D. J. (Daniel John) Cunningham.

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

. (page 18 of 44)
Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 18 of 44)
Font size
QR-code for this ebook


deep branch of the ulnar nerve.

The branches which spring from the deep volar arch are :
(i) the recurrent a few small twigs which run proximally, in
front of the carpus, to anastomose with branches of the volar
carpal arch ; (2) perforating branches, which pass dorsally in the
proximal parts of the interosseous spaces to anastomose with
the dorsal metacarpal arteries ; and (3) the volar metacarpal
branches three in number which pass distally, volar to the
interosseous spaces, and unite, near the roots of the fingers,
with the corresponding volar digital arteries from the
superficial volar arch. Sometimes the volar metacarpal
branches are large and take the place of the corresponding
volar digital arteries.

Ramus Profundus Nervi Ulnaris. The deep branch of
the ulnar nerve springs from the parent trunk on the
volar aspect of the transverse carpal ligament, and gives
off a branch which supplies the three short muscles of the
little finger. Accompanied by the deep branch of the ulnar
artery, it sinks into the interval between the abductor and
flexor digiti quinti brevis, and turns laterally across the palm,
i lie



i68



THE SUPERIOR EXTREMITY



deep to the flexor tendons. Near the lateral border of the
palm the deep branch of the ulnar nerve breaks up into
terminal twigs which supply the adductor pollicis and the first
dorsal interosseous muscle. In its course across the palm it
lies along the concavity or proximal border of the deep volar
arch, and sends three fine branches distally in front of the
three interosseous spaces. They supply the interosseous
muscles in the spaces, while the medial two give branches



Os capitatum
Os multangulum minus
Os naviculare manus
Abductor pollicis brevis
Os multangulum majus

Opponens pollicis /
Abductor pollicis loi



Flexor carpi radial is



M.I.

Adductor pollicis




Os lunatum



Os hamatum
Os triquetrum

Flexor carpi ulnaris

Os pisiforme

Abductor digiti quinti

Flexor digiti

quinti brevis

Flexor carpi ulnaris



Opponens digiti quinti



Palmar interossei



FiG. 73. Volar aspect of the Bones of the Carpus and Metacarpus
with Muscular Attachments mapped out.



also to the medial two lumbrical muscles. The third
lumbrical has frequently a double nerve supply; it receives
a branch from the deep part of the ulnar nerve, and, not
uncommonly, a second twig from the median nerve enters
its volar aspect.

The deep branch of the ulnar nerve may, therefore, be said
to supply all the muscles of the palm which lie to the medial
side of the tendon of the flexor pollicis longus, whilst the
median nerve supplies the three muscles which lie to the
lateral side of that tendon. There are two exceptions to this
generalisation, viz., the lateral two lumbrical muscles, which lie



FOREARM AND HAND 169

upon the medial side of the tendon, and are yet supplied
by the median nerve.

Dissection. Clean the adductor of the thumb and then
examine the short muscles of the thumb and revise the short
muscles of the little finger.

The Short Muscles of the Thumb. Three of the short
muscles of the thumb have already been dissected. All four
are now displayed, with the exception of the deep head of
the short flexor, which cannot be seen until the adductor
has been reflected. Their relations and attachments
should now be studied. Three of the four, the abductor
pollicis brevis, the superficial head of the flexor pollicis
brevis and the opponens pollicis lie on the lateral side of
the tendon of the flexor pollicis longus ; the fourth muscle,
the adductor pollicis, is on the medial side of that tendon.

The abductor pollicis brevis forms the most prominent and
lateral part of the ball of the thumb. The superficial head
of the flexor pollicis brevis is immediately medial to the
abductor; the opponens is deep to both of them and is
exposed when they are pulled apart, or when they are
reflected. The fan-shaped adductor pollicis lies deeply in
the palm. It is imperfectly separated into a proximal or
oblique portion and a distal or transverse portion. The
separation is produced by the radial artery as it enters the
palm through the first interosseous space. The deep head
of the flexor pollicis brevis is concealed by the adductor,
and cannot be seen at this stage of the dissection.

The branch of the median nerve which supplies the
three muscles which lie lateral to the tendon of the
flexor pollicis longus has already been found (p. 155),
and the twigs to the adductor which are derived from the
deep branch of the ulnar nerve have also been traced (p. 166).

M. Abductor Pollicis Brevis. The short abductor of the
thumb arises from the volar aspect of the transverse carpal
ligament and from the ridge on the os multangulum
majus. It is inserted into the lateral sesamoid bone of
the thumb, into the lateral side of the base of the first
phalanx, and to a slight extent into the extensor tendon
on the dorsum of the first phalanx. It is supplied by the
median nerve.

M. Flexor Pollicis Brevis (Caput Superficialis). The



i7o THE SUPERIOR EXTREMITY

superficial head of the short flexor of the thumb takes origin
from the transverse carpal ligament. It is inserted into the
lateral sesamoid bone of the thumb, and into the lateral side
of the proximal phalanx, and it is supplied by the median
nerve. (For the deep head see below.)

M. Opponens Pollicis. The opponens muscle of the
thumb springs from the transverse carpal ligament and the
ridge on the volar surface of the os multangulum majus. Its
fibres spread out as they approach their insertion into the
whole length of the radial border and the adjacent part of the
volar surface of the metacarpal bone of the thumb. It is
supplied by the median nerve.

M. Adductor Pollicis. The adductor of the thumb
consists of an oblique and a transverse part. The oblique
part arises from the os capitatum, and the bases of the
second and third metacarpal bones (Fig. 73). In some
cases it has a slip of origin from the os multangulum minus.
The transverse part springs from the distal two-thirds of the
volar border of the third metacarpal bone. The two parts
converge as they pass to their insertion into the medial
sesamoid bone of the thumb and the medial side of its
proximal phalanx. In many cases a slip of muscle fibres leaves
the lateral side of the oblique part of the adductor, passes
dorsal to the tendon of the flexor pollicis longus, and fuses
with the superficial head of the flexor pollicis brevis. Both
parts of the muscle are supplied by twigs from the deep
division of the ulnar nerve.

At this stage of the dissection the short muscles of the
little finger, the abductor, the short flexor and the
opponens, should be revised (see p. 152).

Dissection. To display the branches of the palmar parts of
the radial artery and the deep head of the flexor pollicis brevis,
cut through the two parts of the adductor pollicis midway
between their origins and insertions, and turn the separated
portions aside. The deep head of the flexor pollicis brevis lies
along the ulnar border of the metacarpal bone of the thumb,
and the radial artery will be found entering the palm between
the two heads of the first dorsal interosseous muscle at the
proximal end of the first interosseous space. Its last two branches,
the princeps pollicis and the volar radial artery of the index
finger, spring from it as soon as it enters the palm, and whilst
it still lies behind the oblique part of the adductor pollicis.

The Deep Head of the Flexor Pollicis Brevis. This weak slip of
muscle lies along the medial side of the metacarpal bone of the thumb



FOREARM AND HAND 171

between the radial head of the first dorsal interosseous muscle and the
adductor pollicis. It arises from the ulnar side of the base of the first
metacarpal bone and is inserted into the ulnar side of the base of the
first phalanx of the thumb. It is supplied by a twig from the deep
division of the ulnar nerve.

Arteria Volaris Indicis Radialis, et Arteria Princeps
Pollicis (O.T. Radialis Indicis and Princeps Pollicis Arteries).
These arteries spring from the radial, as it enters the
palm, between the first and second metacarpal bones.

The volar radial artery of the index digit runs distally between
the transverse part of the adductor pollicis and the first dorsal
interosseous muscle to the lateral border of the index, along
which it proceeds as its lateral volar digital artery.

The princeps pollicis artery takes a course distally and
laterally, under cover of the oblique part of the adductor
pollicis, and gains the volar aspect of the metacarpal bone of
the thumb. There it lies dorsal to the tendon of the flexor
pollicis longus, and divides into two terminal branches, one
for each side of the free part of the thumb. The branches
make their appearance in the interval between the adductor
and the superficial head of the flexor pollicis brevis, and run
distally, one on each side of the tendon of the long flexor.

Surgical Anatomy of the Palm and Fingers. When an abscess forms
in the intermediate compartment of the palm early surgical interference is
urgently called for. The dense palmar aponeurosis effectually prevents the
passage of the pus to the surface of the palm, whilst an easy route proximally,
into the forearm, is offered to it by the open carpal tunnel, through which
the flexor tendons enter the palm. It is necessary, therefore, that before
this can occur the surgeon should make an opening in the palm by means
of which the pus can escape.

In making such an incision it is important to bear in mind the position of
the various vessels which occupy the intermediate compartment of the palm.
As previously stated, the level of the superficial volar arch can be indicated
by drawing a line transversely across the palm from the distal margin of
the outstretched thumb. The deep volar arch lies half an inch more proxi-
mally. The volar digital arteries, which spring from the convexity of the
superficial volar arch, run in line with the clefts between the fingers. An
incision, therefore, which is made distal to the superficial volar arch and in
a direction corresponding to the central line of one of the fingers, may be
considered free from danger in so far as the vessels are concerned.

The loose mucous sheath which envelops the flexor tendons as they pass
deep to the transverse carpal ligament has been seen to extend proximally
into the distal part of the forearm, and distally into the palm. When the
sheath is attacked by inflammatory action it is apt to become distended
with fluid (thecal ganglion), and the anatomical arrangement of the parts at
once offers an explanation of the appearance which is presented. There is
a bulging in the palm, and a bulging in the distal part of the forearm, but
no swelling at all at the wrist. There the dense transverse carpal ligament
resists the expansion of the mucous sheath, and an hour-glass constriction



172 THE SUPERIOR EXTREMITY

is evident at that level. The lines along which incisions should be made
into the volar compartments of the palm and the mucous sheaths of the
flexor tendon are shown in Fig. 71.

The fingers are subject to an inflammatory process, termed whitlow,
and, in connection with this, it is essential to remember that the flexor
fibrous sheath ends on the base of the distal phalanx in each digit.
When the whitlow occurs more distally, in the pulp of the finger, the vitality
of the distal part of the ungual phalanx is endangered, but the flexor
tendons may be regarded as being tolerably safe. When the inflammation
occurs more proximally, and involves the flexor sheath, as it generally does,
sloughing of the tendons is to be apprehended, unless an immediate
opening is made. No slight superficial incision will suffice. The
knife must be carried deep into the centre of the finger, so as to freely
lay open the sheath containing the tendons. Early interference in cases
of whitlow of the thumb and little finger is even more urgently required
than in the case of the other three digits, because the digital mucous
sheaths of the former are, as a rule, connected with the great common
mucous sheath of the flexor tendons, and so offer a ready means for the
proximal extension of the inflammatory action.

Every amputation of the fingers proximal to the insertion of the tendons
of the flexor profundus involves the opening of the flexor sheaths, and no
doubt explains the occasional occurrence of palmar trouble after operations
of that kind. The open tubes offer a ready passage by means of which
septic material may travel proximally into the palm, and, in the case of
the thumb and little finger, into the carpal tunnel and distal part of the
forearm.



DORSUM AND LATERAL BORDER OF THE FOREARM.

The structures which still remain to be dissected in this
region are :

1. The supinator and extensor muscles.

2. The dorsal interosseous artery.

3. The perforating or terminal branch of the volar interosseous artery.

4. The dorsal interosseous nerve.

Before the dissection is proceeded with, the cutaneous
veins and nerves and the deep fascia, previously displayed,
should be re-examined. The two main cutaneous veins
are seen. Both ascend from the venous plexus on the
dorsum of the hand, and both turn round a border of the
forearm to gain its volar surface, but whilst the cephalic
vein turns round the distal third of the radial border, the
basilic ascends to a much more proximal level before it
turns round the ulnar border.

The cutaneous nerves are four in number: (i) The
dorsal branch of the lateral cutaneous nerve of the forearm,
on the lateral side ; (2) the dorsal branch of the medial
cutaneous nerve of the forearm on the medial side ; (3) in the



FOREARM AND HAND 173

intermediate area the distal branch of the dorsal cutaneous
nerve of the forearm ; (4) the superficial division of the radial
nerve appearing from under cover of the brachio - radialis
about 8 cm. (3^ inches) proximal to the wrist. Thus three of
the terminal branches of the brachial plexus are represented
on the dorsum of the forearm the musculo-cutaneous nerve
by the lateral cutaneous nerve of the forearm ; the medial
cutaneous nerve of the forearm ; and the radial nerve by
its superficial division, and by the dorsal cutaneous nerve
of the forearm.

In the dorsum of the hand the distribution of the super-
ficial branch of the radial nerve and the dorsal branch of
the ulnar nerve have already been examined (pp. 71, 72);
the radial nerve supplies the greater part of the skin of
the dorsum of the hand and three and a half digits the
thumb, and the proximal parts of the index, the middle,
and half the ring fingers whilst the dorsal branch of the
ulnar nerve supplies the remaining half of the ring finger and
the little finger. The skin of the distal parts of the index,
the middle, and half the ring fingers is supplied, as already
noted (p. 159), by twigs of the digital branches of the
median nerve.

Dissection. Remove the cutaneous vessels and nerves from
the dorsum of the forearm and hand, then revise the deep fascia.

The Deep Fascia. The deep fascia of the dorsum of the
forearm is stronger than the deep fascia of the volar aspect.
Its proximal part is strengthened by expansion from the
triceps, and near the elbow it is intimately connected with
the muscles of the back of the forearm which take part
of their origin from its deep surface. It is closely attached
to the whole length of the dorsal border of the ulna, and
in the regions of the distal ends of the radius and ulna and
the back of the carpus it is thickened by numerous trans-
verse fibres which constitute the ligamentum carpi dorsale.

Dissection. The dorsal carpal ligament must be left in situ
until the dissection of the dorsal parts of the forearm and hand
is completed. To secure its retention in an uninjured condition,
isolate it by cutting carefully through the deep fascia parallel with
its proximal border. Whilst making the incision, care must be
taken to avoid injury to the mucous sheaths of the extensor
tendons which lie immediately subjacent to the deep fascia.
When the front of the forearm was dissected, the radial flap of
deep fascia was reflected only as far as the radial border of the



174 THE SUPERIOR EXTREMITY

forearm. Now continue the reflection until the attachment of
the flap to the posterior border of the ulna is reached. As the
reflection proceeds, the intermuscular septa which pass from the
deep surface of the deep fascia between the muscles of the dorsum
of the forearm must be divided.

Superficial Muscles. The muscles in this region consist
of a superficial and a deep group. The superficial muscles,
named from the lateral to the medial border of the
forearm, are: (i) the brachio - radialis ; (2) the extensor
carpi radialis longus; (3) the extensor carpi radialis brevis;
(4) the extensor digitorum communis ; (5) the extensor digiti
quinti proprius ; (6) the extensor carpi ulnaris; and (7) the
anconaeus. This group therefore comprises one flexor of
the elbow, three extensors of the wrist, two extensors of the
fingers, and a feeble extensor of the forearm at the elbow
joint, viz., the anconaeus. In the distal part of the forearm
the extensor digitorum communis is separated from the
extensor carpi radialis brevis by a narrow interval, in which
appear two muscles belonging to the deep group. The two
muscles in question turn round the lateral margin of the fore-
arm, superficial to the radial extensors of the wrist, and end in
tendons which go to the thumb. The proximal of the two
muscles is the abductor pollicis longus, the distal is the
.extensor pollicis brevis, but they lie in such close contact,
and so intimately are their tendons connected, that in many
cases they appear, at first sight, to be blended together by their
margins. After they have become superficial, the abductor
pollicis longus and the extensor pollicis brevis turn round
the radial border of the forearm superficial to the radial
extensors of the wrist, and as they descend to the thumb
they lie in the groove on the lateral surface of the styloid
process of the radius in which they are retained by the
most lateral part of the dorsal carpal ligament (Fig. 74).

A short distance proximal to the dorsal carpal ligament
on the radial side of the tendons of the extensor digitorum
a third muscle of the deep group also comes into view ; it is
the extensor pollicis longus. Its tendon crosses the radial
extensors of the wrist at the distal border of the dorsal
carpal ligament.

Dissection. The skin of the dorsum of the hand has already
been removed, and the cutaneous nerves and veins have been
displayed. The thin deep fascia is still in position, but it will
not prevent a successful demonstration of the mucous sheaths



PLATE X



Triceps muscle ~

Lateral intermuscular septum
Fascial insertion of triceps
(reflected)



Lateral epicondyle

Olecranon



Anconaeus muscle"
Deep fascia (reflected)



Dorsal surface of ulna



Extensor carpi ulnaris
muscle



Extensoi digiti quinti _
muscle



Dorsal interosseous
artery



Extensor indicis muscle
Ulna

Capsule of distal radio-
ulnar joint



Dorsal carpal branch of

ulnar artery

Third dorsal metacarpal

artery

Abductor digiti quinti
muscle




Brachio-radialis muscle
Brachialis muscle



Biceps brachii



Cephalic vein



Lateral cutaneous nerve of
forearm (musculo-cutaneous)



Extensor carpi radialis
longus muscle



. Extensor carpi radialis
brevis muscle

- Extensor digitorum
communis muscle



- Abductor pollicis longus muscle



Extensor pollicis brevisjmuscle
Radius

Dorsal carpal ligament

Tendon of abductor pollicis longus
Radial artery

Tendon of extensor pollicis brevis
_ Dorsal carpal branch of radial
- artery

Tendon of extensor pollicis
longus muscle'

Dorsal digital arteries of thumb
Tendon of extensor indicis
muscle

First dorsal interosseous
muscle



FIG. 74. Dissection of the Dorsal Aspect of the Forearm.



FOREARM AND HAND



175



of the extensor tendons, which should be attempted before the
superficial extensor muscles are cleaned. Introduce a blow-
pipe into each mucous sheath immediately proximal to the



A. radialis "



Sheath of flexor pollicis longus'

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

M. abductor pollicis brevis -




Brachio-radialis

. abductor pollicis
longus
M. extensor pollicis brevis

M. extensor pollicis longus



^_, .Ligamentum carpi dorsale

Mucous sheath of extensor
" carpi radialis longus

- Articular capsule of wrist

A. radialis

Sheath of extensor carpi

radialis brevis

Sheath extensor pollicis longus

Sheath of extensor digitorum

communis



M. interosseus dorsalis
primus

- M. adductor pollicis



FIG. 75. Dissection of the Lateral Side of the Left Wrist and Hand
showing Mucous Sheaths of Tendons.

dorsal carpal ligament and then inflate the sheath. Commence
with the sheath of the abductor pollicis longus and the extensor
pollicis brevis ; then inflate in succession the sheaths of the
radial extensors of the wrist, the common extensor ot the fingers,
the extensor digiti quinti, and the extensor carpi ulnaris. A
better demonstration of the mucous sheaths may be made by



1 76 THE SUPERIOR EXTREMITY

injecting them, by means of a large hypodermic syringe, with a
thin solution of coloured starch. If the sheaths have been
injured, and it is not possible to distend them, then open each and
examine its extent with the aid of a blunt probe.

The Mucous Sheaths of the Extensor Tendons. Seven
mucous sheaths surround the tendons which pass under cover
of the dorsal carpal ligament. Two lie along the distal part
of the radial border of the forearm ; they are the sheaths of
the abductor pollicis longus and the extensor pollicis brevis.
They may communicate with one another. From the radial
to the ulnar border the remaining five sheaths are arranged
in the following order: the sheath of the extensor carpi
radialis longus, the sheath of the extensor carpi radialis
brevis, a sheath common to the extensor digitorum com-
munis and the extensor indicis, the sheath of the extensor
digiti quinti, and the sheath of the extensor carpi ulnaris.

The proximal limit of the sheaths lies at, or slightly proxi-
mal to, the dorsal carpal ligament. The sheaths of the
abductor pollicis longus and the radial and ulnar extensors
of the carpus are prolonged distally to the insertions of the
tendons of these muscles. As regards the sheaths of the
extensors of the fingers and thumb, it may be said, speaking
generally, that they terminate distally about the level of the
mid-length of the hand (Figs. 75, 76).

Dissection. The brachio -radialis has already been dissected ;
the other superficial muscles must now be cleaned and, as far
as possible, isolated from one another. The isolation of the distal
parts is not difficult, but the proximal parts spring not only from
the humerus and the super jacent deep fascia, but also from
strong intermuscular septa which intervene between adjacent
muscles. To isolate the proximal parts of the muscles, therefore,
the dissector must split the intermuscular septa with the scalpel
and so isolate each muscle as far as its bony origin.

M. Brachio-radialis (O.T. Supinator Longus). The brachio-
radialis muscle lies more on the volar than on the dorsal
surface of the forearm. It takes origin, in the arm, from
the proximal two- thirds of the lateral epicondylar ridge of the
humerus and from the lateral intermuscular septum. Near
the middle of the forearm a flat tendon emerges from its
fleshy belly, and proceeds distally to gain insertion into the
lateral aspect of the expanded distal extremity of the radius,
at the base of the styloid process. The nerve of supply is
a branch of the radial nerve (O.T. mttsculo- spiral), which



FOREARM AND HAND



177



enters the muscle proximal to the elbow. The main action
of the muscle is flexion of the elbow, but it can help to
initiate supination of the prone forearm and pronation of
the supine forearm.



M. abductor pollicis longu?



Radius-

M. extensor carpi radialis brevis -
M. extensor carpi radialis longus-



Tendon of M. extensor

pollicis brevis

Sheath of extensor pollicis brevis



A. radialis.
Sheath of extensor
pollicis longus



M. adductor pollicis

M. interosseus
dorsalis primus



. extensor digitorum communis
M. extensor carpi ulnaris

Ulna

M. extensor digiti quinti proprius

Styloid process of ulna



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 18 of 44)