Sciatic nerve

The sciatic nerve is the longest and largest nerve in the human body. It runs from the lower back through the back of the leg, and down to the toes. Any type of pain and/or neurological symptoms that are felt along the sciatic nerve is referred to as sciatica.

1. SCIATIC NERVE

2. INTRO Sciatic nerve is the thickest nerve in the body It begins in the pelvis and terminates into popliteal fossa by dividing into tibial and common peroneal nerves.

3. ORIGIN AND ROOT VALUE This is the largest branch of sacral plexus. Its root value is L4,L5,S1,S2,S3. It is made up of two parts , the tibial part and the common peroneal part. The tibial part is formed by the ventral divisions of anterior primary rami (ventral rami) of L4,L5,S1,S2,S3 . The common peroneal part is formed by the dorsal divisions of the anterior primary rami (ventral rami) of L4,L5,S1,S2

4. ORIGIN

5. Course & Distribution It leaves the pelvis through greater sciatic foramen, below the piriformis & passes in the gluteal region (between ischial tuberosity & greater trochanter ) then to posterior compartment of thigh . Termination In the middle of the back of the thigh (apex of the popliteal fossa) It divides into 2 terminal branches: Tibial & Common Peroneal (Fibular).

6. Anatomical Course The sciatic nerve is derived from the  lumbosacral plexus . After its formation, it leaves the pelvis and enters the gluteal region via greater sciatic foramen. It emerges inferiorly to the  piriformis  muscle and descends in an inferolateral direction. As the nerve moves through the gluteal region, it crosses the posterior surface of the superior gemellus , obturator internus, inferior gemellus and quadratus femoris muscles. It then enters the posterior thigh by passing deep to the long head of the  biceps femoris . Within the posterior thigh, the nerve gives rise to branches to the hamstring muscles and adductor magnus . When the sciatic nerve reaches the apex of the  popliteal fossa , it terminates by bifurcating into the tibial and common fibular nerves.

7. BRANCHES OF SCIATIC NERVE 1. Cutaneous : To all leg & foot directly or indirectly EXCEPT : Areas supplied by the saphenous nerve ( branch of femoral nerve ).

8. BRANCHES OF SCIATIC NERVE 2 . Muscular : To Hamstrings : It is one of the three posterior thigh muscles in between the hip and knee (m-l, semimembranosus, semitendonosus , and biceps femoris ) (flexors of knee & extensors of the hip). (through tibial part) to : Hamstring part of Adductor Magnus . ,(ischial part) Long head of Biceps Femoris . Semitendinosus. Semimembranosus. NB. The short head of biceps receives its branch (common peroneal) nerve.

9. BRANCHES OF SCIATIC NERVE

10. The sciatic nerve is most frequently injured by…? I- Badly placed intramuscular injections in the gluteal region. To avoid this, injections should be done into the gluteus maximus or medius (into the upper outer quadrant of buttock I n 90% of injuries, the common peroneal nerve is the mostly affected. Why? - The common peroneal nerve fibers lie superficial in the sciatic nerve. CAUSES OF SCIATIC NERVE INJURY

11. EFFECT OF SCIATIC NERVE INJURY MOTOR EFFECTS PARALYSIS OF MOVEMENTS AFFECTED HAMSTRING Flexion of knee and extension of hip ALL MUSCLES OF LEG AND FOOT All muscles of leg and foot SENSORY EFFECTS Loss of sensation of areas supplied by sciatic nerve (below knee) EXCEPT area supplied by saphenous nerve

12. OTHER CLINICAL ANATOMY SLEEPING FOOT : When a person sits on the edge of a hard table or chair, the nerve gets compressed between the edge of the table and femur. It results in the numbness of lower limb. But the sensations come back when foot is hit on the ground a few times. SCIATICA : It is the shooting pain along the cutaneous distribution of the sciatic nerve and its terminal branches, chiefly the common peroneal. Pain usually begins in the gluteal region, and radiates along the back of the thigh, and the lateral side of the leg, to the dorsum of the foot.

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