The effect of variation in arm position on sagittal spinal alignment

Area of Science:

• Spine surgery and radiology
• Orthopedic biomechanics
• Radiographic imaging analysis

Background:

• Sagittal spinal alignment is crucial for overall health and balance.
• The influence of arm positioning on radiographic sagittal alignment is understudied.
• Standardized radiographic techniques are essential for accurate spinal assessment.

Purpose of the Study:

• To assess the impact of varying arm positions on spinal sagittal alignment.
• To determine if prior spinal fusion affects the influence of arm position on alignment.
• To provide evidence-based recommendations for radiographic positioning.

Main Methods:

• Prospective radiographic analysis of 80 patients (40 with, 40 without prior spinal fusion).
• Standardized lateral long cassette radiographs taken with arms at 90° and 30° shoulder flexion.
• Measurement and statistical comparison of segmental, regional, and global sagittal alignments.

Main Results:

• No significant difference in segmental/regional alignment between fused and non-fused groups.
• A statistically significant negative shift in sagittal vertical axis (SVA) occurred with 90° vs. 30° arm flexion (P=0.038) in fused patients.
• Trend towards SVA shift in non-fused patients (P=0.119) but not statistically significant.

Conclusions:

• Arm position critically influences sagittal vertical axis measurements.
• The effect of arm position on SVA is more pronounced in patients with prior spinal fusion.
• Recommend 30° arm flexion for standardized lateral whole-spine radiography to ensure consistent sagittal alignment assessment.