Computer-assisted periacetabular screw placement: Comparison of different fluoroscopy-based navigation procedures with conventional technique.

The current gold standard for operatively treated acetabular fractures is open reduction and internal fixation. Fractures with minimal displacement may be stabilised by minimally invasive methods such as percutaneous periacetabular screws. However, their placement is a demanding procedure due to the complex pelvic anatomy. The aim of this study was to evaluate the accuracy of periacetabular screw placement assessing pre-defined placement corridors and comparing different fluoroscopy-based navigation procedures and the conventional technique. For each screw an individual periacetabular placement corridor was preoperatively planned using the planning software iPlan CMF(©) 3.0 (BrainLAB). 210 screws (retrograde anterior column screws, retrograde posterior column screws, supraacetabular ilium screws) were placed in an artificial Synbone pelvis model (30 hemipelves) and in human cadaver specimen (30 hemipelves). 2D- and 3D-fluoroscopy-based navigation procedures were compared to the conventional technique. Insertion time and radiation exposure to specimen were also recorded. The achieved screw position was postoperatively assessed by an Iso-C(3D) scan. Perforations of bony cortices or articular surfaces were analysed and the screw deviation severity (difference of the operatively achieved screw position and the preoperatively planned screw position in reference to the pre-defined corridors) was determined using image fusion. Using 3D-fluoroscopy-based navigation, the screw perforation rate (7%) was significantly lower compared to 2D-fluoroscopy-based navigation (20%). For all screws, the deviation severity was significantly lower using a 3D- compared to a 2D-fluoroscopy-based navigation and the conventional technique. Analysing the posterior column screws, the screw deviation severity was significantly lower using 3D- compared to 2D-fluoroscopy-based navigation. However, for the anterior column screw, the screw deviation severity was similar regardless of the imaging method. Despite the advantages of the 3D-fluoroscopy-based navigation, this method led to significantly longer total procedure and fluoroscopic times, and the applied radiation dose was significantly higher. Percutaneous periacetabular screw placement is demanding. Especially for posterior column screws, due to a lower perforation rate and a higher accuracy in periacetabular screw placement, 3D-fluoroscopy-based navigation procedure appears to be the method of choice for image guidance in acetabular surgery.