On the Influence of Incorrect Idealized Joint Axes to the Design Process of Orthoses

According to the analysis of the Global Burden of Disease (GBD) approximately 1.71 billion people worldwide suffer from musculoskeletal disorders. For the treatment of gait pathologies ankle foot orthoses (AFO) are used in the field of rehabilitation and physiotherapy. However, conventional AFOs are pre-terminated to fit a wide range of user groups. For the development of a real patient-centered AFO precise information about the individual joint axes position and orientation for each patient are necessary. This contribution illustrates the great influence of idealized joint axis, which are commonly used in generic skeleton systems in musculoskeletal simulation software for the prediction of ankle forces. For the testmodel it is shown, that the idealized ankle joint axis differ 21% regarding the resulting joint forces in comparison to the real axis. Furthermore, it is shown that 3D scanning methods can provide similarly good results in the determination of joint axes like high-cost (magnetic resonance) or radiation-risk (computed tomography) methods.