Lumbosacral trunk

The lumbosacral trunk is the distal trunk of the lumbar plexus arising from the anterior rami of the L4 and L5 nerve roots which contributes to the sacral plexus.

Gross anatomy

Origin

It arises from anterior rami of L4-L5 roots of the lumbar plexus.

Course

• emerges over the medial border of the iliacus muscle, medial to the psoas major muscle
• it descends to join with the S1 nerve root to contribute to the sacral plexus

Branches

The lumbosacral trunk contributes fibers to the:

• sciatic nerve (L4-S3)
• superior gluteal nerve (L4-S1)
• inferior gluteal nerve (L5-S2)
• nerve to quadratus femoris and inferior gemellus muscles (L4-S1)
• nerve to internal obturator and superior gemellus muscles (L5-S2)