Abstract
Introduction
Computer-assisted methods for acetabulum cup navigation have shown to be able to improve the accuracy of the procedure, but are time-consuming and difficult to use. The goal of this project was to develop an easy-to-use navigation technique, requiring minimal equipment for acetabular cup alignment.
Material
A preoperative CT scan was obtained, a 3D model of the acetabulum was created, the pelvic plane determined and the cup orientation planned. A registration area, which included the accessible part of the acetabular fossa and the surrounding articular surface, was chosen for the individualised guide. A guidance cylinder, aligned along the planned cup orientation, was attached in the centre of the guide.
To transfer the planned alignment information from the registered guide to the impacting of the cup, we developed an intraoperative guidance method based on inertia sensors. The sensors were aligned orthogonal to the central cylinder of the patient-specific guide and the orientation was recorded. At the time of impacting the cup, the sensors were attached to the impactor and the surgeon used the recorded information for the alignment of the impactor.
Results
To measure the accuracy of the proposed registration method, we performed an in-vitro trial on three fresh-frozen hemipelves with seven participants. The deviation between the planned and registered inclination averaged 3.01° (StDev 5.7). In anteversion, we measured an average error of 4.33° (StDev 2.8).
We tested the feasibility of the proposed method in a clinical trial. The postoperative radiographic measured angles in this trial were 45° anteversion (planned 45°) and 25° inclination (planned 20°).
Discussion
We introduce a novel method for computer-assisted cup alignment, which is easy to integrate into the surgical workflow. Our preliminary results suggest that this method is accurate. However, further clinical studies are necessary to verify its clinical feasibility and accuracy.
