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removed but the cutaneous nerves are still present, and
the dissector should revise them before proceeding with the
dissection.

On the medial side are branches of the intercosto-brachial
nerve ; lateral to them lies the posterior brachial cutaneous
branch of the radial nerve, and, along the lateral margin of
the arm, is the dorsal cutaneous nerve of the forearm, also
a branch of the radial nerve.

Dissection. Make a vertical incision through the deep fascia
as far as the olecranon of the ulna, and a transverse incision
across the olecranon from one epicondyle to the other, taking
care not to injure the dorsal cutaneous nerve of the forearm.
Reflect the flaps of deep fascia to their respective sides until
their continuity with the medial and lateral intermuscular septa
respectively is demonstrated. As the medial flap is reflected,
avoid injury to the ulnar nerve which descends towards the
medial epicondyle on the medial head of the triceps. It is
accompanied by the superior ulnar collateral artery. When
the reflection of the flaps is completed clean the triceps muscle
and define carefully its attachments to the scapula, to the humerus,
and to the ulna.

M. Triceps Brachii. The triceps muscle occupies the
entire posterior osteo-fascial compartment of the arm. It
arises by a long head from the scapula, and by two shorter
heads, lateral and medial, from the humerus. The fleshy
fibres of the three heads join a common tendon, which is
inserted into the proximal surface of the olecranon of the



DORSUM OF THE ARM



Teres minor
Infraspinatus



Triceps (lateral i
head)



Deltoid 4i :



Brachialis -
Sulcus for radial



ulna. The superficial
part of the muscle is, for
the most part, formed by
the long head and the
lateral head of the muscle.
The medial head is deeply
placed ; only a very small
portion of it appears super-
ficially, in the distal part
of the arm, on each side
of the common tendon of
insertion.

The long head of the
triceps arises, by a flattened
tendon, from the rough
triangular impression on
the upper part of the
axillary border and the
lower aspect of the neck
of the scapula in the in-
terval between the teres
minor and subscapularis
muscles (Fig. 24, p. 46).

The two humeral heads
take origin from the pos-
terior aspect of the hum-
erus ; and if it is borne in
mind that no fibres arise
from the sulcus for the
radial nerve and that the
groove intervenes between
the origins of the two
heads, their relations will
be easily understood. The
dissector should provide
himself with a humerus,
and, having first identified
the sulcus for the radial

nerve, proceed to map out

. FIG. 48. Dorsal aspect of the Humerus

the areas Of attachment with Attachments of Muscles mapped out.

of the humeral heads of

the triceps as they are exhibited in the dissected part.

VOL. I 8



Medial epi-
condyle



"| Origin
J-ofex-
J tensors



Anconaeus



ii4 THE SUPERIOR EXTREMITY

The lateral head of the triceps arises from the lateral and
posterior aspect of the body of the humerus, proximal to the
sulcus for the radial nerve. It takes origin, by short tendin-
ous fibres, along a line which passes distally from the insertion
of the teres minor to the proximal border of the sulcus for
the radial nerve. But it derives fibres also from a strong
fascial bridge or arch which is thrown over the groove so as
to give protection to the profunda brachii artery and the
radial nerve. The strength and position of this arch can be
estimated by thrusting the handle of the knife distally and
laterally in the sulcus for the radial nerve, and along the
course of the nerve and artery, under the lateral head of
the triceps. By its distal end the arch is connected with the
lateral intermuscular septum.

The medial head of the triceps is placed distal to the sulcus
for the radial nerve. Its proximal end, which is narrow and
pointed, lies close to the distal end of the insertion of the
teres major. The origin gradually widens as the sulcus for
the radial nerve passes towards the lateral border of the
humerus, and in the distal third of the arm it covers the
posterior surface of the humerus from the lateral to the medial
border (Fig. 48). It springs also from the posterior surface
of the medial intermuscular septum, and from the distal part
of the corresponding surface of the lateral intermuscular
septum. The medial head of the triceps, therefore, has very
much the same origin from the posterior surface of the bone
that the brachialis has from the anterior aspect.

The dissector should now study the common tendon of
insertion of the triceps. The long and the lateral heads end
in a broad, flat tendon, which is inserted into the back part
of the proximal surface of the olecranon, and at the same
time gives off, on the lateral side, a strong expansion to the
fascia of the forearm as it covers the anconseus muscle. The
short fleshy fibres of the medial head are, for the most part,
inserted into the deep surface of the common tendon, but a
considerable number find direct attachment to the olecranon,
whilst a few of the deepest fibres are inserted into the loose
posterior part of the capsule of the elbow-joint. The latter
fibres have been described as a separate muscle under the
name of subanconceus. The triceps is supplied by branches
from the radial nerve. It is an extensor of the elbow-joint
and an adductor of the arm.



DORSUM OF THE ARM 115

Dissection. In order that the radial nerve and the profunda
brachii artery may be fully exposed, the lateral head of the
triceps must be divided. Thrust the handle of a knife along the
sulcus for the radial nerve, and under the muscle. The handle
will then give the direction in which the lateral head of the
triceps should be severed. Beyond cleaning the nerve and its
branches, and the profunda brachii artery, as they lie in the
groove, no further dissection is necessary.

Nervus Radialis (O.T. Musculo-Spiral Nerve). The radial
nerve is the direct continuation of the posterior cord of the
brachial plexus after it has furnished, in the axilla, the two
subscapular nerves, the thoraco-dorsal nerve, and the axillary
nerve. In the first instance, the radial nerve proceeds distally,
behind the distal part of the axillary artery and the proximal
part of the brachial artery. It soon leaves the anterior aspect
of the arm, however, and, inclining backwards, with the pro-
funda brachii artery, enters the interval between the long and
the medial heads of the triceps, and reaches the sulcus for the
radial nerve. In that it passes round the back of the body of
the humerus, under cover of the lateral head of the triceps, and
on the lateral side of the limb it pierces the lateral intermuscular
septum and passes into the anterior compartment of the arm,
where it has already been dissected. There it lies deeply, in
the interval between the brachialis on the medial side and
the brachio-radialis and extensor carpi radialis longus on the
lateral side, and it ends at the level of the lateral epicondyle of
the humerus by dividing into two terminal branches, viz., the
ramus superficial (O.T. radial) and the ramus profundus
(O.T. posterior interosseous). The radial nerve presents,
therefore, very different relations as it is traced from its origin
to its termination: (i) between the subscapularis, latissimus
dorsi, teres major, and long head of the triceps, which support
it behind, and the axillary and brachial arteries which are
placed in front of it ; (2) between the long and the medial heads
of the triceps ; (3) in the sulcus for the radial nerve, between
the bone and the lateral head of the triceps ; (4) in the
interval between the brachialis on the medial side, and the
brachio-radialis and extensor carpi radialis longus on the
lateral side.

The branches which proceed from the radial nerve are
muscular, cutaneous, articular and terminal.

The cutaneous branches are two in number, and have already
been traced. They are (i) the posterior cutaneous nerve of



u6



THE SUPERIOR EXTREMITY



the arm, and (2) and (3) the dorsal cutaneous nerves of the
forearm.

The muscular branches are distributed to the three heads

Spine of scapula Suprascapular nerve
Transverse scapular artery | |



Infraspinatus
Circumflex, scap.
artery (O.T.)
clorsalis scap.
Teres minor

Subscapularis



Teres major

Triang. space
Quadrangular space

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




Brachial artery
Triceps, lateral head

N. to triceps, medial head - -



Ulnar nerve
Medial epicondyle -

N. to flex. carp. uln.

Olecranon J



Subacromial bursa

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

. Deltoid

Axillary nerve
(sup. branch)
Axillary nerve
(inf. branch)



Lateral brachial
cutaneous nerve



- Lateral head of triceps

Radial nerve (O.T.
musculo-spiral)



Ant. branch of profunda
artery of arm



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

Brachialis



Lateral epicondyle
Recurrent inter-
osseous artery

Anconseus
Ext. dig. comm.
and dig. quint.
Ext. carpi ulnaris



FiG. 49. 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.



of the triceps, to the anconaeus, to the lateral fibres of the
brachialis, to the brachio-radialis, and to the extensor carpi
radialis longus. The branches to the three last-named
muscles spring from the trunk of the nerve after it has



DORSUM OF THE ARM 117

pierced the lateral intermuscular septum. One of the
branches to the medial head of the triceps is a long slender
nerve, termed the ulnar collateral nerve, on account of its
association with the ulnar nerve in the arm. The branch to
the anconaeus is a long slender twig which passes through
the substance of the medial head of the triceps on its way
to the anconaeus (Fig. 49).

The terminal branches are the superficial ramus, which
is a purely cutaneous nerve, and the deep ramus, which is
continued into the dorsal part of the forearm as the dorsal
interosseous nerve, and is distributed to the muscles on
the dorsal aspect of the forearm, and to the radio-carpal
joint. These nerves will be followed later.

Arteria Profunda Brachii. The profunda brachii artery
has been already seen taking origin from the brachial trunk,
about 25 mm. distal to the lower margin of the teres major
muscle. It accompanies the radial nerve, and its relations
to the three heads of the triceps and the sulcus for the
radial nerve are exactly the same as those of the nerve.
Before it reaches the lateral intermuscular septum, it ends
by dividing into two terminal branches an anterior and a
posterior. The anterior and smaller branch accompanies the
radial nerve through the septum, and follows it distally to the
anterior aspect of the lateral epicondyle of the humerus,
where it anastomoses with the radial recurrent artery. The
posterior, larger branch descends on the posterior surface of
the lateral intermuscular septum, and anastomoses on the
back of the lateral epicondyle of the humerus with the
interosseous recurrent artery.

The branches which proceed from the profunda brachii
artery are distributed chiefly to the three heads of the triceps
muscle. One twig runs proximally between the long and
lateral heads of the muscle, and anastomoses with the posterior
circumflex artery of the humerus. In that way a link is
established between the axillary and brachial systems of
branches.

Dissection. The ulnar nerve, with the superior ulnar col-
lateral artery, and the slender ulnar collateral nerve, can now
be satisfactorily followed, as they proceed distally upon the
posterior aspect of the medial intermuscular septum. They are
covered by a thin layer of fleshy fibres belonging to the medial
head of the triceps. The posterior branch of the inferior ulnar
collateral artery, after it has pierced the medial septum, should



n8 THE SUPERIOR EXTREMITY

also be dissected out. As a rule, a transverse anastomosing
twig passes between that vessel and the posterior terminal part
of the profunda brachii artery. It lies upon the posterior aspect
of the humerus, immediately proximal to the elbow-joint, and
can be exposed by dividing the triceps muscle a short distance
proximal to the olecranon. At the same time the fleshy fibres
of the medial head of the triceps, which are inserted into the
posterior part of the capsule of the elbow- joint, and constitute
the subanconceus muscle, should be examined. Lastly, raise
the distal piece of the triceps from the elbow-joint, and look
for a small bursa mucosa between the deep surface of the triceps
tendon and the anterior part of the proximal aspect of the
olecranon. Then revise the medial and lateral intermuscular
septa which are now fully exposed.

The Medial and Lateral Intermuscular Septa. The

medial intermuscular septum is the stronger ; it separates the
medial part of the medial head of the triceps from the
brachialis, gives attachment to both the muscles, and extends,
as a strong membrane, from the medial epicondyle to the in-
sertion of the coraco-brachialis. Then it becomes less distinct,
but it can be traced proximally to the lower part of the medial
lip of the intertubercular sulcus. At the level of the in-
sertion of the coraco-brachialis it is pierced by the ulnar nerve
and the superior ulnar collateral artery, which descend posterior
to it to the medial epicondyle. A short distance above the
medial epicondyle it is pierced by the posterior branch of
the inferior ulnar collateral artery.

The lateral intermuscular septum is weaker than the
medial. It extends from the lateral epicondyle to the in-
sertion of the deltoid muscle, with which it blends, and it
separates the lateral part of the medial head of the triceps,
which is attached to its posterior surface, from the upper
lateral part of the brachialis, the brachio-radialis and the
extensor carpi radialis longus which spring from its anterior
surface. At the junction of the middle and distal thirds
of the arm it is pierced by the radial nerve and the anterior
branch of the profunda artery, which afterwards descend
along its anterior aspect, between the brachialis medially and
the brachio-radialis and the extensor carpi radialis longus
laterally.



SHOULDER-JOINT



119



ARTICULATIO HUMERI (SHOULDER-JOINT).

After the structures situated in the arm have been examined
the dissection of the shoulder-joint should be commenced, in
order that the ligaments may be examined before they have
become too dry.

The shoulder-joint belongs to the enarthrodial or ball and




Supraspinatus



Scapula



Subscapularis



Serratus anterior



Capsule of joint

Humerus
Deltoid

Fold of capsule
of joint



Posterior circumflex artery
of humerus and axillary
(O.T. circumflex) nerve



Teres major

Radial (O.T. musculo-spiral)
nerve



Latissimus dorsi



FIG. 50. Frontal or vertical transverse section through the Left
Shoulder-joint. (Viewed from behind. )

socket sub-group of the diarthrodial or completely movable
joints. The socket is formed by the glenoid cavity of the
scapula and the ball is the spheroidal head of the humerus.

In no joint in the body are the movements so free and so
varied in their character as in the shoulder-joint. This is
rendered necessary by the many functions which are performed
by the upper limb. Freedom of movement is provided for in
two ways (i) by the large size of the head of the humerus,
in comparison with the small dimensions and shallow character



120



THE SUPERIOR EXTREMITY



of the glenoid cavity ; (2) by the great laxity of the ligament-
ous structures which connect the humerus with the scapula.
These provisions for allowing an extensive range of movement
at this articulation might, at first sight, lead one to doubt the
security of the joint. Its strength certainly does not lie in
the adaptation of the bony surfaces to one another, nor in
the strength of its ligaments. It lies (i) in the powerful
muscles by which it is closely surrounded; (2) in the over-
hanging coraco-acromial arch, which forms, as it were, a



Coraco-acromial
ligament

Coracoid process /



Acromion



Coraco-humeral
ligament



Communication
between joint-
cavity and sub-
scapular bursa



Capsule of joint




FIG. 51. Shoulder-joint as seen from the front.

secondary socket for the head of the humerus, and effectually
prevents any displacement in an upward direction ; and (3)
in atmospheric pressure, which exercises a powerful influence
in keeping the opposed surfaces in contact with each other.

On all aspects, except over a small area below, the loose,
ligamentous capsule which envelops the shoulder-joint is
supported by muscles, the tendons of which are more or less
intimately connected with it. Above, it is covered by the
supraspinatus ; behind, the infraspinatus and teres minor are
applied to it ; in front is the subscapularis. Below, the
capsule is to a certain extent unsupported by muscles, and



SHOULDER-JOINT 1 2 1

there it is prolonged downwards, in the form of a fold, in the
ordinary dependent position of the limb (Figs. 50, 53). When,
however, the arm is abducted, the fold is obliterated, and the
head of the bone rests upon the inferior part of the capsule,
which now receives partial support from two muscles which
are stretched under it, viz. the long head of the triceps and
the teres major. Still, this must be regarded as the weakest
part of the joint, and consequently dislocation of the head of
the humerus downwards into the axilla, through the inferior
part of the capsule, is an occurrence of considerable frequency.
When the dislocation occurs, the axillary vessels and nerve
which lie close to the capsule may be injured.

Dissection. The capsuie of the shoulder- joint has already
been exposed by the reflection of the muscles immediately
adjacent to its anterior, superior, and posterior aspects, and
the bursa between its anterior surface and the subscapularis
has been examined. To expose the capsule more fully, untie
the axillary vessels and nerves from the coracoid process ; cut
through the tendon of origin of the coraco-brachialis and the
short head of the biceps brachii and displace the muscles down-
wards. Cut through the teres major about its middle and the
long head of the triceps about 25 mm. (one inch) distal to its
origin and turn both muscles aside. Turn aside the divided sub-
scapularis, supraspinatus, infraspinatus and teres minor muscles.
Note that whilst the supraspinatus, infraspinatus and teres
minor completely cover the upper and posterior part of the
capsule, a small interval exists between the anterior border of
the supraspinatus and the upper border of the subscapularis.
In that interval the subacromial bursa is in relation with the
capsule, and occasionally, but very rarely, a communication
exists between the cavity of the bursa and the cavity of the
joint. Re-examine the bursa which lies between the sub-
scapularis and the front of the capsule, and note that its aperture
of communication with the joint is situated near the root of
the coracoid process. Thoroughly clean the outer surface of the
capsule. Note the laxity of the capsule, and define its attach-
ments to the margin of the glenoid cavity and to the lateral
border of the root of the coracoid process.

The ligaments of the shoulder-joint are :

Capsula articularis

Lig. coracohumerale.
Lig. glenohumerale superius.
medium.

inferius.

Labrum glenoidale.

Capsula Articularis. The fibrous stratum of the articular
capsule is a fairly dense and strong membrane which envelops



122



THE SUPERIOR EXTREMITY



the articulation on all sides. It is attached to the scapula
around the margin of the glenoid cavity, but is attached
directly to the bone only at the upper part ; elsewhere it
blends with the outer surface of the labrum glenoidale, which
is attached to the margin of the cavity for the purpose of
increasing its depth. Laterally the capsule is attached to



Coraco-humeral ligament



Superior gleno
humeral ligamen

Middle gleno-
humeral ligament



Inferior gleno-
humeral ligament



N. musculo-cutaneus




M. biceps brachii



Infraspinatus bursa



Labrum glenoidale



N. ulnaris| |

N. cutaneus antibrachii medialis | |

A. axillaris |

V. axillaris



'. \ '. N. axillaris
|| A. et v. circ. humeri
| N. radialis
N. medianus



FIG. 52. Semi-diagrammatic representation of a dissection of a Sagittal
section through the Right Shoulder. The subscapular bursa is shown
connected with the cavity of the joint between the superior and middle
gleno-humeral bands of the articular capsule.

the anatomical neck of the humerus and to the transverse
ligament of the humerus, which bridges across the top of the
intertubercular sulcus from the greater to the lesser tubercle.
The attachment of the upper part of the fibrous stratum to
the humerus is quite close to the articular surface of the
head, but the attachment of the lower part is some distance
( 1 2-1 6 mm.) from the articular surface; consequently a con-
siderable part of the lower portion of the anatomical neck is
inside the fibrous stratum of the capsule and is covered by



SHOULDER-JOINT 123

the synovial stratum (Fig. 53). This cannot be seen until
the capsule has been opened.

The fibrous stratum of the capsule is not complete at all
points. Its continuity is always broken by two and some-
times by three or four apertures, and where the lateral margin
of the fibrous stratum is attached to the transverse ligament
of the humerus there is an aperture below the margin.
Prolongations of the synovial stratum are protruded through



Capsula articularis



Transverse

humeral -

ligament

Tuberculum

minus

Tuberculum
majus



Posterior humeral
circumflex vessels
and axillary nerve




"~<^ *- Labrum glenoidale
'



r^vr - -Capsula articularis
- r N. axillaris



^\ Posterior humeral
'circumflex vessels



FIG. 53. Diagram of a Frontal Section of the Right Shoulder

all the apertures which are present. The largest opening is
in the antero- medial part near the root of the coracoid
process, and the prolongation of the synovial stratum which
passes through it forms the subscapular bursa, which separates
the subscapularis from the front of the capsule and from the
front of the neck of the scapula. The dissector should note
carefully the size and the position of this opening because
the head of the humerus is occasionally driven through it,
instead of through the lower part of the capsule, when the
joint is dislocated.



i2 4 THE SUPERIOR EXTREMITY

The second constant aperture is that below the transverse
ligament of the humerus at the top of the intertubercular
sulcus. It is much smaller than the aperture in front, and
through it the tendon of the long head of the biceps, which
springs from the apex of the glenoid cavity, emerges from the
joint. The tendon is enclosed in a tubular prolongation of
the synovial stratum which surrounds it and lines the inter-
tubercular sulcus (Fig. 53). It is not often that a third
opening is found in the fibrous stratum. It is situated, when
present, in the postero- lateral part of the capsule and
permits the protrusion of the synovial stratum to form a bursa
under cover of the infraspinatus muscle (Fig. 52). Still
more rarely the subacromial bursa communicates with the
cavity of the joint through an opening which is situated
between the supraspinatus and subscapularis muscles.

In four situations the fibrous stratum of the capsule is
thickened by longitudinal bands of fibres which pass from
the scapula to the humerus. One of the thickenings, the
coraco-humeral ligament, can be seen from the exterior; the
other three, the gleno-humeral ligaments^ are thickenings of
the inner surface of the fibrous stratum of the capsule and
can be seen only from the interior of the joint.

Ligamentum Coracohumerale. The coraco-humeral liga-
ment is placed upon the superior aspect of the joint. It is
a broad band of great strength, which is more or less com-
pletely incorporated with the capsule. Proximally, it is fixed
to the root and lateral border of the coracoid process of the
scapula, and it passes thence, obliquely distally and laterally,
to gain attachment to the two tubercles of the humerus, and
to the transverse humeral ligament, which forms a strong arch
over the upper part of the intertubercular sulcus.

Ligamenta Glenohumeralia. There are three gleno-



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