Polymer-based composite hip prostheses

A composite hip prosthesis (CHP) made from poly(ether-imide) reinforced wit h carbon and glass fibres was manufactured and characterized. The main obje ctive of the study was to evaluate the effect of fibre organization on the mechanical properties of the composite femoral implant and compare with the bone. A stacking sequence of drop-off plies of carbon/glass fibres reinfor cing poly(ether-imide) (PEI) constitutes a symmetrical and balanced CHP. Th e hip was manufactured according to the finite element modelling (FEM) desi gn and using the compression moulding and water-jet technologies. The measu red stress-strain data according to tensile, flexural and torsional tests s howed agreement with the numerical calculation. Young's modulus and the str ength in tension are uniform along the stem axis (40 GPa and 600 MPa, respe ctively) while the elastic modulus in bending varies from 10 to 60 GPa in t he tip-head direction. The composite stem showed a linear load-displacement relation up to 4500 N without breaking. Mechanical behaviour of the CHP is compared to that of a canine femur. Comparison with metal prostheses has a lso been undertaken. CHPs control stress-strain distributions, and hence th e mechanical signals to bone, through a material-structure design. (C) 2000 Elsevier Science S.A. All rights reserved.