The crural diaphragm refers specifically to the lumbar (posterior) portion of the diaphragm formed by the right and left crura, which originate from the lumbar vertebral bodies and encircle the esophagus at the esophageal hiatus. The crural diaphragm is anatomically and functionally distinct from the costal diaphragm portions and plays a critical role in lower esophageal sphincter physiology as the extrinsic sphincter component.
| Origin | Right crus: anterior surface of vertebral bodies and discs L1-L3; Left crus: anterior surface of vertebral bodies and discs L1-L2; medial arcuate ligament bridges above the psoas on each side |
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| Insertion | Central tendon of the diaphragm, with the right and left crura decussating anterior to the aorta to form the esophageal hiatus; the right crus forms both walls of the hiatus in 52% of individuals |
| Nerve Supply | Phrenic nerves (C3-C5) |
| Blood Supply | Inferior phrenic arteries |
| Actions | The crural diaphragm acts as the extrinsic component of the lower esophageal sphincter (LES): it augments LES pressure during inspiration (when intraabdominal pressure rises) and during straining, generating a pinch mechanism around the esophageal hiatus; this crural pinch is lost when the stomach herniates into the chest (hiatal hernia), explaining the reflux mechanism |
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The crural diaphragm is the anatomical target of hiatal hernia repair and anti-reflux surgery. In laparoscopic Nissen fundoplication, crural approximation (bringing the two crura together with interrupted non-absorbable sutures posterior to the esophagus) restores the normal hiatal anatomy and the crural pinch mechanism on the LES. Inadequate crural closure is the most common cause of fundoplication failure and hiatal hernia recurrence. The right crus, forming the dominant component of the esophageal hiatus, is the primary structure manipulated in hiatal hernia repair and in esophagomyotomy (Heller myotomy) for achalasia.
Widening of the esophageal hiatus from crural laxity or disruption allows the gastroesophageal junction and proximal stomach to herniate into the posterior mediastinum, eliminating the crural pinch LES augmentation and producing gastroesophageal reflux; laparoscopic crural approximation with mesh reinforcement for large hiatal defects restores the normal crural anatomy.
