Abstract
Introduction: The stress and strain in the proximal femur after total hip arthroplasty are influenced by the geometry of the implant in addition to its materials properties and applied loading. The addition of a third taper in the medio-lateral plane may provide additional stability and improved load transmission.
Aim: To examine the relative stability of double and triple tapered stems in two finite element (FE) models.
Methods: The geometry of a polished, double-tapered and a triple-tapered stem were scanned using a three dimensional technique. Two FE models of the stems were created using PATRAN. The models were analysed using the ABAQUS. Tied and sliding contact conditions were allowed between the implants and the cement mantle. The interface at the distal tip of the stem was removed to represent the scenario with a distal centraliser present.
Results: When tied contact was assumed, both stems displayed similar von Mises’ stress distributions. The peak stresses remained constant in the double tapered stem, with a marked translation of regions of high stress towards the distal tip with the introduction of sliding contact conditions. Peak stresses in the triple tapered stem decreased, but displayed a more continuous distribution along the implant with sliding contact. Torsional loading of the stems reduced the magnitude of the distal tip stresses.
Conclusions: The triple-tapered geometry displayed a more even distribution of stresses along the length of the implant. The double-tapered geometry displayed a high stress state at the distal tip of the implant.
The abstracts were prepared by Professor A. J. Thurston. Correspondence should be addressed to him at the Department of Surgery, Wellington School of Medicine, PO Box 7343, Wellington South, New Zealand
