Legaye and colleagues tested whether pelvic incidence, a fixed anatomical pelvic angle, governs pelvic orientation and lumbar lordosis and so regulates sagittal spinal balance.
Cross‑sectional radiographic study of 49 normal adults and 66 scoliotic women, analyzed by correlation and regression.
Methods
Design
Cross‑sectional radiographic study
Data source
Standing orthogonal plain radiographs
Patients
49 normal adults (28 men, 21 women)
Normal group mean age 24, volunteer medical and physical therapy students
66 scoliotic women, mean age 33 (range 10 to 84)
Scoliotic curves lumbar in 24 and thoracolumbar in 42
Exposure
Pelvic incidence
Cobb angle and apical vertebral rotation in scoliosis
Outcomes
Sacral slope
Pelvic tilt
Lumbar lordosis
Predicted vs measured lordosis
Key Findings
In normal adults, pelvic incidence correlated strongly with sacral slope (r = 0.83752).
Sacral slope was in turn closely related to lumbar lordosis in normal adults (r = 0.85943).
In the 66 scoliotic women these correlations remained significant but were weaker, at r = 0.65645 for incidence vs sacral slope and r = 0.80409 for sacral slope vs lordosis.
The authors' predictive equation for lordosis matched measured values with r = 0.94948 in normal adults.
In scoliosis, the equation reached r = 0.92426 using sagittal parameters alone and r = 0.94118 after adding Cobb angle and apical rotation.
The authors describe this as the first statistical demonstration that vertebral axial rotation reduces lordosis in scoliotic patients.
Board pearl
Pelvic incidence is a fixed anatomical angle equal to sacral slope plus pelvic tilt, so the two positional angles trade off against each other around it.
Authors' conclusion
The pelvic incidence appears to be the main axis of the sagittal balance of the spine.
Legaye and colleagues tested whether pelvic incidence, a fixed anatomical pelvic angle, governs pelvic orientation and lumbar lordosis and so regulates sagittal spinal balance.
Cross‑sectional radiographic study of 49 normal adults and 66 scoliotic women, analyzed by correlation and regression.
Methods
Design
Cross‑sectional radiographic study
Data source
Standing orthogonal plain radiographs
Patients
49 normal adults (28 men, 21 women)
Normal group mean age 24, volunteer medical and physical therapy students
66 scoliotic women, mean age 33 (range 10 to 84)
Scoliotic curves lumbar in 24 and thoracolumbar in 42
Exposure
Pelvic incidence
Cobb angle and apical vertebral rotation in scoliosis
Outcomes
Sacral slope
Pelvic tilt
Lumbar lordosis
Predicted vs measured lordosis
Key Findings
In normal adults, pelvic incidence correlated strongly with sacral slope (r = 0.83752).
Sacral slope was in turn closely related to lumbar lordosis in normal adults (r = 0.85943).
In the 66 scoliotic women these correlations remained significant but were weaker, at r = 0.65645 for incidence vs sacral slope and r = 0.80409 for sacral slope vs lordosis.
The authors' predictive equation for lordosis matched measured values with r = 0.94948 in normal adults.
In scoliosis, the equation reached r = 0.92426 using sagittal parameters alone and r = 0.94118 after adding Cobb angle and apical rotation.
The authors describe this as the first statistical demonstration that vertebral axial rotation reduces lordosis in scoliotic patients.
Board pearl
Pelvic incidence is a fixed anatomical angle equal to sacral slope plus pelvic tilt, so the two positional angles trade off against each other around it.
Authors' conclusion
The pelvic incidence appears to be the main axis of the sagittal balance of the spine.