Sciatic nerve

SCIATIC NERVE

• Thickest nerve in the body & Largest branch of sacral plexus.
• Sciatic nerve ( also called ischiadic nerve, ischiatic nerve) is a large nerve in humans and other animals. 
• Root: L4-S3.
• It is actually the tibial and common peroneal nerves enclosed in a common sheath above the knee or popliteal fossa.
• It courses in the posterior compartment of thigh.
• Supplies hamstring muscles including ischiocondylar (hamstring) portion of adductor magnus.

BRANCHES:

1. Tibial Nerve
2. Common Peroneal Nerve.

COURSE:

• In pelvis: lies in front of piriformis.
• Sciatic nerve leaves the pelvis and runs posteriorly in the thigh.
• In the upper angle of popliteal fossa, sciatic nerve divides into tibial nerve and common peroneal nerve
• In gluteal region: the nerve enters the gluteal region through greater sciatic foramen below the piriformis.

RELATIONS:

Relations in gluteal region:

1. Superficial or posterior: gluteus maximus
2. Deep or anterior: body of the ischium, tendon of obturator internus with gemelli, Quadratus femoris, obturator externus , capsule of hip joint & upper transverse fibres of adductor magnus.
3. Medial: inferior gluteal nerve and vessels
4. In the thigh: the nerve enters the back of the thigh at the lower border of the gluteus maximus.

Relations in thigh region:

1. Superficial or posterior: nerve is crossed by long head of biceps femoris.
2. Deep or anterior: nerve lies on the & supplies adductor magnus.
3. Medial: semi membranosus Ex semitendinosus

Lateral: biceps femoris.       

• The sciatic nerve in the buttock lies deep to the gluteus maximus muscle, midway between the greater rochanter and the ischial tuberosity.

CLINICAL SIGNIFICANCE:

• A posterior dislocation of the hip joint will generally injure the sciatic nerve.
• A herniated disc or pressure from the uterus during pregnancy may damage the nerve roots, resulting in a condition called sciatica (sharp pain in the gluteal region that extends down the post. side of the thigh.)
• An improperly administered injection into the buttock may injure the sciatic nerve.