LAUSR

AIM Unstable posterior pelvic ring injuries should be stabilised successfully by percutaneous iliosacral screwing. The intervention takes place under intraoperative fluoroscopic guidance. The inlet and outlet views are crucial and are performed by tilting the image intensifier. Safely interpreting fluoroscopic views can be challenging in certain clinical scenarios. We demonstrated on a series of patients howpreoperative CT scans can be used to anticipate the appropriate intraoperative inlet and outlet fluoroscopic views and positioning of the patient on the operating table, thereby avoiding possible operating table obstacles. MATERIALS AND METHODS We analysed at random 30 pelvic CT scans from patients of different ages and both sexes, utilising the sagittal reconstructions. Inlet and outlet angle measurements were calculated on the scans to determine the appropriate intraoperative inlet and outlet views. RESULTS The analysed CT scans showed an average inlet view of 22.3° (range 10.4°-39.8°) and an average outlet view of 42.3° (range 31.5°-53.1°). Sex and age had no influence on results. The calculated required free space under the operating table for unobstructed tilting of the C-arm was a minimum of 145cm. CONCLUSION The significant anatomic variations of the posterior pelvic ring have been well documented in the literature. The angles required to obtain appropriate intraoperative inlet and outlet views are not perpendicular and differ greatly from traditional settings, which directed the beam 45° caudally and 45° cranially. The fluoroscopic beam would need to be angled differently in each patient to obtain ideal cardinal views that ultimately assist in safe iliosacral screw placement. To avoid collision of the C-arm with the operating table, it is essential to provide secure free space under the operating table of at least 145cm.