3D stress MRI for studying the functional pathologies of the ankle complex

This project is a result of a marriage between two independent activities that existed for quite some time within two collaborative groups: (1) the development of a mechanical linkage device and its utilization to test externally the flexibility characteristics of the ankle complex under load; (2) the development of an MR imaging and image analysis methodology to characterize the internal 3D movements of bones of the ankle complex. In the resulting methodology, which we term stress MRI ( sMRI for short), the ankle is MR imaged in various foot configurations while held in place by the linkage device with controlled load proven to detect hindfoot instability. Subsequently the acquired images are subjected to a series of image processing and analysis steps to yield a set of parameters to describe the morphology, architecture, and kinematics of the bones of the ankle complex. These parameters are computed from images acquired for 14 normal ankles (of 7 subjects, including the left and the right ankle) and for 8 cadaveric ankles, the latter in five different situations consisting of intact ankle, two ligaments - the CFL and ATFL - sectioned serially, and then after the two ligaments are surgically reconstructed by using two procedures. The results indicate that (i) there is considerable left-to-right symmetry in the ankles; (ii) ligament damage causes a few parameters to change significantly; (iii) both ankle and subtalar motions occur in inversion and anterior drawer; (iv) in vitro motion is generally greater than in vivo motion; (v) the surgical procedures are effective in achieving normalcy, yet there are differences in their performance.