The Study of Force Sensors Calibration for Custom-Made Scoliosis Orthosis Application

Adolescent Idiopathic Scoliosis (AIS) is a spinal deformity that affects individuals aged 10 to 18. The conservative treatment involves spinal orthoses, with its effectiveness relying on consistent wear time and the precise application of corrective forces. However, inconsistencies in force application create challenges in ensuring optimal patient outcomes. This study focuses on calibrating the Force Sensing Resistor (FSR) 406 sensors to investigate force measurement accuracy before integrating them into a custom scoliosis orthosis. The system utilizes an Arduino-based microcontroller. Calibration results demonstrated that the sensors exhibited high accuracy, with mean accuracy values above 92% across the range of applied forces. For example, Sensor 1 showed a mean accuracy of 96.90% at 25 N and 92.28% at 100 N, while Sensor 2 demonstrated accuracy ranging from 99.56% at 25 N to 95.75% at 100 N, and Sensor 3 achieved accuracies from 94.01% at 25 N to 97.17% at 100 N. However, slight reductions in accuracy were observed at higher force levels. The derived exponential calibration equations for each sensor allowed for the precise conversion of voltage data to force measurements. The calibration also revealed that the sensors provide stable readings with smaller deviations at lower force levels, highlighting their reliability for monitoring corrective forces. This study serves as an initial phase, with plans to eventually test the sensor-integrated orthosis with actual scoliosis patients and establish a foundation for future research on force monitoring.