Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index) — free guideline decision tool
Acromiohumeral interval, critical shoulder angle, acromion index and Bigliani type for rotator-cuff tear and osteoarthritis tendency. 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.
| AI: glenoid plane → lateral acromion | 32 mm |
|---|---|
| AI: glenoid plane → lateral humeral head | 48 mm |
| Bigliani acromion type (Y view) | Type II: curved |
| Acromiohumeral interval | 8 mm |
| Critical shoulder angle | 34 ° |
→Acromiohumeral interval8mm
- Acromiohumeral interval：8 mm → 7–14 mm: normal
- Critical shoulder angle：34 ° → 30–35°: normal
- Acromion index：0.67 → < 0.7: normal (~0.6)
Common questions
What is Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index)?
Acromiohumeral interval, critical shoulder angle, acromion index and Bigliani type for rotator-cuff tear and osteoarthritis tendency. Includes how to measure and what each value means. Instant, browser-side.
How is Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index) calculated? What is the core formula?
Acromiohumeral interval < 7 mm: suggests massive / full-thickness cuff tear (supra- and infraspinatus) Acromiohumeral interval 7–14 mm: normal Acromiohumeral interval > 14 mm: widened (effusion, inferior subluxation, etc.) Critical shoulder angle < 30°: associated with glenohumeral osteoarthritis Critical shoulder angle 30–35°: normal Critical shoulder angle > 35°: associated with degenerative cuff tear Acromion index < 0.7: normal (~0.6) Acromion index ≥ 0.7: large lateral extension, associated with cuff tear
When is Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index) used?
Shoulder imaging: true AP, Y view and 3D CT — rotator cuff disease and instability reporting and procedure selection.
What are the key clinical points for Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index)?
True AP (Grashey) view tangential to the glenohumeral joint. 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 Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index)?
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 Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index) 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 Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index) calculated in practice? Can you show a worked example?
Inputs: AI: glenoid plane → lateral acromion 32 mm, AI: glenoid plane → lateral humeral head 48 mm, Bigliani acromion type (Y view) Type II: curved, Acromiohumeral interval 8 mm, Critical shoulder angle 34 ° → Result: Acromiohumeral interval 8 mm（Acromiohumeral interval: 8 mm → 7–14 mm: normal, Critical shoulder angle: 34 ° → 30–35°: normal, Acromion index: 0.67 → < 0.7: normal (~0.6)）
Run Shoulder Measurements (Acromiohumeral Interval / Critical Shoulder Angle / Acromion Index) now
Acromiohumeral interval, critical shoulder angle, acromion index and Bigliani type for rotator-cuff tear and osteoarthritis tendency. Includes how to measure and what each value means. Instant, browser-side.
Open guideline tool →For licensed clinicians. Not a substitute for clinical judgement.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.