Differences in cervical sagittal alignment between the standing and sitting positions

Area of Science:

• Spine surgery
• Orthopedics
• Radiography

Background:

• Sagittal spinal alignment is typically assessed standing, but significant posture-dependent differences exist in lumbopelvic alignment.
• Cervical alignment is influenced by lumbopelvic alignment, suggesting posture affects the entire spine.

Purpose of the Study:

• To investigate differences in cervical sagittal alignment between standing and sitting positions.
• To hypothesize that cervical sagittal alignments vary between standing and sitting postures.

Main Methods:

• Whole spine radiography was performed on 108 patients with spinal degenerative diseases in both standing and sitting positions.
• Key parameters measured included cervical lordosis (CL), C2-7 SVA, T1S, C7-S1 SVA, TK, LL, SS, PT, and PI.
• Patients were categorized into Decreased (ΔCL < -3°), Unchanged (-3° ≤ ΔCL ≤ 3°), and Increased (ΔCL > 3°) groups based on CL changes between postures.

Main Results:

• The Unchanged group (UG) exhibited alignment closer to ideal standards in the standing position.
• In the sitting position, all groups showed posterior pelvic rotation and flattened lumbar lordosis; the Decreased group (DG) had significantly higher C2-7 SVA than the UG.
• The Increased group (IG) showed a higher PI-LL mismatch in the standing position compared to the UG.

Conclusions:

• Cervical lordosis (CL) changed between standing and sitting in 58.3% of individuals.
• Patients with good baseline spinal alignment maintained stable cervical alignment.
• Positional changes in CL may be linked to pre-existing spinal imbalances and PI-LL mismatch.