This prospective multicenter study enrolled 492 consecutive adult spinal deformity patients across 11 U.S. sites. It asked which radiographic parameters best predict patient disability and derived specific thresholds for severe impairment. Coronal Cobb angle — the historical gold standard — was far less predictive than sagittal spinopelvic measurements.
When you read a long-cassette standing lateral radiograph on an adult deformity patient, three numbers tell you almost everything about how disabled that patient is: pelvic tilt, SVA, and PI-LL mismatch.
If PT ≥22°, SVA ≥47 mm, or PI-LL ≥11°, the patient is likely in the severe disability range (ODI >40). When all three are exceeded simultaneously, the patient almost certainly needs operative discussion — 31% of surgical patients hit all three versus 15% of nonoperative patients.
Of the three, PI-LL mismatch is the one to fix. SVA and PT are compensatory postures the body adopts when lordosis can't match pelvic incidence. Correct the PI-LL mismatch with an osteotomy, and SVA and PT should improve as consequences.
One important caveat the authors themselves make: these thresholds guide assessment, but surgical decisions must also account for patient expectations, comorbidities, and risk tolerance. The numbers alone do not constitute an operative indication.
This prospective multicenter study enrolled 492 consecutive adult spinal deformity patients across 11 U.S. sites. It asked which radiographic parameters best predict patient disability and derived specific thresholds for severe impairment. Coronal Cobb angle — the historical gold standard — was far less predictive than sagittal spinopelvic measurements.
When you read a long-cassette standing lateral radiograph on an adult deformity patient, three numbers tell you almost everything about how disabled that patient is: pelvic tilt, SVA, and PI-LL mismatch.
If PT ≥22°, SVA ≥47 mm, or PI-LL ≥11°, the patient is likely in the severe disability range (ODI >40). When all three are exceeded simultaneously, the patient almost certainly needs operative discussion — 31% of surgical patients hit all three versus 15% of nonoperative patients.
Of the three, PI-LL mismatch is the one to fix. SVA and PT are compensatory postures the body adopts when lordosis can't match pelvic incidence. Correct the PI-LL mismatch with an osteotomy, and SVA and PT should improve as consequences.
One important caveat the authors themselves make: these thresholds guide assessment, but surgical decisions must also account for patient expectations, comorbidities, and risk tolerance. The numbers alone do not constitute an operative indication.