A novel instrumented outsole for real-time foot kinematics measurement: validation across different speeds and simulated foot landing in Cerebral Palsy gait

Neuromuscular disorders in Cerebral Palsy (CP) patients lead to foot deformities and affect foot biomechanics leading to compromised gait. Thus, measurement of the foot kinematic measurement is of particular interest to understand and characterize the walking pattern among CP patients. The objective of the present work is to develop a wearable instrument to measure foot kinematics such as foot-to-ground angle in three-dimensional planes and to measure the foot clearance i.e., toe and heel clearances. A template-based outsole was developed that incorporated an optical distance sensor located anatomically on the outsole and the magnetometer to measure the foot kinematics. The developed system was validated against the reference marker-based motion capture system (from Noraxon). The data from eight able-bodied participants were acquired simultaneously from both the systems (developed and the reference system) at three different walking speeds. A CoP based feedback was presented to the participants to shift the sagittal CoP anteriorly, posteriorly and normal to simulate the walking pattern of CP patients with three different foot landing strategies. Pearson's correlation coefficient of more than or equal to 0.62, root mean square error of less than or equal to 7.81 degrees and limit of agreement of more than or equal to 95% is found. Furthermore, a wireless wristband is developed and validated for real-time vibrotactile feedback. The measurement accuracy reported with outsole while participants simulated CP gait shows the potential of present work in real-time foot kinematics detection in CP patients. The instrumentation is wearable, low-cost, easy to use and implement.