Spinal Alignment in Asymptomatic Adults With Negative Sagittal Balance

Area of Science:

• Spinal biomechanics and alignment.
• Radiologic assessment of sagittal balance.

Background:

• Limited understanding of negative sagittal imbalance compared to positive imbalance.
• Investigating backward spinal alignment in asymptomatic individuals.

Purpose of the Study:

• To examine spinal alignment in asymptomatic adults with negative sagittal balance.
• To determine the physiological limit of negative sagittal balance.

Main Methods:

• Cross-sectional radiologic study of 106 asymptomatic adults with sagittal vertical axis (SVA) ≤-3 cm.
• Measurement of global sagittal parameters including SVA, T1 pelvic angle (T1PA), and others.
• Analysis of spinal alignment using Roussouly types and pelvic incidence (PI).

Main Results:

• Mean SVA was -4.3±1.1 cm, indicating common negative balance.
• Sagittal vertical axis (SVA) most frequently landed at the S2 sacral segment (53.8%).
• No predominant Roussouly types or pelvic incidence (PI) patterns were observed.

Conclusions:

• Negative sagittal balance is not uncommon in young asymptomatic adults.
• Anterior pelvic rotation may be a compensatory mechanism for negative balance.
• The physiological limit of posterior C7 SVA displacement does not extend beyond the sacrum.