The Pelvic Inlet and Outlet Radiographic View in Filipinos A retrospective study of CT scan measurements and 3-Dimensional Computed Tomography Reconstructions

Background: Injuries to the pelvic ring pose a significant challenge requiring urgent multidisciplinary management. Adequate radiological evaluation is essential in assessing these injuries. The standard radiologic evaluation of the pelvis includes an AP, inlet, and outlet view. The inlet and outlet view are classically taught to be orthogonally taken with a 45-degree angulation from the anteroposterior plane. However, there is growing evidence that there is a significant individual variation within the population and these values need to be re-analyzed.

Materials and Methods: This is a retrospective study done in a level I trauma center. A total of 110 patients (62 males and 48 females) older than 18, who had clinically indicated Computed Tomography (CT) scan done without any pelvic pathologies were included. A 3D Multiplanar reconstruction (MPR) and 3D reconstruction CT scans were derived from the DICOM images and various methods were used to analyze the ideal angulations based on the 2-Dimensional and 3-Dimensional images rendered.

Statistical analysis: Mean and standard deviation were calculated for each angle measured with a comparison between gender and presence or absence of dysmorphic sacra. A correlational analysis was then done comparing the angles obtained on the sagittal CT scan from the 3D MPR and the ideal inlet and outlet angle from the 3D reconstructed images. 

Results: The mean caudal angulation for the inlet view was 31.448 ± 7.25° with no significant difference for the normal and dysmorphic sacrum and the mean cephalad angulation for screening for the ideal outlet view was 38.39 ± 6.96° with individuals with dysmorphic sacra having an angulation 5° more than the normal group 

Conclusion: The study re-evaluated the ideal screening inlet and outlet angulations in the Filipino population which demonstrated a mean of 31° of caudal angulation for the inlet view and a mean of 38° of cephalad angulation on outlet views.

Keywords: Pelvis, Pelvic Fracture, Inlet angle, Outlet Angle, CT scan 3D reconstruction