Determination of the acetabular cup implant stability using an acoustic method based on the impact between the hammer and the ancillary

Abstract

The hemispherical acetabular cup (AC) implant is used during total hip replacement surgery and is inserted in the acetabulum using impacts applied with an orthopedic hammer. However, the assessment of the AC implant primary stability remains difficult. The aim of this study was to investigate the feasibility of retrieving the AC implant stability based on impact signal analyses. AC implants with various sizes were inserted in 12 cadaveric hips following the same protocol as the one employed in the clinic. An instrumented hammer was then used to measure the variation of the force as a function of time produced during the impact between the hammer and the ancillary. Then, an indicator I was determined for each impact based on the impact momentum. A significant correlation (R² = 0.69) was found between I and the pull-out force. Moreover, a tridimensional axisymmetric finite element model was developed to simulate the insertion processes of the AC implant into bone tissue during impacts. The variation of the force applied between the hammer and the ancillary was analyzed and the numerical results were compared with the experimental results. The results show the potential of impact analysis to retrieve the bone-implant contact properties.