Development of a Customized Wrist Orthosis for Flexion and Extension Treatment Using Reverse Engineering and 3D Printing

Hand disability implies impairment and limitation in daily activities, affecting patient's life quality. Broken bones, congenital conditions or cerebrovascular diseases frequently demand the use of structural support in the form of orthoses. Orthoses are categorized according to their mechanical functions in: static, static progressive or dynamic. While static orthoses are usually made of a single piece and do not allow movement, static progressive and dynamic orthoses are made of a main body with assembled with mechanical elements such as rods, pins, straps, springs, etc., thus allowing a limited amount of movement. Hand orthoses demand a high degree of personalization to suit patients' anatomy and pathology. A new application of the reverse engineering is proposed. Here is described a new multidisciplinary method for the development of static progressive and dynamic orthoses for the hand for the rehabilitation of hand disabilities. The method involves the image acquisition of the patient's anatomy and the mechanical design of the orthosis by Computer Aided Design (CAD) software. This method offers a high degree of personalization and the development of low volume hand orthoses with a reduction of weight at low cost by using 3D printing. The case presented on this paper is the design of an original dynamic orthosis for flexion and extension treatment of the wrist. The main body of the orthosis was designed using the data from Computer Tomography (CT) scan images and a CAD software to fit the hand anatomy. Mechanical elements were chosen to provide a variation from 0 degrees up to 90 degrees of extension, and up to 90 degrees of flexion with mechanical resistance to assist in the improvement of the wrist flexor muscles strength.