EXPLORING GENDER‐DEPENDENT DIFFERENCES IN PATTERNS OF CARTILAGE LOSS USING RESPONSIVENESS HEAT MAPS: DATA FROM THE OAI

Abstract

Understanding gender-specific differences in patterns of cartilage loss can improve our knowledge of the pathogenesis of knee osteoarthritis (KOA) development and progression and may inform clinical trials of treatments for KOA. Quantitative cartilage assessment using segmentation software offers an ideal method for appreciating these patterns. The goal of our study was to examine gender differences in patterns of cartilage loss in the central weight-bearing regions of the medial femur (MF), lateral femur (LF), medial tibia (MT), and lateral tibia (LT) using cartilage segmentation software. We measured cartilage volume change in the indexed knee of 480 subjects with Kellgren-Lawrence (KL) 2 and 3 from the OAI at the baseline (BL) and 96-month (mo) time points using the local area cartilage segmentation (LACS) method. Briefly, the LACS method uses robust coordinate systems fixed to anatomical landmarks to find the cartilage volume or thickness in consistent sub-regions on each cartilage plate. (See Figure 1.) Using the coordinate systems, LACS permits assessment of change in much smaller sub-regions through the use of responsiveness heat maps. The average age, BMI, and KL score were 59.5years, 28.7kg/m 2 , 2.03 (males) and 60.5years, 28.8kg/m 2 , 1.99 (females). Figure 2 shows heat map images of the change in cartilage volume from BL to 96mo for males and females. The intensity of the colors (red for loss, blue for gain) represents the standardized response mean (SRM) value at each location. We observed more focused thinning for females in the lateral/posterior portion of the MF and the medial side of the LT. An increase in cartilage thickness in the posterior side of the LF sub-region was also observed for females, as shown with the blue area. Similar patterns were observed for other follow-up time points (i.e., BL to 24mo, BL to 48mo, and BL to 72mo) and when stratifying by age, BMI and KL score. Heat maps of smaller subregions were capable of illustrating gender-specific differences in patterns of cartilage loss, differences that may offer insight into the variation of gender differences in the natural history of KOA. Heat maps of cartilage thickness changes may be useful in evaluating the benefit of interventions for KOA. NIH AR071409 none CORRESPONDENCE ADDRESS: jduryea@bwh.harvard.edu .