D. J. (Daniel John) Cunningham.

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

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and ulnar terminal branches. The volar branch passes either
deep or superficial to the median cubital vein and then descends
to the wrist. It supplies the skin of the ulnar half of the volar
aspect of the forearm. The ulnar branch passes either anterior
or posterior to the medial epicondyle and then along the ulnar
margin of the forearm. It supplies the skin of the ulnar margin
and of the ulnar part of the dorsum of the forearm as far as the
wrist.

After the medial cutaneous nerve of the forearm has been
dissected, trace the remains of the posterior supraclavicular nerves
through the fat over the proximal part of the deltoid ; they supply
the skin over the proximal half of the deltoid muscle. When
they have been traced to their terminations make an incision
through the fat along the distal half of the posterior border of the
deltoid and secure the lateral cutaneous nerve of the arm. It is a
branch of the axillary nerve and will be found turning round the
posterior border of the deltoid at the junction of the proximal
two-thirds with the distal-third of the muscle (Figs. 31, 32, 33).
It runs forwards across the muscle and supplies the skin over its
distal half.

To find the proximal and distal branches of the dorsal cutane-
ous nerve of the forearm dissect in the fat between the lateral
epicondyle of the humerus and the insertion of the deltoid.
They are branches of the radial nerve and both are occasionally
difficult to find. The proximal branch usually pierces the deep
fascia a little distal to the insertion of the deltoid (Figs. 31, 32).
It supplies the skin of the lateral part of the anterior aspect of
the arm as far as the elbow. The distal branch will be found
about one inch nearer the lateral epicondyle. It passes behind
the lateral epicondyle and then descends along the dorsal aspect
of the forearm to the wrist.

After the distal branch of the dorsal cutaneous nerve of the
forearm has been traced to its termination, find the lateral
cutaneous nerve of the forearm. It is the continuation of the
musculo-cutaneous nerve. It appears at the lateral border of
i 5b



70 THE SUPERIOR EXTREMITY

the biceps under cover of the cephalic vein, about 25 mm.
above the point where the medial cubital vein leaves the cephalic
vein. Soon after it enters the superficial fascia it divides into
a volar and a dorsal branch. The volar branch descends along
the radial part of the volar aspect of the forearm to the ball of the
thumb, and the dorsal branch may be traced distally on the dorsal
aspect of the radial side of the forearm as far as the wrist.

The posterior cutaneous nerve of the arm was found during
the dissection of the axilla springing from the proximal part of
the radial nerve. Now it must be traced along the dorsal aspect
of the arm to the elbow. It supplies the skin of the dorsum of
the arm from the axilla to the elbow (Fig. 32).

After the posterior cutaneous nerve of the arm has been
cleaned, place the limb on its dorsal surface and look for the
palmar cutaneous branches of the median and ulnar nerves.

They both pierce the deep fascia of the forearm about 30
mm. proximal to the wrist. The palmar cutaneous branch of
the median nerve lies in the line of the medial border of the
proximal end of the ball of the thumb (thenar eminence) and it
extends to the middle of the palm. The palmar cutaneous
branch of the ulnar nerve lies in the line of the middle of the
ball of the little finger (hypothenar eminence) ; it also extends to
the level of the middle of the palm (Fig. 31).

After the distribution of the palmar cutaneous nerves has
been seen clear away the superficial fascia of the palm from the
interval between the thenar and hypothenar eminences to the
bases of the digits to expose the intermediate part of the palmar
aponeurosis, that is, the deep fascia of the palm. Note that the
superficial fascia in the area under consideration is dense. It is
divided into small lobules by fibrous septa which pass from the
skin to the palmar aponeurosis. When the intermediate part of
the palmar aponeurosis is exposed it will be found to be triangular
in outline. The apex lies at the wrist where it is continuous with
the deep fascia of the forearm. The base is at the level of the
distal ends of the metacarpal bones, and it divides into five pieces,
one for each finger and a less definite slip for the thumb. A
bundle of transverse fibres will be met with in the fold of skin
which crosses the proximal ends of the interdigital clefts. It is
the superficial transverse ligament of the hand, and it must be
divided opposite the clefts in order that the volar digital nerves
which supply the adjacent sides of the clefts may be followed.

The volar digital nerves are seven in number. The first and
second pass to the thumb, one to its radial and one to its ulnar
side. They are accompanied by branches of the princeps pollicis
artery. They will be found at the medial margin of the thenar
eminence and must be traced to the end of the thumb. The third
appears at the lateral margin of the slip of the palmar aponeurosis
to the index-finger. It runs along the radial side of the finger
accompanied by the volar radialis indicis artery. The fourth,
fifth, and sixth will be found between the slips of the inter-
mediate part of the palmar aponeurosis in line with the first,
second, and third interdigital clefts respectively. Each is ac-
companied by a volar digital artery, and like the artery it divides
to supply the adjacent sides of the fingers which bound the cleft
opposite which it lies. The seventh supplies the ulnar side of
the little finger. It appears at the distal border of the palmaris



PLATE III



Nn. supraclaviculares







N. cutaneus brachii lateralis



V. cephalica
N. cutaneus antibrachii dorsalis, ramus superior



N. cutaneus antibrachii dorsalis, ramus inferi



N. cutaneus ant



N. cutaneus antibrachii
,' medialis, rami superiores



N. cutaneus brachii medialis
. basilica
N. cutaneus antibrachii medialis



ibrachii lateralis.'



V. cephalica



V. mediana cubiti on lacertus fibrosus
V. basilica

N. cutaneus antibrachii medialis,

ramus ulnaris

N. cutaneus antibrachii medialis,
ramus volaris



N. cutaneus antibrachii medialis, ramus volaris



Nn. digitales- -



N. ulnaris, ramus cutaneus palmaris
A ,;// v ~ N. medianus, ramus cutaneus palmaris



M. palmaris brevis



; Nn. digitales



FIG. 31. Superficial Nerves and Veins of the Anterior Aspect
of the Superior Extremity.




PLATE IV



Nn. supraclavicular




N. cutaneus brachii
posterioris

N. intercostobrachialis



N. cutaneus brachii medialisK
I



N. cutaneus antibrachii medialis, _\
ramus ulnaris



N. cutaneus brachii lateralis



N. cutaneus antibrachii dorsalis, ramus superior
N. cutaneus antibrachii dorsalis, rarnus inferior



N. cutaneus antibrachii lateralis



. V. basilica



1 N. ulnaris, ramus dorsalis manus




N. radialis superficialis
- V. cephalica



FIG. 32. Superficial Veins and Nerves of the Posterioi Aspect
of the Superior Extremity.



DISSECTION OF SUPERFICIAL STRUCTURES 71

brevis muscle and is accompanied by a digital artery. The five
most lateral digital nerves are branches of the median nerve, the
two most medial are branches of the ulnar nerve, therefore the
median nerve supplies three and a half digits, the thumb, the
index, the middle and half the ring digit, and the ulnar supplies
the remaining one and a half, viz., the little finger and half the
ring finger.

As the branches of the median nerve to the fingers are followed
along the fingers they will be found to send branches not only to
the volar surfaces but also to the dorsal surfaces in the regions
of the second and terminal phalanges.

The careful dissector will note that some of the finer branches of the
digital nerves terminate in minute ovoid bodies embedded in the fat.
They are the Pacinian touch corpuscles and are associated with the sense
of touch.

Two other cutaneous nerves have still to be dissected ; they are
the dorsal branch of the ulnar nerve and the superficial division
of the radial nerve. Both are distributed to the dorsum of the
hand and to the dorsal aspects of the digits.

The dorsal branch of the ulnar nerve must be sought for as
it turns round the ulnar border of the wrist immediately distal
to the styloid process of the ulna. It gives a branch to the ulnar
side of the little finger and a branch to supply the adjacent sides
of the ring and little fingers ; the latter communicates with the
most medial branch of the superficial division of the radial nerve.

The superficial branch of the radial nerve will be found at
the radial border of the forearm. It appears from under cover
of the tendon of the brachio-radialis about 8 cm. (3^ inches)
above the wrist, and, as it descends to the hand, it breaks up
into five branches ; one to each side of the thumb, one to the
radial side of the index-finger, one to the adjacent sides of the
index and middle fingers, and one to the adjacent sides of the
middle and ring fingers. The last branch is connected with the
adjacent ramus of the dorsal branch of the ulnar nerve by a
communicating twig. A palmar cutaneous branch is distributed
to the ball of the thumb either from the trunk of the superficial
part of the radial nerve or from the branch to the radial side
of the thumb. The dorsal digital nerves of the thumb can be
traced to the end of the thumb, those of the index digit to the
proximal end of the second phalanx, those of the middle finger
to the middle of the second phalanx and those of the ring and
little fingers to the proximal end of the terminal phalanx. The
remaining parts of the dorsal aspects of the fingers are supplied
by the volar digital nerves. The important practical point is
that parts of the dorsal surface of the index, middle, and ring
digits are supplied not by the radial but by the median nerve.

The arrangement of the nerves on the dorsum of the hand is very
variable. That described above is usually met with, but not uncommonly
the ulnar nerve supplies a larger and the radial nerve a smaller area.
The reverse arrangement is also found.

When the dissection of the cutaneous nerves of the superior
extremity is completed remove the remains of the fatty superficial
fascia and proceed to the study of the deep fascia,
i 5c



72 THE SUPERIOR EXTREMITY

Deep Fascia. The deep fascia of the superior extremity
consists chiefly of transverse fibres, which are bound together
by oblique and longitudinal fibres. The oblique and longi-
tudinal fibres become specially developed in certain situations
which will be noted later. The deep fascia is fairly strong in
the region of the shoulder over the deltoid muscle. Over
the posterior part of the deltoid and the adjoining part of the
infraspinatus, which covers the lower part of the back of the
scapula, it becomes dense, and it is closely attached by deep
processes to the axillary border of the scapula. Over the
front of the arm, where it covers the biceps muscle, it is thin,
but it is much stronger at the back of the arm, over the triceps.
On each side, extending proximally from the lateral and the
medial epicondyles deep expansions bind it to the lateral
and medial supra -epicondylar ridges of the humerus. The
expansions are known as the lateral and medial inter muscular
septa, because they separate the muscles on the front from
those at the back of the arm. At the elbow it is thickened
and strengthened by tendinous fibres, which pass to it from
the biceps and triceps muscles, and it is closely attached to
the lateral and medial epicondyles of the humerus and to
the olecranon of the ulna. A special thickening called the
lacertus fibrosus (Fig. 31) is found at the front of the elbow.
It extends from the medial border of the proximal part of
the biceps tendon and the adjacent part of the muscle to the
medial side of the proximal part of the forearm. It separates
the median cubital vein, which lies superficial to it, from the
brachial artery, which is deep to it. The volar branch of
the medial cutaneous nerve of the forearm usually passes
between the lacertus fibrosus and the median cubital vein.

In the forearm the deep fascia is strong over the proximal
parts of the muscles which spring from the medial and the
lateral epicondyle. Then it becomes thin, especially on the
volar aspect. On the dorsal aspect it is bound to the whole
length of the posterior border of the ulna by a deep
extension which intervenes between the muscles on the
dorsal and volar parts of the medial side of the forearm.

At the wrist the transverse fibres of the deep fascia
become very obvious, and they form two marked transverse
bands ; one on the volar aspect called the transverse carpal
ligament and one on the dorsal aspect called the dorsal carpal
ligament.



DISSECTION OF SUPERFICIAL STRUCTURES 73

Both the bands are bound to the adjacent bones and
they act as straps which bind down the tendons, which pass
deep to them, and prevent them from springing away from
the bones when the hand is bent volarwards or dorsally.

The transverse carpal ligament is attached on the ulnar
side to the pisiform bone and the hook of the hamatum,
and on the radial side to the tubercle of the navicular bone
and the ridges on the volar surface of the multangulum majus.

Five structures cross the superficial aspect of the trans-
verse carpal ligament: (i) the ulnar artery; (2) the ulnar
nerve ; (3) the palmar cutaneous branch of the ulnar nerve ;
(4) the palmar cutaneous branch of the median nerve; (5)
the tendon of the palmaris longus. The palmar cutaneous
branches of the median and ulnar nerves have already been
seen. The ulnar artery and nerve pierce the deep fascia
proximal to the transverse carpal ligament, pass across its
superficial surface close to the lateral side of the pisiform
bone and disappear deep to the palmaris brevis. As they
cross the ligament they are bound down to it by a slip of
fascia, called the volar carpal ligament, which passes from the
pisiform bone to the superficial surface of the transverse
carpal ligament. The tendon of the palmaris longus pierces
the deep fascia proximal to the transverse carpal ligament,
crosses it and blends with the apex of the intermediate part
of the palmar aponeurosis which is attached to the distal
border of the ligament.

Distal to the transverse carpal ligament the deep fascia is
called the palmar aponeurosis, of which there are three parts,
(i) A relatively thin lateral part which covers the muscles of
the thenar eminence; (2) a relatively thin medial part o\er
the muscles of the hypothenar eminence ; and (3) a strong
intermediate part which conceals and protects the main
vessels, nerves, and the tendons passing to the fingers. The
lateral and medial parts consist mainly of transverse fibres ;
the intermediate part on the other hand is formed principally
by strong longitudinal fibres bound together by transverse
fibres.

The intermediate part of the palmar aponeurosis is triangular
in outline. Its apex blends with the tendon of the palmaris
longus and the transverse carpal ligament. Its borders
blend with the thinner lateral and medial parts, and from
them septa, which will be dissected later, pass into the depths



74 THE SUPERIOR EXTREMITY

of the palm. The distal margin or base lies at the level of
the heads of the metacarpal bones, and it divides into five
processes, one for each finger and a more slender process for
the thumb. Each process passes to the corresponding digit
where it blends with the volar surface of the sheath of the
flexor tendons, and it sends a process on each side of the
digit which join the deep fascia on the dorsal surface.

The dorsal carpal ligament is attached on the radial side
to the volar margin of the styloid process of the radius and
on the ulnar side to the fascia on the medial side of the
wrist. The space between it and the distal ends of the
radius and ulna is divided into six compartments by septa,
which pass from its deep surface to the ridges on the radius
and to the head and styloid process of the ulna. The com-
partments transmit the tendons which pass from the dorsum
of the forearm to the dorsum of the hand and to the dorsal
aspects of the fingers. Its superficial surface is crossed by
the terminal branches of the superficial division of the
radial nerve and by the cephalic and basilic veins. The
distal border of the dorsal carpal ligament is continuous
with the thin deep fascia of the hand, which is prolonged
into the dorsal aspects of the digits.

When the study of the deep fascia of the superior
extremity has been completed return to the shoulder region ;
verify again the attachments of the muscles which connected
the scapula and the clavicle with the trunk ; afterwards cut
away the superfluous parts of the muscles, leaving about one
inch of each for revision. Then proceed to the general
study of the shoulder region.

Muscles inserted into the Clavicle and Scapula. The insertions of
the muscles which have already been divided must first engage the
attention of the student. They should be carefully defined and the
precise extent of each studied. Begin with the omo - hyoid, which
springs from the superior border of the scapula ; then deal in the same
way with the levator scapula, rhomboideus minor and major, which
are attached to the vertebral border of the bone, and the serratus anterior,
which is inserted into the costal aspect of the medial and inferior angles,
and the intervening portion of the vertebral border of the scapula. The
insertion of the pectoralis minor into the coracoid process, and of the
trapezius into both clavicle and scapula, should also be thoroughly re-
examined.



SHOULDER SCAPULAR REGION 75

SHOULDER SCAPULAR REGION.

In the dissection of this region the following parts must be
studied :

1. Cutaneous nerves of the shoulder.

2. Deep fascia.

3. Deltoid muscle.

4. Sub-acromial bursa.

5. Anterior and posterior circumflex vessels of the humerus.

6. Axillary (circumflex) nerve.

7. Circumflex scapular artery.

8. Subscapularis muscle.

9. Supraspinatus, infraspinatus, teres minor, and teres major muscles.

10. Bursse in connection with the shoulder -joint.

11. Suprascapular nerve and transverse scapular artery.

12. Acromio-clavicular joint, and the coraco-acromial arch.

Nervi Cutanei (Cutaneous Nerves). The nerves which lie
in the superficial fascia of the shoulder region are derived
from two different sources. They are :

1. Posterior supraclavicular nerves from the third and fourth cervical

nerves.

2. Cutaneous branches from the axillary nerve (circumflex).

They have already been secured and cleaned.

The posterior supraclavicular nerves cross the lateral third
of the clavicle and the insertion of the trapezius, under cover
of the platysma. They were divided when the limb was
removed, and the distal ends have been followed over the
proximal half of the deltoid.

The cutaneous branches of the axillary nerve consist
(a) of a large branch, the lateral cutaneous nerve of the arm^
which turns round the posterior border of the deltoid muscle,
and (ft) of several fine filaments which pierce the substance
of the deltoid muscle, and appear at irregular intervals on
its surface (Fig. 33). The latter are difficult to secure, but the
lateral brachial cutaneous nerve has already been found and
cleaned (see p. 69). It turns round the posterior border,
and is distributed over the distal part of the deltoid region.

Deep Fascia. It has already been noted that the deep
fascia over the deltoid is fairly strong, and that as it passes
from the deltoid to the muscles which spring from the lower
part of the posterior aspect of the scapula, it becomes strong
and dense over the infraspinatus, the teres minor and the
teres major. In the lower scapular region it is firmly attached
to the limits of the infraspinous fossa in which the infra-



7 6



THE SUPERIOR EXTREMITY



spinatus takes origin, and it presents other very apparent
connections. Thus, a strong septum, proceeding from its



Lateral end of clavicle
'Margin of acromion
Pectoralis major
Cephalic vein

Deltoid




Cutaneous branches of axillary
-(O.T. circumflex) nerve piercing
deltoid

Lateral brachial cutaneous
branch of axillary nerve



Biceps

Lateral head of triceps

Brachialis

Proximal branch of dorsal
cutaneous nerve of forearm

Cephalic vein

Distal branch of dorsal cutaneous
nerve of forearm

Brachio-radialis
Tendon of triceps



Olecranon
Extensor carpi radialis longus



FIG. 33. The Deltoid Muscle and the lateral aspect of the Arm.

deep surface, will be noticed to dip in between the infra-
spinatus and teres minor muscles, and then, as it proceeds
forwards, it gives a thin covering to the teres minor, teres
major, and the deltoid. Indeed, it may be said to split into



SHOULDER SCAPULAR REGION 77

two lamellae a superficial and a deep, which, as they pass
forwards, enclose between them the deltoid muscle.

Dissection. Place a small block in the axilla, fix the scapula
to it with hooks and bend the arm over the block to make the
fibres of the deltoid tense. Detach the lateral brachial cutaneous
branch of the axillary nerve from the deep fascia, and turn it
backwards to the point where it curves round the posterior
border of the deltoid ; then clean the deltoid. On the left side
commence at its posterior border, make an incision through the
deep fascia along the whole length of that border and reflect the
deep fascia forwards. On the right side commence in front,
where the fascia has already been partly reflected during the
dissection of the axillary region, and reflect the fascia backwards.

M. Deltoideus. The deltoid muscle is composed of
short, coarse fasciculi, and as its name implies it is of
triangular form. Its proximal end or base arises : (i) from
the anterior border and the adjacent part of the upper
surface of the lateral third of the clavicle ; (2) from the
lateral border of the acromion ; and (3) from the inferior
lip of the posterior border of the spine of the scapula. Its
origin corresponds closely with the insertion of the trapezius.
Its fasciculi converge rapidly as they pass distally to the
pointed tendinous insertion on the rough deltoid tubercle
situated in the middle of the antero- lateral surface of the
body of the humerus (Fig. 45). The muscle is an abductor,
and a medial and lateral rotator of the humerus, and it is
supplied by branches of the anterior division of the axillary
nerve which enter its deep surface.

Dissection. Place the limb on its posterior aspect. Release
the axillary vessels, and the nerves, from the coracoid process and
clean the angle between the humerus and the scapula. Follow
the axillary nerve and the posterior circumflex humeral artery
backwards. They will be found to enter a cleft between the
subscapularis above and the teres major below. Separate those
muscles and a triangular interval will be displayed. It is bounded
laterally by the surgical neck of the humerus. Crossing the space
from above downwards, behind the subscapularis and the teres
major is the long head of the triceps. It divides the triangular
interval into a lateralpart called the quadrangular space and a
medial part called the triangular space. The axillary nerve and
the posterior humeral circumflex artery pass through the quad-
rangular space. Now reverse the limb, push the posterior
border of the deltoid forwards and find the axillary nerve and
the posterior humeral circumflex artery. They emerge from
the quadrangular space and pass forwards round the lateral
surface of the surgical neck of the humerus.

At this stage of the dissection the deltoid muscle must be
reflected. Cut it away from its origin from the clavicle, acromion,



78 THE SUPERIOR EXTREMITY

and spine of the scapula, and turn it towards its insertion into
the humerus, taking care not to injure the circumflex humeral
arteries and the axillary nerve. Note the tendinous intersections
which run through the substance of the muscle, then clean the
vessels and nerves which are exposed. The axillary nerve
enters the back part of the shoulder region through the posterior
part of the quadrangular space, accompanied by the posterior
humeral circumflex vessels, and at once divides into an anterior
and a posterior division. Before it divides, whilst it is in the
quadrangular space, immediately below the shoulder-joint, it
gives off an articular twig to the joint, which should be secured.
The anterior division accompanies the posterior humeral cir-



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 9 of 44)