Lumbo sacral plexus

LUMBOSACRAL

PLEXUSDr. Khadija Iqbal

Lets revise and then go ahead

Muscles

• Muscles of the thigh are arranged in

three compartments separated by

intermuscular septa

medial compartment of thigh

• six muscles

• Gracilis-obturator nerve

• pectineus- femoral nerve

• adductor longus,

• adductor brevis

• adductor magnus-sciatic nerve

• obturator externus

•

anterior compartment of thigh

• sartorius

• four large quadriceps femoris muscles

(rectus femoris, vastus lateralis, vastus

medialis, and vastus intermedius).

• the terminal ends of the psoas major

• and iliacus muscles pass into the upper

part of the anterior compartment from

sites of origin on the posterior abdominal

wall.

• The posterior compartment of thigh

contains three large muscles termed the

'hamstrings'. All are innervated by the

sciatic nerve.

Adductor canal

• Laterally vastus medialis

• Anteromedially sartorius

• Posteriorly adductor longus

15

.

Anterior rami of

upper 4 lumbar

spinal nerves (+L5)

and from the

contribution of

subcostal nerve

(T12)

in the lumbar

region, within

the psoas major

muscle.

Lat

femora

l

obturator

20

.

(L2-L4)

largest branch

both motor and sensory.

Emerges from the lateral

border of the psoas major

Flexors of the hip and

extensors of the knee

Skin of the anterior and

lateral thigh, medial leg

and foot

21

.

largest cutaneous

branch of the femoral

nerve

continuation of the

femoral nerve

Skin of medial aspects

of leg and foot

22

.

Emerges from the medial

border of the psoas

major

Leaves the lesser

pelvis through

the obturator canal

Skin on the superior

medial thigh

Adductor muscles of the

leg

Gluteal region

deep group of small muscles,

• piriformis, obturator internus, gemellus

superior, gemellus inferior, and quadratus

femoris;

superficial group

gluteus minimus, gluteus medius, and

gluteus maximus-

• the tensor fasciae latae,

Second lecture

24.4.13

31

.

Sensory and motor innervation of the whole

lower limb

arises from the spinal roots L1-S4

Lumbal plexus

Sacral plexus

32

.

Descending part of

the L4 nerve unites

with the anterior

ramus of the L5

nerve to form the

lumbosacral trunk.

Participates in the

formation of the

sacral plexus with

the anterior rami

of S1-S4 nerves.

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34

43

44

.

o Leaves the

gluteal region by

passing deep to

the long head of

the biceps

femoris,at the

lower margin of

the quadratus

femoris muscle

o Divides into the

common peroneal

and tibial

nerves, at a

variable site

above the

popliteal fossa

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46

L4

L5

S1

S2

S3

Semitendinosis

Biceps femoris

semimembranosus

Ham

str

ings

Gastrocnemius

and posterior

compartment of

the leg and foot

Tibial

nerve

Common

peroneal

nerve Deep peroneal

nerveAnterior

compartment of

leg

Lateral

compartment of leg

Superficial peroneal

nerve

Motor Branches of the

Sciatic Nerve

48

Greater sciatic foramen

• The greater sciatic foramen is formed on the posterolateral pelvic wall and is the major route for structures to pass between the pelvis and the gluteal region of the lower limb . The margins of the foramen are formed by:

• the greater sciatic notch;• parts of the upper borders of the sacrospinous and sacrotuberous ligaments;• the lateral border of the sacrum. •

•

• The piriformis muscle passes out of the pelvis into the gluteal region through the greater sciatic foramen and separates the foramen into two parts, a part above the muscle and a part below:

• the superior gluteal nerve and vessels pass through the greater sciatic foramen above the piriformis;

• the sciatic nerve, inferior gluteal nerves and vessels, pudendal nerve and internal pudendal vessels, posterior cutaneous nerve of thigh, nerve to the obturator internus and gemellus superior and the nerve to the quadratus femoris and gemellus inferior pass through the greater sciatic foramen below the muscle.

•

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Lesser sciatic foramen

• The lesser sciatic foramen is inferior to the greater sciatic foramen on the posterolateral pelvic wall .It is also inferior to the lateral attachment of the pelvic floor to the pelvic wall and therefore connects the gluteal region with the perineum:

• the tendon of obturator internus passes from the lateral pelvic wall through the lesser sciatic foramen into the gluteal region to insert on the femur;

• the pudendal nerve and internal pudendal vessels, which first exit the pelvis by passing through the greater sciatic foramen below the piriformis muscle, enter the perineum below the pelvic floor by passing around the ischial spine and sacrospinous ligament and medially through the lesser sciatic foramen.

•

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Trendelenburg's Test

• – assesses functioning of hip abductors

• Stand behind patient and ask to stand on

one leg for 30 seconds

• Pelvis should tilt up on side of unsupported

leg = Trendelenburg negative (normal)

• If pelvis tilts down towards unsupported leg =

Trendelenburg positive (pathological)

• Repeat for other leg

53

A 51-year-old man experiences a loss of

skin sensation along the medial

compartment of the thigh. No other

areas of skin are affected. Which of the

following best describes the area of deficit?

A. L2 dermatome

B. L3dermatome

C. L4 dermatome

D. Cutaneous field of the femoral nerve

E. Cutaneous field of the obturator nerve

F. Cutaneous field of the saphenous nerve

27. A 55-year-old man has difficulty

extending his hip while walking up a flight

of stairs.He experiences no cutaneous

deficits. Which damaged nerve is most

likely responsible

for causing this man’s symptoms?

A. Inferior gluteal nerve

B. S1 nerve root

C. S2 nerve root

D. Superior gluteal nerve

28. A 33-year-old man’s pelvis drops on

the right side when

he steps with his right foot. He has no

cutaneous deficits.

Which nerve lesion is most likely causing

this problem?

A. Femoral nerve

B. Inferior gluteal nerve

C. Obturator nerve

D. Superior gluteal nerve

E. Tibial nerve