Ceramic prosthetic femoral head: the effect of the contact stress distribution

摘要

'Burst' fracture of alumina and zirconia femoral component in hip is a phenomenon, which has been assumed to occur due to the tensile hoop stresses within the femoral head. The aim of this study was to determine the effect of material properties and taper design on the stresses developed in the ceramic femoral head using finite element analysis [FEA]. An axisymmetric 3D finite element model of a 22mm diameter femoral head and taper was generated in PATRAN and analysed using ABAQUS. The common 8/10 (10mm) and a Zimmer 6~0 (11.5mm) tapers were modelled. To represent manufacturing tolerances the taper contact was varied by introducing angular mismatch of +-4 minutes. The 3~(rd) Principal stresses (hoop) were marginally higher with a CoCrMo taper compared to a Ti6Al4V taper. Taper mismatch had a significant impact on the femoral head stresses. A smaller taper (10mm) with an acuter angle almost doubled the 3~(rd) principal stresses. Material properties and geometry is found to effect the hoop stresses generated in the femoral head. Increased rigidity led to higher stress at the taper interface. Although the stresses calculated were below the failure criteria of the materials, in mismatched tapers the induced stresses under certain geometric conditions can possibly reach to relatively critical levels.