Estimation of the relative pose of the femoral and acetabular components in a visual aided system for total hip replacement surgeries

In total hip replacement (THR) surgeries, the placement of the femoral and acetabular components within the safe zone is not guaranteed when using the freehand technique of operation. To improve the accuracy of the positioning, a visual aided system for THR which estimates and displays the relative pose of femoral and acetabular components is proposed. The system is composed of a dedicated femoral head trial with a miniature camera set inside the femoral head and a acetabular prosthesis trial with designated patterns placed on the internal surface of the liner. By analyzing the liner images taken by the camera, a set of correspondences between the 3D points and their 2D projections can be established. Then the relative pose is estimated using the correspondences as input. Finally, the result is displayed in 3D graphics in vivo. The system has been evaluated under the simulation with rotation quaternion and translation vector and the experimental results have validated the effectiveness of the proposed method.