Mass customation of foot orthosis for rheumatoid arthritis

Abstract

Rheumatoid arthritis (RA) is an inflammatory disease, which can cause pain, stiffness, and swelling in the joints of hands and feet. The foot is a major site for RA involvement and a major source of disability resulting from this disease. This paper introduces research which aims to create a mass customisation process for customised orthoses for patients with RA. 3D laser scanning, and gait analysis will be used to generate the orthosis geometry and rapid manufacturing, namely the selective laser sintering (SLS) process, will be used to produce the orthoses. The SLS process enables the incorporation of compositional functional elements, such as locally adjusted stiffness or flexibility, into the orthosis design. The process involved two central elements. The first was a literature survey to identify orthotic design rules for foot impairments in RA. This survey will form a platform for the design rule development and will be complemented by data obtained from two patient trials. The second is a virtual three-segment foot model, created in Anybody dynamics modelling software which can be motivated by data measured from patients using 3D motion capture and force plate systems. Once the measured data has been applied to the model, a virtual insole can be used to simulate the effects of various features in the orthosis. Considerable variation was noted in the literature for types of material, design and methods of orthotic construction. Pressure redistribution using cushioning materials was consistently mapped to painful deformed joints. Orthoses with contoured surfaces, either customor mass produced in thermoplastic materials of varying stiffness and density were mapped to joint motion control and deformity prevention. The paper will also describe applying patient gait data to the Anybody model, and then altering the gait pattern by applying the insole model. Future work will also be discussed. Introduction The purpose of this project is to create a process that will produce customised foot orthoses for rheumatoid arthritis sufferers. Currently, the production of foot orthosis is time-consuming, and expensive, with delivery times up to six weeks, during which the disease can alter the foot further. Improved clinical outcomes can be connected to custom foot orthoses, when compared against mass-produced orthosis. The novelty of this project is the application of mass-customisation principles and layermanufacturing technology to existing clinical processes. Currently the design of orthoses is very much a craft and there are only a few standardised procedures when subscribing them. To assist the design, a set of design rules and a virtual gait model will be created.