Sacral plexus

Dr Craig Hacking and Dr Henry Knipe et al.

The sacral plexus is formed by anterior rami of L4 to S5 and its branches innervate the pelvis, perineum and lower limb.

Gross anatomy

The sacral plexus forms on the anterior belly of the piriformis muscle and is formed by the lumbosacral trunk (L4-5) of the lumbar plexus, which enters the pelvis coursing medially to psoas major and unites with the ventral rami of the S1 to S4 nerve roots, which emerge from the anterior foramen of the sacrum. It forms a triangular shape with an inferiorly pointing apex. 

The anterior sacral rami give off six branches and then divide into the anterior and posterior division, each giving off further branches (see below). 

Branches
Anterior rami

See: mnemonic.

Anterior division of anterior rami

See: mnemonic.

Posterior division of anterior rami

See: mnemonic.

Relations

Variant anatomy

  • common peroneal and tibial parts of the sciatic nerve fail to unite and course into the lower limb separately
  • additional caudal nerve root contribution to the sacral plexus 6
Abdominal and pelvic anatomy
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Article Information

rID: 29885
Section: Anatomy
Synonyms or Alternate Spellings:
  • Sacral nerve plexus

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Cases and Figures

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    Figure 1: sacral plexus diagrams
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