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--- segmental_instability [2025/07/01 18:52] – administrador
+++ segmental_instability [2025/07/01 18:58] (current) – [📸 Imaging Criteria] administrador
@@ Line 31: / Line 31: @@
     * > 3.5 mm of translation
     * > 11° of angular motion between adjacent vertebrae
+===== Angular Motion Criteria for Segmental Instability =====
+To assess **segmental instability** radiographically, dynamic **flexion–extension X-rays** are performed. One important metric is **angular motion** between vertebral segments.
+==== 📐 Angular Instability Thresholds (Lumbar Spine) ====
+  * **L1–L5:** > 10–15° of angular motion between flexion and extension
+  * **L5–S1:** > 20° of angular motion
+==== Example Illustration ====
+Assume flexion and extension lateral radiographs show the following angles:
+^ Segment ^ Flexion Angle ^ Extension Angle ^ Angular Motion ^ Interpretation ^
+| L4–L5   |  5°            | 25°              | 20°            | ✅ Instability (exceeds 15°) |
+| L5–S1   |  10°           | 33°              | 23°            | ✅ Instability (exceeds 20°) |
+| L3–L4   |  12°           | 20°              | 8°             | ❌ Normal (below threshold)  |
+==== 🧮 How to Measure ====
+  * Draw lines along the endplates of adjacent vertebral bodies (e.g., L4 inferior endplate and L5 superior endplate)
+  * Measure the angle formed in flexion and extension
+  * Subtract to get the **range of angular motion**
+==== 📝 Note ====
+The threshold values may vary slightly by source, but generally:
+  * > 15° at L4–L5 or above is considered unstable
+  * > 20° at L5–S1 accounts for the normally greater mobility at this junction
 === 2. MRI ===