Quadratus lumborum muscle
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View Dan Mahon's current disclosures- Quadratus lumborum muscles
The quadratus lumborum muscle is a paired, irregular quadrilateral muscle that forms part of the posterior abdominal wall.
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Summary
origin: transverse process L5 vertebra, iliolumbar ligament and internal rim iliac crest
insertion: transverse processes L1-L4, inferior margin of medial half 12th rib
action: extension and lateral flexion of vertebral column; fixes 12th rib during inspiration to stabilize the diaphragm
blood supply: branches of the lumbar arteries and other smaller arterial branches, as described below
innervation: ventral rami of the 12th thoracic nerve and L1-L4 spinal nerves
Gross anatomy
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:
psoas muscle (major and minor)
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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 1
when one muscle contracts, lateral flexion of vertebral column
when both muscles contract, extension of 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 3
References
- 1. NA. Gray's anatomy. Elsevier. ISBN:0808923714. Read it at Google Books - Find it at Amazon
- 2. Moore KL, Dalley AF, Agur AM. Clinically Oriented Anatomy. Lippincott Williams & Wilkins. ISBN:1451119453. Read it at Google Books - Find it at Amazon
- 3. Engstrom CM, Walker DG, Kippers V et-al. Quadratus lumborum asymmetry and L4 pars injury in fast bowlers: a prospective MR study. Med Sci Sports Exerc. 2007;39 (6): 910-7. doi:10.1249/mss.0b013e3180408e25 - Pubmed citation
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