MRI is widely accepted as a non-invasive technique for visualizing the morphology of healthy and damaged of degenerate articular cartilage. In order to visualize early pathological changes of in vivo cartilage, use of parameter selective MR imaging is combined with relaxation time and diffusion constant mapping which makes it possible for the first time to perform a biochemical evaluation of cartilage in vivo. As well as assessing the biochemical properties, it is important to assess the biomechanical properties of cartilage, to make a full functional assessment of articular cartilage, this is particularly important in cartilage implants.
The aim of this project is to further develop and validate individual MR parameters for evaluating biomechanical properties of cartilage, in particular cartilage stiffness. In order to fore fill the aims of this project we propose a 3 phase approach with in vitro, in situ and in vivo studies. MRI techniques including T1 and T2 relaxation time mapping, diffusion measurements, and sodium MRI will evaluate cartilage under controlled mechanical loading. The parameters measured in normal and degenerative cartilage using MRI will be correlated to the results of biochemical, histological and biomechanical tests. In vivo MRI studies of the biochemical and biomechanical properties of articular cartilage and cartilage implants require the application of controlled reproducible loads throughout the range of movement; therefore, as part of the project we will develop an MRI compatible kinematic device.
For the planned MR visualization of the biomechanical properties of cartilage, optimal 3D segmentation and 3D reconstruction techniques of the cartilage layers must be developed. Image analysis will allow dynamic visualization of joint motion as well as determination of quantitative parameters including thickness, volume, surface area and joint contact area under physiological loading. This 3D visualization approach ensures that the evaluation of biochemical and biomechanical properties of articular cartilage can be performed under realistic mechanical loading of the joint.
So far, such information has only been available through arthroscopic surgery. Thus, along with the basic science research on the biomechanics of articular cartilage, this non-invasive MR method also offers improved diagnosis, follow-up and rehabilitation of patients with cartilage disorders or implants.