Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA) — free guideline decision tool
Enter PI, PT, LL, SVA (± SS): checks PI = PT + SS and gives SRS-Schwab sagittal modifiers (PI−LL, PT, SVA) and Roussouly type. Includes how to measure and what each value means. Instant, browser-side.
Open guideline tool →Guideline-based
Implements the decision logic from published clinical guidelines.
Runs in your browser
No installation. Enter the patient's values and get a guideline recommendation instantly.
Data stays local
Nothing is uploaded. Results are for licensed clinicians only.
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 +)
Common questions
What is Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA)?
Enter PI, PT, LL, SVA (± SS): checks PI = PT + SS and gives SRS-Schwab sagittal modifiers (PI−LL, PT, SVA) and Roussouly type. Includes how to measure and what each value means. Instant, browser-side.
How is Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA) calculated? What is the core formula?
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)
When is Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA) used?
Spine imaging: standing full-spine films, flexion/extension views, CT/MRI — scoliosis follow-up, adult deformity, stenosis reporting and surgical planning.
What are the key clinical points for Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA)?
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.
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 +)）
Run Spinopelvic Sagittal Alignment (PI / PT / SS / LL / SVA) now
Enter PI, PT, LL, SVA (± SS): checks PI = PT + SS and gives SRS-Schwab sagittal modifiers (PI−LL, PT, SVA) and Roussouly type. Includes how to measure and what each value means. Instant, browser-side.
Open guideline tool →For licensed clinicians. Not a substitute for clinical judgement.
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