Dissection of the Gluteal Region

1
Dissection of the Gluteal Region
2
Place the cadaver in the prone position.Palpate
again the following bony landmarks the iliac
crests, which end in front at the anterior
superior iliac spine and behind at the posterior
superior iliac spine. Identify the iliac
tubercle, the ischial tuberosity, the greater
trochanter of the femour, and the tip of the
coccyx. Reexamine the landmarks on yourself.
3
Make a horizontal skin incision from the midline
posteriorly along the upper border of the iliac
crest to the iliac tubercle. If the perineum has
not been dissected, make a vertical midline
incision down the back of the lower lumbar
region, sacrum, and coccyx, and encircle the anus.
4
Now make a transverse incision on the back of
the thigh about 5 cm below the fold of the
buttock. Connect the incision so that the skin
flap and subcutaneous tissue can be turned
laterally.
5
Cutaneous Nerves. Now remove the thick layer of
superficial fascia along the lines of the skin
incisions, starting in the area of the posterior
superior iliac spine and working downward and
laterally.
6
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7
When removing the fascia, attempt to identify the
cutaneous branches of the upper three lumbar and
upper three sacral nerves as they cross the
posterior part of the iliac crest. Also identify
the lateral branches of the iliohypogastric and
twelfth thoracic nerves as they cross the
anterior part of the iliac crest.
8
Preserve the branches from the posterior
cutaneous nerve of the thigh (posterior femoral
cutaneous nerve ) and, if possible, those from
the lateral cutaneous nerve of the thigh (
lateral femoral cutaneous nerve).
9
Gluteal Muscles. Clean the deep fascia covering
the gluteus maximus and gluteus medius muscles.
Carefully define the upper and lower borders of
the gluteus maximus muscle and, without damaging
the underlying structures, incise the deep fascia
along these borders.
10
Now insert your fingers beneath the upper and
lower borders of this muscle and separate it from
the deep structures. With a curved incision, cut
the gluteus maximus free from its origin,
starting in the region of the posterior superior
iliac spine. Reflect the muscle laterally to its
insertion into the iliotibial tract and the femur.
11
Avoid damaging the underlying gluteus medius
muscle and the sacrotuberous ligament. Identify
and clean the inferior gluteal nerve and vessels
as they enter the deep surface of the gluteus
maximus. Identify the bursae over the greater
trochanter and the ischial tubersity.
12
Identify and clean the following muscles in the
gluteal region from above downward1. The tensor
fasciae latae as it passes downward from the
anterior superior iliac sipne to be inserted into
the iliotibial tract.
13
2. The gluteus medius muscle, whose fibers
converge to be inserted intothe lateral surface
of the greater trochanter.3. The piriformis
muscle, which emerges from the greater sciatic
foramen and is inserted into the upper border of
the greater trochanter.
14
Cut through the origin of the gluteus medius and
reflect it downward and laterally to its
insertion on the greater trochanter.
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16
Nerves and Blood Vessels of the Gluteal
Region.Identify, clean, and study the following
nerves and vessels in the gluteal region, using
the piriformis muscle as the central key
structure.
17
At the superior border of the piriformis,
identify1. The superior gluteal nerve, which
emerges from the greater sciatic foramen and
supplies the gluteus medius and minimus and the
tensor fasciae latae muscles.
18
2. The superior gluteal artery, a branch of the
internal iliac artery that emerges from the
greater sciatic foramen to enter the gluteal
region.
19
At the lower border of the piriformis muscle,
identify1. The sciatic nerve, the largest nerve
in the body, which emerges from the greater
foramen to pass downward into the back of the
thigh.
20
Occasionally, the peroneal part of the sciatic
nerve leaves the sciatic nerve high in the pelvis
and appears in the gluteal region by passing
above or through the piriformis muscle. The
sciatic nerve ususlly gives no branches in the
gluteal region.
21
2. The inferior gluteal nerve, which also emerges
from the greater sciatic foramen and supplies the
gluteus maximus muscle.3. The inferior gluteal
artery, a branch of the internal iliac artery,
which also emerges from the greater sciatic
foramen.
22
4. The posterior cutaneous nerve of the thigh,
which passes downward from the greater sciatic
foramen on the posterior surface of the sciatic
nerve. It leaves the gluteal region by passing
superficial to the biceps femoris.
23
Identify the gluteal branches to the skin over
the lower medial quadrant of the buttock and the
perineal branch, which passes medial to the
scrotum or labium majus.
24
5. The pudenal nerve, the nerve to the obturator
internus, and the internal pudendal artery, which
enter the gluteal region briefly through the
greater sciatic foramen. They cross the ischial
spine and then enter the perineum through the
lesser sciatic foramen. The nerve to the
obturator internus gives off a small branch that
supplies the superior gemellus muscle.
25
6. The nerve to the quadratus femoris, which
leaves the pelvis through the greater sciatic
foramen and runs downward anterior to the sciatic
nerve, the gemelli,and the tendon of the
obturator internus. Identify its branches to the
inferior gemellus and the quadratus femoris
muscles.
26
Where necessary, remove the veins that accompany
the arteries in order to clarify your
dissection.
27
It is most important that you confirm the
position of the sciatic nerve in relation to the
greater trochanter and the ischial tuberosity.
Replace the gluteus medius and maximus muscles in
their correct anatomical position.
28
Now relate the sciatic nerve to the gluteus
maximus muscle remember that a large number of
intramuscular injections are introduced into this
muscle and that the sciatic nerve must not be
damaged. Note that the upper lateral quadrant of
this muscle lies a safe distance away from the
sciatic nerve.
29
Clean the ischial tuberosity and note the
attachment of the sacrotuberous ligament and the
origins of the hamstring muscles.
30
Dissection of the Back of the Thigh
31
Make a transvers skin incision at the level of
the midcalf. Make a vertical skin incision down
the midline on the back of the thigh, connecting
the transverse incision below the buttock to the
transverse incision on the midcalf.
32
Reflect the skin flaps medially and laterally.
Try to identify some of the branches of the
posterior cutaneous nerve of the thigh along the
middle of the back of the thigh. Remove the
superficial fascia.
33
Incise in the midline the deep fascia on the back
of the thigh from the gluteal region to the calf.
Reflect the cut edges medially and laterally.
34
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35
Identify and clean the hamstring muscles, namely,
the biceps femoris, the semimembranosus, and the
semitendinosus. Confirm that these muscles arise
from the ischial tuberosity. Identify the short
head of the biceps, which arises from the shaft
of the femur.
36
Sciatic Nerve. Follow the sciatic nerve from the
gluteal region deep to the long head of the
biceps femoris. Note that it descends in the
midline of the thigh, that it is overlapped
posteriorly by the adjacent margins of the biceps
femoris and semimembranosus muscles, and that it
lies on the posterior aspect of the adductor
magnus muscle.
37
In the lower third of the thigh the sciatic nerve
divides into the tibial and common peroneal
nerve. Occasionally the sciatic nerve divides
into its two terminal branches at a higher level.
38
Identify the following branches of the sciatic
nerve1. Muscular branches to the long head of
the biceps femoris, the semitendinosus, the
semimembranosus, and the ischial fibers
(hamstring part) of the adductor magnus. These
branches arise from the tibial component of the
sciatic nerve and run medially, a short distance
below the ischial tuberosity, to supply the
muscles.
39
2. Tibial Nerve.3. Common peroneal
nerve.Detach the hamstring muscles from the
ischial tuberosity and fully expose the posterior
surface of the adductor magnus. Define the
insertion of the muscle into the femur. Identify
the four perforating arteries, which are branches
of the profunda femoris that pierce the adductor
magnus.
40
Trace the tendons of the sartorius, gracilis, and
semitendinosus muscles to their insertions on the
medial surface of the shaft of the tibia.
41
Dissection of the Popliteal Fossa
42
Identify and clean the boundaries of the
popliteal fossa. Note that the upper lateral
pboundary is formed by the biceps femoris and
that the upper medial boundary is formed by the
semitendinosus and semimembranosus muscles. The
lower boundaries are formed by the medial and
lateral heads of the gastrocnemius muscle.
43
Separate the medial and lateral heads of the
gastrocnemius muscle and identify the plantaris
muscle. Expose and clean the common peroneal and
tibial nerves and their branches.
44
Common Peroneal Nerve. Having arisen from the
sciatic nerve, the common peroneal nerve runs
downward through the popliteal fossa, following
the medial border of the biceps femoris muscle.
Note that it leaves the fossa by crossing
superficially the lateral head of the
gastrocnemius muscle. It then passes posterior to
the head of the fibula and winds laterally around
the neck of the bone to enter the substance of
the peroneus longus muscle.
45
Identify the following branches of the common
peroneal nerve1. Cutaneous a. The peroneal
communicating nerve, which runs downward and
joins the medial sural cutaneous nerve to form
the sural nerve.b. The lateral sural cutaneous
nerve, which supplies the skin on the lateral
side of the back of the leg.
46
2. Muscular branches to the short head of the
biceps femoris muscle.3. Articular branches to
the knee joint.
47
Tibial Nerve. Follow this nerve from its origin
from the sciatic nerve, downward through the
popliteal fossa. It lies first on the lateral
side of the popliteal artery, then posterior to
it, and finally medial to it. Note that the
popliteal vein lies between the nerve and the
artery through its course. The tibial nerve
leaves the fossa by passing beneath the soleus
muscle.
48
Identify the following branches of the tibial
nerve1. Cutaneous. The medial sural cutaneous
nerve descends between the two heads of the
gastrocnemius muscle and is usually joined by the
peroneal communicating branch of the common
peroneal nerve to form the sural nerve.
49
2. Muscular branches. These supply both heads of
the gastrocnemius and the plantaris, soleus, and
popliteus. Note that the nerve to the popliteus
runs down over the muscle and then winds around
the lower border to supply the popliteus on its
anterior surface.3. Articular branches to the
knee joint.
50
Now Clean the popliteal artery and vein.Popliteal
Artery. Trace the popliteal artery through the
popliteal fossa. Note that it begins as a
continuation of the femoral artery at the opening
in the adductor magnus. The artery ends at the
lower border of the popliteus by dividing into
anterior and posterior tibial arteries.
51
Identify the following branches of the popliteal
artery1. Muscular branches to the neighboring
muscles.2. Articular branches to the knee joint.
52
Popliteal Vein. Confirm that the popliteal vein
is formed by the union of the venae comitantes of
the anterior and posterior tibial veins at the
lower border of the popliteus muscle. It ends by
becoming the femoral vein at the opening of the
adductor magnus.
53
Identify the following tributaries of the
popliteal vein1. Muscular and articular
veins.2. Small saphenous vein.
54
Having removed all the fatty areolar tissue from
the popliteal fossa, identify the structures that
form the floor of the fossa. These structures
are, from above downward (1) the popliteal
surface of the femur, (2) the oblique ligament
on the back of the knee joint, and (3)the fascia
covering the popliteus muscle.
55
Dissect of the Anterior Fascial Compartment of
the Thigh
56
Place the cadaver in the supine position.Make a
vertical skin incision down the middle of the
anterior surface of the thigh from the oblique
incision down over the patella to the tibial
tuberosity. Then make a transverse skin incision
on the front of the leg just below the knee at
the level of the tibial tuberosity. Reflect the
medial and lateral skin flaps to the medial and
lateral margins of the thigh, respectively.
57
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58
Superficial nerves, vesels, and lymph
nodes.Carefully dissect away the fatty
superficial fascia of the front of the thigh,
preserving the lateral cutaneous nerve of the
thigh (lateral femoral cutaneous nerve), which
emerges from beneath the lateral end of the
inguinal ligament, and intermediate and medial
(femoral) cutaneous nerves, which are branches of
the femoral nerve.
59
Identify the important great saphenous vein,
which enters the thigh from behind the medial
side of the knee joint. Note that it passes
through the lower part of the saphenous opening
in the deep fascia and joins the femoral vein
about 4cm below and lateral to the pubic tubercle.
60
Identify the three tributaries of the great
saphenous vein, namely, (1)the superficial
circumflex iliac vein, (2)the superficial
epigastric vein, and (3)the superficial external
pudendal vein.These veins correspond with three
branches of the femoral artery, and they should
be located in this region.
61
Identify the horizontal group and vertical group
of the superficial inguinal lymph nodes. The
horizontal group is situated about one
finger-breadth below the inguinal ligament, and
the vertical group runs alongside the terminal
part of the great saphenous veins.
62
Deep fascia of the thigh.Clean the margins of
the saphenous opening in the deep fascia of the
thigh and understand the structures entering and
leaving it. The saphenous opening is filled with
loose fascia called the cribriform fascia.
Realize that the deep fascia of the thigh (fascia
lata) encloses the thigh like a trouser leg and
that its upper end is attached to the pelvis and
its associated ligaments.
63
Identify the iliotibial tract on the lateral
side. Understand that three fascial septa pass
from the inner aspect of the deep fascial sheath
of the thigh to the linea aspera of the femur and
thus divide the thigh intothree compartments.
64
Identify the inguinal ligament and by means of an
oblique incision separate the deep fascia of the
thigh from the lower edge of the ligament. Now
make a vertical incision through the deep fascia
down the middle of the thigh to the patella.
65
Reflect the cut edges medially and laterally.
Working from lateral to medial, identify the
following muscles the tensor fasciae latae, the
vastus lateralis, the rectus femoris, the
pectineus, the adductor longus, the adductor
magnus, and the gracilis. Clean these muscles.
66
Femoral triangle.Define the boundaries and floor
of the femoral triangle. Note that the base is
formed by the inguinal ligament, the lateral
border by the sartorius muscle, and the medial
border by the medial border of the adductor
longus muscle.
67
Identify and clean the following structures in
the femoral triangle (1)the femoral nerve,
(2)the femoral artery, (3)the femoral vein, and
(4)the deep inguinal lymph nodes.
68
Identify the following branches of the femoral
nerve1. Cutaneous nerves of the thigh.2.
Nerves to the muscles.3. Saphenous nerve. This
runs inferiorly and crosses the femoral artery.
It pierces the deep fascia on the medial side
of the knee, after emerging between the tendons
of the sartorius and gracilis. Its further course
in the leg will be studied later.
69
Identify the following branches of the femoral
artery1. The superficial circumflex iliac
artery.2. The superficial epigastric artery.3.
The superficial external pudendal artery.4. The
deep external pudendal artery runs medially
either anterior or posterior to the femoral vein
to the external genitalia.
70
5. The profunda femoris artery is a large branch
that arises from the lateral side of the artery
about 4cm below the inguinal ligament. It passes
behind the femoral vessels and the adductor
longus muscle. Note that at its origin it gives
off the medial and lateral femoral circumflex
arteries.6. The descending genicular artery.
71
Femoral Sheath. Identify and carefully clean the
femoral sheath.Understand that it is a downward
protrusion into the thigh of the fascial envelope
lining the abdominal walls and that it surrounds
the femoral vessels and lynphatic vessels for
about 2.5cm below the inguinal ligament.
72
The sheath is cone-shaped and is divided into
three compartments. The lateral compartment is
occupied by the femoral artery.The middle
compartment is occupied by the femoral vein. The
small but very important medial compartment is
occupied by connective tissue and lymphatic
vessels it is called femoral canal. The upper
opening of the femoral canal is called the
femoral ring.
73
Note the relations of the femoral sheath to
(1)the inguinal ligament, (2)the lacunar
ligament,(3)the superior ramus of the pubis and
the pectineus muscle.
74
Adductor (Subsartorial) Canal. Elevate the
sartorius muscle so that it can be shifted from
side to side. Examine the walls of the adductor
canal. Note that the subsartorial canal
commences above at the apex of the femoral
triangle and ends below at the opening in the
adductor magnus.
75
Verify that the anteromedial wall is formed by a
fibrous sheet deep to the sartorius and that the
posterior wall is formed by the adductor longus
and magnus.
76
Note that the lateral wall is formed by the
vastus medialis. Identify and clean the following
contents (1)the femoral artery, (2)the femoral
vein, (3)the saphenous nerve, (4)the nerve to
the vastus medialis, (5)the posterior division
of the obturator nerve.
77
Dissect of the Medial Fascial Compartment of the
Thigh
78
On the medial side of the thigh, examine again
the gracilis, adductor longus, and pectineus
muscles. Trace the straplike gracilis to its
insertion into the upper part of the medial
surface of the shaft of the tibia. Follow the
adductor longus and pectineus to their insertion
on the linea aspera on the posterior surface of
the femur.
79
Carefully transect the pectineus muscle close to
its origin from the superior ramus of the pubis
and examine the underlying adductor brevis and
obturator externus muscles. Clean the adductor
brevis and identify the obturator nerve.
80
Follow the profunda femoris artery as it passes
behind the adductor longus muscle. Identify the
four perforating arteries, which are branches of
the profunda artery. Clean the obturator nerve
and its branches.
81
Obturator nerve. The obturator nerve enters the
thigh through the upper part of the obturator
foramen, known as the obturator ananl. While in
the canal, it divides into anterior and posterior
divisions
82
1. The anterior division should be identified as
it passes downward in front of the obturator
externus and adductor brevis muscles. It lies
behind the pectineus and adductor longus. Verify
that it gives branches to the gracilis, adductor
brevis, and adductor longus and occasionally to
the pectineus. It ends by supplying the femoral
artery.
83
2. The posterior division should be identifies as
it pierces the obturator externus and passes
downward posterior to the adductor brevis and in
front of the adductor magnus. Trace the nerve
through the opening in the adductor magnus, where
it supplies the back of the knee joint. Identify
the muscular branches to the obturator externus,
to the adductor part of the adductor magnus, and
occasionally to the adductor brevis.
84
Dissection of the Anterior Fascial Compartment of
the Leg
85
Place the cadaver in the supine position.Make a
midline skin incision down the front of the leg
and dorsum of the foot as far as the root of the
toes. make a transverse skin incision at the
level of the malleoli and another across the
dorsum of the foot at the root of the toes.
Reflect the skin flaps medially and laterally.
86
Cutaneous Nerves and Superficial Vein.Identify
in the superficial fasscia the cutaneous nerves.
The superficial peroneal nerve pierces the deep
fasscia at the junction of the middle and distal
thirds of the leg. Trace the superficial
peronealnerve downward to its termination on the
dorsum of the foot and toes.
87
The cutaneous branch of the deep peroneal nerve
pierces the deep fascia between the first and
second metatarsal bones to supply the skin of the
adjacent sides of the first and second toes. The
saphenous nerve passes down the medial side of
the shaft of the tibia with the great saphenous
vein.
88
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89
Secure in the superficial fassccia of the dorsum
of the foot the dorsal venous arch. Define the
origin of the great saphenous vein and follow it
up the leg anterior to the medial malleolus.
Identify the origin of the small saphenous vein
and follow it up posterior to the lateral
malleolus.
90
Deep Fascia and Extensor Retinacula.Remove the
remains of the superficial fascia and clean the
deep fascia. Identify and dissect out the
superior and inferior extensor retinacula, which
are thickenings of the deep fascia. Note that
the inferior extensor retinaculum is Y-shaped.
91
Incise the deep fascia down the front of the leg
as far as the superior extensor retinaculum.
Reflect the flaps of deep fascia medially and
laterally and open the anterior compartment of
the leg. Note that the deep fascia is attached to
the underlying muscles, which take partial origin
from the deep surface of the fascia.
92
Now identify and clean the muscles of the
anterior fascial compartment and follow their
tendons distally.
93
Muscles of the Anterior Compartment of the
LegTibialis anterior. Comfirm that the tibilis
anterior arises from the upper half of the
lateral surface of the tibia and from the
interosseous membrane and passes through both
extensor retinacula to be attached to the medial
cuneiform bone and the adjoining base of the
first metatarsal bone.
94
Extensor digitorum longus. Comfirm that this
muscle arises from the upper two-thirds of the
anterior surface of the fibula and from the
interosseous membrane and that it passes behind
the superior and through the inferior extensor
retinacula. Trace the four tendons as they
diverge to pass to the lateral four toes.
95
Incise the skin along the dorsal surface of the
second toe and reflect the medial and lateral
flaps. Study the insertion of the extensor
digitorum longus into that toe. Note the
formation of the dorsal extensor expansion. The
central part of the expansion is inserted into
the base of the middle phalant and the two
lateral parts converge to be inserted into the
base of the distal phalanx.
96
Peroneus tertius. Study the origin of this
muscle from the lower third of the anterior
surface of the fibula and the interosseous
membrane. Follow the tendon to its insertion into
the medial side of the dorsal aspect of the base
of the first metatarsal bone.
97
Extensor hallucis longus. Note that this muscle
arises from the middle half of the anterior
surface of the fibula and from the interosseous
membrane. Follow the tendon behind the superior
and through the inferior extensor retinacula.
98
Cut through the superior and inferior extensor
retinacula and separate the tendon of the
tibialis anterior from the tendons of the
extensor digitorum longus. Identify and clean the
anterior tibial artery and the deep peroneal
nerve.
99
Arteries and Nerves of the Anterior Compartment
of the Leg
100
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101
Anterior tibial artery. This is one of the
terminal branches of the poplitea artery, and it
enters the anterior compartment of the leg by
piercing the interosseous membrane close to the
neck of the fibula. It descends on the anterior
surface of the interosseous membrane and the
lower part of the lower end of the tibia.
102
Note that the anterior tibial artery is crossed
anteriorly by the tendons of the extensor
hallucis longus.In front of the ankle joint the
anterior tibial artery lies midway between the
malleoli and becomes the dorsalis pedis artery.
103
Identify the following branches of the anterior
tibial artery1. Muscular branches to
neighboring muscles.2. Anastomotic branches,
which anastomose with branches of other arteries
around the knee and ankle joint.
104
Deep Peroneal Nerve. This is one of the terminal
branches of the common peroneal nerve. Confirm
that it enters the anterior compartment by
piercing the upper part of the extensor digitorum
longus. Trace the deep peroneal nerve inferiorly
and note its deep position and its close
relationship to the anterior tibial artery.
105
Confirm that the deep peroneal nerve supplies the
four muscles of the anterior fascial compartment
of the leg.
106
Dissection of the Lateral Compartment of the Leg
107
Make a vertical incision in the deep fascia
covering the lateral compartment of the leg and
expose the underlying peroneus longus and brevis
muscles.
108
Clean the peroneus longus muscle and note that it
arises from the upper two-thirds of the lateral
surface of the fibula.Follow the peroneus longus
tendon behind the lateral malleolus beneath the
superior peroneal retinaculum. Trace the tendon
forward on the lateral surface of the calcabeum
below the peroneal tubercle. Here it is held in
place by the inferior peroneal retinaculum.
Follow the tendon to the groove on the inferior
aspect of the cuboid as it passes into the sole
of the foot.
109
Now study the peroneus brevis by displaceing the
peroneus longus laterally. Confirm that the
peroneus brevis arises from the lower two-thirds
of the lateral surface of the fibula. Follow the
tendon behind the lateral malleolus and note that
it is covered by the tendon of the peroneus
longus muscle. Having passed beneath the superior
and inferior peroneal retinacula, the tendon is
inserted into the base of the fifth metatarsal
bone.
110
Follow the common peroneal nerve from the
popliteal fossa to where it winds around the neck
of the fibula to enter the substance of the
peroneus longus muscle. Identify the origin of
the deep and superficial peroneal nerves from the
common peroneal nerve.
111
Trace the deep peroneal nerve into the anterior
compartment of the leg. Follow the superficial
peroneal nerve downward onto the dorsum of the
foot. Note its branches to the peroneus longus
and brevis muscles.
112
Finally, transect the peroneal retinacula and
examine the underlying tendons. Before leaving
the front of the leg, examine the ligamentum
patellae and examine its insertion into the
tuberosity of the tibia. Examine also the flat
tendons of insertion of the sartorius, gracilis,
and semitendinosus into the upper part of the
medial surface of the shaft of the tibia.
Identify again the saphenous nerve and great
saphenous vein as they run down the medial side
of the leg.
113
Dissection of the Posterior Compartment of the Leg
114
Place the cadaver in the prone position.Make a
midline skin incision down the back of the leg to
the heel. Make a tranverse skin incision at the
level of the malleoli.Reflect the skin flaps.
Remove the subcutaneous tissue but preserve the
sural nerve and the small saphenous vein. Now
slit the deep fascia in the line of the skin
incision and reflect the fascial flaps.The
posterior compartment of the leg is now open.
115
Clean and define the flexor retinaculum. It is a
strong band of deep fascia that extends downward
and backward from the medial malleolus to the
calcaneum.
116
Muscles of the Posterior Compartment of the Leg.
Understand that the muscles of this compartment
are arranged in superficial and deep layers. The
superficial group of muscles consists of the
gastrocnemius, plantaris, and soleus the deep
group consists of the popliteus, flexor digitorum
longus, flexor hallucis longus, and tibialis
posterior.
117
Examine again the two heads of the gastrocnemius
muscle and the plantaris. Follow the
gastrocnemius inferiorly to the tendocalcaneus.
Transect the medial and lateral heads of the
gastrocnemius distal to where they receive their
nerve supply.
118
Note that the long tendon of the plantaris
descends obliquely in the interval between the
gastrocneius and soleus and then along the medial
border of the tendocalcaneus, to be attached to
the posterior surface of the calcaneum.
119
Divide the plantaris below its origin. Clean and
study the soleus muscle. Confirm that it has an
inverted V-shaped origin from the soleal line on
the posterior surface of the tibia, from the
upper quarter of the posterior surface of the
shaft of the fibula, and from a fibrous arch
between these bones. Note that the muscle joins
the anterior part of the tendocalcaneus. Identify
the nerve supply of the soleus muscle from the
tibial nerve.
120
Cut through the tibial origin of the soleus and
reflect the gastrocnemius, plantaris, and soleus
laterally. Identify the deep transverse fascia or
intermuscular septum that separates the
superficial from the deep muscles in the
posterior compartment. Divide the deep transverse
fascia and expose the posterior tibial vessels
and the tibial nerve.
121
Study the deep muscles, namely, the popliteus,
flexor digitorum longus, flexor hallucis longus,
and tibialis posterior.
122
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123
Arteries and Nerves of the Posterior Compartment
of the Leg.Posterior tibial artery. This artery
is one of the terminal branches of the popliteal
artery. Trace it downward on the posterior
surface of the tibialis posterior muscle and on
the posterior surface of the tibia below. Confirm
that the posterior tibial artery passes behind
the medial malleous, deep to the flexor
retinaculum, and terminates by dividing into
medial and lateral plantar arteries.
124
Identify the follow branches of the posterior
tibial artery 1. Peroneal artery. This arises
high up in the posterior compartment and descends
behind the fibula, either within the substance of
the flexor hallucis longus muscle or posterior to
it. It gives off a perforating branch that
pierces the interosseous menbrane to reach the
lower part of the front of the leg.
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2. Muscular branches, which are distributed to
neighboring muscles.3. Nutrient artery to the
tibia.4. Anastomotic branches, which join other
arteries around the ankle joint.5. Medial and
lateral plantar arteries.
126
Tibial nerve. This nerve is one of the terminal
branches of the sciatic nerve. The tibial nerve
runs down the back of the leg accompanying the
posterior tibial artery. Note that the nerve lies
at first on the medial side of the posterior
tibial artery, then crosses posterior to it, and
finally lies on its lateral side. The nerve
passes behind the medial malleolus and beneath
the flexor retinaculum, where it divides into the
medial and lateral plantar nerve.