While performing a midline lumbar epidural using the loss-of-resistance technique, the assistant notes a sudden disappearance of resistance to gentle pressure on the glass syringe at a depth of about 5 cm. Entry into which structure produces this characteristic loss of resistance?
- A Interspinous ligament
- B Ligamentum flavum ✓
- C Posterior longitudinal ligament
- D Supraspinous ligament
Correct answer: B. Ligamentum flavum
Explanation
The ligamentum flavum is dense, elastic and offers marked resistance to the advancing needle or saline-filled syringe. When the tip passes through it into the epidural space, which contains fat, vessels and negative pressure relative to the atmosphere, saline is suddenly aspirated in or the plunger sinks, giving the classic loss of resistance. The supraspinous, interspinous and posterior longitudinal ligaments offer continuous moderate resistance rather than an abrupt end point.
Reference: Miller's Anesthesia, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.