Summary: Sagittal standing radiographs of the whole spine and pelvis in 200 adults (100 asymptomatic volunteers, 100 sagittally imbalanced patients who had a subsequent balancing operation) demonstrated useful parameters for the evaluation of sagittal imbalace as well as considerations for correction of sagittal imbalance. The T12 lower endplate ‐ horizontal angle was the simplest and the most correlative.
Introduction: To compare the sagittal plane alignment of the spine between normal asymptomatic adults (NA) and sagittaly imbalanced patients (SI).
Methods: Sagittal standing radiographs of the whole spine and pelvis in 200 adults (100 asymptomatic volunteers, 100 sagitally imbalanced patients who had a subsequent balancing operation) were evaluated. The following parameters were included: thoracic kyphosis (T5‐T12), T12 lower rnd plate‐horizontal angle, lumbar lordosis (T12‐S1), sacral slope, pelvic incidence, pelvic tilt, C7 plumb, T12 plumb, C7 plumb to bicoxofemoral head distance and distance from posterosuperior endplate of S1 to bicoxofemoral head.
Results: The mean differences between two groups were 5° for thoracic kyphosis (32 NA vs. 26 SI), 31° for T12 horizontal angle (‐22 NA vs. 10 SI), 45° for lumbar lordosis (‐60 NA vs. ‐15 SI), 14° for sacral slope (38 NA vs. 24 SI), 19° for pelvic tilt (13 NA vs. 32 SI) and 5° for pelvic incidence (51 NA vs. 57 SI). The mean differences between two groups were 16.3cm for sagittal vertical axis (‐0.9cm NA vs. 15.5cm SI), 12.2cm for C7 plumb to bicoxofemoral head distance (‐4.9cm NA vs. 7.4cm SI), 4.6cm for T12 plumb to S1 (‐1.9cm NA vs. 2.8cm SI) and 4.1 cm for S1 to bicoxofemoral head distance (4cm NA vs. 8.1cm SI). Sagittal vertical axis had strong positive correlation with C7 plumb to bicoxofemoral head distance (r=0.96); T12‐horizontal angle (r=0.83); pelvic incidence+thoracic kyphosis+lumbar lordosis (r=0.80); T12‐horizontal angle+thoracic kyphosis (r=0.77); lumbar lordosis (r=0.74); and thoracic kyphosis+lumbar lordosis (r=0.69).
Conclusion: These spinal sagittal parameters can be used as a baseline in the evaluation of sagittaly imbalanced patients as well as consideration for correction of sagittaly imbalanced patients. T12‐horizontal angle is the simplest and the most correlative to the sagittal vertical axis.
Significance: T12‐horizontal angle is the simplest and the most correlative to the sagittal vertical axis.