An Analytical Approach for Assisting Scoliosis Brace Casting

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Abstract

Adolescent idiopathic scoliosis (AIS) is a spinal disorder causing abnormal curvature of the spine in three dimensions (3D), starting in the patient’s adolescence, and having no known cause. Bracing is the most common non-surgical method of treating AIS, but the brace design is heavily reliant on orthotists’ experience. As more research is done, objective approaches have been shown to lead to more consistent results. Thus, numerical analysis of brace treatment and better brace construction are the focus of this research. The aims of this research are to 1) generate a mathematical model to estimate spinal flexibility to assist brace treatment; 2) develop and test a 3D brace casting frame to assist orthotists to make braces; and 3) design a simulation algorithm to predict the casting outcomes. The mathematical model of spinal flexibility used a single-variable linear regression as a function of 5 predictor variables to determine the best predictors. Fourteen patients’ data were used to develop and validate the model. The highest coefficient of determination was 0.43 for thoracic curve with the length of the curve acting as the predictor.

In addition, a novel brace casting frame was designed and built to hold a patient in place with forces applied to the body in three-dimensions. Force and angle measurements were recorded during casting for modeling purposes. The frame had been used in brace casting clinics on two occasions, demonstrating its durability and feasibility to assist brace casting.

The correction algorithm was developed in MATLAB using lumped element analysis, based on data from radiographs and spinal flexibility information from ultrasound measurements. The pads’ force magnitudes and locations were simulated to obtain the optimal in-brace correction, with an allowed force value between -70 N and +70 N. The forces could take 5 values between these limits and the program was iterated with progressively smaller windows. Promising simulation results were obtained on a sample of 11 patients, including one validated in the clinic, with results within reasonable deviation of the actual in-brace corrections. This research ultimately will allow an increase in the objectification and quantification of brace casting for AIS, leading to better brace treatment.

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