MRI Study on Tibial Nerve of the Ankle Canal and Its Branches: A method of multiplanar reconstruction with three-dimensional dual-excitation balanced steady-state free precession sequence

Abstract

Background: The display of tibial nerve and its branches in the ankle canal is helpful for the diagnosis of local lesions and compression, and also for clinical observation and surgical planning.The aim of this study was to investigate the feasibility of three-dimensional dual-excitation balanced steady-state free precession sequence (3D-FIESTA-C) multiplanar reconstruction (MPR) display of tibial nerve and its branches of the ankle canal.The subjects were 20 healthy volunteers (40 ankles), aged 22-50, with no history of ankle joint desease. 3D-FIESTA-Csequence was used in the 3.0t magnetic resonance equipment for imaging. During the scanning, each foot was at a 90-degree angle to the tibia so that the results of measurement are more accurate .The tibial nerve of the ankle canal and its branches were displayed and measured at the same level through multiplanar reconstruction.Results: Most of the tibial nerve bifurcation points were located in the ankle canal (57.5%), few (42.5%) were located at the proximal end of the ankle canal, and none was found away from the distal end. The bifurcation between the medial plantar nerve and the lateral plantar nerve is on the line between the tip of the medial malleolus and the calcaneus, and it’s angle is between 6° and 35°.The average cross-sectional diameter of the medial plantar nerve is about mm, and the lateral plantar nerve about mm. In MPR images, the display rates of both the medial calcaneal nerve and the subcalcaneal nerve were 100%, and the starting point of the subcalcaneal nerve was always at the distal end of the starting point of the medial calcaneal nerve. In 55% of cases, there were more than 2 medial calcaneal nerve innervations.Conclusion: The 3D-FIESTA-C MPR can display the morphological features and positions of tibial nerve and its branches. By measuring the distance between each bifurcation point, the tip of the medial malleolus and the angle between this line and the horizontal line that passes the tip of the medial malleolus, the bifurcation point’s projection position on the body surface can be accurately marked. This method not only benefited the imaging diagnosis of tibial nerve and branch-related lesions of the ankle canal, but also provided a good imaging basis to plan the clinical operation of the ankle canal and avoid surgical injury.