The Effect of Pelvic Position on Pelvic Incidence

Ahmadi, Saeed; Falsafi, Mani; Ghaemian, Naser; Shirafkan, Hoda; Afshar, Amir Mahmoud

doi:10.22034/ijos.2025.547942.1166

The Effect of Pelvic Position on Pelvic Incidence

Document Type : Original Article

Authors

Saeed Ahmadi ¹ ^¶

Mani Falsafi ²

Naser Ghaemian ¹

Hoda Shirafkan ³

Amir Mahmoud Afshar ¹

¹ Clinical Research Development Center, Shahid Beheshti Hospital, Babol University of Medical Sciences, Babol, Iran.

² Department of orthopedics, Faculty of Medicine, Babol University of Medical Sciences, Babol, Iran

³ Social determinants of health research center, health research institute, Babol university of medical Sciences, Babol, Iran.

https://doi.org/10.22034/ijos.2025.547942.1166

Abstract

Abstract
Introduction: Given the importance of the stability of the pelvic incidence (PI) angle in evaluating spinal alignment and its significance in spinal fixation during surgical procedures, this study aims to investigate the PI angle and compare it in two positions: Full Flexion and Full Extension.
Materials & Methods: This cross-sectional study assessed 44 student volunteers using dynamic radiographic evaluation in two positions: Full Flexion and Full Extension. Dynamic radiographs were taken in two conditions: (1) seated with maximum forward bending (Full Flexion) and (2) lying supine with legs hanging off the edge of the bed to their maximum extent (Full Extension). The PI angle was measured using the PACS software.
Results & Discussion: The mean PI angles in the Full Flexion and Full Extension positions were not equal, demonstrating positional changes. The mean PI angle in Full Flexion was higher than in Full Extension. The mean difference in PI angle between the two positions was 3.6±3.9 degrees. In females, the mean PI angle in Full Flexion was 55.83±11.23 degrees, which was higher than in males (53.22±7.62 degrees), though this difference was not statistically significant (P = 0.390). In Full Extension, the mean PI angle in females was 51.61±9.87 degrees, which was again higher than in males (49.65±7.05 degrees), but the difference was not statistically significant (P = 0.608).
Conclusion: The study results indicate that pelvic positioning affects pelvic incidence, and PI measurements are not constant across different positions. Furthermore, PI in the Full Flexion position was greater than in the Full Extension position.

Keywords

Pelvis

Spine

Patient positioning

Subjects