Musculus quadratus lumborum

The quadratus lumborum muscle is a paired, irregular quadrilateral muscle that forms part of the posterior abdominal wall.

Summary

• location: posterior abdominal wall
• attachments: inferior margin of 12th rib and upper four lumbar transverse processes, iliac crest and iliolumbar ligament
• blood supply
  • branches of the lumbar arteries
  • other smaller arterial branches, as described below
• innervation
  • ventral rami of the 12th thoracic nerve
  • L1-L4 spinal nerves
• action: extension and lateral flexion of vertebral column; fixes 12th rib during inspiration to stabilize the diaphragm

Gross anatomy

Attachments

• origin: medial half of inferior margin of 12th rib and upper four lumbar transverse processes
• insertion: iliolumbar ligament and internal rim of iliac crest

Relations

The muscle is a thick, irregular, quadrilateral-shaped muscle sheet that lies in the posterior abdominal wall on each side of the lumbar vertebrae. It is superficial to the psoas major muscle.

Anterior relations include:

• colon
• kidney
• psoas muscle (major and minor)
• diaphragm
• subcostal, ilioinguinal and iliohypogastric nerves

Arterial supply

The quadratus lumborum muscle is supplied by:

• branches of the lumbar arteries
• the arteria lumbalis ima
• the lumbar branch of the iliolumbar artery
• branches of the subcostal artery

Innervation

• ventral rami of the 12th thoracic nerve
• L1-L4 spinal nerves

Action

Multiple actions, including:

• muscle of inspiration
  • fixation of the last rib
  • stabilization of lower attachments of the diaphragm
    • proposed to provide a base for controlled diaphragmatic relaxation to facilitate precise adjustments required for speech and singing
• when one muscle contracts, lateral flexion of vertebral column 
• when both sides contract, extends the lumbar spine

Variant anatomy

• extent of attachment to the last rib varies

Related pathology

• implications in unilateral lower back pain
• may be enlarged in cricket fast bowlers who injure their L4 pars interarticularis

Siehe auch:

• Bauchmuskulatur

und weiter:

• arterielle Versorgung Musculus quadratus lumborum