Portable system for gait analysis of children with cerebral palsy

Introduction Main concerns about using optoelectronic systems as the standard tool to perform gait analysis in Children with Cerebral Palsy (cCP) are: 1) the unnatural way cCP normally walk in unfamiliar environments, like laboratories; 2) the possibility to acquire only short walking trials, due to limited measuring volume, and 3) difficulty to identify the representative gait cycles among those acquired. The MTx (Xsens Technologies, NL) is a wearable motion analysis system consisting of lightweight Sensing Units (SU) incorporating 3D accelerometers, gyroscopes and magnetometers. Based on MTx, a new biomechanical protocol was proposed (OutWalk, [1]) which allows to perform 3D kinematic data collection and real-time processing of hundreds of consecutive gait cycles in open space areas. The aims of this study were to test OutWalk: 1) ease of use in cCP, 2) reliability, and 3) ability to classify the pathological functional strategy used during walking. Materials and methods One female diplegic CP child (SI, 10 years old) participated in the experiment. According to [1], 8 SU were applied respectively on thorax, pelvis, thighs, shanks, and feet. To allow estimation of 1) static straight posture and 2) functional knee axis of rotation, SI lied down in supine position. During the static acquisition a therapist assured joints being neither flexed nor hyperextended. Furthermore, the therapist performed passively a pure knee flexion-extension trial on SI. Subsequently, 4 long gait trials consisting of more than 13 gait cycles each were acquired in a pediatric gym. The 3D kinematics of hip, knee and ankle were online elaborated then offline automatically segmented by using [2]. The protocol reliability was assessed by analyzing the maximum root mean square (RMS) distance between every possible couple of gait cycles. The relation between the clinical diagnosis and the OutWalk gait analysis results was investigated. Results It took 18 minutes to perform SU application, the static and functional calibrations, and the acquisition of the gait trails. During walking SI experienced no hindrance caused by Mtx. Figure 1 reports kinematic gait analysis results of an uninterrupted walk of 15 cycles. For each kinematic variable, the maximum RMS distance between every possible couple of gait cycles is reported in degrees in table 1. The kinematic report in figure 1 suggests: - normal pattern of hip movement, - knees always in flexion, the left with less range of movement, - ankles always in dorsiflexion but maintaining a good range of movement. Discussion and conclusions Clinical investigation on SI found crouch knees, absence of foot equine and an overall good quality of walk. These signs can all be recognized in kinematic report (figure 1), indicating that OutWalk has acquired the representative pathologic synergies of SI’s spontaneous walk. If compared to natural intra-subject variability [3], this protocol appears to have high level of reliability, but its accuracy and precision should be further investigated. In conclusion, OutWalk based on MTx technology, resulted non constraining measurement device that allowed fast acquisition and on-line elaboration of 3D joint kinematics on the walking of a CP child in a real life environment. Future developments and visions Future studies should focus on developing 1) a software upgrade that allows online division of gait into strides and 2) an algorithm able to classify gait deviations and able to suggest the diplegic form of CP with respect to the classification proposed by Ferrari et al. [4]. In order to perform a more comprehensive gait analysis including dynamic information about load distribution on the soles and joint kinetic on lower limbs, the Mtx system should be synchronized and integrated with an in-shoe pressure measuring system. References [1] Cutti et al. (2008). Outdoor gait analysis using inertial and magnetic sensors: part 1 - protocol description...