In vivo talocrural and subtalar kinematics: a non-invasive 3D dynamic MRI study.

Background: To improve diagnostic accuracy, prevent injury, and reduce the effect of impairments on hindfoot function, an understanding of the combined in vivo kinematics of the talocrural and subtalar joints is critical. Therefore, the purpose of this study was to test the feasibility of quantifying talocrural and subtalar joint kinematics using fast-phase contrast (fast-PC) MRI, a noninvasive, in-vivo technique for the study of three-dimensional joint motion.

Methods: Nine normal ankles and two ankles with a Stieda process were studied. Subjects were each placed supine in a 1.5 T MRI and asked to maintain a repeated dorsiflexion-plantarflexion movement while a full sagittal-oblique fast-PC dataset was acquired. The orientation and position of the calcaneus, talus, and tibia were individually quantified from these data.

Results: The precision and accuracy of tracking calcaneal, talar, and tibial movement was excellent. The three-dimensional subtalar kinematics demonstrated that the talus and calcaneus do not move as a single unit. Most calcaneal-tibial supination occurred at the talocrural joint. The ankles with a Stieda process had markedly different kinematics from each other as well as from the normal group.

Conclusions: This study demonstrated that fast-PC MRI is a viable, precise, and accurate technique for studying hindfoot kinematics and is potentially a useful clinical diagnostic tool. The findings call into question the earlier anatomical studies on which much of clinical practice on the foot and ankle is based. Since a clear link was found between anatomical variation and altered rearfoot kinematics, future study is warranted.