Optimal material selection for the construction of a paediatric prosthetic knee

Abstract

The material selection of prostheses in developing countries is currently biased towards what is readily available and ignores important criteria such as patient comfort and structural strength. In this study, the ELECTRE III multiple attribute decision-making method was applied to the material selection of a paediatric prosthetic knee. Light metals were considered as candidates for selection. While composites are light, they are not suitable for use in components with sliding and mating surfaces such as a prosthetic knee. Plastics are prone to failure. Candidate materials were evaluated on criteria related to patient fatigue and comfort, structural stability and material cost. The patient fatigue and comfort requirement was evaluated using material density as the weight of the prosthesis affects the comfort level. Finite element analyses simulating the ISO 10328:2006 standard for structural testing of lower limb prostheses were used to evaluate the structural strength suitability of the candidate materials. The present day prices of the raw material of the candidates were used as an index of material cost. Wrought aluminium alloy aluminium 7175 was ranked highest while titanium alloys were ranked below these due to their higher cost. Cast aluminium alloys ranked lowest due to their poor structural performance. The study, using ELECTRE III, a rigorous multi-criteria decision analysis method, shows that aluminium 7175 is the optimal light metal material for a paediatric prosthetic knee.