A Novel Method for Estimating Three-Dimensional Apical Vertebral Rotation Using Two-Dimensional Coronal Cobb Angle...

Area of Science:

• Orthopedics
• Radiology
• Biomechanical Engineering

Background:

• Quantifying vertebral rotation in adolescent idiopathic scoliosis (AIS) using 2D imaging is difficult due to the inability to directly visualize the axial plane.
• Accurate assessment of 3D vertebral rotation is crucial for understanding AIS progression and planning treatment.

Purpose of the Study:

• To develop a simple mathematical formula for estimating 3D apical vertebral rotation (AVR) in AIS.
• To correlate routinely obtained 2D spinal measurements with 3D AVR using a large cohort of 3D spinal reconstructions.

Main Methods:

• A retrospective cohort analysis of 279 3D spinal reconstructions for thoracic major AIS patients.
• 2D measurements (thoracic Cobb angle, T5-T12 thoracic kyphosis) were correlated with 3D AVR.
• A multivariable regression model was developed and validated on separate cohorts.

Main Results:

• A formula was derived: 3D AVR = 0.26*(T5-T12 kyphosis) + 0.34*(coronal Cobb) - 5.38.
• The model demonstrated good performance in the development cohort (R=0.739, r²=0.54) and generalizability in the validation cohort (R=0.703).
• The mean absolute error was less than 5°, indicating high accuracy.

Conclusions:

• A validated mathematical model can accurately estimate 3D AVR in AIS patients using standard 2D measurements.
• This method offers a valuable, instrument-free alternative for routine AIS evaluation and surgical preparation.
• The model's accuracy is comparable to existing methods but simpler to implement.