Abnormal tibiofemoral contact mechanics in subjects with medial and lateral compartment articular cartilage lesions

s / Osteoarthritis and Cartilage 23 (2015) A82eA416 A306 481 ABNORMAL TIBIOFEMORAL CONTACT MECHANICS IN SUBJECTS WITH MEDIAL AND LATERAL COMPARTMENT ARTICULAR CARTILAGE LESIONS S.Y. Segev, D. Kumar, L. Nardo, V. Pedoia, T.M. Link, S. Majumdar, R.B. Souza. Univ. of California San Francisco, San Francisco, CA, USA Purpose: To evaluate the changes in cartilage-on-cartilage contact areas and medial and lateral contact area centroid movement in the tibiofemoral joint during knee flexion and extension using MRI in subjects with and without tibiofemoral cartilage lesion. Methods: Subjects from an observational study on knee Osteoarthritis (OA), including both subjects with andwithout radiographic OA, (n1⁄4 94 Mean age 1⁄4 54.1±10.5 years; Mean BMI 1⁄4: 24.4±3.4 kg/m2; Men:Women 1⁄4 35:59) underwent 2D fast-spin echo (FSE) MR imaging at 0 and 30 of knee flexion under axial loading (25% bodyweight). For subjects with radiographic OA, the more severe knee was enrolled. For subjects without radiographic OA, the enrolled knee was randomly selected. A fluid sensitive-fat-saturated 3D fast spin-echo sequence with variable flip angle (CUBE) was acquired in order to grade cartilage lesions using a semi-quantitative score. Subjects were then stratified into those with and without cartilage lesions at the tibiofemoral joint. Tibiofemoral contact area was defined on FSE images as the area of contact between the tibial and femoral articular cartilage, excluding meniscus contact area and joint fluid. This region of contact was semiautomatically segmented separately in the medial and lateral knee compartment using Bezier-splines created with in-house software written in Matlab. Contact area centroid position was determined by evaluation of the contact area on a defined anatomic coordinate system embedded within the tibia. Differences in medial and lateral contact area at flexed and extended conditions, and medial and lateral contact area centroid translations were compared between subjects with and without cartilage lesions using analysis of co-variance (ANCOVA), adjusted for age, gender, knee alignment, and BMI. Results: Subjects with medial compartment cartilage lesions (n1⁄428) had greater contact area in the affected compartment during extension (Figure 1, 361 vs. 270 mm2; p1⁄40.025), but not flexion (Figure 1, 287 vs. 219mm2; p1⁄40.146) when compared to subjects without lesions (n1⁄466). No differences in contact area in the lateral compartment were observed between subjects with and without medial compartment lesions. In contrast, subjects with lesions in the lateral compartment (n1⁄418) were found to have greater contact area than subjects without lesions (n1⁄476) in both extension (Figure 2, 366 vs. 271 mm2; p1⁄40.009) and flexion (Figure 2, 326 vs. 224 mm2; p1⁄40.002) as well as in the contralateral compartment while in full extension (Figure 2, 374 vs. 279 mm2; p1⁄40.012). With regard to contact kinematics, subjects with medial compartment lesions had greater anterior-posterior translation of the medial contact centroid when moving from extension to flexion (Figure 3, Figure 4, p1⁄40.047). No differences in anterior-posterior centroid translations were observed in either the medial or lateral compartment of subjects with lateral compartment lesions. Conclusions: Contact mechanics in subjects with cartilage lesions are significantly different compared to those without lesions. The higher contact area in subjects with cartilage lesions is likely due to the changes in the ability of the cartilage to adapt to loading, expanding the contact surface as the cartilage adjacent to the lesion gives way to the load. This phenomenon is coupled with abnormal contact kinematics in persons with cartilage lesions. While the normal kinematics of knee flexion requires the femur to slide back on the tibial plateau, our data suggests that the movement in the affected compartment is greater in knees with medial compartment cartilage lesions. This finding could be related to knee instability, an extremely common symptom in patients with OA. Taken together, these differences may be responsible for more rapid cartilage degeneration in individuals with OA. Abstracts / Osteoarthritis and Cartilage 23 (2015) A82eA416 A307s / Osteoarthritis and Cartilage 23 (2015) A82eA416 A307 482 SERUM LEVELS OF RESISTIN AND INTERLEUKIN-17 ARE ASSOCIATED WITH INCREASED CARTILAGE DEFECTS AND BONE MARROW LESIONS IN PATIENTS WITH KNEE SYMPTOMATIC OSTEOARTHRITIS K. Wang y, J. Xu y, J. Cai y, S. Zheng y, X. Yang y, C. Ding zy. yDept. of Rheumatology and Immunology, First Affiliated Hosp. of Anhui Med. Univ., Hefei, China; zMenzies Inst. of Med. Res., Univ. of Tasmania,