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membrane. It contains the tibialis posterior muscle (Fig. 142).



368 THE INFERIOR EXTREMITY

Dissection. The dissector must now proceed to the dissection
of the contents of the three sections of the posterior osteo-fascial
compartment, commencing with the superficial section.

First clean carefully the laciniate ligament, and secure the
medial calcanean branches of the posterior tibial artery and of the
tibial nerve which pierce it. Note that it is continuous proximally
with the deep fascia of the posterior part of the leg, and that distally
it gives attachment to the abductor hallucis ; then make a longi-
tudinal incision through the deep fascia, down the middle of
the back of the leg, from the popliteal region proximally to the
calcaneus distally. Turn the two flaps so defined to the medial
and lateral sides respectively. Detach the distal end of the
medial flap from the ligamentum laciniatum, but do not injure
that ligament, and detach the distal end of the lateral flap from
the superior peroneal retinaculum, but, if possible^ avoid injury
to the retinaculum. Note the attachment of the medial flap
to the medial border of the tibia, and the connection of the
lateral flap with the posterior fibular septum, by means of which
attachment to the lateral crest of the fibula is attained (Figs.
152, 155).

When the connections of the deep fascia have been displayed,
make an opening into the mucous sheath of the tendo calcaneus,
at one or other border of the tendon, and, by inflation, injection
or exploration with a blunt probe, attempt to demonstrate the
extent of the sheath, which is somewhat variable. Next clean
the gastrocnemius and the tendo calcaneus, and remove the
thick pad of fat which lies in front of the tendo calcaneus, and
separates it from the first fascial septum of the posterior compart-
ment. Now examine the distal portion of the first fascial septum
and note the important part it plays in binding down the muscles
of the middle section of the compartment, and in the formation
of the ligamentum laciniatum.

If the medial head of the gastrocnemius was not divided
when the popliteal fossa was dissected, divide it now, at the
level of the knee joint, and turn it laterally ; then clean the sural
arteries from the popliteal trunk, and the branches of the tibial
nerve which supply the gastrocnemius. Raise the proximal
part of the divided muscle, and note the bursa which intervenes
between it and the semimembranosus. The bursa usually
communicates with a bursa under cover of the semimembranosus
which, in its turn, communicates with the cavity of the knee
joint. Open the bursa and explore its extent with a blunt probe,
if that has not already been done (see p. 309). Next follow the
nerve to the soleus, which was found when the popliteal fossa
was dissected (see p. 310). It springs from the tibial nerve in
the popliteal fossa, on the medial side of the popliteal artery,
crosses the posterior surface of the distal part of the artery,
passes between the plantaris and the lateral head of the gastro-
cnemius, and enters the posterior surface of the soleus. When
the nerve to the soleus has been cleaned and followed to its
termination, clean the plantaris, and follow its slender tendon
to its insertion into the posterior surface of the calcaneus on the
medial side of the tendo calcaneus.

Superficial Muscles. The superficial muscles of the calf
of the leg are three in number, viz., the gastrocnemius, the



THE LEG



369



Adductor
magnus



plantaris, and the soleus. The gastrocnemius is the most
superficial ; the soleus is placed under cover of the gastro-
cnemius ; whilst the slender plantaris extends distally and
medially between them. The tendons of insertion of the
gastrocnemius and soleus unite to form the tendo calcaneus
(tendo Achillis).

M. Gastrocnemius. The gastrocnemius is a strong muscle.
It arises, by two heads, from the posterior part of the distal end
of the femur. Both heads have been already studied in
connection with the popliteal fossa, which they bound in its
distal part. The lateral head springs from an impression on
the lateral surface of the lateral condyle of the femur, and
also from a small portion
of the popliteal area of the
bone, immediately proximal
to the lateral condyle.
The medial head takes Medialhead
origin from the proximal ofgastro-

c , ,. , cnemius

part of the medial con-
dyle, and also from a rough
ridge on the adjacent part
of the popliteal surface of
the femur. The two fleshy
bellies swell out as they
pass distally, and end, near
the middle of the leg, in a
thin aponeurotic tendon.
They do not blend with
each other, and are usually
separated by a furrow, at
the bottom of which the flattened tendon, to which the fasciculi
of both heads are attached, may be seen. The medial head is
the more bulky of the two, and it extends further distally than
the lateral head. The flattened tendon in which they
terminate narrows slightly as it descends, and, a short distance
distal to the middle of the leg, it blends with the stouter
tendon of the soleus to form the tendo calcaneus (tendo
Achillis).

The gastrocnemius is supplied by the tibial nerve. It is
a plantar flexor of the foot and a flexor of the knee, but it
cannot act efficiently both on the knee and the ankle joint at
the same time. Therefore, if the foot is in the position of

VOL. i 24




Posterior cruciate
ligament



Anterior cruciate
ligament



FIG. 162. Posterior aspect of distal por-
tion of Femur, with Attachments of
Muscles mapped out.



370 THE INFERIOR EXTREMITY

plantar flexion it cannot flex the knee, and if the knee is
flexed it cannot act upon the ankle. It is important to
remember these facts in association with fractures of the
distal part of the femur.

M. Plantaris. The small fleshy belly of the plantaris is not
more than three or four inches long. It lies along the medial
side, and partly under cover, of the lateral head of the gastro-
cnemius. It arises from the popliteal surface of the femur,
immediately proximal to the lateral condyle. It ends in a
slender tendon, which is remarkable for its great length. The
tendon proceeds distally and medially, between the gastro-
cnemius and soleus, and then runs along the medial side of the
tendo calcaneus (Achillis) to gain insertion into the posterior
aspect of the calcaneus. It is frequently closely connected
with the tendo calcaneus, and sometimes becomes blended with
it, or with the fascia of the leg above the level of calcaneus.

The plantaris is supplied by a branch from the tibial nerve.
Its actions are similar to those of the gastrocnemius.

Dissection. Divide the lateral head of the gastrocnemius,
at the level of the knee joint. Turn the proximal part upwards,
and examine it to see if it contains a sesamoid bone which is
sometimes present (Fig. 185) ; then look for a bursa which is
occasionally present between it and the posterior part of the
capsule of the knee joint. Turn the distal part downwards and
note the manner in which the two heads join their thin aponeuro-
tic tendon, and the union of the tendon with the tendon of the
soleus to form the tendo calcaneus. Now clean the posterior
surface of the soleus, note its origin from (i) the back of the
head, and the proximal part of the posterior surface of the body
of the fibula, (2) the fibrous arch over the distal end of the popliteal
artery, (3) the oblique line of the tibia, and (4) the middle
third of the medial border of the tibia. Note also the manner
in which the majority of its fibres end in the strong tendon which
blends with the tendon of the gastrocnemius to form the tendo
cakaneus, whilst some of them pass directly to the deep surface
of the tendo calcaneus.

M. Soleus. The soleus is a flat, thick, and powerful
muscle which arises from both bones of the leg, as well as
from a strong fibrous arch which is thrown across the popliteal
vessels. Its fibular origin is from the posterior surface of
the head and the proximal third of the posterior surface
of the body of the bone ; by its tibial origin it is attached to
the linea poplitea of the tibia, distal to the popliteal surface,
and, more distally, to the medial border of the bone as far
as the middle of the leg (Fig. 166, p. 376). The soleus ends



THE LEG 371

in a strong, stout tendon which joins with the tendon of
the gastrocnemius to form the tendo calcaneus (Achillis).
Branches from the tibial nerve supply the soleus. It is a
plantar flexor of the foot.

Tendo Calcaneus (Achillis). This is the most powerful
tendon in the body. It narrows as it descends, but near the
heel it again expands slightly. It is inserted into the middle
portion of the posterior surface of the calcaneus. The fleshy
fibres of the soleus are continued distally on its deep
surface to within a short distance of the heel. A mucous
bursa intervenes between the tendo calcaneus and the
proximal part of the posterior surface of the calcaneus.

Dissection. Divide the soleus muscle along its line of origin
from the tibia and separate it from the fibrous arch over the
vessels and the tibial nerve ; then turn it to the lateral side
and secure the branches which the muscle receives from the
peroneal and posterior tibial arteries.

The first fascial septum which stretches across the posterior
osteo-fascial compartment is now fully exposed. Note its
attachments to the tibia and fibula (see p. 367), and its
continuity, distally, with the laciniate ligament. Separate it
carefully from the laciniate -ligament, but do not injure the
ligament ; then divide it longitudinally along the middle line of
the leg and turn the two pieces, one medially and the other
laterally. The middle section of the posterior osteo-fascial
compartment is now opened up and two muscles, the tibial nerve,
the termination of the popliteal artery, the commencements
of the anterior and posterior tibial arteries are exposed, the
vessels and the nerve being embedded in some loose areolar
tissue. The muscle on the medial side is the long flexor
of the toes, the muscle on the lateral side is the long flexor of
the great toe. In the distal part of the leg, emerging from under
cover of the medial border of the tendon of the long flexor of
the toes, the tendon of the tibialis posterior will be seen. Clean
first the tibial nerve and secure the branches which it gives to
the flexor digitorum longus, the flexor hallucis longus, and the
tibialis posterior ; they arise as a rule in the upper part of the leg.
Next clean the termination of the popliteal artery, the first part
of the anterior tibial artery and its fibular and posterior tibial
recurrent branches, then the posterior tibial vessels and their
branches and tributaries. The peroneal branch of the posterior
tibial artery arises about 25 mm. distal to the commencement
of the parent trunk, and immediately proximal to the point
where the tibial nerve crosses posterior to the posterior tibial
artery. It soon disappears under cover of the flexor hallucis
longus ; do not trace it at present beyond the point of dis-
appearance. After the nerve and vessels are displayed clean first
the flexor digitorum longus and then the flexor hallucis longus.
When that has been done separate the two muscles and push
the flexor hallucis longus laterally, separating its deep surface
from the posterior surface of the second fascial septum of the



372 THE INFERIOR EXTREMITY

posterior osteo-fascial compartment, and from the distal part of
the interosseous membrane, to both of which it is attached.
As the fibula is approached the peroneal branch of the posterior
tibial artery will be found descending between the flexor hallucis
longus and the posterior surface of the second fascial septum,
which separates it from the tibialis posterior. Trace the artery
distally. Below the level of the origin of the tibialis posterior
it lies on the posterior surface of the interosseous membrane,
and immediately above the distal tibio-fibular joint it gives off
the perforating branch, which was seen in the dissection of the
dorsum of the foot (p. 350). Now pull the distal part of the
flexor hallucis longus medially and follow the distal part of the
peroneal artery behind the ankle joint and along the medial
side of the peronaei tendons to the lateral side of the calcaneus.
In order to expose its terminal branches the peroneal retinacula
must be divided, and it may be necessary to displace the peroneal
tendons.

Termination of the Popliteal Artery. The termination of
the popliteal artery, which was concealed by the proximal
border of the soleus, is now fully exposed. It ends at the
distal border of the popliteus, where it divides into its two
terminal branches, the anterior and posterior tibial arteries.
At the same point the venae comites of the anterior and
posterior tibial arteries join to form the commencement of
the popliteal vein.

Arteria Tibialis Anterior. The anterior tibial artery passes
forwards, between the two heads of the tibialis posterior
muscle, to the anterior region of the leg, where it has already
been dissected. Whilst still in the back of the leg the
anterior tibial artery gives off a posterior recurrent tibial
and a fibular branch. The posterior tibial recurrent is a
small twig which is not always present. It runs proximally,
under cover of the popliteus muscle, to the back of the knee
joint. The fibular branch runs laterally, on the neck of the
fibula, and is distributed to the muscles and integument in
that neighbourhood.

Arteria Tibialis Posterior. The posterior tibial artery is
the larger of the two terminal branches of the popliteal trunk.
It takes origin a't the distal border of the popliteus muscle and
ends, by dividing into the lateral and medial plantar arteries
in the hollow on the medial side of the calcaneus, under
cover of the ligamentum laciniatum. In the first instance
the artery is placed, between the two bones of the leg, upon
the fascia covering the posterior surface of the tibialis posterior
muscle ; but, as it passes distally it inclines gradually medially,



PLATE XXXII



Semitendinosus - r
Semimemb
Medial femoral circumflex vein



idinosus *>
Dranosus ' \



Medial cutaneous nerve of the calf
Lateral head of gaatrocnemiu
Small saphenous vein
Anastomotic peroneal nerve



Co



Tibial ner

Tendo calcaneus
Sural nerve
mmunicating artery ,



Flexor hallucis longus

Lateral plantar nerve

Medial calcanean nerve

Calcanean branch of lateral plantar
artery




v Posterior branch of medial cutaneous
r- nerve of the thigh
*_. Vastus medialis

Gracilis

Patellar branch of saphenous nerve

Sartorius



Saphenous nerve



.Great saphenous vein



Medial head of gastrocnemius



Posterior tibial artery

^ibialis posterior (tendon)

Flexor digitorum longus (tendon)
Laciniate ligament



Medial plantar nerve
Abductor hallucis



FIG. 163. Dissection of the Posterior Aspect of the Leg viewed from behind

and medially.

Note the numerous anastomoses between the great and the small
saphenous veins.



PLATE XXXIII



Medial femoral circumflex vein -

Biceps femoris '-. |^+
Common peroneal nerve -
Tibial nerve -.



Anastomotic peroneal nerve _.
Lateral head of gastrocnemius _

Medial cutaneous nerve of the calf .
Lateral cutaneous nerve of the calf -

Gastrocnemius -1



Great saphenous vein

Sartorius

Gracilis
Semitendinosus

Semimembranosus



- Medial5head of gastrocnemius
-Small saphenous vein

I

| -Gastrocnemius
Communication to great saphenous



Peroneus longus-.
Soleus _|

Peroneus brevis



- Soleus



- Communication from great saphenous vein



Sural nerve -

Small saphenous vein -
Lateral posterior-malleolar artery



Peroneal retinaculutn



Flexor hallucis longus
[Communicating vein
Tendo calcaneus
Calcaneus



FIG, 164. Dissection of the Posterior Aspect of the Leg viewed from

behind and laterally.

In the specimen there were numerous large anastomosing channels between
the small and the great saphenous vein.



THE LEG 373

and at its termination it lies midway between the prominence
of the calcaneus and the medial malleolus.

In its proximal two-thirds the posterior tibial artery is situated
deeply, being covered by the superficial muscles of the calf.
In the distal third of the leg, where it lies between the tendo
calcaneus and the medial border of the tibia, it is relatively
superficial and is covered merely by the integument and two
layers of fascia. More distally it is covered by the ligamentum
laciniatum. Proximo-distally it rests against the fascia on the
tibialis posterior, the flexor digitorum longus, the tibia, and
the posterior aspect of the ankle joint (Fig. 163).

Throughout its entire course the posterior tibial artery is
closely accompanied by two vena comites. The tibial nerve
is at first on its medial side, but it soon crosses behind the
vessel, and then proceeds distally on its lateral side.

The following are the branches which issue from the
posterior tibial artery :



1. Kami musculares.

2. Rami cutanei.

3. A. nutricia tibiae.

4. A. peronsea.



5. Rami calcanei mediales.

3. Ramus communicans.

7, A. plantaris medialis.

S. A. plantaris lateralis.



Arteria Peronaea. Although the peroneal artery is not
the first it is, as a rule, the largest branch of the posterior
tibial. It arises about 25 mm. or so distal to the com-
mencement of the parent trunk, and at first runs, obliquely
distally, and laterally, to the fibula. In this first part of its
course it rests against the fascia covering the tibialis posterior
and it is covered by the soleus ; then it descends along the
medial crest of the fibula, covered by the flexor hallucis longus
and lying first, against the fascia covering the tibialis
posterior, and next, against the interosseous membrane. Im-
mediately above the ankle joint it emerges from under cover
of the flexor hallucis longus, passes behind the distal tibio-
fibular joint and the ankle joint, medial to the peronaei
tendons, and it breaks up on the lateral aspect of the
calcaneus into a number of lateral calcanean branches.

The branches of the peroneal artery are : (i) muscular
branches to the adjacent muscles ; (2) a nutrient branch to
the fibula; (3) the perforating branch which pierces the
interosseous membrane near the distal tibio-fibular joint, and
has already been dissected on the dorsum of the foot (see



374 . THE INFERIOR EXTREMITY

P- 35) '> (4) a communicating branch, which springs from the

Tibial nerve (O.T. internal popliteal nerve)

Common peroneal nerve (O.T. external

Popliteal artery [popliteal)

M. semimembranosus

M. gastrocnemius (lateral head)

M. plan tar is

M. gastrocnemius (medial head)



Tendon of semimembranosus
^ Medial inferior genicular artery
Lateral inferior genicular artery

Popliteal vessels

M. popliteus

Nerve to popliteus

Common peroneal nerve
Termination of popliteal artery
^Soleus (cut)
Tibia
Fibula

Posterior tibial vessel and tibial nerve
Peroneal vessels
Nutrient artery to fibula




M. peronseus longus
M. flexor hallucis longus
M. tibialis posterior
M. flexor digitorum longus



Tibial nerve

(O.T. posterior tibial)

Posterior tibial vessels

Flexor hallucis longus
Flexor digitorum longus
Tibialis posterior

Tubercle on back of talus (os trigonum)
Bursa

Ligamentum laciniatum (O.T. internal annular
%)
^.Tendo calcaneus



FIG. 165. Deep Dissection of the Back of the Leg.

medial side of the peroneal artery about one inch proximal
to the distal end of the tibia, and passes medially, anterior



THE LEG 375

or posterior to flexor hallucis longus, to join the posterior
tibial artery; (5) the terminal lateral calcanean branches.

The peroneal artery is sometimes as large as the con-
tinuation of the posterior tibial artery beyond the point of
origin of the peroneal. In such cases the perforating branch
may be large, and may partially or entirely replace the dorsalis
pedis artery, or the communicating branch to the posterior
tibial artery may be large.

The peroneal artery is accompanied by venae comites,
and, in the proximal part of its extent, it is also accompanied
by the nerve to the flexor hallucis longus.

The nutrient artery springs from the posterior tibial close
to its origin, and, after giving some twigs to muscles, enters
the nutrient foramen of the tibia. It is remarkable on
account of its large size.

The muscular branches supply the deep muscles on the
back of the leg, and one or two of large size enter the soleus.

The cutaneous branches are given to the skin on the medial
aspect of the leg.

The communicating branch is given off about an inch
proximal to the distal end of the tibia. It passes transversely
laterally, under cover of the flexor hallucis longus or superficial
to it, and joins the peroneal artery (Figs. 163, 164, 165).

The medial calcanean branches pierce the ligamentum
laciniatum, and accompany the nerves of the same name
to the skin of the heel and the sole.

Crural Part of Nervus Tibialis (O.T. Posterior Tibial
Nerve). The tibial nerve is continued from the popliteal fossa
through the posterior region of the leg to the hollow between
the heel and the medial malleolus, where it divides into the
lateral and medial plantar nerves. The division takes place
proximal to the division of the posterior tibial artery. The
nerve accompanies the posterior tibial vessels, and presents the
same relations. For a short distance, in the proximal part of
the leg, it lies on the medial side of the posterior tibial artery,
but it soon crosses superficial to the artery, and is then con-
tinued distally, and, for the remainder of its course, lies on
the lateral side of the vessel.

It supplies (a) muscular branches to the tibialis posterior,
flexor hallucis longus, flexor digitorum longus, and soleus ;
(ft) cutaneous twigs the medial calcanean branches which spring
from it close to its termination, and pierce the ligamentum



THE INFERIOR EXTREMITY



M. sernimembranosus



M. soleus



u



Iff JE



I



Groove for tibialis
sterior



laciniatum to reach the in-
tegument of the heel and sole
of the foot ; and (c) articular
filaments to the ankle joint.

Deep Muscles. The pop-
liteus muscle will be seen lying
upon the posterior aspect of
the knee joint and upon the
posterior surface of the tibia
proximal to the linea poplitea.
Its tendon of origin lies within
the capsule of the knee joint,
and cannot be properly
studied until that articula-
tion is dissected.

Note the strong fascia which
covers the posterior surface of the
popliteus, and trace it proximally
and medially to the medial side of
the knee. There it becomes con-
tinuous with the tendon of the
semimembranosus, and through it,
therefore, the semimembranosus
may be regarded as having an in-
sertion into the linea poplitea of the
tibia.



The flexor hallucis longus
is placed upon the posterior
aspect of the fibula, and its
tendon will be noticed groov-
ing the posterior border of
the talus as it passes distally
and forwards to gain the sole
of the foot. The flexor digi-
torum longus lies upon the tibia.
The tibialis posterior rests upon
the interosseous membrane
and between the fleshy bellies
of the two flexors but upon a
of deeper plane.

M. Popliteus. The pop-
liteus muscle arises by a stout
narrow tendon, within the capsule of the knee joint, from the



posterior
Groove for flexor hallucis longus

FIG. 1 66. Posterior aspect
Bones of Leg with Attach-
ments of Muscles mapped out.



THE LEG 377

anterior part of the popliteal groove on the lateral surface
of the lateral condyle of the femur. The tendon pierces
the posterior part of the capsule of the knee joint, and the
fleshy fibres which arise from it are directed medially and
distally, and spread out to obtain insertion into the posterior
surface of the tibia proximal to the linea pop'litea, and also
into the fascia which covers the muscle.

The nerve to the popliteus has already been seen to arise
from the tibial nerve. It can now be seen hooking round the
distal margin of the muscle to reach its anterior surface.
The popliteus is a flexor of the knee and a medial rotator
of the leg.

M. Flexor Hallucis Longus. The long flexor of the great
toe is a powerful muscle which arises from the posterior
surface of the fibula, distal to the origin of the soleus, from
the posterior fibular septum, and from the surface of the
fascia covering the tibialis posterior. After passing behind
the ankle joint its tendon occupies a deep groove on the



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