Introduction The use of intraoperative fluoroscopy is becoming more common during total hip arthroplasty. Current techniques are limited by inaccuracy, since the projection angle of the image is unknown, and by the need to obtain multiple images, including of the contralateral hip. The current study assesses the accuracy of a method that uses preoperative 3D knowledge to measure cup orientation on a single image of the affected hip during surgery. Methods Surgery plans are created using CT imaging. Following completion of the plan, a postoperative CT of the patient is simulated according to that plan. Simulated fluoroscopic images are then created. Intraoperatively, a single fluoroscopic image centered on the hip is acquired and its projection angle is determined by matching to the simulated images. Cup orientation is then calculated using the known projection model. The cup orientation calculated on the fluoroscopic image was then compared to a previously validated method 1 of measurement using bilateral simultaneous EOS imaging post-operatively. Results Component orientation calculated using a single intraoperative fluoroscopic ipsilateral hip image was assessed so far in 19 hips. Compared to postoperative biplane EOS measurements, the range of error for anteversion was −3 to +2 degrees (average 0.4, sd 1.4) and the range of error for inclination was −3 to 4 degrees (average 0.1, sd 1.9). Conclusion The current study uses 2D images generated from a 3D plan for 2D-2D matching and component position assessment on a single ipsilateral hip image. The preliminary results demonstrate the potential to improve accuracy and reduce radiation in fluoroscopically-guided THR using 3D-informed navigation.
Heimann et al. (Thu,) studied this question.