Innovative use of 4D scanner for gait analysis of neurological disorders: A case study

4D scanners (4DSC) are innovative photogrammetry-based 3D/4D capture and analysis systems for anthropometric static and dynamic measurements. Recent research studies have been carried out to demonstrate its validity for kinematic gait assessment [1] and to evaluate the effects of technical marker location on traditional kinematic analysis [2]. Compared to 3D systems, 4DSC allow to capture more detail of human motion, including precise volumes and shapes of body segments that can be used to make more accurate calculations [3]. 4DSC also provides a 3D dynamic avatar reconstruction to visual analysis in 360º vision and information of anthropometric measures in motion. Due to these unique features, 4DSC have set a new direction in motion analysis, especially related with pathological conditions of the nervous system [4]. Can “4D scans” provide significant information related to dynamic soft tissue behavior to improve clinical understanding in neurological disorders gait motion analysis? A case study was conducted with 16-year-old male participant diagnosed of cerebellum ataxia with hypoplasia associated to motor alteration, but able to walk without assistance. Parents’ written consent was obtained. Participant performed consecutive gait repetitions (3 for each limb) at self-selected speed at IBV Human Analysis Laboratory. Tests were recorded with Move4D scanner and Dinascan/IBV force plate. Kinematic and dynamic gait parameters were calculated from the data recorded using AMHPlus/IBV software. Additionally, changes in the calf shape during gait were calculated from the Move4D data using custom developed Python algorithms. Leg calf surface was determined as the posterior area of the mesh at each leg, between tibial tuberosity projection and midpoint of Achilles tendon. At each instant of the gait cycle, the positions of the vertices of those areas were rotated and translated keeping their relative distances, in order to match their positions in the reference posture as closely as possible. Deformation of the skin was measured as the field of 3D distances between the reference points and their displaced positions. That amount of deformation at each instant was quantified for both legs, as the sum of the eigenvectors of that field of deformations (in mm). 4DSC results allowed to objectify gait kinetic and kinematic alterations and a different pattern in soft tissue deformation between legs (see Figure), which were consistent with the clinical impression. Figure. Differences in calf surface deformation and reaction forces between limbs during single leg support. Representation of mesh extracted from Move4D data during gait on top.Download : Download high-res image (105KB)Download : Download full-size image Information extracted from Move4D allows to eliminate remaining limitations of traditional gait motion analysis systems. Recent studies propose methodologies to predict human muscle activity from skin surface behavior [5,6]. Single system solution for kinematics analysis and soft tissue deformation can open future research and clinical applications related to dynamic morphology changes and muscle activity.