Sockets for limb prostheses: a review of existing technologies and open challenges

In the prosthetics field, one of the most important bottlenecks is still the human-machine interface, namely the socket. Indeed, several amputees still reject their prostheses or report a low satisfaction level, due to factors dealing with the socket-tissues interaction. The aim of this paper is to describe the main parameters (displacements, stress, volume fluctuations and temperature) that affect the stump-socket interface and reduce the comfort of limb prostheses. In the review, a classification of the different socket types proposed in the literature is reported, together with an analysis of advantages and disadvantages of the different solutions, from multiple viewpoints. A specific focus concerns the technological solutions available commercially and in the state-of-the-art to face an altered distribution of stresses on the residual limb tissues, volume fluctuations affecting the stump overtime, and temperature variations affecting the residual tissues within the socket. The open challenges in this research field are highlighted and the possible future routes are discussed, towards the ambitious objective of achieving an advanced socket able to self-adapt in real-time to the complex interplay of factors affecting the stump, during both static and dynamic tasks.