Computerised Tomography Analysis of Pelvic Inlet and Outlet Fluoroscopic View Angles.

BACKGROUND: Pelvic inlet and outlet fluoroscopy views are routinely used in operative treatment of posterior pelvic ring injuries. In this study, we aimed to evaluate the angles of pelvic inlet and outlet fluoroscopic view, their differences with hip flexion and the correlation of these differences with sacral slope changes.
MATERIALS AND METHODS: Sagittal reconstructions of 100 lumbopelvic CT were used to measure sacral slope, pelvic inlet and outlet view angles. The range of pelvic inlet-outlet view angles and their relation with age, sex and sacral slope were analyzed. In ten of these 100 patients, who were undergone a second CT imaging, hips were passively flexed to 60° to change pelvic tilt. The difference in sacral slope and pelvic inlet-outlet view angles in different positions were compared.
RESULTS: Mean angles for inlet view, outlet view and sacral slope were 28.9, 41.4 and 37.0, respectively. There was no difference between males and females (p > 0.05). Pelvic outlet angles had a negative correlation with age (p < 0.05). Sacral slope changes with hip flexion showed a negative correlation with inlet angles and positive correlation with outlet angles (p < 0.05). The differences in sacral slope, pelvic inlet and outlet view angles between two measurements were equal.
CONCLUSIONS: The pelvic inlet and outlet view angles shows a wide range without a standard so we suggest preoperative CT scan to plan the optimal angles before pelvic ring surgery. The difference in these angles due to pelvic tilt during the surgery may be corrected by measuring the sacral slope difference. © Indian Orthopaedics Association 2020.