3D positioning for revision total hip replacement surgery by dual-modality tomography

A new approach based on electrical capacitance tomography (ECT) and electrical resistance tomography (ERT) is proposed to providing real-time 3D images for revision total hip replacements (THRs), attempting to navigate a drilling/milling tool in the femoral bone during the surgery. An ECT/ERT dual-modality sensor adopts the conventional ECT sensor structure with internal electrodes and voltage excitation. The capacitance and conductance are measured by an impedance analyzer based system. With the prior knowledge of the shape and diameter of the femoral bone and the drilling/milling tool, the 3D imaging process during the revision THR surgery can be simplified to estimate the cross-sectional position of the femur and the cross-sectional and axial position of the drilling/milling head. Experiments were carried out with an aluminum rod inserted in empty cavity of a cemented femoral bone surrounded by saline solution. The cross-sectional position of the femur is derived by a weighted mean method and the axial position by a linear function. 3D images for visualizing the revision THR process is generated in MatLab. The initial result is promising, providing the possibility of visualizing the surgery process using the ECT/ERT dual-modality.