🧍 Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA)
UseSpine imaging: standing full-spine films, flexion/extension views, CT/MRI — scoliosis follow-up, adult deform…
SourceSchwab F, et al. Scoliosis Research Society-Schwab adult spinal deformity classification. Spine 201…
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
Methodology · worked example, guidelines & full notes
Standing full-spine lateral radiograph including both femoral heads and C7.
When to use
Spine imaging: standing full-spine films, flexion/extension views, CT/MRI — scoliosis follow-up, adult deformity, stenosis reporting and surgical planning.
How it works
PI − LL < −10°: LL exceeds PI (hyperlordosis) PI − LL −10–10°: matched (Schwab 0) PI − LL 10–20°: moderate mismatch (Schwab +) PI − LL > 20°: marked mismatch (Schwab ++) Pelvic tilt (PT) < 20°: no compensation (Schwab 0) Pelvic tilt (PT) 20–30°: moderate pelvic retroversion (Schwab +) Pelvic tilt (PT) > 30°: marked retroversion (Schwab ++) Sagittal vertical axis (SVA) < 40 mm: balanced (Schwab 0) Sagittal vertical axis (SVA) 40–95 mm: moderate positive imbalance (Schwab +) Sagittal vertical axis (SVA) > 95 mm: marked positive imbalance (Schwab ++) Sacral slope (SS) < 35°: Roussouly type 1 or 2 (low SS) Sacral slope (SS) 35–45°: Roussouly type 3 (balanced) Sacral slope (SS) > 45°: Roussouly type 4 (high SS, long lordosis)
Key points
- Standing full-spine lateral radiograph including both femoral heads and C7.
- Each value is graded against published reference ranges.
- Measurement technique and positioning change the numbers — compare like with like on follow-up.
- Part of the YuanDoctor MSK measurement topic.
References
- Schwab F, et al. Scoliosis Research Society-Schwab adult spinal deformity classification. Spine 2012;37:1077-1082
- Legaye J, Duval-Beaupère G, et al. Pelvic incidence. Eur Spine J 1998;7:99-103
- Roussouly P, et al. Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis. Spine 2005;30:346-353
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| PI | 55 ° |
|---|---|
| PT | 24 ° |
| LL (L1–S1) | 38 ° |
| SS (optional; else PI − PT) | 31 ° |
| Sagittal vertical axis (SVA) | 45 mm |
→PI − LL17°
- PI − LL：17 ° → 10–20°: moderate mismatch (Schwab +)
- Pelvic tilt (PT)：24 ° → 20–30°: moderate pelvic retroversion (Schwab +)
- Sagittal vertical axis (SVA)：45 mm → 40–95 mm: moderate positive imbalance (Schwab +)
Verification & sources · governance
FAQ
Frequently asked questions
- What are the limits and cautions when using Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- Does Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA) calculated in practice? Can you show a worked example?
- Inputs: PI 55 °, PT 24 °, LL (L1–S1) 38 °, SS (optional; else PI − PT) 31 °, Sagittal vertical axis (SVA) 45 mm → Result: PI − LL 17 °（PI − LL: 17 ° → 10–20°: moderate mismatch (Schwab +), Pelvic tilt (PT): 24 ° → 20–30°: moderate pelvic retroversion (Schwab +), Sagittal vertical axis (SVA): 45 mm → 40–95 mm: moderate positive imbalance (Schwab +)）