Comparison of three methods for measuring C0-1 angles and C0-2 angles

Area of Science:

• Orthopedics
• Radiology
• Spine Surgery

Background:

• The upper and lower cervical spine exhibit a compensatory relationship in sagittal alignment.
• Previous studies show varied methods for measuring upper cervical sagittal parameters.
• This study compares three methods for upper cervical sagittal parameter measurement.

Purpose of the Study:

• To compare the reliability of three reference lines (FHL, FML, ML) for measuring upper cervical sagittal parameters (C0-1 and C0-2 angles).
• To evaluate the correlation between upper and lower cervical sagittal alignment using different measurement methods.

Main Methods:

• Retrospective analysis of 263 lateral cervical radiographs.
• Measurement of C0-1 and C0-2 angles using Frankfort horizontal line (FHL), foramen magnum line (FML), and McGregor line (ML).
• Intraclass correlation (ICC) for reliability; Pearson's correlation for parameter relationships.

Main Results:

• McGregor line (ML) demonstrated higher interobserver and intraobserver ICC values for C0-1 and C0-2 angles compared to FML and FHL.
• All measured upper cervical angles showed a negative correlation with the C2-7 angle (lower cervical alignment).
• Upper sagittal parameters measured by FHL showed the strongest correlation with C2-7 angle, with correlations increasing with age.

Conclusions:

• The McGregor line (ML) provides a more reliable method for measuring C0-1 and C0-2 angles.
• The Frankfort horizontal line (FHL) is more suitable for evaluating the compensatory mechanism between the upper and lower cervical spine.