ANATOMY OF SCIATIC NERVE AND FOOT DROP

Sciatic nerve ppt

1. ANATOMY OF SCIATIC NERVE AND FOOT DROP Dr. Bipul Borthakur Professor, DEPT OF ORTHOPAEDICS SILCHAR MEDICAL COLLEGE AND HOSPITAL

2. INTRODUCTION Sciatic nerve is the largest nerve trunk and longest in the body. We have 2 sciatic nerves, the right and left nerves, supplying each lower limb. The sciatic nerve starts in the lower spine, follows through the buttock, down to the back of thigh and leg, finally ending in the foot.

3. ORIGIN The sciatic nerve is formed by the combination of lumbar (lower) and sacral spine-- L4, L5, S1, S2, S3 of the Lumbosacral trunk. The 5 nerves group together near the front surface of the pyriformis muscle deep into the buttock to form a large,thick band of Sciatic nerve. The nerve is typically responsible for both motor and sensory functions of the lower body.

4. COURSE OF SCIATIC NERVE The Sacral nerve is derived from the lumbosacral plexus After its formation from the group of nerves E xits the pelvis below the pyriformis T hrough the Greater sciatic foramen Deep to gluteus maximus muscle Crosses the Superior gemellus , O bturator internus , Inferior gemelles , Quadratus femoris .

5. Enters the Posterior thigh Deep to the long head of Biceps femoris Hamstrings muscles, Adductor magnus . At the apex of popliteal fossa ( ie upper 2/3 and lower 1/3 of thigh) Terminates by bifurcating into TIBIAL NERVE and COMMON FIBULAR or PERONEAL NERVE

6. BRANCHES OF SCIATIC NERVE TIBIAL NERVE Travels inferiorly in the popliteal fossa Genicular branches to knee Supplying gastrocnemius, plantaris , soleus, popliteus In the back of leg, it travels with tibial vessels Lies superficial to tibialis posterior Deep to flexor digitorum longus

7. GENICULAR BRANCHES Superior medial genicular nerve Middle genicular nerve Inferior medial genicular nerve CUTANEOUS BRANCH Sural nerve Medial calcaneal branches TERMINAL BRANCH Medial plantar nerves Lateral plantar nerves

8. MUSCULAR BRANCHES BACK OF THIGH POPLITEAL FOSSA Long head of Biceps femoris 1. Gastrocnemius Semitendinosus 2. P lantaris Semimembranosus 3. Soleus Ischial part of adductor magnus 4. Popliteus BACK OF LEG S oleus Flexor digitorum longus Flexor hallucis longus Tibialis posterior

9. COMMON FIBULAR NERVE Course Along the medial border of biceps femoris Down to the head of fibula Enter the anterior compartment of leg Wraps around posterolateral aspect of the neck of fibula Pierces the substance of peroneus longus MUSCULAR BRANCH Short head of Biceps Femoris

10. CUTANEOUS BRANCHES Lateral sural cutaneous nerve of calf Peroneal communicating nerve/ Sural communicating nerve ARTICULAR BRANCHES Superior lateral genicular nerve Inferior lateral genicular nerve Recurrent genicular nerve TERMINAL BRANCH Deep peroneal nerve Superficial peroneal nerve

11. DEEP PERONEAL NERVE MUSCULAR BRANCHES ANTERIOR COMPARTMENT OF LEG Tibialis anterior Extensor hallucis longus Extensor digitorum longus Peroneus tertius DORSUM OF FOOT Extensor digitorum brevis CUTANEOUS BRANCHES Dorsal Digital nerves

12. SUPERFICIAL PERONEAL NERVE LATERAL COMPARTMENT OF LEG Peroneus longus Peroneus brevis CUTANEOUS BRANCHES Medial cutaneous branch Lateral cutaneous branch

13. Common Peroneal Nerve Injury Most commonly injured nerve in lower limb because it winds superficially around neck of fibulla . Common causes of injury: Fracture neck of fibulla Pressure on head of fibulla due to applied plaster cast or sharp edge of bed during sleep

14. Deformity Foot drop ( paralysis of muscles of extensor and peroneal compt ) Foot inversion ( due to paralysis of peroneus longus and brevis ) Abnormal gait ( S teppage gait ) Sensory loss( Anterior and lateral sides of neck, dorsum of foot and toes including medial side of big toe) SURGICAL TREATMENT : Rerouting T ibialis posterior to the front( Tibialis posterior is supplied by Tibial nerve)

15. FUNCTIONS OF SCIATIC NERVE MOTOR FUNCTIONS TIBIAL PART OF SCIATIC NERVE supply-- POSTERIOR COMPARTMENT OF THIGH Knee flexion Weak extensors of hip POSTERIOR COMPARTMENT OF LEG AND FOOT Plantar flexion of foot Flexion of toes Foot inversion

16. COMMON PERONEAL/FIBULAR NERVE DEEP PERONEAL NERVE supply-- ANTERIOR COMPARTMENT OF LEG AND FOOT Dorsiflexion Extension of toes Foot inversion SUPERFICIAL PERONEAL NERVE supply-- LATERAL COMPARTMENT OF LEG AND FOOT Foot eversion

17. SENSORY FUNCTIONS SURAL NERVE supply-- Skin of lower ½ of back of leg Whole lateral foot till little toe LATERAL CUTANEOUS NERVE OF CALF supply-- Skin of upper 2/3 rd of lateral leg (both front and behind) PERONEAL OR SURAL COMMUNICATING NERVE supply-- Skin of lateral area of leg

18. DORSAL DIGITAL NERVES supply-- Cleft between 1 st and 2 nd toes MEDIAL CALCANEAL NERVE supply-- Heel and medial side of sole of foot SUPERFICIAL PERONEAL NERVE supply-- L ower 1/3 rd lateral Side leg Dorsum of foot Medial side of toe Cleft between 2 nd and 3 rd toes Cleft between 3 rd and 4 th toes Cleft between 4 th and 5 th toes

19. FOOT DROP Foot drop or drop foot is the inability to lift the front part of foot from the ankle due to significant weakness of ankle and toe dorsiflexion. It is a sign of underlying disorder neurological, muscular, anatomical. SIGNS AND SYMPTOM Stepping gait- Because the patient tends to walk with an exaggerated flexion of hip and knees to prevent the toes from catching on the ground during swing phase as preventing the foot from dragging on the floor. Foot – Plantar flexion In some cases, the skin on the leg, foot and toes feels numb, tingling sensation Sensory loss- Back of leg ,lateral part of leg, dorsum of foot

20. CAUSES ETIOLOGY Foot drop is caused by weakness or paralysis of the muscles involved in lifting the front part of the foot caused by- 1.NERVE INJURY Most common cause is Peroneal nerve injury or compression. Sciatic nerve injury or compression Trauma Injury during knee or hip replacement surgeries Sports injury Child birth Leprosy A nerve root injury called PINCHED NERVE in the spine can cause footdrop . Diabetes are more susceptible

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22. 2. MUSCLE DISORDER Muscular dystrophy Inherited diseases causing progressive muscle weakness Polio Charcot-Marie Tooth disease 3. BRAIN AND SPINE DISORDERS Stroke Multiple sclerosis Amyotrophic lateral sclerosis Cerebral palsy Guillian barre Syndrome Cauda Equina Syndrome

23. RISK FACTORS PERONEAL NERVE CONTROLS THE MUSCLES THAT LIFT OUR FOOT. ACTIVITIES THAT COMPRESS THIS NERVE CAN INCREASE THE RISK OF FOOTDROP-- Spending long hours sittng crosslegged /squatting Prolonged kneeling Time spent in leg cast

24. DIAGNOSIS USUALLY DIAGNOSED DURING A PHYSICAL EXAMINATION. GAIT OF THE PATIENT LABORATORY STUDIES - BLOOD SUGAR, ESR, CRP, SERUM PROTIEN ELECTROPHORESIS, VITAMIN B12 RADIOGRAPHY- 1. PLAIN X-RAYS- FRACTURE,BONE LESIONS OR SOFT TISSUE MASS 2. ULTRASONOGRAPHY- CHECK FOR CYSTS OR TUMOURS, SWELLING ON NERVE 3. MRI- TUMOR OR COMPRESSIVE MASS LESION, SOFT TISSUE LESIONS COMPRESSING THE NERVE

25. NERVE TEST STUDY MUSCLES AND NERVE, CONFIRM THE TYPE OF NEUROPATHY 1. ELECTROMYOGRAPHY 2. NERVE CONDUCTION STUDY

26. TREATMENT Treatment for Foot drop depends on the cause. If the cause is successfully treated, foot drop might improve or even disappear If the cause cannot be treated, foot drop can be permanent. TREATMENT INCLUDES— 1. ANKLE-FOOT ORTHOSIS (AFO Brace) OR SPLINTS to support foot and ankle.

27. PHYSICAL THERAPY - To strengthen leg muscles and maintain range of movement in knee and ankle, Stretching exercises. NERVE STIMULATION OPTIMISE GLUCOSE IN DIABTEIC PATIENTS MANAGE VITAMIN DEFICIENCIES PAINFUL PARESTHESIA- Sympathetic blocking agents OR Amitriptyline, Nortriptyline , Pregabalin , Gabapentin Recombinant Erythropoietin is a drug used in 5000U/kg over 1 week after nerve injury.

28. SURGERY NERVE REPAIR/ DECOMPRESSION Using a longitudinal posterolateral incision centered over fibular head and paralleling the biceps tendon and fibula and identifying the peroneal nerve which is released. A wider exposure used if immediate repair or grafting required. Allograft nerve graft is an alternative to autografts for nerve reconstruction. TENDON TRANSFER

29. MONITORING After a nerve exploration or graft procedure Weight bearing as tolerated is allowed with 2-3 day period of immobilisation Ankle foot orthosis may be used post surgery. After tendon transfer, patient is placed in a cast Non- weightbearing for atleast 6 weeks Physiotherapy for gait training is followed