CHARACTERIZATION OF A MODEL OF OSTEOARTHRITIS IN THE RABBIT KNEE

A new computerized method of histomorphometry was used to assess the d evelopment of osteoarthritis (OA) in a rabbit model. Three groups of 1 0 New Zealand White rabbits with closed epiphyses underwent unilateral anterior cruciate ligament transection (ACLT) and contralateral arthr otomy (sham). Groups were killed at 4, 8 and 12 weeks. At the time of death the femoral condyles were assessed grossly following the applica tion of India ink using the following grading scale. Grade 1: intact s urface; grade 2: minimal fibrillation; grade 3: overt fibrillation; gr ade 4: erosion. All histological sections were assessed using a color image analysis system. The mean thickness and area were measured for a defined cartilage region. The root mean square surface roughness (bas ed on deviations from an idealized smooth surface) was calculated to a ssess the surface profile of the articular cartilage. The results were as follows. After ACLT, no full-thickness ulceration was noted at 4 w eeks. Four of the medial femoral condyles at 8 weeks and six at 12 wee ks showed full-thickness ulceration of the articular cartilage. The pe r cent cartilage area and cartilage thickness (ACLT divided by sham) i n almost all regions showed decreases with time, indicating progressiv e erosion. The surface of the ACLT knees was much rougher than that of sham of the knees. These results demonstrate the usefulness of a quan titative methodology using a computerized video analysis system to ass ess the articular cartilage following ACLT in a rabbit model for the d evelopment of OA.