Sacral Plexus

Question 1

Describe the roots and position of the sacral plexus

Answer 1

Arises from ventral rami of S1-S4 (contributions from L4-5)

• Lies anterior to piriformis and posterior pelvic wall
• Exits pelvis via greater sciatic foramen

Question 2

Name the major branches of the sacral plexus

Answer 2

• Sciatic nerve
• Superior gluteal nerve
• Inferior gluteal nerve
• Quadratus Femoris + Gemellus inferior (L4-S1)
• Obturator Internus and Gemellus Superior (L5-S2)
• Piriformis (S1-2)

Question 3

Describe the sciatic nerve

Answer 3

• Ventral rami of L4-S3
• essentially 2 nerves in one bundle
• leaves pelvis via greater sciatic foramen (inf to piriformis)
• runs deep to hamstrings + piriformis (posterior to adductors + deep external rotators)
• divides at popliteal fossa - in lower 1/3 of posterior thigh (tibial nerve + common peroneal nerve)
  Innervates:
  > Hamstrings
  > Adductor magnus (ischial head)

Question 4

Describe the superior gluteal nerve

Answer 4

Roots: Ventral Rami of L4-S1
Innervates: Gluteus Medius
: Gluteus Minimus
: TFL

Question 5

Describe the inferior gluteal nerve

Answer 5

Roots: L5-S2
Innervates: Gluteus Maximus

Question 6

Describe the Tibial Nerve

Answer 6

Fibres from L4-S3
Runs centrally down posterior leg, into tarsal tunnel then splits to medial and lateral plantar nerves 
Motor: 
> superficial posterior compartment 
- Gastrocnemius
- Plantaris
- Soleus
> deep posterior compartment
- popliteus
- Tibialis Posterior
- FDL
- FHL 
Sensory: Sural nerve with common peroneal nerves (skin of lateral lower 1/3 of leg)

Question 7

Describe the Lateral Plantar Nerve

Answer 7

Motor: 
- Abductor Digiti Minimi
- Quadratus Plantae
- Lumbricals 2-4
- Adductor Hallucis
- Flexor Digiti Minimi Brevis
- Plantar and Dorsal Interossei
Sensory; 
- skin of 5th toe and lateral half of 4th toe

Question 8

Describe the Medial Plantar Nerve

Answer 8

Motor
- Abductor Hallucis 
- FDB
- FHB
- 1st lumbrical
Sensory;
- skin medial to big toe
- skin between 1st and 4th toes

Question 9

Describe the Common Peroneal nerve

Answer 9

Fibres from L4-S2
- wraps around neck of fibula head
- splits into deep + superficial branches
* No muscular innervation
Sensory: contributes to sural nerve (skin over lateral 1/3 of lower leg)

Question 10

Describe the superficial peroneal nerve

Answer 10

Motor;
- Peroneus Longus
- Peroneus Brevis
Sensory 
- skin over lateral leg
- then splits into medial and lateral cutaneous branches

Question 11

Describe the deep peroneal nerve

Answer 11

Motor:
- Tibialis Anterior
- EDL
- EHL
- Peroneus Tertius
Sensory
- ankle joint

splits into medial and lateral branches
Medial: 
- 1st tarsal and MTP joint
- skin to between 1st and 2nd toe
Lateral 
- EDB
- Tarsals and MTP joints