Anatomical distribution of areas of preserved cartilage in advanced femorotibial osteoarthritis using CT arthrography (Part 1)  P. Omoumi, N. Michoux, E. Thienpont, F.W. Roemer, B.C. Vande Berg  Osteoarthritis and Cartilage  Volume 23, Issue 1, Pages 83-87 (January 2015) DOI: 10.1016/j.joca.2014.10.006 Copyright © 2014 Osteoarthritis Research Society International Terms and Conditions

Fig. 1 Division of cartilage into areas. (a) Drawing showing an inferior view of the femoral condyles. Each condylar articular surface was divided from medial to lateral into six sagittal reformats (1–6 in (a) and (c)), perpendicular to the posterior condylar axis (black dotted line), which connects the most posterior points of the medial and lateral posterior condyles. The interslice gap was automatically adjusted to the size of the knee. (b) Sagittal reformat four (dashed red line in (a)) of knee CT arthrogram showing a grid placed on the medial condyle, dividing the articular cartilage from posterior to anterior. The grid was composed of 24 radial segments of 15° each was drawn with the 0° line placed horizontally. It was printed on a transparent paper and taped on the dedicated workstation monitor. The sagittal reformats of each femorotibial joint were uploaded on the workstation and zoomed in by a factor of 2.5. The third reformat of each condyle was panned so that the −45° line (white line) would intersect the most posterior aspect of the distal femoral physeal line and so that the center of the grid would project halfway between the two intersections of this −45° line and the condylar cartilage. Once positioned, the six reformats on each compartment were analyzed successively with no additional manipulation other than scrolling. The anterior border of the femorotibial joint articular surface (i.e., the delineation between the femorotibial and the femoropatellar joints) corresponded to the 120° in our grid (dashed blue line). (c) Datasheet representing femoral and tibial cartilage areas from one knee, each column representing data from one sagittal reformat. Grades for sagittal reformat 4 are represented in the dashed red box. Note areas −30/−45° on the condyle and +30°/+45° and +105/+120° on the tibia that were considered non-assessable because they included the articular margins. Osteoarthritis and Cartilage 2015 23, 83-87DOI: (10.1016/j.joca.2014.10.006) Copyright © 2014 Osteoarthritis Research Society International Terms and Conditions

Fig. 2 Color map shows proportion of femorotibial cartilage areas that were considered preserved by observer 1. Numbers are percentages (%) for each area, followed in parentheses by numbers used to calculate percentages. The total number of cases that were assessed varied for each area. Osteoarthritis and Cartilage 2015 23, 83-87DOI: (10.1016/j.joca.2014.10.006) Copyright © 2014 Osteoarthritis Research Society International Terms and Conditions