Since it is largely automated and uses unambiguous anatomical landmarks, the new method is highly reproducible and can be made on a standard posteroanterior (PA) knee radiograph by a relatively unskilled reader.

OBJECTIVE To assess the responsiveness and reader time of a novel semi-automated tool to detect knee cartilage loss over two years in subjects with knee OA. METHODS 122 subjects from the OAI Progression Cohort were selected. A reader used the software method to segment cartilage on DESS scans in the medial compartment of the femur from the baseline and 24-month visits. Change in cartilage volume (ΔV) was measured at a fixed weight-bearing (WB) location with respect to the three-dimensional coordinate system based on cylindrical coordinates. Change was measured for five regions of varying WB surface area centered on the fixed point. The average change (ΔV), the standard deviation (SD) of ΔV and the standardized response mean (SRM) are reported. RESULTS The SRM value was −0.52 for the largest region and decreased in magnitude as smaller regions of cartilage were probed. The average evaluation time was less than 20 minutes per knee compartment, split approximately evenly between a technician and a trained reader. CONCLUSION The results establish that measurement of cartilage loss in a local region can be done efficiently and that the resultant measures are responsive to loss of cartilage over time. The coordinate system can potentially be used to objectively examine and establish a consistent location for all knees that is most responsive to change in cartilage volume. This technique can provide an objective quantitative measure of cartilage loss rapidly and could substantially reduce study costs for large trials and datasets.

Introduction Quantitative cartilage morphometry is a valuable tool to assess osteoarthritis (OA) progression. Current methodologies generally evaluate cartilage morphometry in a full or partial sub-region of the cartilage plates. This report describes the evaluation of a semi-automated cartilage segmentation software tool capable of quantifying cartilage loss in a local indexed region. Methods We examined the baseline and 24 month follow up MRI image sets of twenty-four subjects from the progression cohort of Osteoarthritis Initiative (OAI), using the Kellgren-Lawrence (KL) score of 3 at baseline as the inclusion criteria. A radiologist independently marked a single region of local thinning for each subject, and three additional readers, blinded to time point, segmented the cartilage using a semi-automated software method. Each baseline-24 month segmentation pair was then registered in 3D and the change in cartilage volume was measured. Results After 3D registration, the change in cartilage volume was calculated in specified regions centered at the marked point, and for the entire medial compartment of femur. The responsiveness was quantified using the SRM values and the percentage of subjects that showed a loss in cartilage volume. The most responsive measure of change was SRM = −1.21, and was found for a region of 10 mm from the indexed point. Discussion The results suggest that measurement of cartilage loss in a local region is superior to larger areas and to the total plate. There also may be an optimal region size (10 mm from an indexed point) in which to measure change. In principle, the method is substantially faster than segmenting entire plates or sub-regions.

Articular cartilage abnormalities of the FPFC are common and were demonstrated in 24% of patients or 30% of cases. Lateral FPFC abnormalities occur 2.5 times more frequently than medial FPFC abnormalities and were more frequently focal compared with medial cohorts. BME is associated in 36.5% of cases.