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THE LEG 347

comes to the surface. It takes origin posterior to the extensor
digitorum longus, from an extremely narrow strip of the
anterior part of the medial surface of the body of the fibula,
in its middle two-fourths, and also from the adjoining part of
the interosseous membrane. Its tendon passes deep to the
transverse ligament, crosses in front of the distal part of the
anterior tibial artery, and passing distally in front of the ankle
joint reaches the dorsum of the foot deep to the cruciate
ligament (Fig. 342). It is inserted into the dorsal aspect of
the base of the ungual phalanx of the great toe. 1 It is not
joined by the most medial tendon of the extensor digitorum
brevis. The extensor hallucis longus is supplied by the
deep peroneal nerve. It is an extensor of all the joints of the
great toe and a dorsi-flexor of the foot.

M. Peronseus Tertius. The peronseus tertius is a small
muscle which is continuous at its origin with the extensor
digitorum longus. It arises from the distal fourth of the
anterior part of the medial surface ot the fibula, and from a
corresponding extent of the interosseous membrane. It
receives fibres also from the distal part of the anterior
fibular septum, which intervenes between it and the peronaeus
brevis. Its slender tendon is inserted into the dorsal surface
of the expanded base of the fifth metatarsal bone. It is
supplied by the deep peroneal nerve. It is a dorsi-flexor of
the ankle joint and an evertor of the foot.

Arteria Tibialis Anterior. The anterior tibial artery is
the smaller of the two terminal branches of the popliteal.
It takes origin in the posterior region of the leg, at the distal
border of the popliteus muscle, and at the level of the
tuberosity of the tibia (see Fig. 135). It enters the anterior
crural region by passing forwards through the opening in the
proximal part of the interosseous membrane. As it passes
forwards it lies close to the medial side of the neck of the
fibula, where it appears in the present dissection. In the
anterior part of the leg it takes a straight course distally
to the ankle joint. Then it reaches the dorsum of the
foot, and receives the name of dor sails pedis.

In the proximal two-thirds of the leg the anterior tibial
artery is very deeply placed. It lies upon the interosseous
membrane, in the interval between the tibialis anterior on the
medial side, and the extensor digitorum longus and the

1 In most cases it gives a slip to the base of the proximal phalanx also.



348 THE INFERIOR EXTREMITY

extensor hallucis longus on the lateral side. In the distal
third of the leg, where the muscles give place to their tendons,
the artery comes nearer to the surface. In that part of its
course it rests upon the tibia and is overlapped on the lateral
side by the extensor hallucis longus. Immediately proximal
to the ankle joint the tendon of the extensor hallucis longus
crosses superficial to the artery and so comes to lie on its
medial side.

Two vena comites closely accompany the anterior tibial
artery, and send short communicating branches both anterior
and posterior to it. The deep peroneal nerve is also intimately
related to it. It joins the artery a short distance distal to
the knee, and soon takes up a position anterior to the vessel.
Near the ankle joint the nerve, as a rule, again lies on the
lateral side of the artery. Whilst the artery is still in the
back part of the leg it gives off a fibular and a posterior
tibial recurrent branch which will be seen in a subsequent
dissection (see p. 403).

On the front of the leg the anterior tibial artery gives off
the following branches :

1. Muscular. I 3. A. malleolaris anterior medialis.

2. A. recurrens tibialis anterior. | 4. A. malleolaris anterior lateralis.

The muscular branches are numerous, and come off at
irregular points along the whole length of the artery. They
supply the muscles of the anterior crural region.

The anterior tibial recurrent artery is a small vessel
which springs from the anterior tibial immediately after it
reaches the front of the leg. It turns proximally, on the
lateral condyle of the tibia, in the fibres of the tibialis anterior
muscle. Its terminal twigs reach the front of the knee joint,
and anastomose with the inferior genicular branches of the
popliteal artery.

Malleolar Arteries. These arteries take origin immediately
proximal to the ankle joint. The lateral anterior malleolar
artery is the larger of the two. It passes laterally under
cover of the tendons of the extensor digitorum longus and
peronaeus tertius, to reach the lateral surface of the lateral
malleolus, and it anastomoses with the perforating branch of the
peroneal artery and with the lateral tarsal artery. The medial
anterior malleolar artery runs medially, under cover of the



THE LEG



349



tendons of the extensor hallucis longus and tibialis anterior.
It inosculates with branches from the posterior tibial artery.

Arteria Dorsalis Pedis. The dorsal artery of the foot is
the continuation of the anterior tibial. It begins, anterior to
the ankle joint, at a
point midway be-
tween the two mal-
leoli, and it extends
forwards, upon the
dorsal part of the
talus, and across the
navicular, and the
second cuneiform
bone, to the posterior
part of the first in-
terosseous space.
There it leaves the
dorsum of the foot,
by dipping plantar-
wards between the
two heads of the
first dorsal interosse-
ous muscle, to reach
the plantar region,
where it unites with
the lateral plantar
artery in the forma-
tion of the plantar
arch. Its relations
on the dorsum of the
foot are very simple.

(1) It lies in the in-
terval between the
tendon of the exten-
sor hallucis longus on
the medial side and
the most medial ten-
don of the extensor digitorum longus on the lateral side.

(2) It is crossed first by the proximal band of the cruciate
ligament, then by the distal band, and near its termination it
is crossed by the tendon of the extensor hallucis brevis ; with
those exceptions the vessel is covered merely by the integu-




M. tibialis anterior

M. extensor digitorum longus

M. peronaeus brevis
M. peronaeus longus

M. extensor hallucis longus

Tibia

M. peronaeus tertius
Fibula

Transverse ligament
Extensor hallucis longus
Dorsalis pedis artery
Cruciate ligament
Deep peroneal nerve
Tibialis anterior

Lat. br. of deep

peroneal nerve
Extensor hallucis
longus
Peronaeus tertius

M. extensor digitorum
"brevis
Arcuate artery



lendons of extensor
iigitorum longus



FIG. 156. Dissection of the Dorsum of the Foot.



350 THE INFERIOR EXTREMITY

ment and fasciae. (3) The medial terminal branch of the
deep peroneal nerve lies along its lateral side, 1 and two vena
comites accompany it.

As the dorsalis pedis artery traverses the dorsum of the
foot it gives off several twigs to the medial margin of the foot,
and three named branches which pass laterally :

1. Aa. tarsese mediales.

2. A. tarsea lateralis.

3. A. arcuata.

4. A. metatarsea dorsalis prima.

Arterise Tarsese Mediales. The medial tarsal branches
two or more in number, spring from the medial side of the
dorsalis pedis and descend across the medial border of the
foot to anastomose with branches of the medial plantar
artery.

A. Tarsea Lateralis et A. Arcuata (O.T. Tarsal and
Metatarsal). The lateral tarsal artery arises opposite the
navicular bone, and the arcuate artery arises near the bases of
the metatarsal bones. They both run laterally, under cover of
the extensor hallucis brevis and the extensor digitorum
brevis, to reach the lateral margin of the foot. There they
anastomose with branches of the lateral plantar artery. The
lateral tarsal artery anastomoses also with the lateral malleolar
and peroneal arteries.

From the arch which is formed by the arcuate artery
three dorsal metatarsal arteries proceed, one to each of the
lateral three interosseous spaces, and at the clefts between
the toes they divide and supply dorsal digital twigs to the
adjacent sides of the second, third, fourth, and fifth toes.
From the most lateral dorsal metatarsal artery a twig is given
to the lateral side of the little toe.

A. Metatarsea Dorsalis Prima (O.T. First Dorsal Interos-
seous). The first dorsal metatarsal artery is a small vessel
which takes origin from the dorsalis pedis, at the point where
that vessel turns plantarwards to reach the plantar region of
the foot. From its origin it continues forwards, upon the
first dorsal interosseous muscle, and divides into dorsal digital
branches for the medial side of the great toe and the adjacent
sides of the great toe and second toe. 2

Perforating Branch of Peroneal Artery (O.T. Anterior

1 The nerve sometimes descends along its medial side.
' 2 For the branches from the dorsalis pedis in the plantar region see p. 398.



THE LEG 351

Peroneal Artery). This branch of the peroneal artery arises
in the posterior region of the leg. It pierces the interosseous
membrane from 35 to 50 mm. above the lateral malleolus, and
so enters the anterior region. There it descends upon the
distal part of the fibula, under cover of the peronseus tertius,
and its terminal branches anastomose with the lateral malleolar
and lateral tarsal arteries.

Mm. Extensor Hallucis Brevis et Extensor Digitorum
Brevis. The short extensor of the great toe and the short
extensor of the toes may now be examined. They are the
muscles which form the fleshy cushion on the dorsum of the
foot. They arise together from the anterior part of the
dorsal surface of the calcaneus, immediately posterior to the
cuboid bone, and also from the stem of the cruciate ligament.
The common muscular mass breaks up into four segments.
The most medial of the four is called the short extensor of the
great toe. It ends in a tendon which is inserted into the base
of the first phalanx of the great toe. On its way from its
origin to its insertion it crosses the superficial surface of the
distal part of the dorsalis pedis artery. It is supplied by the
lateral branch of the deep peroneal nerve and it is an extensor
of the metatarso-phalangeal joint of the great toe.

The remaining three segments of the muscular mass are
described collectively as the short extensor of the toes. They
end in tendons which join the long extensor tendons going
to the second, third, and fourth toes, and, by means of the
extensor expansion (see p. 346), they gain insertion into the
second and terminal phalanges of those toes. The short
extensor of the toes like the extensor hallucis brevis is
supplied by the lateral branch of the deep peroneal nerve,
and it acts as an extensor of the interphalangeal and metatarso-
phalangeal joints of the toes to which it is distributed.

Nervus Peronseus Profundus (O.T. Anterior Tibial). The
deep peroneal nerve is one of the terminal branches of the
common peroneal nerve. It arises between the proximal
part of the peronaeus longus and the neck of the fibula, then
it pierces the anterior fibular septum and the extensor
digitorum longus, and so enters the anterior compartment
of the leg. In that compartment it descends obliquely until
it joins the anterior tibial vessels, a short distance distal to
the lateral condyle of the tibia. In the remainder of its
course it accompanies the anterior tibial vessels, in the first



35 2



THE INFERIOR EXTREMITY



instance lying lateral to them, then anterior; but near the
ankle joint it again, as a rule, lies on their lateral side. It
passes posterior to the transverse and cruciate ligaments,
and ends by dividing into a medial and a lateral branch.

In its course through the leg the deep peroneal nerve
gives muscular branches to the extensor digitorum longus, the
tibialis anterior, the extensor hallucis longus, and the peronoeus
tertius ; and a fine articular twig to the ankle joint.



Extensor hallucis longus
Anterior tibial vessels and

deep peroneal nerv
Extensor digitorum
longus
Peronaeus tertius -/ //wsm.&&&$Xi3:&

M




Peronaeus brevis

Peroneal
retinaculum

Peronaeus longus



M. abductor
digiti quinti

Plantar aponeurosis



Transverse ligament
Tibialis anterior



Tibia



Talus

Tibialis posterior
Deltoid ligament

Flexor digitorum
longus

Medial plantar artery
Medial plantar nerve
Flexor hallucis longus
M. abductor hallucis

Lateral plantar nerve
Lateral plantar artery
M. flexor digitorum brevis



FIG. 157. Frontal section through the Left Ankle Joint, Talus,
and Calcaneus (Paterson).



The medial terminal branch of the deep peroneal nerve is
continued forwards upon the dorsum of the foot along the
lateral side of the dorsalis pedis artery. 1 At the posterior end
of the first interosseous space, it pierces the deep fascia, and
divides to supply the contiguous margins of the great toe and
the second toe (p. 337). Before it reaches the surface, it
furnishes articular twigs to the tarso-metatarsal and metatarso-

1 Not uncommonly it crosses superficial to the artery and descends
along its medial side.



THE LEG 353

phalangeal joints of the great toe, and frequently, also, a
fine muscular twig to the dorsal surface of the first dorsal
interosseous muscle.

The lateral terminal branch of the deep peroneal nerve
turns abruptly laterally, under cover of the extensor digitorum
brevis, and ends on the dorsum of the tarsus in a gangliform
enlargement. Branches proceed from the enlargement to
supply the extensor digitorum brevis and the numerous
articulations in the neighbourhood. One fine filament can,
in some cases, be traced to the second dorsal interosseous
muscle. The terminal swelling resembles closely the corre-
sponding enlargement in which the dorsal interosseous nerve
of the superior extremity ends (see p. 185).

Ligamentum Transversum Cruris et Ligamentum Cruciatum
(O.T. Anterior Annular Ligament). The dissector should
now re-examine the transverse and cruciate ligaments, and
the arrangement of the structures which pass deep to them.
The transverse ligament is attached to the fibula by its lateral
end, and to the tibia by its medial extremity. If the
fibular attachment is divided, and the ligament is thrown
medially, it will be seen to contain a distinct compartment for
the tibialis anterior and its mucous sheath.

The cruciate ligament is the more important of the two.
Its attachments have already been noted (p. 339). Examine
the manner in which it holds the tendons in position. It
consists of two layers, and these, by separating at certain
points and becoming reunited at others, form three distinct
compartments. The tendon of the tibialis anterior passes
through the medial compartment, the tendon of the ex-
tensor hallucis longus traverses the intermediate one, and the
tendons of the extensor digitorum longus and peronaeus
tertius are transmitted through the lateral compartment.
As the tendons pass through the compartments of the
ligaments, and for some distance proximal to the transverse
ligament and distal to the cruciate ligament, they are
surrounded by mucous sheaths (see p. 341). Lastly, note
the position of the anterior tibial vessels and the deep
peroneal nerve as they pass under cover of the ligaments.
They lie between the extensor hallucis longus and the
extensor digitorum longus (Fig. 156, p. 349).



VOL. i 23



354



THE INFERIOR EXTREMITY



PERONEAL OR LATERAL CRURAL REGION.

Before the peroneal region is opened up, the dissector
should examine the mucous sheaths of the tendons of the
peronaeus longus and brevis. Behind and below the lateral
malleolus the two tendons are enclosed in a common sheath,
but immediately posterior to the trochlear process of the
calcaneus the common sheath is separated into two portions,



M. extensor digitorum longus
tibialis anterior



Sheath of extensor digitorum longus
icath of tibialis anterior




Tendo calcaneus
Retinaculum mm.
peronaeorum sup.

Bursa



Sheath of
peronaeus longus



Retinaculum mm.
peronaeorum inf.



Abductor digiti quinti

M. peronceus brevis | M. flexor digiti quinti brevis

M. extensor digitorum brevis '| M - adductor digiti quinti.

M. peronoeus tertius

FIG. 158. Dissection of Leg and Foot showing Mucous Sheath of Tendons.

one for each tendon (Fig. 158). The upper portion, which
surrounds the continuation of the peronaeus brevis tendon,
extends forwards almost to the insertion of the tendon into
the base of the fifth metatarsal bone. The lower portion,
which surrounds the continuation of the peronaeus longus
tendon, may accompany that tendon to its insertion into the
lateral side of the base of the first metatarsal bone, or it may
end, at the lateral border of the cuboid bone, as the tendon
turns medially into the sole of the foot. In the latter case
the part of the tendon which lies in the sole has a separate
mucous sheath. The sheaths should either be inflated, or



THE LEG 355

injected, or examined with a probe in the manner indicated
when the sheaths of the extensors were described (see p. 341).

Dissection. After the mucous sheaths of the peronaei tendons
have been examined, the lateral compartment of the leg must
be opened up to display its contents. Divide the deep fascia
over the peronaei muscles by a longitudinal incision, and turn
the flaps aside until their continuity with the anterior and
posterior fibular septa is demonstrated, but do not injure the
peroneal retinacula.

Enclosed within the lateral compartment of the leg are the
following structures:

1. The peronasus longus.

2. The peronseus brevis.

3. The termination of the common peroneal nerve.

4. The superficial peroneal nerve.

M. Peronseus Longus. The peronseus longus muscle
arises from the head and from the lateral surface of the shaft
of the fibula in its proximal two-thirds. Surfaces of origin are
also afforded to it by the fascia which covers it, and by the
two fibular intermuscular septa. It ends, a short distance
proximal to the ankle, in a long tendon, which is continued
distally posterior to the lateral malleolus. Gaining the lateral
border of the foot, it proceeds forwards, on the lateral surface
of the calcaneus, to the groove on the plantar surface of the
cuboid, which conducts it obliquely into the sole. Its
insertion will be examined at a later period (see p. 400). It
is supplied by the superficial peroneal nerve (O.T. musculo-
cutaneous) and is a plantar flexor and evertor of the foot.

M. Peronseus Brevis. The peronaeus brevis muscle arises
from the distal two-thirds of the lateral surface of the body
of the fibula, anterior and distal to the peronaeus longus,
and from the fibular intermuscular septum on each side
of it. Its tendon descends, posterior to the lateral malleolus,
and then turns forwards, on the lateral surface of the calcaneus,
to gain an insertion into the projecting base of the metatarsal
bone of the little toe. 1

As the tendons of the two peronsei muscles proceed
distally, in the hollow between the lateral malleolus and the
posterior prominence of the calcaneus, they are held in place
by the superior peroneal retinaculum^ and their movements are

1 A small tendinous slip will, sometimes, be observed to proceed forwards
from the tendon of the peronseus brevis to join the tendon of the long
extensor on the dorsum of the little toe. This is the peronceus digiti quinti.
I 23 a



356 THE INFERIOR EXTREMITY

facilitated by the presence of a common mucous sheath. On
the lateral surface of the calcaneus the tendons are retained
in position by the inferior peroneal retinaculum, but each tendon
lies in a separate compartment surrounded by its own special
prolongation of the mucous sheath. At the back of the
lateral malleolus, the tendon of the peronaeus brevis is
anterior to the tendon of the peronaeus longus and therefore
between it and the fibula, consequently as the two tendons
turn forwards along the lateral side of the calcaneus the
tendon of the peronoeus brevis occupies a higher position
than the tendon of the peronaeus longus and passes above
the trochlear process of the calcaneus, which intervenes
between the mucous sheaths of the two tendons. The
peronaeus brevis is supplied by the superficial peroneal nerve.
It is a plantar flexor and an evertor of the foot.

N. Peronaeus Communis (O.T. External Popliteal Nerve).
The common peroneal nerve has previously been traced as
far as the neck of the fibula. At that point it disappears
from view by passing forwards between the peronaeus longus
muscle and the bone. The muscle must therefore be care-
fully turned aside from its origin in order that the nerve may
be followed to its termination. As it lies between the peronaeus
longus and the neck of the fibula it gives off a small
recurrent articular branch to the knee joint, and then divides
into the deep and superficial peroneal nerves.

The recurrent branch pierces the extensor digitorum longus,
and then accompanies theanterior tibial recurrent artery through
the upper fibres of the tibialis anterior. It gives twigs to
the tibialis anterior, but its terminal filaments are distributed
to the synovial stratum of the capsule of the knee joint.

The deep peroneal nerve pierces the proximal part of the
extensor digitorum longus to reach the anterior region of the
leg, where it has already been dissected.

N. Peronseus Superficialis (O.T. Musculo-Cutaneous Nerve).
The superficial peroneal nerve passes distally in the sub-
stance of the peronaeus longus ; reaches the interval between
the two peronaei muscles ; gives branches to both ; and
then lies between the peronaeus brevis and the extensor
digitorum longus. In the distal third of the leg it pierces the
deep fascia, becomes cutaneous, and divides into a medial
and a lateral branch, which have been called the medial and
intermediate dorsal cutaneous nerves of the foot (p. 338).



THE LEG 357



MEDIAL CRURAL REGION.

This region corresponds to the subcutaneous or medial
surface of the tibia. The deep fascia blends with the peri-
osteum of the bone, and the structures which have to be
examined are :

1. The great saphenous vein.

2. The saphenous nerve.

3. The expanded tendons of insertion of the sartorius, semitendinosus, and

gracilis.

4. The tibial collateral ligament of the knee joint.
5.. The inferior medial genicular artery.

6. The inferior medial articular nerve.

Dissection. The great saphenous vein and the saphenous
nerve have already been cleaned where they lie upon the distal
third of the medial surface of the tibia. Now remove the remains
of the superficial fascia from the region of the medial surface
of the tibia, then again examine the insertions of the sartorius,
gracilis, and semitendinosus.

The expanded terminal parts of the tendons of the
sartorius, gracilis, and semitendinosus are all inserted into
the proximal third of the medial surface of the tibia. Note
how the sartorius overlaps the tendons of the other two, and
how the tendon of the gracilis overlaps the proximal part of
the tendon of the semitendinosus. Mucous bursae separate
the tendons from each other.

Under cover of the sartorius, gracilis, and semitendinosus,
and separated from them by a bursa, the tibial collateral
ligament of the knee joint extends distally, for a short distance,
upon the medial aspect of the body of the tibia. Passing
forwards under cover of the ligament, so as to gain the
anterior aspect of the knee, are the inferior medial genicular
vessels and the inferior medial articular nerve.

As the great saphenous vein and the saphenous nerve
cross the distal third of the medial surface of the tibia, they
are very liable to injury because they lie quite superficially
between the skin and the bone.



POSTERIOR CRURAL REGION.

The following is a list of the structures which are met
with in this dissection :



358 THE INFERIOR EXTREMITY

I Sunerficial veins / Great saphenous vein.
ins ' \Smallsaphenousvein.

2. Cutaneous nerves.

3. Deep fascia.

fGastrocnemius.

4. Superficial muscles of the calf, -! Plantaris.

[Soleus.

5. Tendo calcaneus (Achillis) and its bursa.

6. Posterior tibial vessels.

7. Tibial nerve.

( Popliteus.

8. Deep muscles, J i. r . hallu f cis lon g us '

j Tibiahs posterior.

\, Flexor digitorum longus.

9. Ligamentum laciniatum.

Dissection. Reflection of Skin. The limb must now be
placed on its anterior aspect, and the muscles of the calf rendered
tense by dorsi-flexing the foot at the ankle joint. That position
should be maintained by the aid of hooks, fastened to the toes
and to the under surface of the table. The skin has already been
reflected to the medial and lateral borders of the leg and foot.



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 35 of 44)