Table 1.
Radiologically assessed variables of balance derived from measurements on lateral and posteroanterior radiographs
| Variable | Description |
|---|---|
| Sagittal balance | Assessment from lateral radiograph |
| Sagittal C7PL (mm) | Distance between C7P and posterosuperior corner of S1 vertebral body * |
| Sagittal GL (mm) | Distance between GL and posterosuperior corner of S1 vertebral body * |
| Sagittal GL–CFH (mm) | The horizontal distance between the GL and the center of the bicoxofemoral axis† |
| Lumbar lordosis Cobb angle (°) | The angle between the superior end plate of T12 and the superior end plate of S1 |
| Coronal balance | Assessment from posteroanterior radiograph |
| Coronal C7PL (mm) | Distance between C7PL and central sacral vertebral line‡ |
| Coronal GL (mm) | Distance between GL and central sacral vertebral line‡ |
| Coronal GL–CFH (mm) | The horizontal distance between the GL and the center of the bicoxofemoral axis§ |
| Lateral olisthesis (mm) | Relative to the lower vertebral body, the upper vertebral body lateral slip distance |
| Pelvic variables | Assessment from lateral radiograph |
| Pelvic incidence (PI, °) | Angle between the line perpendicular to the S1 end plate at its midpoint and the line connecting this point to the middle axis of the femoral heads |
| Sacral slope (SS, °) | Angle between the line connecting the superior end plate of S1 and a horizontal line |
| Pelvic tilt (PT, °) | Angle between the line connecting the midpoint of the sacral plate to the middle axis of femoral heads and a vertical line |
Note: *, positive when in front of the posterosuperior corner of the S1 vertebral body; †, positive when in front of the CFH, negative when behind the CFH; ‡, positive when to the right of the central sacral vertebral line; §, positive when to the right of the CFH. CSVL, central sacral vertebral line; SSVL, sagittal sacral vertical line (posterosuperior corner of S1 vertebral body).