Ligamentum Flavum Thickest L4-L5 — FRCA Primary MCQ
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Correct answer: E — L4-L5
The ligamentum flavum (yellow ligament — contains elastic tissue) increases in thickness from the cervical to lumbar region. It is thickest at L4-L5 (approximately 5-6 mm) where epidural and spinal anaesthesia are most commonly performed. Its elasticity provides the characteristic 'springy' resistance during epidural needle advancement and the 'give' on entering the epidural space.
Reference: RCoA 2021 Primary FRCA Curriculum