Reducing Socket Discomfort and Torsional Stresses for Individuals With Lower-Limb Amputation Using a Novel Prosthesis

Abstract

Individuals with lower-limb amputation often suffer pain and discomfort at the socket-residual limb interface after using their prosthesis. A portion of this pain and discomfort can be isolated to the transverse plane. It has been shown that the inherent geometry of the bones in the ankle joint produce motion in the transverse plane; however, prosthetic limbs generally only function in the sagittal plane. Torsion adapters are a clinical product used to passively allow rotation in the transverse plane at the pylon level of a prosthesis. These adapters have been shown to relieve skin problems, but they introduce a perceived decrease in stability. Olson made a first iteration Torsionally Active Prosthesis (TAP) in a pilot study which showed that a powered prosthesis operating in the transverse plane can reduce transverse socket torque. The study presented in this thesis continued Olson’s preliminary work by iterating on the TAP’s design and testing more human subjects. By coupling sagittal plane rotation with transverse plane rotation, this study hypothesizes that there exists a coupling ratio (CR) that minimizes peak transverse-plane socket torque and maximizes user satisfaction. Participants (n=3) tested the TAP under a range of CRs for three different walking regimes: straight walking, prosthesis inside circle walking, and prosthesis outside circle walking. Initial results suggest a small CR will minimize socket torque within each walking regime. For straight walking, a small or zero CR may minimize socket torque. For circle walking, a small, nonzero CR may also minimize socket torque independent of whether the prosthesis is on the inside or outside limb. Initial results for comfort level showed that changing CRs did not present any trends. Further human subject tests with the TAP are warranted because increasing the comfort level and residual limb health of users is of significant clinical interest.