'Leg bank' automates and simplifies development of prosthetic sockets

A team led by Dr Arjan Buis, from Strathclyde’s Department of Biomedical Engineering, has developed the innovative system, known as Majicast, to manufacture lower limb prosthetic sockets that fit prostheses securely to patients’ residual limbs.

To cast for a new prosthesis, the residual limbs of the amputee are immersed in a tank of water one at a time, with a membrane material wrapped around them. The person’s body weight is then used to load this - similar to loading a prosthesis during gait. This pressure casting deforms the soft tissue, under a uniform load. When a limb is subject to uniform external pressure, there will be an internal equilibrium pressure at which the soft tissue has maximum load-bearing function, and where internal shear stresses are minimised.

Using this casting method, the soft tissue is ideally positioned in its stiffest form for load transfer. This means vertical movement of the limb in the socket - or pistoning - is limited, reducing deep shear stresses and so shear and friction related problems that can cause soft tissue damage and discomfort.