After completion of this session, students should be able to discuss, identify, and describe: The anatomical factors predisposing to nerve injuries. The anatomy of deformity, weakness and sensory loss following the nerve injury. The applied anatomy of clinical examination for specific nerves. Surgical anatomy of treating nerve injuries.

1. Dr.AkramJaffar
Applied Anatomy of Nerve Injuries in the Lower LimbApplied Anatomy of Nerve Injuries in the Lower Limb
Sciatic nerveSciatic nerve
Akram Jaffar, Ph.D.
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References and suggested reading
• Ellis H (2006): Clinical anatomy, A revision and applied anatomy for clinical students.
11th
Ed. Blackwell Publishing. Massachusetts
• Moore KL & Dalley AF (2006): Clinically oriented anatomy. 5th
ed. Lippincott Williams
& Wilkins. Baltimore
• Brust JCM (2007): Current Diagnosis & Treatment in Neurology. 2nd
ed. McGraw-Hill
Professional.
• Hamdan FB, Jaffar AA, & Ossi RG (2008): The propensity of the common peroneal
nerve in thigh level injuries. J Trauma. 64:300-303.

3. Dr.AkramJaffar
Objectives
After completion of this session, students should be able to discuss, identify, and describe:
– The anatomical factors predisposing to nerve injuries.
– The anatomy of deformity, weakness and sensory loss following the nerve injury.
– The applied anatomy of clinical examination for specific nerves.
– Surgical anatomy of treating nerve injuries.

4. Dr.AkramJaffar
Sciatic nerve
• A branch of the sacral plexus L4, 5, S1, 2, &3.
• The largest nerve in the body.
• Consists of two nerves bound together: the tibial and
common peroneal nerves.
• The two nerves usually separate just proximal to the
popliteal fossa, but may do so when they leave the
pelvis, in this case the tibial component passes
inferior to piriformis muscle while the common
peroneal passes through piriformis or superior to it.
Tibial n.
Common peroneal n.
Tibial n.
Common peroneal n.
piriformis

5. Dr.AkramJaffar
Sciatic nerve injury
• Stab wounds
• Fractures of the pelvis
• Posterior dislocation of the hip joint
• Badly-placed intramuscular injection in the
gluteal region
Sciatic n.
Posterior dislocation of the hip joint

6. Dr.AkramJaffar
IM injections and the sciatic nerve
• Surface markings of the sciatic
nerve:
– Emerges from the pelvis midway
between the posterior superior
iliac spine (indicated by a skin
dimple) and the ischial
tuberosity.
– Leaves the gluteal region
midway between the ischial
tuberosity and the greater
trochanter.
• The extent of the gluteal region: from
the iliac crest superiorly to the gluteal
fold inferiorly. DO NOT restrict the
area to the most prominent part.
Post. Sup. Iliac spine
Ischial tuberosity
Greater
trochanter

7. Dr.AkramJaffar
IM injections and the sciatic nerve
• There are no nerves and vessels of
importance lateral to the sciatic
nerve.
• Injections can be made safely into
the superior lateral quadrant of the
gluteal region where the injection is
made into gluteus medius muscle,
the part that is not covered by
gluteus maximus.
Sciatic n.

8. Dr.AkramJaffar
Mapping safe area for gluteal IM injection
1. Superior lateral quadrant of the gluteal region.
2. Superior to a line extending between posterior superior iliac spine and the tip of the
greater trochanter.
3. The index finger is placed on the anterior superior iliac spine. The fingers are spread
posteriorly along the iliac crest until the middle finger feels the tubercle of the iliac
crest. Injection can be made safely in the triangular area between the index and
middle fingers.

9. Dr.AkramJaffar
Sciatic nerve injury
Deformity
• Weak flexion of the knee.
Cause
• The hamstring muscles (main flexors
of the knee) are paralyzed. Sartorius
(femoral n.) and gracilis (obturator n.)
can still flex the knee.

10. Dr.AkramJaffar
Sciatic nerve injury
Deformity
• Foot drop.
• Wasting of the calf muscles
• Loss of Achilles tendon reflex
Cause
• Paralysis of muscles of the extensor
and peroneal compartments (supplied
by the common peroneal n.). The
weight of the foot causes it to be
plantar flexed.
• Muscles supplied by the tibial n.
• Gastrocnemius, soleus and plantaris
(supplied by the tibial nerve).
Wasting of calf muscles
Foot drop

11. Dr.AkramJaffar
Sciatic nerve injury
Sensory loss
• Below the knee.
• May lead to trophic ulcer
Cause
• except for the area supplied by the
saphenous nerve (femoral nerve)
• Medial and lateral plantar nerves.
Medial
plantar n.
lateral
plantar n.
Saphenous n.
Lat. Plantar n.
Med. Plantar n.
Trophic ulcer