Sacral plexus anterior divisions
Divisions · S1 S2 S3 S4
The anterior (ventral) divisions of the sacral rami lie on piriformis behind the internal iliac vessels. Together with L4–L5 fibres from the trunk they form the tibial part of the sciatic nerve, the pudendal nerve and the nerves to quadratus femoris and obturator internus.
Traced from the start
- S1 anterior ramusS2 anterior ramusS3 anterior ramusS4 anterior ramus
- Sacral plexus anterior divisions
Detail
- Forms
- Tibial component of the sciatic (L4–S3), pudendal (S2–S4), nerve to quadratus femoris (L4–S1), nerve to obturator internus (L5–S2)
- Relations
- Piriformis behind; internal iliac vessels, ureter and rectum in front
When it goes wrong
Locally invasive pelvic malignancy (cervix, rectum, prostate) or radiation plexopathy infiltrating the sacral plexus
Deep buttock pain radiating down the posterior leg with progressive multi-root weakness, patchy sensory loss and sphincter change — a sacral plexopathy rather than a single-root pattern
Practise this structure
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