Design of a controlled-stiffness composite proximal femoral prosthesis

The design and prototype manufacture of a controlled-stiffness composite femoral prosthesis is described. The prosthesis is composed of a cobalt-chrome core surrounded by a flexible composite outer layer. By varying the composite layer thickness it was possible to control the prosthesis stiffness. The new design was critically assessed by means of finite-element method and its predicted performance compared with those of conventional, single-modulus prostheses. A simple model based on composite beam theory was used to determine the optimum thickness of the composite material. The composite was made of an epoxy resin reinforced with braided hybrid carbon-glass pre-forms. A prototype incorporating the novel concept design was manufactured by using the compression moulding technique.