Coronal balance is one of the features that needs to be assessed on long spine radiographs obtained for spinal deformity, particularly scoliosis. It measures whether or not the upper spine is located over the midline (normal) or off to one side.
To assess coronal balance, a vertical (plumb) line is drawn downwards from the mid-point of the C7 vertebral body (exactly in the same way as for the assessment of sagittal balance 1. This needs to be performed on erect full-length spine radiographs without lateral bending. The horizontal distance between this plumb line and the midline of the sacrum or central sacral vertical line is measured. The position of this line is then termed positive, neutral or negative, depending on distance and direction from the midline 1.
- positive balance: the plumb line passes to the right of the midline, by more than 2 cm
- neutral balance: the plumb line passes within 2 cm of the midline
- negative balance: the plumb line passes to the left of the midline, by more than 2 cm