This document provides information on the lumbosacral plexus and innervation of the lower limb. It discusses the muscles of the thigh and their nerve innervation. It describes the anterior, posterior, and medial compartments of the thigh. It also discusses the formation of the femoral, obturator, and sciatic nerves from the lumbosacral plexus and their cutaneous innervation territories in the lower limb. Additionally, it provides information on the greater and lesser sciatic foramina and their anatomical structures.

1. LUMBOSACRAL
PLEXUS
Dr. Khadija Iqbal

2. Lets revise and then go ahead

3. Muscles
• Muscles of the thigh are arranged in
three compartments separated by
intermuscular septa

5. medial compartment of thigh
• six muscles
• Gracilis-obturator nerve
• pectineus- femoral nerve
• adductor longus,
• adductor brevis
• adductor magnus-sciatic nerve
• obturator externus
•

7. 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.

9. • The posterior compartment of thigh
contains three large muscles termed the
'hamstrings'. All are innervated by the
sciatic nerve.

13. Adductor canal
• Laterally vastus medialis
• Anteromedially sartorius
• Posteriorly adductor longus

15. 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.

17. Lat
femora
l
obturator

20. 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. 21
.
largest cutaneous
branch of the femoral
nerve
continuation of the
femoral nerve
Skin of medial aspects
of leg and foot

22. 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

28. 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,

29. Second lecture
24.4.13

31. 31
.
Sensory and motor innervation of the whole
lower limb
arises from the spinal roots L1-S4
Lumbal plexus
Sacral plexus

32. 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.

33. 33

34. 34

43. 43

44. 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

45. 45

46. 46

47. L4
L5
S1
S2
S3
Semitendinosis
Biceps femoris
semimembranosus
Hamstrings
Gastrocnemius
and posterior
compartment of
the leg and foot
Tibial
nerve
Common
peroneal
nerve Deep peroneal
nerve
Anterior
compartment of
leg
Lateral
compartment of leg
Superficial peroneal
nerve
Motor Branches of the
Sciatic Nerve

48. 48

49. 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.
•
49

50. 50

51. 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.
•
51

52. 52

53. 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

54. 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

56. 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

57. 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