Friction of prosthetic interfaces used by transtibial amputees

• In-vivo friction and adhesion tests of elastomeric prosthetic interfaces and skin.
• Interfaces surface energies and contact angles with water were measured.
• COF and adhesion are correlated and depend on subjects' specifications/body region.
• All interfaces show COF high enough to ensure suspension and prevent skin injury.
• The role of the different friction components was analyzed.

The interface is a protective cover that establishes the contact between the prosthesis structure and the stump skin. The friction between the interface and the skin surface plays a key role to maintain adequate fit, in order to improve suspension and avoid skin injuries. The aim of this work is the study of the friction between the human skin and three common interface materials: block copolymer, silicone gel and elastomer. Coefficient of friction (COF) was assessed using a handheld probe, which allows the measurement of the contact forces during the sliding motion of the tested material against skin. Pull-off tests and contact angle measurements were also performed to quantify the adhesion force and surface energies, respectively. It was concluded that COF depends on the material nature but also on subject's specifications and anatomical region. Silicone elastomer showed the highest COF and adhesion energy. A correlation between these two variables was demonstrated.

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