Design and prototyping of a robotic hip reeducation device

Nowadays, with more than 400 000 interventions per year in the United States, total hip arthroplasty (THA) has become one of the most successful surgeries of modern medicine [1]. In fact, it offers a last resort, when medications, neither the use of walking supports, improve the persistent pain and disability in everyday tasks. In the context of the hip post-operative rehabilitation, Mr. Thanh Binh Nguyên investigated the importance of the Gluteus Medius in the lateral stabilization of the pelvis. He noticed that insufficiency of this muscle usually manifested after a THA, impacts patient daily activities, such as walking. Thus, he believed that special attention should be given to the muscle during the rehabilitation program. For that purpose, the idea of building an automated solution, to replace the physically demanding and time-consuming conventional therapy, arose naturally out of his mind. Even if several therapeutic devices are already commercialized, they are limited to passive movements. This is where this project came into play, to improve the physical recovery of hip abductors by adjusting the generated movements according to a patient’s behavior. Hence, this thesis aims to provide a detailed design of an assistive device performing hip abduction and adduction exercises. After a brief state of the art of rehabilitation practices, we noticed that the existing robotic solutions are difficult to transport and do not minimize the stresses inside the hip. For that purpose, this thesis includes the modeling of an exhaustive set of mechanisms, in the search of the most compact and less harming device to the weakened joint. By reviewing the linear actuation technologies, selecting the required instrumentation tools and exploring the mechanical solutions minimizing bulkiness, we suggest a design solution. The final prototype is a flattened transportable device which provides an accurate hip exercising shortly after the surgery. For its use, the device sits over the patient's bed (or therapy table) where the operated leg is mobilized by a support shell. Equipped with a belt-driven linear guide, the support moves back and forth, generating the abduction and adduction of the hip. In addition, the patient effort is collected with a miniature force sensor, in order to provide an adapted motor torque, through a real-time control. Nevertheless, several aspects should be further investigated, mainly concerning the validation of the simulated models, as well as the design and selection of a suitable controlling strategy.