Projection angle for C-arm-assisted insertion of posterior acetabular column screws

Abstract

Objective To explore the optimal projection angle when cannulated screws are placed into the posterior acetabular column under the help of a C-arm fluoroscopic unit. Methods Twenty acetabular sides in 10 corpses were scanned with CT to find the scan plane which contained the maximum cross section of the femoral head. On this scan plane, we measured angle α which was between the posterior surface of the posterior column and the coronal plane, and angle β which was between the posterior surface of the posterior column and the acetabular fringe plane. Results Angle α was 28. 2°± 2. 3° and angle β was 95.4°± 5.3°. Conclusions When the projection direction is paralleled with the posterior surface of the posterior column, the angle between the bulb and the coronal plane is about 30°, 15° more than the obturator oblique view. Compared with the obturator oblique view, 30° can show more exactly the spatial relation between the screw and the posterior surface of the posterior column. The direction perpendicular to the acetabulum fringe plane can also be considered for projection. Key words: Surgical procedures, minimally invasive; Tomography, spiral computed; Tomography, X-ray computed; Bone nails