Conceptual design of orthosis for clubfoot model developed using image reconstruction techniques

Abstract

Clubfoot is one of the most common deformities distributed worldwide in the ratio of 1to 2 per live births. The subjects with clubfoot have their foot twisted at the ankle, which makes them walk on the lateral surface of the foot. This study involves the design of an orthosis, which is an externally applied device that regulates the musculoskeletal functions of the foot. An infant with clubfoot deformity is selected for this study. Computed tomography (CT) images of the clubfoot with 1 mm slice thickness were captured and fed in MIMICS, an image processing software, where in 3D clubfoot model was developed. Rapid prototyping (RP) model of the clubfoot was prepared using Stratasys FORTUS 360mc. This prototype is taken as reference for designing the orthosis for clubfoot treatment. Considering, the level of deformity, its nature, bean ratio, and age of the subject different conceptual models are developed. The deep heel cup (Model I) orthosis, provides required support for the heel to regulate bone growth and to counteract unbalanced forces. Spiral encloser (Model II) orthosis is supported from the thigh and wounds around the tibia to promote bone growth in the required profile. A mechanical orthosis (Model III) with adjustable supports was developed to cater subject to attain normal posture. Considering the complex profile of the foot and orthosis assembly, Solid 45 – tetrahedral elements are used for meshing. By applying necessary material properties and loading conditions, the structural analysis of the assembly was performed to predict the stress distribution and the pattern of bone growth. The finite element analysis on mechanical orthosis (Model III) shows a maximum displacement of 1.45 mm and the maximum stress of 0.79 N/mm². This study can be further extended by manufacturing and testing the orthosis on different subjects.