Development of a Navigation Tool for Revision Total Hip Surgery Based on Electrical Impedance Tomography

An aging population has led to a dramatic rise in total hip replacements (THRs) and revision THRs. Clinically, revision THR is more difficult to perform and is associated with a higher risk than the primary one. To reduce the risk and to enhance the operation efficiency, a new approach based on electrical capacitance tomography (ECT) and electrical resistance tomography (ERT) is proposed to provide real-time 3-D images, aiming to navigate a drilling/milling tool in the femur during surgery. An ECT/ERT dual modality sensor adopts the conventional ECT sensor design with internal electrodes and voltage excitation. The capacitance and conductance are measured by an impedance analyzer-based system. With prior knowledge of the shape and diameter of the femur and the drilling/milling tool, 3-D imaging of the revision THR surgery can be realized by estimating the cross-sectional position of the femur and the cross-sectional and axial positions of the drilling/milling head. Experiments were carried out with an aluminum rod inserted in the empty cavity of a cemented femoral bone surrounded by saline solution. The position of the femur is derived by a weighted mean method, and the axial position of the rod is estimated by a linear function. Initial 3-D images for visualizing the revision THR process is generated in MATLAB, confirming the feasibility of visualizing the surgery process by this proposed approach.