb.sp), and thickness (tb.th). The four measures were calculated for 20 consecutive central slices within a 15mm x 3.75mm region of interest placed in the peri-articular medial tibia and then averaged. Intratester reproducibility was high (ICC = 0.99). The association between demographic data or knee-specific data (from the 24-month OAI visit) and trabecular morphometry were evaluated with independent sample t-tests or Wilcoxon rank-sum tests (when applicable) and Spearman correlations. Among a subset of 285 patients with 24-month joint space narrowing (JSN) scores, four forward-selection multiple linear regression models were used to further evaluate the associations between patient characteristics and each trabecular morphometry measure. Results: Participants were 66±9 years of age, body mass index 29.6±4.8 kg/m, and 50% female. Peri-articular trabecular morphometry was averaged (± standard deviation) for the cohort: BVF = 0.12±0.08, tb.sp = 1.53±1.25mm, tb.n = 0.86±0.39mm−1, and tb.th = 0.13±0.03mm. Peri-articular trabecular morphometry was not significantly different (p > 0.05) between participants with or without college degrees (n = 208, n = 127; respectively), with or without history of smoking (n =147, n = 188; respectively), and with or without knee symptoms at the 24month OAI visit (n = 191, n = 145; respectively). Many variables were associated with trabecular morphometry (see table). Age correlated with BVF (r = −0.16), tb.n (r = −0.18), and tb.sp (r = 0.17), but not tb.th (r = −0.08). Body mass index also correlated with BVF (r = 0.12), tb.n (r = 0.14), and tb.sp (r = −0.14), but not tb.th (r = 0.07). The 400-meter walk time (24-month visit) was related to tb.sp (r = 0.12). In multiple linear regression models, the presence of medial JSN and female gender were associated with all 4 trabecular morphometry measures. Three patient characteristics were associated with select measures: age (associated with tb.sp, tb.n), history of knee injury/surgery (associated with BVF, tb.th), and race (associated with tb.th).