Changes of spinopelvic parameters in different positions

Area of Science:

• Spine biomechanics
• Radiographic analysis
• Pelvic anatomy

Background:

• Spinopelvic parameters are crucial for spinal alignment.
• Pelvic incidence (PI) is a key parameter influencing sagittal balance.
• Understanding positional changes in these parameters is important for clinical assessment.

Purpose of the Study:

• To evaluate changes in spinopelvic parameters between standing and supine positions.
• To assess the variability of pelvic incidence (PI) in different postures.
• To compare PI measurements from radiography and CT scans.

Main Methods:

• Patients underwent standing whole-spine radiography, pelvic CT, and lumbar MRI.
• Pelvic parameters (PT, SS, PI) and lumbar lordosis (LL) were measured by two observers.
• Patients were subgrouped based on PI change (less vs. higher).

Main Results:

• Radiographic PI was significantly higher than CT-derived PI.
• In patients with less PI change (SG1), PT and LL decreased, while SS increased from standing to supine.
• In patients with higher PI change (SG2), PT and PI decreased significantly from standing to supine.
• SG2 exhibited significantly greater pelvic parameters and sagittal vertical axis on radiograph, and LL on MRI compared to SG1.

Conclusions:

• Most patients showed alignment changes with stable PI, decreased PT/LL, and increased SS when moving from standing to supine.
• A subset of patients displayed decreased PT/PI and fixed SS/LL.
• Higher PI change is associated with elevated pelvic parameters and sagittal vertical axis, and fixed LL.