D. J. (Daniel John) Cunningham.

Cunningham's manual of practical anatomy (Volume 1) online

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Digital synovial sheaths




Ridge on os multangulum majus - r - -
Transverse carpal ligament ...

Tuberosity of navicular bone



-. Pisiform




FIG. 58. The Synovial Sheaths of the Wrist and Hand. The positions of
various incisions for the evacuation of pus are also shown.

i and 2. Incisions into the common palmar sheath, placed between the median and
ulnar nerves.

3. Incision uniting i and 2.

4. Incision into the proximal part of the sheath of flexor pollicis longus. It is placed
between the radial artery and the median nerve.

5. Incision into the distal part of the sheath of flexor pollicis longus.

6. Incision into the thenar space.

7. Incision over terminal phalanx.

8. 9 and 10. Incisions into the digital sheaths. They lie opposite the shafts of the
phalanges.

digitorum sublimis and flexor digitorum profundus is some-
times divided by a vertical partition into two compartments,
and the lateral of them communicates, by means of a small
i 96



136



THE SUPERIOR EXTREMITY



aperture near the proximal border of the transverse carpal
ligament, with the mucous sheath of the tendon of the flexor
pollicis longus.



A. radialis



Sheath of flexor pollicis longus r

Sheath of flexor carpi radialis -
Sheath of abductor pollicis longus
Sheath of extensor pollicis brevis



M. abductor pollicis brevis -




Brach io-radial is

M. abductor pollicis
longus
-M. extensor pollicis brevis

M. extensor pollicis longus



carpi dorsale

Mucous sheath of extensor
carpi radialis longus .

Articular capsule of wrist

A. radialis

Sheath of extensor carpi

radialis brevis

Sheath extensorpollicislongus

Sheath of extensor digitorum

communis



M. interosseus dorsalis
primus

-M.' adductor pollicis



FIG. 59. Dissection of the Lateral Side of the Left Wrist and Hand
showing Mucous Sheaths of Tendons.



The Constitution of Mucous Sheaths of Tendons. The

student should understand the nature of mucous sheaths
which surround tendons, where they pass through fascial or
osteo-fascial canals. The majority of the mucous sheaths



FOREARM AND HAND 137

are double-walled tubes. At their extremities the outer and
inner walls are bound together, and the space between the
two walls, the so-called cavity of the sheath, is thus closed.
The cavity of the sheath is a potential cavity only, and
it contains merely sufficient mucous fluid to lubricate the
adjacent surfaces, and facilitate their free play over one
another.

The inner wall of the tube surrounds the tendon and
adheres to its surface. The outer wall lines the canal
through which the tendon passes and adheres to it. But
the ends of the sheaths project beyond the limits of the
canals which they line; therefore, as the tendons move

Transverse carpal ligament Tendons of flexor digitorum sublimis

Median nerve
Tendon of flexor pollicis longus

Tendon of flexor
carpi radialis




Tendons of flexor digitorum profundus

FIG. 60. Diagram illustrating the relation of the Synovial Sheaths to the
Flexor Tendons at the level of the transverse carpal ligament.

proximally and distally, the opposite ends of the sheaths
can be invaginated and evaginated, thus allowing for the
free play of the tendons.

When a sheath becomes inflamed the adjacent surfaces
of its two walls are at first roughened, and when the tendon
moves, friction, which can be heard and felt, occurs and
pain is caused. Then the fluid between the two walls
increases in amount, the sheath becomes distended as if it
had been injected, and its position becomes apparent. At
the same time the friction ceases, but the distension of
the walls stretches the nerves, and pain is still felt.

Some mucous sheaths, for example the mucous sheath
of the flexors of the fingers, are not complete tubes, but
merely invaginated sacs (Fig. 60).



138 THE SUPERIOR EXTREMITY

Dissection. The superficial muscles which arise from the
medial epicondyle of the humerus must now be cleaned.
Commence with the most lateral of the group, thepronator teres,
and follow it from its origin to its insertion into the middle of
the lateral surface of the radius. To expose the insertion the
brachio-radialis and the long and short radial extensors of the
carpus which cover it must be pulled aside. As the distal part of
the pronator teres is being cleaned be careful not to injure the thin
radial origin of the flexor digitorum sublimis which lies behind
it. Separate the proximal part of the pronator teres from the
flexor carpi radialis by dividing the intermuscular septum
between them. Divide the superficial head of the pronator teres,
turn the proximal part towards the medial epicondyle and the
distal part towards the radius and follow the deep head between
the median nerve and the ulnar artery to its origin from the
coronoid process of the ulna. After the pronator teres has been
examined clean the flexor carpi radialis, but do not follow its
tendon of insertion beyond the proximal edge of the transverse
carpal ligament, where it enters a special osteo-fibrous canal
through which it will be traced in a later dissection. Now clean
the palmaris longus ; trace its tendon to the intermediate part
of the palmar aponeurosis, and note that as it crosses the
transverse carpal ligament its deep surface is attached to the
ligament. 1

The most medial muscle of the group, the flexor carpi ulnaris,
must now be cleaned. Note that its tendon of insertion lies
along the volar border of the distal part of the muscle. This is
a point of practical importance, for the tendon is used as a guide
during operations upon the ulnar nerve and artery in the distal
part of the forearm. Clean both heads of origin of the flexor
carpi ulnaris, one from the medial epicondyle and one from the
medial border of the olecranon of the ulna, and note that the
ulnar nerve, accompanied by the superior ulnar collateral artery,
disappears between them. Separate the proximal part of the
flexor carpi ulnaris from the adjacent parts of the palmaris longus
and the flexor digitorum sublimis by splitting the septa between
them; secure the ulnar nerve and its branches to the flexor
carpi ulnaris and the flexor digitorum profundus on the deep
surface of the flexor carpi ulnaris. Follow the ulnar nerve
distally. At the junction of the proximal and middle thirds
of the forearm it is joined by the ulnar artery, which appears
from under cover of the medial border of the flexor digitorum
sublimis. Clean the artery and nerve, as far as the lateral
side of the pisiform bone, and find the origins of the dorsal
and palmar branches of the nerve, which were seen when the
superficial structures of the palm and on the dorsum of the
hand were dissected (p. 70). Secure also the volar carpal
branch of the artery which arises near the proximal border of
the transverse carpal ligament.

To get a good view of the flexor digitorum sublimis divide
the palmaris longus and the flexor carpi radialis at the middle
of the forearm. Turn the proximal parts of both the muscles
upwards and separate them from the pronator teres and the
flexor sublimis by splitting the intervening intermuscular septa.

1 The palmaris longus is not uncommonly absent.



FOREARM AND HAND 139

Pull the pronator teres laterally and secure the median nerve
as it emerges between the superficial and deep heads of the
muscle and before it disappears between the radial and humeral
parts of the flexor digitorum sublimis. Then clean the flexor
sublimis, being careful not to injure the thin sheet of fibres by
which it takes origin from the volar border of the radius. Clean
the four tendons in which the flexor sublimis terminates. They
are arranged in pairs, two anterior which pass to the middle and
ring fingers, and two posterior for the index and little fingers.
Pull upon the tendons and note the results. Note also that the
median nerve, after it emerges from between the two heads of
the pronator teres, disappears again between the humeral and radial
origins of the flexor sublimis to reappear at the lateral border
of the muscle a short distance proximal to the wrist, where it
lies under cover of the radial border of the tendon of the palmaris
longus. The tendons of the flexor digitorum sublimis must
not be followed further than the transverse carpal ligament at
present. The terminal parts will be displayed in a later dissection.

Common Origin of the Superficial Muscles. The five
muscles which constitute the superficial group are very closely
associated with each other at the elbow indeed, they may
be said to arise by a common origin from the front of the
medial epicondyle of the humerus. In addition they all
derive fibres from the investing deep fascia of the limb, near
the elbow, and from the strong fibrous septa which pass be-
tween the muscles from the deep surface of investing fascia.
The pronator teres, the flexor sublimis, and the flexor carpi
ulnaris, have additional heads of origin (Figs. 61, 62).

M. Pronator Teres. The pronator teres muscle crosses
the proximal half of the front of the forearm obliquely. It
arises by two heads, viz., a humeral and an ulnar. The
humeral head constitutes the chief bulk of the muscle. It
springs from the proximal part of the medial epicondyle of
the humerus, and also slightly, by fleshy fibres, from the distal
part of the medial epicondylar ridge. The fascia covering it
and the fibrous septum on its medial side also contribute fibres.
The ulnar head is placed deeply, and it may be recognised
from the fact that it intervenes between the median nerve
and the ulnar artery. The ulnar head is very variable in
size. As a rule, it is a small fleshy slip, but sometimes it is
chiefly fibrous. It arises from the medial border of the
coronoid process of the ulna (Fig. 64, p. 147), and soon
joins the deep surface of the humeral head. The muscle,
thus formed, passes obliquely distally and laterally, and ends
in a tendon which gains insertion into a rough impression
upon the middle of the lateral surface of the radius (Fig. 64,



1 40 THE SUPERIOR EXTREMITY

p. 147). This attachment is placed on the summit of the
chief curve of the radius, an arrangement which enables the
muscle to exercise its pronating action at a great advantage.
Close to its insertion the pronator teres is crossed by the
radial artery and it is covered by the brachio-radialis muscle.
It is supplied by the median nerve. It is a pronator of the
forearm and hand and a flexor of the elbow.

M. Flexor Carpi Radialis. The flexor carpi radialis arises
from the common tendon, from the fascia of the forearm
and the fibrous septa which intervene between it and the
adjacent muscles. Its fleshy belly gives place, a short distance
distal to the middle of the forearm, to a long flattened tendon,
which, at the wrist, traverses the groove on the front of the
os multangulum majus, in a special compartment of the trans-
verse carpal ligament (Fig. 60, p. 137). It is inserted into
the volar aspect of the base of the metacarpal bone of the
index, and slightly also into the base of the metacarpal bone
of the middle finger. Its relations to the transverse carpal
ligament, and also its attachment to the metacarpus, will be
exposed and studied at a later stage of the dissection. It
is a flexor of the wrist and elbow joints and assists in
producing abduction of the hand. It is supplied by the
median nerve.

M. Palmaris Longus. The palmaris longus is a long slender
muscle, which is not always present. It springs from the
common origin, the fascial investment of the forearm and the
fibrous septum on each side of it. Its tendon pierces the
deep fascia immediately proximal to the wrist, and then passes
distally, superficial to the transverse carpal ligament, to join the
strong intermediate portion of the palmar aponeurosis. Very
frequently it gives a slip to the abductor pollicis brevis. It is
supplied by the median nerve, and is a flexor of the radio-
carpal and elbow joints.

M. Flexor Carpi Ulnaris. The ulnar flexor of the carpus
muscle arises by two heads. One of them is incorporated
with the common origin from the medial epicondyle; the
other springs from the medial border of the olecranon of the
ulna, and also by an aponeurotic attachment from the dorsal
border of the same bone in its proximal two-thirds. Fibres
are derived also from the investing fascia and the inter-
muscular septum on its lateral side. The two heads of origin
of the flexor carpi ulnaris bridge across the interval between



PLATE VII'



Biceps brachii. muscle



Lateral cutaneous nerve of fore-
arm (musculo-cutaneus)



Brachialis muscle

Brachio-radialis muscle

Tendon of biceps brachii

Ulnar artery

Radial arterj



Extensor carpi radialis brevis
muscle



Tendon of extensor carpi radialis
longus



Radial artery
Flexor digitorum sublimis muscle || f:

Flexor pollicis longus muscl

Superficial branch of radial nerv

Pronator quadratus muscle
Tendon of abductor pollicis longus

Radius
Radial artery -

Tendons of abductor pollicis longus

and extensor pollicis brevis "

Superficial volar arte




Medial cutaneous nerve of forearm

Basilic vein

Deep fascia of arm

Medial intermuscular septum

Brachialis muscle
Brachial artery

L

^gDeep fascia of forearm (reflected)
Median nerve'

Pronator teres muscle



Lacertus fiorosus

Flexor carpi radialis muscle
Palmaris longus muscle
Flexor carpi ulnaris muscle



Tendons of flexor digitorum sublimis



Median nerve
~ Tendon of flexor pollicis longus

- Ulnar artery.

Ulnar nerve

Transverse carpal ligament
Pisiform bone



FIG. 61. Superficial Dissection of the Muscles, Arteries, and Nerves of the

Anterior Aspect of the Forearm.
Part of the radial artery was removed to show some of its deep relations.



PLATE VIII



Biceps brachii muscle
,Brachialis muscle

Part of brachio-radialis muscle
Nerve to brachio-radiali i



Lateral cutaneous nerve of

forearm (musculo-cutaneus)

Radial nerve

Nerve to extensor carpi
radialis longus

Superficial branch of radial nerve

Dorsal interosseous nerve
Radial recurrent artery

Nerve to extensor carpi
radialis brevis

Supihator muscle



Volar interosseous nerve

Extensor carpi radialis

longus muscle

Extensor carpi radialis

brevis muscle

Pronator teres muscle -

Radial artery -



Flexor digitorum sublimis muscle
Flexor pollicis longus muscle -
Tendon of brachio-radialis -



Tendon of abductor pollicis longus-
Pronator quadratus muscle

Superficial branch of radial nerve

Radius

Tendon of flexor carpi radialis



Superficial volar artery -




Medial cutaneous nerve of forearm
on basilic vein



Median nerve

Brachial artery

Medial intermuscular septum

Lacertus fibrosus

rachialis muscle

- Nerve to pronator teres

Pronator teres muscle
uperficial head)
Nerve to flexor carpi
radialis, palmaris longus,
and flexor digitorum
sublimis

-Nerve to flexor digitorum
sublimis

Deep head of pronator teres
muscle

Superficial head of pronator
teres muscle
Palmaris longus muscle

lumero-ulnar part of flexor
digitorum sublimis muscle



Radial part of flexor digitorum
sublimis muscle



Flexor digitorum profundus muscle

Median nerve with accompanying
artery

Tendons of flexor digitorum sublimis

Tendon of flexor carpi ulnaris
Ulnar artery

Tendon of palmaris longus
Ulnar nerve

Transverse carpal ligament
^isiform bone

Palmaris brevis muscle



FIG. 62. Deep Dissection of the Muscles, Vessels, and Nerves of the

front, of the Forearm.



FOREARM AND HAND 141

the medial epicondyle of the humerus and the olecranon, and
between them the ulnar nerve is prolonged distally into the
forearm. The tendon appears upon the volar border of the
muscle, and is inserted into the pisiform bone. The flexor
carpi ulnaris is supplied by the ulnar nerve. It is a flexor
and adductor of the hand and a flexor of the elbow.

M. Flexor Digitonun Sublimis. The flexor sublimis re-
ceives this name because it is placed upon the superficial
aspect of the flexor profundus. For the most part it lies
deeper than the other superficial muscles (Fig. 61). It is a
powerful muscle which arises from the medial epicondyle of
the humerus by the common tendon it takes origin also
from the ulnar collateral ligament of the elbow- joint, from
the medial margin of the coronoid process of the ulna, the
volar surface of the radius (Figs. 45, 64), and the fascial
intermuscular septa in relation to it. The radial head of
origin is a thin fleshy stratum which is attached to the
volar border of the radius, from its proximal end to a
variable distance beyond the insertion of the pronator teres
muscle. Four tendons issue from the fleshy mass ; they
enter the palm by passing under cover of the transverse carpal
ligament, and go to the medial four digits. Their insertions
will be seen later, but, in the meantime, note that at the wrist,
and for a short distance proximal to it, they are enveloped
by the mucous sheath previously mentioned, and also that, as
they pass behind the transverse carpal ligament, they lie in
pairs the tendons to the ring and middle fingers being placed
on the volar aspect of those for the index and little fingers.
The flexor digitorum sublimis is supplied by the median
nerve. It is a flexor of the first interphalangeal joints of
the fingers, the metacarpo-phalangeal joints, the wrist joint,
and the elbow joint.

The dissector who examines the flexor digitorum sublimis in detail
will find that the part which arises from the humerus divides into
a superficial and a deep portion, and that each portion subdivides
in two parts, a lateral and a medial. The lateral part of the superficial
portion unites with fibres which spring from the radius ; then the combined
fibres pass to the tendon for the middle finger. The medial part of
the superficial portion receives additional fibres from the deeper portion,
and ends in the tendon for the ring finger. The lateral part of the
deeper portion is a digastric muscle ; it ends in the tendon for the
index finger. The medial part of the deeper portion ends in the tendon
for the little finger ; it is a small muscular belly which frequently
receives fibres from the intermediate tendon of the lateral part of the
deeper portion of the muscle.



142 THE SUPERIOR EXTREMITY

Dissection. Cut through the radial part of the flexor digi-
torum sublimis at its union with the humeral portion. Pull
the main mass of the muscle towards the medial side of the
forearm, and turn the radial portion towards its origin. Then
clean the median nerve, the branch of the anterior interosseous
artery which accompanies the nerve, and the anterior surface
of the flexor pollicis longus which springs from the volar surface
of the radius ; and the flexor digitorum profundus, which arises
from the volar and medial surfaces of the ulna. Then secure the
volar interosseous branch of the median nerve. It springs from
the median nerve as the latter emerges from between the two
heads of the pronator teres. Find also the common interosseous
branch of the ulnar artery. It arises in, or immediately distal
to, the cubital fossa, and must be looked for behind the deep head
of the pronator teres. Almost at once it divides into volar and
dorsal interosseous branches. The dorsal branch passes backwards
above the interosseous membrane to the dorsal part of the fore-
arm, where it will be dissected later. Now separate the adjacent
borders of the flexor pollicis longus and the flexor digitorum
profundus and follow the volar interosseous artery and nerve
to the point where they disappear behind the pronator quadratus
in the distal third of the forearm. Clean the pronator quadratus,
then proceed to study the structures exposed.

Arteria Ulnaris. The ulnar artery is the larger of the
two terminal branches of the brachial trunk. It takes origin,
in the cubital fossa, at the level of the neck of the radius. In
the proximal third of the forearm it inclines obliquely distally
and medially, and then it proceeds straight down to the
wrist. It enters the palm by passing anterior to the transverse
carpal ligament. In the proximal oblique portion of its course
the vessel is deeply placed, and is crossed by both heads of the
pronator teres, the flexor carpi radialis, the palmaris longus,
the flexor digitorum sublimis and the median nerve. Its distal,
vertical part is overlapped on the medial side by the flexor
carpi ulnaris, but a short distance proximal to the wrist it
becomes superficial, and lies in the interval between the
tendon of the flexor carpi ulnaris on the medial side and the
tendons of the flexor sublimis on the lateral side. As it lies
on the transverse carpal ligament it is separated from the
lateral side of the pisiform bone by the ulnar nerve, and is
covered by a strong band of fascia, the volar carpal ligament
(pp. 129, 162), which lies superficial to the transverse liga-
ment. Throughout its entire course it is accompanied by
two vena comites. It has important relationships with the
median and ulnar nerves. The median nerve, which lies
upon its medial side at its origin, soon crosses it, but at
the point of crossing the nerve is separated from the artery



FOREARM AND HAND 143

by the deep head of the pronator teres. The ulnar nerve in
the proximal third of the forearm is separated from the
vessel by a wide interval, but in the distal two-thirds of the
forearm it closely accompanies the artery, and lies on its
medial side.

In the cubital fossa the ulnar artery rests upon the
brachialis ; more distally it is in contact posteriorly with the
flexor digitorum profundus ; whilst at the wrist the artery lies
upon the superficial surface of the transverse carpal ligament.

Branches of the Ulnar Artery. In the forearm the ulnar
artery gives off the following branches :



1. A. recurrens ulnaris volaris.

2. A. recurrens ulnaris dorsalis.

3. A. interossea communis.



4. A. carpea volaris.

5. A. carpea dorsalis.

6. Rami musculares.



The muscular branches are of small size, and come off at
variable points for the supply of the neighbouring muscles.

The volar ulnar recurrent artery (O.T. anterior ulnar re-
current) is the smaller of the two recurrent branches. It runs
proximally, anterior to the medial epicondyle of the humerus,
in the interval between the pronator teres and the brachialis
muscles, and it anastomoses with the anterior terminal branch
of the inferior ulnar collateral artery.

The dorsal ulnar recurrent artery (O.T. posterior ulnar
recurrent] passes medially, under cover of the flexor digitorum
sublimis, and then turns proximally, between the two heads
of origin of the flexor carpi ulnaris, to gain the interval
between the medial epicondyle of the humerus and the
olecranon, on the dorsal aspect of the limb. There it becomes
associated with the ulnar nerve, and anastomoses with the
posterior terminal branch of the inferior ulnar collateral artery
and with the superior ulnar collateral artery.

It is not uncommon to find the two recurrent arteries
arising from the ulnar trunk by a short common stem.

The common interosseous artery is a short, wide trunk, which
takes origin immediately distal to the recurrent branches,
about 25 mm. (one inch) from the commencement of the ulnar
artery. It passes dorsally to the proximal margin of the
interosseous membrane, where it divides into two terminal
branches, viz., the volar (O.T. anterior] and the dorsal (O.T.
posterior] interosseous arteries.

The arteria interossea dorsalis passes backwards above



144 THE SUPERIOR EXTREMITY

the proximal border of the interosseous membrane to the
dorsal part of the forearm, where it will be dissected at a
later period.

The arteria interossea volaris descends on the anterior
surface of the interosseous membrane, between the adjacent
margins of the flexor pollicis longus and the flexor digitorum
profundus, which must be separated as the artery is followed.
At the proximal border of the pronator quadratus it pierces
the interosseous membrane and passes to the dorsal part
of the forearm, where its terminal part will be seen at a
later period. As it descends on the volar surface of the
interosseous membrane it gives twigs to the adjacent muscles,
and the following named branches :

i. Arteria mediana.

2 and 3. Nutrient to radius and ulna.

4. Volar communicating.

The arteria mediana is a long slender vessel which
accompanies the median nerve to the palm of the hand,
where it sometimes terminates in the superficial volar arch.
The nutrient arteries enter the nutrient foramina of the
radius and ulna. The volar communicating artery descends



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