Hands Free Hydro Cast – Optimising Trans-femoral Socket Design and Maximising Rehabilitation Potential Buis AWP, McGarry A, Kamyab M, Murray KD, Hillman S Biomedical Engineering, University of Strathclyde, Glasgow, UK Introduction • • • • • Statement of problem (Why) Implementation of a “good” fit Methodology (What & How) Results conclusion Statement of problem • The purpose of a socket is to provide a mechanical connection between the skeleton and the rigid structure of the prosthesis. • The dominating concepts are the Quad and Ischial cont. • • • How stabilising are those sockets? Are they reproducible? Can we do better? Implementation of a “good” fit • Socket fit criteria: o As “stiff” as possible coupling o No tissue damage o Minimum discomfort Implementation tools; o Surface matching o Volume matching • Is it possible to distribute the load to the different transmission elements in a controlled way? • Yes, if the force flow distributes itself proportionally to the stiffness of the available path! Implementation of a “good” fit Rubber Block Metal Block Rubber Block “Let nature deform the soft tissues in such a way that the stiffest path principle is achieved” Methodology • Copy of the existing Ischial containment socket. • Pressure cast socket according the Hydro cast principle. Methodology (work packages) 1. Dynamic interface pressure 2. Femoral stability 3. User performance outcome measures • • (ideally shear) Kinetic (forces) Kinematic (position in space and time) Methodology • Dynamic interface pressure • Validated Tekscan™ pressure measurement system Methodology • Femoral stability Methodology • User performance outcome measures • • Kinetic (forces) Kinematic (position in space and time) Results • A Dynamic interface pressure M P L Ischial containment Hydro Sensor Results Ultra sound Anterior Medial X section socket Video Results Lateral Lateral A P Medial Hydro Cast P A Medial Ischial Containment Results • User performance outcome measures Summary • Speed slightly higher with the old socket, but it was noted that the subject’s speed increased as she became more accustomed to the new socket. • Stride length slightly longer with the old socket, effected via increased step length bilaterally. • • • Cadence and double support time much the same for both conditions. Single support time on the right a little decreased with the new socket. Clear differences between pistoning and gapping were observed. Indicating that the Hydro concept is more stable. Conclusion • • • • No significant pressure distribution differences. Shear should be investigated! No significant Kinetic and kinematic differences. Significant stability differences in direction, pistoning and gapping in favour of the Hydro concept prosthesis. Thank you!