A total system approach to optimising the skin-socket interface

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Lower limb prosthetics have proven to be an extremely successful intervention, providing mobility to people with congenital limb deficiencies or who have suffered amputation. To achieve adequate function, a lower limb prosthetic requires extreme resilience from the skin on the limb stump. During use, all loads are transferred through the socket-skin interface, meaning the skin is subjected to significant loading through shear stresses. These increased demands on the skin may result in a variety of injuries. Indeed, over 40% of amputees suffer from dermatoses on the stump [1] and up to 22% of users discontinue the use of their prosthetic in the first year [2]. Seminal Bioengineering research has shown that skin damage from tissue deformations resulting from interface pressures and shear forces is initiated by two primary mechanisms: (i)direct cell deformation where the internal mechanical conditions generated within the tissues lead to a loss of cell membrane integrity [3], and (ii) prolonged tissue deformation which results in occlusion of blood and lymphatic vessels leading to compromised transport of oxygen-carrying blood cells and accumulation of waste products and toxins, respectively [4, 5]. The skin-socket interface forms a biomechanical system in which the interaction strongly depends on all components of the system namely: the socket material and its surface finish, the loads that are transmitted through the interface, the characteristics of the skin and the local micro-climate in the socket. Most research into the stump-socket interface, including that of the PI and Co-Is in this project, typically focuses only on one component of the system (Masen: prosthesis-skin interface; Higgins: skin response in vitro; Worsley: skin response in-vivo). In this research project, we propose to optimise the skin-socket interface using a system approach that does not simply focus on only one of the components of the interface, but instead considers all relevant components. This combined approach will inform us of the critical dependencies between parameters and enable us to deliver the knowledge required to optimise design of this complex interface.