Biomechanical research of the endoskeletal trans-tibial monolimb

Monolimb, a new type of lower-limb prostheses with the socket and the shank integrated from a piece of thermoplastic material, is an alternative to conventional prosthesis for lower cost and weight. However, the design criterion of monolimbs is still absent. In this study, a three-dimensional finite element model was constructed according to an endoskeletal trans-tibial monolimb. Based on this model, the effects of wall thickness, material properties and loading conditions on the stress distributions in the monolimbs and the stumps were analyzed. The results indicated that the introduction of increased thickness of shank was proven to be useful for the design of monolimb. Further studies could promote the suitable choice of the wall thickness of monolimb for amputees. The stresses in the monolimb and the stump were hardly sensitive to the material properties of monolimb, so polypropylene homopolymer with low cost, easy fabrication and high yield stress was optimal for the material of monolimb. Because the peak stresses in the monolimb and the stump at Heel Off were higher than the other stance phases, the load conditions of Hell Off should be chiefly considered into the design of monolimb. The information could provide a reference for the design and optimization of monolimbs.