Prospective radiographic study of 160 asymptomatic young adults quantifying normal variation in lumbar and pelvic sagittal alignment. Proposes a four-type classification based on sacral slope that explains why lordosis differs so dramatically between normal individuals. Answers the question: what does normal sagittal spinal alignment actually look like, and how much does it vary?
The standard teaching that the spine is 'kyphotic T1–T12 and lordotic L1–L5' implies a single normal — this paper dismantles that assumption with data. Lordosis spans 41° to 82° in perfectly healthy adults, and that range is entirely explained by pelvic morphology, not spinal pathology.
When you plan a lumbar fusion, measuring pelvic incidence on the preoperative lateral is not optional. PI sets the sacral slope, and sacral slope sets the lordosis target. The PI minus lumbar lordosis mismatch concept used in adult deformity surgery traces directly to the normative relationships quantified here.
Roussouly type also carries prognostic weight before a patient is symptomatic. Flat-back Types 1 and 2 are your disc herniation patients; hyperlordotic Type 4 patients are heading toward stenosis. Recognizing morphologic type on a preoperative lateral radiograph informs likely disease trajectory and the risk of adjacent-segment degeneration after fusion.
The computerized measurement method reported interobserver reliability of ICC 0.92–0.99, confirming these measurements are reproducible enough for routine surgical planning, not just research use.
Prospective radiographic study of 160 asymptomatic young adults quantifying normal variation in lumbar and pelvic sagittal alignment. Proposes a four-type classification based on sacral slope that explains why lordosis differs so dramatically between normal individuals. Answers the question: what does normal sagittal spinal alignment actually look like, and how much does it vary?
The standard teaching that the spine is 'kyphotic T1–T12 and lordotic L1–L5' implies a single normal — this paper dismantles that assumption with data. Lordosis spans 41° to 82° in perfectly healthy adults, and that range is entirely explained by pelvic morphology, not spinal pathology.
When you plan a lumbar fusion, measuring pelvic incidence on the preoperative lateral is not optional. PI sets the sacral slope, and sacral slope sets the lordosis target. The PI minus lumbar lordosis mismatch concept used in adult deformity surgery traces directly to the normative relationships quantified here.
Roussouly type also carries prognostic weight before a patient is symptomatic. Flat-back Types 1 and 2 are your disc herniation patients; hyperlordotic Type 4 patients are heading toward stenosis. Recognizing morphologic type on a preoperative lateral radiograph informs likely disease trajectory and the risk of adjacent-segment degeneration after fusion.
The computerized measurement method reported interobserver reliability of ICC 0.92–0.99, confirming these measurements are reproducible enough for routine surgical planning, not just research use.