Robot-assisted ankle rehabilitation: a review

Aim: The aim of this review paper is to summarize recent developments and research in robotics, relevant to the field of ankle rehabilitation, to overview new findings and determine the actual state of the art.Method: The literature search was performed using scientific and medical databases (Scopus, PubMed and Web of Science) and other websites related to robots used in the area of ankle rehabilitation, analysing studies from 1950s to present. Information about the mechanical and kinematic specifications, actuation and stage of development was extracted from the selected literature.Results: Several types of rehabilitation robots have been considered, and they were classified depending on their architecture and design features. We we found that, regardless of the differences in architectures, only a few of them have been commercialized. The majority of rehabilitation robots designs allows plantarflexion-dorsiflexion movements. Unless some exceptions, most of the wearable robots do not allow the adduction-abduction movement. Neither the physical appearance of the robot nor the user’s perception towards it has not regularly been taken into account in the design stage. This limits the possibility of successful commercialization.Conclusions: Up to the present moment, the main challenges in the field of robot rehabilitation are the lack of unique rehabilitation protocols capable to fulfil the needs of all types of patients and the additional resources to measure the effectiveness of proposals that have not yet been commercialized. Nonetheless, we have mentioned above three areas were the challenges in design are more pressing. The first one is the robot architecture, which still presents some incommodities nowadays to emulate the ankle joint movement in a natural way. Thus, the displacements experienced by the axes in the joint must be adaptable to each patient and a wide range of pathologies. Moreover, many proposals are not been conceived to the purpose of commercialization, and even less to become an object of personal use.Implications for rehabilitationThis review states that the use of robotic devices for ankle rehabilitation is a consolidated paradigm in the ankle’s rehabilitation.Platform-based robots allow to do complex and specialized spatial movements and these architectures endow the device with high stiffness, a balanced force distribution and better adaptability to the mechanical properties of human ankle joints. Unless some exceptions, most of the wearable robots do not allow the adduction-abduction movement.For a full integration of these technologies in the ankle’s rehabilitation field, more clinical evaluations are needed.Regardless of the potential of robotic devices in rehabilitation, only a few of them have been commercialized.