COMPUTER AIDED DESIGN AND FABRICATION OF A CUSTOM ARTICULATED ANKLE FOOT ORTHOSIS

Abstract

Traditional design and manufacturing methods of ankle foot orthosis (AFO) involve manual techniques e.g., casting and molding of the limbs and often depend on trial and error. Three-dimensional scanning allows computer aided design (CAD) tools to be incorporated, however, both approaches rely on the external model of the limb. To design AFO with articulated joint, precise alignment of mechanical and anatomical joint axes is imperative. It is difficult to infer joint axis from external model as it is partially specified by the skeletal structure. In this article, a computer integrated design approach of an articulated AFO has been demonstrated. CAD model of the AFO was developed for a healthy subject's left leg based on the 3D models of skeleton and soft tissue of the limb. Components of the AFO were fabricated by rapid prototyping and CNC machining. The design approach is faster than the traditional techniques and also facilitates exact positioning of articulated ankle joint. The gait analysis indicates that the subject's ankle had to overcome lesser resistance with the custom made AFO compared to a pre-fabricated AFO. Simultaneous viewing of exterior and skeletal geometry might help the clinicians modify the design to enhance performance of the orthotic.