Prospective radiographic study of 300 asymptomatic adult volunteers establishing normative values for sagittal spinopelvic parameters. Quantifies the mathematical relationships among pelvic incidence, sacral slope, lumbar lordosis, thoracic kyphosis, and T9 sagittal offset using regression and principal components analysis. Provides the reference equations surgeons use to set individualized correction targets.
When you fuse a lumbar spine without accounting for pelvic incidence, you are guessing at the correction target. This paper provides the equation: the individual's PI predicts the sacral slope (SS = 7.3 + 0.63 × PI), and sacral slope predicts the required lordosis (MLL = −16 − 1.06 × SS). A patient with PI of 55° needs roughly 60° of lordosis — leave them at 30° and you are building in adjacent-segment failure.
The clinical case in Figure 4 makes this concrete: a patient fused with PI = 55° but only 30° of postoperative lordosis developed L3-L4 pseudarthrosis and degenerative spondylolisthesis within five years. Salvage required posterior wedge osteotomy to recover lordosis.
Before ordering a deformity correction, measure PI on the preop film and use the regression equations in Table V to define your target. A postoperative LL that falls more than roughly 10° below PI is the threshold most subsequent literature uses to define PI-LL mismatch and predict poor outcomes.
Pelvic tilt and thoracic kyphosis are the two independent compensatory mechanisms the body uses when lumbar lordosis is deficient. Elevated PT on a postop film is a red flag that sagittal balance has not truly been restored.
Prospective radiographic study of 300 asymptomatic adult volunteers establishing normative values for sagittal spinopelvic parameters. Quantifies the mathematical relationships among pelvic incidence, sacral slope, lumbar lordosis, thoracic kyphosis, and T9 sagittal offset using regression and principal components analysis. Provides the reference equations surgeons use to set individualized correction targets.
When you fuse a lumbar spine without accounting for pelvic incidence, you are guessing at the correction target. This paper provides the equation: the individual's PI predicts the sacral slope (SS = 7.3 + 0.63 × PI), and sacral slope predicts the required lordosis (MLL = −16 − 1.06 × SS). A patient with PI of 55° needs roughly 60° of lordosis — leave them at 30° and you are building in adjacent-segment failure.
The clinical case in Figure 4 makes this concrete: a patient fused with PI = 55° but only 30° of postoperative lordosis developed L3-L4 pseudarthrosis and degenerative spondylolisthesis within five years. Salvage required posterior wedge osteotomy to recover lordosis.
Before ordering a deformity correction, measure PI on the preop film and use the regression equations in Table V to define your target. A postoperative LL that falls more than roughly 10° below PI is the threshold most subsequent literature uses to define PI-LL mismatch and predict poor outcomes.
Pelvic tilt and thoracic kyphosis are the two independent compensatory mechanisms the body uses when lumbar lordosis is deficient. Elevated PT on a postop film is a red flag that sagittal balance has not truly been restored.