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cumflex artery round the surgical neck of the humerus. It
supplies the deltoid and sends branches through it to the skin on
its superficial surface. Clean both the nerve and the vessel ;
then turn to the posterior branch and secure the twig to the teres
minor muscle, upon which there is a gangliform enlargement.
The posterior branch terminates as the lateral cutaneous nerve of
the arm, which turns round the posterior border of the deltoid
to gain its superficial surface. It has already been dissected
(see p. 69). Clean the teres major and minor muscles which
spring from the posterior surface of the axillary border of the
scapula, and pass to the humerus, and note the strong septum
of deep fascia which separates them. Clean the long head of
the triceps which arises from the upper part of the axillary
border of the scapula. Then examine the subacromial bursa,
which lies directly below the acromion, on the insertion of the
supraspinatus. If the wall of the bursa is quite entire a blow-
pipe may be thrust into it. It can then be distended, and if
unilocular it may be inflated to about the average size of a hen's
egg. It varies much in size, however, in different subjects.
Open the bursa and examine its extent with the finger or a
blunt probe. Its interior is sometimes divided by fibrous parti-
tions into two or more loculi. Now turn the limb on to its
posterior aspect and clean the proximal parts of the coraco-
brachialis and the short head of the biceps brachii which spring,
by a common tendon, from the tip of the coracoid process of the
scapula. Pull the short head of the biceps and the coraco-
brachialis medially and expose the tendon of the long head of the
biceps lying in the intertubercular sulcus of the humerus, but do
not displace it at present. Now pull the short head of the biceps
and the coraco-brachialis laterally and .clean the insertion of the
subscapularis it is inserted into the lesser tubercle of the
humerus on the medial side of the intertubercular sulcus. Clean
also the anterior humeral circumflex artery, trace it to its division
into an ascending branch, which runs to the shoulder -joint
along the intertubercular sulcus, and a transverse branch, which
anastomoses with the posterior humeral circumflex artery, and
then re-examine the structures which lie directly under cover of
the deltoid and note their relative positions.

PARTS UNDER COVER OF THE DELTOID. The deltoid
covers the proximal part of the humerus, and envelops the
region of the shoulder-joint behind, laterally, and in front.
It also covers the coracoid process of the scapula. It is



SHOULDER SCAPULAR REGION 79

separated from the shoulder-joint by the muscles which are
attached to the proximal end of the humerus and by the
subacromial bursa. The full, rounded appearance of the
shoulder is due to the deltoid passing over the proximal end
of the humerus and the muscles attached to it. When the
head of the humerus is dislocated the muscle passes vertically

Descending branch of transverse cervical artery
Suprascapular nerve and transverse
, scapular artery

Coracoid process

Capsule of shoulder -joint
/ Tendon of supraspinatus

Tendon of infra-
spinatus




Subscapular artery
Infrascapular branch
Circumflex scapulae artery
Posterior circumflex artery and ' _

axillary nerve Nerve to teres minor

FIG. 34. Dissection of the Posterior Scapular Region.

from its origin to its insertion, and the dislocation is
recognised by the squareness or flatness of the shoulder.
Under cover of the posterior part of the deltoid are portions
of the muscles which spring from the posterior surface of the
scapula, viz., the infraspinatus, teres major, and teres minor,
and the proximal part of the long head of the triceps, which
arises from the upper part of the axillary border of the
scapula. Under its middle part lie the insertion of the



8o



THE SUPERIOR EXTREMITY



supraspinatus, covered by the subacromial bursa, and the
upper portion of the lateral aspect of the body of the
humerus. Its anterior part covers the coracoid process and



Spine of scapula

Transverse scapular artery |

(O.T. suprascapular)

Supraspinatus



Suprascapular nerve
Deltoid



Infraspinatus
Circumflex, scap.
artery (O.T.)'
dorsalis scap.
Teres minor 4-'

Subscapula



Teres major

Triang. space
Quadrangular space

Triceps, long, head
Radial nerve (O.T. musculo-spiral)




Triceps, lateral head -
N. to triceps, medial head -



Triceps, med. head



Subacromial'bursa

Infraspinatus muscle
Capsule of shoulder-
joint
N. to m. teres minor

Deltoid

Axillary nerve
(sup. branch)

Axillary nerve
(inf. btanch)



Lateral brachial
cutaneous nerve



Lateral head of triceps

Radial nerve (O.T.
musculo-spiral)



Ant. branch of profundr
artery of arm



Post, branch of profundt
artery of arm
Dorsal antibrachial
cutaneous nerve

Brachialis



Ulnar nerve
Medial epicondyle - -

N. to flex. carp. uln. -I

Olecranon ...



Lateral epicondyle
Recurrent inter-
osseous artery

Anconaeus
Kxt. dig. comm.
and dig. quint.
Ext. carpi ulnans

FlG. 35. Dissection of the dorsal aspect of the Arm. The lateral head of
the Triceps has been divided and turned aside to expose the sulcus on
the Humerus for the radial nerve.



the muscles and ligaments which are attached to it, the long
head of the biceps muscle descending in the intertubercular
sulcus, and the insertion of the subscapularis into the lesser
tubercle of the humerus. The muscle also covers the greater



SHOULDER SCAPULAR REGION



81



part of the axillary nerve and the anterior and posterior
humeral circumflex vessels.

Bursa Subacromialis. The subacromial bursa is a large
bursal sac which intervenes between the acromion and deltoid
above, and the muscles which immediately cover the upper
aspect of the capsule of the shoulder-joint below. It facili-
tates the play of the proximal end of the humerus and the



Capsula art




Posterior humeral
circumflex vessels
and axillary nerve



Labrum glenoidale

Capsula articularis
N. axillaris



Posterior humeral
circumflex vessels



FIG. 36. Diagram of a Frontal Section of the Right Shoulder.

attached muscles on the under aspect of the acromion and
deltoid.

The Quadrangular and Triangular Spaces. Neither of
these so-called spaces has any real existence until the
boundaries are artificially separated from one another.
When viewed from the front the triangular space is bounded
above by the subscapularis, below by the teres major, and
laterally by the long head of the triceps, but at the back the
teres minor replaces the subscapularis as the upper boundary.
The circumflex scapular branch of the subscapular artery
enters the space from the front, turns round the axillary

VOL. 1 6



82



THE SUPERIOR EXTREMITY



border of the scapula, anterior to the teres minor, and enters
the infraspinous fossa.

The boundaries of the quadrangular space, as seen from
the front, are the subscapularis above, the teres major
below, the long head of the triceps medially, and the
surgical neck of the humerus laterally. At the back the
teres minor replaces the subscapularis as the upper boundary.
Between the subscapularis anteriorly, and the teres minor
posteriorly, the inferior surface of the capsule of the shoulder-
joint forms the upper boundary of the space, and through the
space, directly below the capsule, pass the axillary nerve and
the posterior humeral circumflex vessels.

Arterise Circumflexse Humeri (O.T. Circumflex Arteries).
The posterior humeral circumflex artery has been already



AA




H. Transverse section of the
humerus immediately distal
to the tubercles.
A, A. Axillary artery.
P.C. Posterior circumflex artery

of the humerus.
A.C. Anterior circumflex artery of

the humerus.
C.N. Axillary nerve.

a. Articular branch.
T.M. Branch to teres minor.
C. Cutaneous branches.



FIG. 37. Diagram of the Circumflex Vessels and the Axillary Nerve.

observed to arise, within the axilla, from the posterior aspect
of the axillary artery, a short distance distal to the subscapular
branch. It at once passes backwards, through the quadri-
lateral space, and, winding round the surgical neck of the
humerus, it is distributed in numerous branches to the deep
surface of the deltoid muscle. Several twigs are given also to
the shoulder-joint and the integument. It anastomoses with
the acromial branch of the thoraco-acromial artery and with
the anterior humeral circumflex artery, and also, by one or
more twigs, which it sends distally to the long head of the
triceps, with the profunda branch of the brachial artery.

The termination of the anterior humeral circumflex artery
can now be more satisfactorily studied, and its anastomosis



SHOULDER SCAPULAR REGION 83

with the posterior humeral circumflex artery established, if the
injection has flowed well. By the anastomosis the arterial
ring which encircles the proximal part of the humerus is
completed.

Nervus Axillaris (O.T. Circumflex Nerve). The axillary



M. triceps
(long head)




Groove for circumflex

artery of scapula

(O.T. dorsahs
scapulae)



. M. latissimus dorsi (scapular slip)
FIG. 38. Dorsum of Scapula with the Attachments of the Muscles mapped out.

nerve accompanies the posterior humeral circumflex artery.
It supplies: (i) an articular twig to the shoulder-joint; (2)
muscular branches to the deltoid and teres minor; and (3)
cutaneous branches to the skin over the distal part of the



84 THE SUPERIOR EXTREMITY

deltoid. It springs from the posterior cord of the brachial
plexus, turns round the lower border of the subscapularis,
and passes backwards, with the posterior humeral circumflex
artery, through the quadrilateral space to the back of the limb.
There it divides into an anterior and a posterior division.
The articular branch takes origin from the trunk of the nerve
in the quadrilateral space, and enters the joint from below.
The posterior division gives off the branch to the teres minor,
and, after furnishing a few twigs to the posterior part of the
deltoid, is continued onwards, as the lateral cutaneous nerve
of the arm> which has already been dissected in the superficial
fascia over the distal part of the deltoid (Figs. 31, 32, 35).
The nerve to the teres minor is distinguished by the presence
of an oval, gangliform swelling upon it.

The anterior division proceeds round the humerus with the
posterior circumflex artery of the humerus, and ends near the
anterior border of the deltoid. It is distributed, by many
branches, to the deep surface of the muscle, whilst a few
fine filaments pierce the deltoid and reach the skin.

Dissection. Clean the coraco-acromial ligament, which
extends from the coracoid process to the acromion. Note that
the coracoid process, the coraco-acromial ligament, and the
acromion form an arch the coraco-acromial arch. The arch
lies above the shoulder- joint, but is separated from it by the
subacromial bursa, and the humeral ends of the supraspinatus,
the infraspinatus, and the subscapularis.

Arcus Coracoacromialis. The coraco-acromial arch should
be examined at the present stage, in order that its relation-
ship to the subacromial bursa and the supraspinatus may be
appreciated. It is the arch which overhangs the shoulder-
joint and protects it from above. It is formed by the
coracoid process, the acromion, and a ligament the coraco-
acromial which stretches between them.

The coraco-acromial ligament is a strong band of a some
what triangular shape. By its base it is attached to the lateral
border of the coracoid process, whilst by its apex it is attached
to the extremity of the acromion (Figs. 51, 52, 54).

The coraco-acromial arch plays a very important part in
the mechanism of the shoulder ; it might almost be said to
form a secondary socket for the humerus. The large sub-
acromial bursa, which intervenes between the acromion and
the muscles immediately covering the capsule of the shoulder-



SHOULDER SCAPULAR REGION 85

joint, facilitates the movements of the proximal end of the
humerus on the inferior surface of the arch ; it has already
been noted (p. 78).

Dissection. Clear away the subacromial bursa and clean
the supraspinatus, following it below the coraco-acromial arch
to its insertion into the greater tubercle of the humerus. Then
clean the fascia from the surface of the subscapularis ; it is a
fairly strong fascia and, near the vertebral border of the scapula,
some of the fibres of the serratus anterior are usually inserted
into it. Now turn the limb on its anterior aspect and remove
the strong fascia which covers the posterior surfaces of the
infraspinatus, the teres minor and the teres major. Divide
first the fascia over the infraspinatus. Incise it from the
vertebral border of the scapula to the greater tubercle of the
humerus. Reflect the upper part to its attachment to the spine
of the scapula and the lower part to the septum which separates
the infraspinatus from the teres minor and major muscles.
Then clear the fascia from the teres minor and major muscles.
As the septum between the teres minor and the infraspinatus
is being investigated be careful to avoid injury to the circumflex
scapular artery. The scapular muscles may now be examined.

M. Supraspinatus. The supraspinatus muscle arises from
the medial two- thirds of the supraspinous fossa, and also,
to a slight degree, from the supraspinous fascia, which covers
it. From this origin the fibres converge, as they pass laterally,
and, proceeding under the acromion, they end in a short,
stout tendon, which is inserted into the uppermost of the three
impressions on the greater tubercle of the humerus (Fig. 45,
p. 107). The tendon is closely adherent to the capsule of the
shoulder-joint. A portion of the supraspinatus is covered by
the trapezius, and in the loose fat which intervenes between
that muscle and the supraspinous fascia some twigs of the
ascending branch of the transverse cervical artery ramify.
The supraspinatus is supplied by the suprascapular nerve ; and
it is an abductor of the arm.

M. Infraspinatus. The infraspinatus muscle arises from
the whole of the infraspinous fossa, with the exception of a
small part of it near the neck of the scapula. It derives
fibres also from the fascia which covers it. Its tendon of
insertion is closely adherent to the capsule of the shoulder-
joint, and is attached to the middle impression on the greater
tubercle of the humerus (Fig. 48, p. 113). It is supplied by the
suprascapular nerve ; and it is an adductor and lateral rotator
of the arm.

M. Teres Minor. The teres minor is the small muscle
I 6 a



86 THE SUPERIOR EXTREMITY

which lies along the lower border of the infraspinatus. It
arises from an elongated flat impression on the dorsal aspect of
the axillary border of the scapula, and from the fascial septa
which intervene between it and the two muscles between
which it lies, viz. the infraspinatus and teres major. It is
inserted into the lowest of the three impressions on the
greater tubercle of the humerus, and also, by fleshy fibres,
into the body of the bone for about 12.5 mm. (half an inch)
distal to the tubercle (Fig. 48, p. 113). As it approaches its
insertion it is separated from the teres major by the long
head of the triceps brachii. The teres minor is supplied by
a branch from the axillary nerve. It is an adductor and
lateral rotator of the arm.

M. Teres Major. The part which the teres major plays in
the formation of the quadrilateral and triangular spaces has
already been seen. It arises from the oval surface on the
dorsum of the scapula close to the inferior angle of the bone
(Fig. 38, p. 83), and also from the septum which the infra-
spinous fascia sends in to separate it from the infraspinatus
and teres minor muscles. It is inserted into the medial
lip of the intertubercular sulcus on the proximal part of the
humerus (Fig. 45, p. 107). It is supplied by the lower
subscapular nerve, and it is an adductor, a medial rotator
and an extensor of the arm.

M. Subscapularis. The subscapularis muscle arises from
the whole of the subscapular fossa, with the exception of
a small portion near the neck of the scapula ; it takes
origin also from the groove which is present on the costal
aspect of the axillary border of the bone (Fig. 24, p. 46).
Its origin is strengthened by tendinous intersections, which
are attached to the ridges on the costal surface of the
scapula. The fleshy fibres thus derived converge upon a
stout tendon, which is inserted into the lesser tubercle of
the humerus ; a few of the lower fibres, however, gain
independent insertion into the body of the humerus distal
to the tubercle (Fig. 45).

As the muscle proceeds laterally to its insertion, it passes
under an arch formed by the coracoid process and the con-
joined origin of the short head of the biceps brachii and the
coraco-brachialis. The subscapularis is supplied by the upper
and lower subscapular nerves. It is an adductor and medial
rotator of the arm.



SHOULDER SCAPULAR REGION 87

Dissection. Pull the long head of the biceps out of the
intertubercular sulcus. Separate the tendon of insertion of
the latissimus dorsi from the anterior surface of the teres major,
noting the small fibrous slip which passes from its inferior
margin to the fascia on the long head of the triceps muscle
(Fig. 1 6) ; then follow the tendon of the latissimus to its
insertion into the floor of the intertubercular sulcus. The
tendon of the latissimus is more or less adherent to the teres
major, but near the humerus a small bursa frequently intervenes
between the two tendons. Now examine carefully the insertions
of the pectoralis major, the latissimus dorsi and the teres major.

Insertions of the Pectoralis Major and Latissimus Dorsi.
As the pectoralis major passes to its insertion into the lateral
lip of the intertubercular sulcus it lies anterior to the great
vessels and nerves of the axilla, to the two heads of the biceps
humeri, and to the coraco-brachialis, whilst the latissimus dorsi
lies behind those structures. The teres major accompanies
the latissimus dorsi as far as the medial lip of the intertuber-
cular sulcus. It therefore does not pass behind the long head
of the biceps humeri.

The tendon of the pectoralis major consists of two laminae.
A separation of the clavicular and sternal portions of the
muscle will bring both laminae into view, and the following
points should be noted in connection with them : (a) that
they are continuous with each other below, or, in other words,
that the tendon is simply folded upon itself; (<) that the
posterior lamina extends to a more proximal level on the
humerus than the anterior, and that a fibrous expansion pro-
ceeds proximally from its superior border, to seek attachment
to the capsule of the shoulder-joint and the lesser tubercle of
the humerus ; (c) that the lower border is connected with the
fascia of the arm.

The narrow, thin, flat, band-like tendon of the latissimus
dorsi lies in front of the insertion of the teres major, but does
not extend so far downwards. Therefore the teres major is
the lowest muscle in the lateral part of the posterior wall of the
axilla, and consequently the last muscle of the posterior axillary
wall upon which the axillary artery rests. The slip of fascia
which passes from the lower margin of the tendon of the
latissimus to the fascia on the long head of the triceps is of
interest inasmuch as it represents the dorsi -epitrochlearis
muscle of other animals.

Dissection. Depress the upper border of the subscapularis
as it passes below the coracoid process, and expose the subscapular



88 THE SUPERIOR EXTREMITY

bursa. Inflate the bursa with a blowpipe, and notice that, as air
is blown in, the capsule of the shoulder- joint is distended. If
the wall of the bursa has been injured in the course of previous
dissections, open it with the scalpel and examine the interior
with a blunt probe. Note its extent and its continuity with the
interior of the shoulder- joint through a large aperture in the
anterior part of the articular capsule.

Bursa Subscapularis. The subscapular bursa is formed
by the prolongation of the synovial stratum of the capsule of
the shoulder- joint through an aperture in the upper and
anterior part of the fibrous stratum. It extends laterally
between the subscapularis and the medial part of the articular
capsule, medially between the subscapularis and the anterior
surface of the neck of the scapula and the root of the coracoid
process, and it facilitates the movement of the subscapularis
on the front of the head and neck of the scapula.

Dissection. Cut through the subscapularis vertically below
the coracoid process, and detach from its deep surface the bursa,
which lies between it and the scapula and the capsule of the
shoulder. Turn the medial part of the muscle towards the
vertebral border of the scapula, and as you detach it from the
bone note the tendinous intersections by which it is connected
with the ridges on the costal surface of the scapula. Note also
the anastomosis between branches of the subscapular and trans-
verse scapular arteries which ramify on its deep surface. Turn
the lateral portion towards the humerus, detaching it from the
lateral part of the front of the capsule of the shoulder to which
it is adherent, and verify its attachment to the lesser tubercle of
the humerus and to the bone immediately distal to the tubercle.
Do not fail to notice that, as it crosses the shoulder- joint to its
insertion, it lies behind the coraco-brachialis and the short head
of the biceps.

Divide the supraspinatus medial to the coracoid process.
Turn the medial part towards the vertebral border of the scapula
and verify its attachment to the spine and to the dorsal surface
of the scapula, and dissect out the branches of the transverse
scapular artery and the suprascapular nerve which pass to its
deep surface. Turn the lateral part towards the humerus,
forcing it beneath the coraco-acromial arch, and as you do that
avoid injury to the transverse scapular vessels and the supra-
scapular nerve which lie beneath it. Note that as the tendon
of the muscle crosses the top of the shoulder- joint it is firmly
attached to the capsule before it reaches its insertion into the
superior facet on the greater tubercle of the humerus. Divide
the infraspinatus medial to the lateral border of the spine of
the scapula. Verify the attachment of the medial part to the
inferior surface of the spine and the dorsal surface of the body
of the scapula, dissecting out the vessels and nerves from its
deep surface. Follow the lateral part to its insertion into the
middle facet on the greater tubercle of the humerus. and, as the
muscle is displaced, take care not to injure the transverse scapular



SHOULDER SCAPULAR REGION 89

vessels, the suprascapular nerve, and the circumflex scapular
vessels which lie between it and the bone. Occasionally there
is a small bursa between it and the posterior surface of the
capsule of the shoulder- joint which communicates with the
cavity of the joint.

Divide the teres minor where the circumflex scapular artery
passes between it and the posterior surface of the axillary border
of the scapula, and verify its origin from the scapula and its
insertion into the inferior facet on the greater tubercle of the
humerus, and to the ridge which descends from the tubercle.

When the infraspinatus and teres minor have been reflected,
look for the inferior transverse ligament of the scapula. It is
a band of fascia which passes from the lateral border of the
spine of the scapula to the posterior border of the glenoid fossa,
arching across the great scapular notch. It protects the infra-
spinous branch of the transverse scapular artery and the supra-
scapular nerve as they pass behind the neck of the scapula from
the supra- to the infraspinous fossa.

Now clean the transverse scapular vessels, and the supra-
scapular nerve and the circumflex scapulae branch of the sub-
scapular artery. Commence with the transverse scapular
artery as it lies medial to the coracoid process, and the supra-
scapular nerve which accompanies it. The artery lies on the
superior transverse ligament of the scapula, immediately medial
to the coracoid process. The nerve passes through the notch
on the superior border of the scapula beneath the ligament.
Follow the artery and nerve behind the neck of the scapula into
the infraspinous fossa, and note that both pass between the neck
of the scapula and the inferior transverse ligament. Then



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