Determining In-Vivo Human Tibiofemoral Cartilage Stiffness Using Dual Fluoroscopy and Magnetic Resonance Imaging
AbstractAnterior cruciate ligament deficiency (ACLD) dramatically increases the risk of knee osteoarthritis (OA). Currently, there is no clinical diagnostic to predict joint degeneration in pre-radiographic OA. The purpose of this research is to develop methods to combine deformation and joint force estimates to determine changes in cartilage stiffness in pre-radiographic OA. Preliminary data were collected for ACLD (n=4, >5 year history) and healthy control (n=5, CON) subjects. 3D bone and cartilage models were created in Amira (FES, Germany) from magnetic resonance (MR) data obtained (GE 3T Discovery 750, USA). Dual-fluoroscopy (DF) images were collected in conjunction with ground reaction forces (GRF)(Bertec, USA) during standing weight bearing. Bone kinematics were determined in Autoscoper (Brown University, USA) and applied to cartilage models. Deformations were quantified as the change in median proximity of model faces (Matlab 2015b, MathWorks, USA). Cartilage deformation was higher in ACLD compared to the CON subject, indicating a reduced ability to resist compressive loading. These results provide proof of concept that cartilage stiffness changes in pre-radiographic OA and in-vivo DF/MR measure is sensitive to alterations in load deformation. Vertical GRF provided physiological loading rate data for analysis with the viscoelastic cartilage deformation response. This MSc will use inverse dynamics to estimate knee joint forces and load-deformation curve-fitting approaches to determine a model for cartilage stiffness mechanics. This research supports the development of novel clinical diagnostics for pre-radiographic OA.  Lohmander et al. 2007 Am. J. Sports Med. 35(10): 1756–1769.  Calvo et al. 2004 OA Cart. 12(11): 878–86.