Design of a computer-aided visual system for Total Hip Replacement surgery

To improve the accuracy of implant placement in Total Hip Replacement (THR) surgeries, this paper proposes a computer-aided visual system for THR which is composed of a customized acetabular cup, a multi-sensor femoral head trial and a computer for data processing and display. The customized trial is of the same size as the real prosthesis. An image sensor, a gyroscope and an e-compass (including an accelerometer and a magnetometer) are adopted in the femoral head trial. Reference patterns are designed and printed on the internal surface of the cup, whose images are taken by the image sensor for estimation of relative pose and position between the femoral head trial and the acetabulum cup. Two methods of pose estimation are adopted in this system: one based on images and the other based on motion data from gyroscope and e-compass. The efficient perspective-n-point (EPNP) algorithm is used in the image-based pose estimation and achieves a rotation relative error of less than 8% and a translation relative error of less than 10%. The complementary algorithm is adopted in the motion-based pose estimation to smooth the results. Experimental results verified the proposed system.