L5 anterior ramus
Roots · L5
Largest lumbar anterior ramus. With the descending branch of L4 it forms the lumbosacral trunk that carries lumbar fibres over the pelvic brim into the sacral plexus.
Detail
- Dermatome
- Lateral leg, dorsum of foot, great toe
- Myotome
- Great-toe extension (EHL), dorsiflexion, hip abduction, inversion and eversion
- Reflex
- None routinely tested (medial hamstring jerk only)
When it goes wrong
L4/5 posterolateral disc prolapse compressing the traversing L5 root (with L5/S1, the commonest level)
Foot drop with weak great-toe extension, weak hip abduction and ankle inversion, numb dorsum of foot and great toe; ankle jerk preserved. Weak inversion and hip abduction separate it from a common fibular palsy
Practise this structure
1 question in the bank tagged Dermatomes.