Which of the following is the correct sequence of anatomical layers encountered during midline approach to lumbar epidural puncture, from skin to epidural space?

Explanation

## Layers of Lumbar Epidural Approach — Midline Anatomy **Key Point:** The correct anatomical sequence from skin to epidural space is: **Skin → Supraspinous ligament → Interspinous ligament → Ligamentum flavum → Epidural space**. ### Layer-by-Layer Anatomy ```mermaid flowchart TD A["Skin & Subcutaneous tissue"]:::action --> B["Supraspinous ligament<br/>(connects spinous processes dorsally)"]:::outcome B --> C["Interspinous ligament<br/>(connects spinous processes ventrally)"]:::outcome C --> D["Ligamentum flavum<br/>(connects laminae; elastic, dense)"]:::outcome D --> E["Epidural space<br/>(contains fat, vessels, nerve roots)"]:::outcome ``` ### Detailed Description | Layer | Composition | Resistance | Clinical Significance | |-------|-------------|-----------|----------------------| | **Supraspinous ligament** | Dense fibrous tissue | High resistance | First ligamentous barrier; palpable | | **Interspinous ligament** | Loose fibrous tissue | Moderate resistance | Lies between spinous processes | | **Ligamentum flavum** | Elastic yellow ligament | Sudden loss of resistance (LOR) | Final barrier; marks epidural space entry | | **Epidural space** | Fat, blood vessels, nerve roots | N/A | Target space for local anesthetic | **High-Yield:** The **loss of resistance (LOR)** technique relies on the sudden give when the needle penetrates the ligamentum flavum — this is the most tactile and reliable confirmation of epidural space entry. **Mnemonic:** **"SILE"** — **S**upraspinous, **I**nterspinous, **L**igamentum flavum, **E**pidural space. **Clinical Pearl:** The ligamentum flavum is unique because it is composed of elastic fibers (yellow), making it feel different from other ligaments. This tactile difference is what experienced practitioners use to confirm correct needle position.