[Percutaneous screw fixation in treatment of fractures of acetabular columns using computer-assisted imaging navigation system: experiment with cadaver model].

Objective: To establish a new imaging protocol to acquire the most appropriate fluoro-images for fluoro-navigated percutaneous fixation of acetabular fracture and to evaluate the safety and efficiency of the procedures.
Methods: Guide needles were inserted into the bilateral anterior and posterior columns of the acetabula of 4 dry human cadaver pelvic skeletons and 4 plastic pelvic models. Then the pelvis skeletons were fixed to imaging guided surgery mimic operation modules. Dynamic fluoroscopy was conducted with C-arm X-ray machine vertically on the 4 virtual planes of the acetabulum, inner, outer, anterior, and posterior from multiple angles. The fluoroscopic images clearly showing the guide needles, anterior and posterior columns, and acetabulum were selected as registration images, and the relative space positions between the C-arm X-ray fluoroscope and pelvis and operation table. Guided by the navigation system, totally 16 titanium hollow screws were inserted into bilateral anterior and posterior columns of acetabula of the 4 pelvis skeletons. The screw positions were estimated by visual method. The time needed to position the C-arm so as to obtain the standard registration image, time needed for fluoroscopy, and operation time, including establishment of navigation system, software interface operation, and screw insertion, were recorded.
Results: All the screws were inserted to the satisfying positions: placed within the desired bony corridor of the column and none of then were inserted into the joint. While inserting the screw into the anterior column fluoroscopy should be conducted with obturated oblique view, obturated inlet view, obturated oblique outlet view, or pelvic AP view. While inserting the screw into the posterior column fluoroscopy should be conducted with iliac-oblique view, obturated oblique view, pelvic inlet view, or obturated oblique outlet view. The total surgical time required for screw insertion was 11.7 min for anterior column, and was 9.2 min for posterior column. 9.5 and 7.3 minutes were needed to position the C-arm X-ray machine so as to obtain the images of the anterior and posterior columns respectively. 2.9 and 1.7 seconds were needed for the actual fluoroscopy during insertion of the screws into the anterior and posterior columns respectively.
Conclusion: The standard registered fluoro-images are different from the conventional standard Judet-Letournel oblique views. How to get appropriate fluoro-images is the key point for fluoro-navigated percutaneous fixation of acetabular fractures.