Skin adaptation in lower limb amputees assessed through Raman spectroscopy and mechanical characterization.

Following lower limb amputation residuum skin from the lower leg is used to reconstruct the residual limb. Unlike skin on the sole of the foot (plantar skin), leg skin is not inherently load bearing. Despite this, leg skin is required to be load bearing in the prosthetic socket. Current hypotheses propose that lower limb amputee skin can adapt to become load bearing with repeated prosthesis use. Here, we show using confocal Raman spectroscopy, mechanical characterization and cytokine analysis that adaptations occur which actually result in impaired barrier function, higher baseline inflammation, increased coefficient of friction and reduced stiffness. Our results demonstrate that repeated frictional trauma does not confer beneficial adaptations in amputee skin. We hypothesize that non-plantar skin lacks the biological capabilities to respond positively to repeated mechanical trauma in the same manner observed in plantar skin. This finding highlights the need for improved therapies as opposed to current mechanical conditioning or product solutions that directly relate to improving load-bearing capacity on the skin of lower limb amputees. This study also highlights the importance of measuring multiple parameters of application-specific skin at different scales for skin tribology applications.