GEOMETRICAL CONSIDERATIONS RELEVANT TO THE INITIAL STABILITY OF HIP PROSTHESES

Luc LABEY

luc.labey@mech.kuleuven.be

Siegfried JAECQUES

siegfried.jaecques@mech.kuleuven.be

Cezar PASTRAV

cezar.pastrav@mech.kuleuven.be

Frederik GELAUDE

frederik.gelaude@mech.kuleuven.be

Michiel MULIER

michiel.mulier@uz.kuleuven.be

Georges VAN DER PERRE

georges.vanderperre@mech.kuleuven.be

Catholic University of Leuven, BELGIUM

Abstract. The stability of hip prostheses is one of the determining factors for their long-term performance. Certainly in the case of cementless implants, where the prosthesis stem is only fixed to the bone by a so-called interference fit, sufficient stability is hard to achieve. Peroperatively manufactured custom-made stems, which give optimal fit and fill of the intramedullary canal, might resist the daily loads on the hip better than standard stems. However, a large variety of stem geometries can be expected with this technique. We used the principle of virtual work and a straightforward mechanical model to obtain algebraic formulas to estimate the role of the geometry of custom-made hip stems on their initial stability. The initial stability of 10 custom-made hip stems was estimated and compared with the stability of the Charnley and 3M Capital hips.
 

Keywords: hip implants, custom-made implants, initial stability, geometry, analytical model

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