Segmental Kinematic Analysis Using a Tridimensional Reconstruction of Rat Hindlimb: Comparison between 2d and 3d Joint Angles

Functional recovery is one of the primary goals of therapeutic intervention in neuromuscular research. Animal models have been widely used to assess motor and sensory functions after induced lesion. Several spatial and kinematic parameters have been reported as sensitive outcome variables to quantify functional recovery: ankle angle, ankle-stance angle, stance/swing ratio, step length ratio, angle of the ankle joint at terminal stance, angle of the ankle joint at midswing, tail height, tail deviation and midline deviation. Eversion, dragging and exorotation of the foot during stance phase is referred by Meek [1] as an important aspect of walking quality. The rotation of the injured paw instead of dragging, contracture of toes, inversion of the feet and plantar flexion of the toes have been described as the main qualitative of abnormalities observed in foot placement during locomotion. Nevertheless there are few published studies where tridimensional kinematics is used to describe rat’s locomotor function [2,3]. What is, this approach is based on the vector dot product, which only enables us the computation of planar angles [4], moreover only sagital plane angular data has been reported. In order to better understand the effects of induced lesions in rat’s locomotor function, a more anatomical and functional approach should be considered. The purpose of the present study is: (1) to perform a segmental kinematic analysis using a tridimensional reconstruction of the rat hindlimb, regarding the morphology and the movement of each segment, (2) to calculate hip, knee, ankle and metatarsophalangeal planar angles (sagital, frontal and transverse planes) and (3) to compare both 3D (Cardan sequence x-y-z) and 2D angles for the peaks of flexion, extension, IC (initial contact), TO (toe-off), midstance, midswing, stance amplitude and swing amplitude in the sagital plane of motion.