Avoiding pitfalls in percutaneous acetabular column screw placement using combined fluoroscopic check-point views: a technical note and case series.

Standard fluoroscopic views may not detect cortical breaches during percutaneous acetabular column screw placement, creating an illusion of safe intraosseous positioning. The purpose of this study was to illustrate use of simple fluoroscopic checkpoint projections-the combined obturator oblique hyper-outlet (COOHO) view for anterior column (AC) screws and two known additional views, outlet and true lateral (TL), for posterior column (PC) screws-as a method to demonstrate extraosseous screw trajectories that might be missed by standard tangential column fluoroscopic views. Six clinical cases are presented as examples of standard orthogonal fluoroscopic views failing to detect extraosseous screw placement. The cases are supplemented by a synthetic pelvic model demonstration to define radiographic landmarks and common screw malposition. Guidewires were advanced in the pelvic model columns, either intraosseous or extraosseous, and their paths were evaluated with standard fluoroscopic views compared to COOHO and outlet and TL views. For the AC, COOHO tangentially profiles the pectineus recess and iliopsoas gutter to unmask in-out-in paths. For the PC, iliac and obturator oblique views may miss medial or posterior breach near the lesser sciatic notch and quadrilateral plate. The outlet and TL views show the vertical extent of the ilioischial line to detect medial or posterior breech and length-orientation errors. The COOHO, outlet and TL views additional projections that improve tangential visualization of high-risk cortices and detection of extraosseous trajectories.