The Surgical Dissection Of The Axillary And Brachial Regions Displaying The Relative Order Of Their Contained Parts

Sources: Surgical Anatomy

All surgical regions have only artificial boundaries; and these, as

might be expected, do not express the same meaning while viewed from

more points than one. These very boundaries themselves, being moveable

parts, must accordingly influence the relative position of the

structures which they bound, and thus either include within or exclude

from the particular region those structures wholly or in part which are

said to e proper to it. Of this kind of conventional surgical boundary

the moveable clavicle is an example; and the bloodvessels which it

overarches manifest consequently neither termination nor origin except

artificially from the fixed position which the bone, R, assumes, as in

Plate 11, or c*, Plate 12. In this position of the arm in relation to

the trunk, the subclavian artery, B, terminates at the point where,

properly speaking, it first takes its name; and from this point to the

posterior fold of the axilla formed by the latissimus dorsi muscle, O,

Plate 11, N, Plate 12, and the anterior fold formed by the great

pectoral muscle, K, Plate 11, I, Plate 12, the continuation of the

subclavian artery is named axillary. From the posterior fold of the

axilla, O P, Plate 11, to the bend of the elbow, the same main vessels

take the name of brachial.



When the axillary space is cut into from the forepart through the great

pectoral muscle, H K, Plate 11, and beneath this through the lesser

pectoral muscle, L I, together with the fascial processes which invest

these muscles anteriorly and posteriorly, the main bloodvessels and

nerves which traverse this space are displayed, holding in general that

relative position which they exhibit in Plate 11. These vessels, with

their accompanying nerves, will be seen continued from those of the

neck; and thus may be attained in one view a comparative estimate of the

cervical and axillary regions, together with their line of union beneath

the clavicle, c*, Plate 12, R, Plate 11, which serves to divide them

surgically.



In the neck, the subclavian artery, B, Plate 11, is seen to be separated

from the subclavian vein, A, by the breadth of the anterior scalenus

muscle, D, as the vessels arch over the first rib, F. In this region of

the course of the vessels, the brachial plexus of nerves, C, ranges

along the outer border of the artery, B, and is separated by the artery

from the vein, A, as all three structures pass beneath the clavicle, R,

and the subclavius muscle, E. From this latter point the vessels and

nerves take the name axillary, and in this axillary region the relative

position of the nerves and vessels to each other and to the adjacent

organs is somewhat changed. For now in the axillary region the vein, a,

is in direct contact with the artery, b, on the forepart and somewhat to

the inner side of which the vein lies; while the nerves, D, d, Plate 12,

embrace the artery in a mesh or plexus of chords, from which it is often

difficult to extricate it, for the purpose of ligaturing, in the dead

subject, much less the living. The axillary plexus of nerves well merits

the name, for I have not found it in any two bodies assuming a similar

order or arrangement. Perhaps the order in which branches spring from

the brachial plexus that is most constantly met with is the one

represented at D, Plate 12, where we find, on the outer border of B, the

axillary artery, a nervous chord, d, giving off a thoracic branch to

pass behind H, the lesser pectoral muscle, while the main chord itself,

d, soon divides into two branches, one the musculo-cutaneous, e, which

pierces G, the coraco-brachialis muscle, and the other which forms one

of the roots of the median nerve, h. Following that order of the nerves

as they are shown in Plate 12, they may be enumerated from without

inwards as follows:--the external or musculo-cutaneous, e; the two roots

of the median, h; the ulnar, f; the musculo-spiral, g; the circumflex,

i; close to which are seen the origins of the internal cutaneous, the

nerve of Wrisberg, some thoracic branches, and posteriorly the

subscapular nerve not seen in this view of the parts.



The branches which come off from the axillary artery are very variable

both as to number and place of origin, but in general will be found

certain branches which answer to the names thoracic, subscapular, and

circumflex. These vessels, together with numerous smaller arteries,

appear to be confined to no fixed point of origin, and on this account

the place of election for passing a ligature around the main axillary

artery sufficiently removed from collateral branches must be always

doubtful. The subscapular artery, Q, Plate 12, is perhaps of all the

other branches that one which manifests the most permanent character;

its point of origin being in general opposite the interval between the

latissimus and sub-scapular muscles, but I have seen it arise from all

parts of the axillary main trunk. If it be required to give, in a

history of the arteries, a full account of all the deviations from the

so-called normal type to which these lesser branches here and elsewhere

are subject, such account can scarcely be said to be called for in this

place.



The form of the axillary space is conical, while the arm is abducted

from the side, and while the osseous and muscular structures remain

entire. The apex of the cone is formed at the root of the neck beneath

the clavicle, R, Plate 11, and the subclavious muscle, E, and between

the coracoid process, L*, of the scapula and the serratus magnus muscle,

as this lies upon the thoracic side; at this apex the subclavian

vessels, A B, enter the axillary space. The base of the cone is below,

looking towards the arm, and is formed in front by the pectoralis major,

K H, and behind by the latissimus dorsi, O, and teres muscles, P,

together with a dense thick fascia; at this base the axillary vessels, a

b, pass out to the arm, and become the brachial vessels, a*b*. The

anterior side of the cone is formed by the great pectoral muscle, H K,

Plate 11, and the lesser pectoral, L I. The inner side is formed by the

serratus magnus muscle, M, Plate 12, on the side of the thorax; the

external side is formed by the scapular and humeral insertion of the

subscapular muscle, the humerus and coraco-brachialis muscle; and the

posterior side is formed by the latissimus dorsi, the teres and body of

the subscapular muscle.



In this axillary region is contained a complicated mass of bloodvessels,

nerves, and lymphatic glands, surrounded by a large quantity of loose

cellular membrane and adipose tissue. All the arterial branches here

found are given off from the axillary artery; and the numerous veins

which accompany these branches enter the axillary vein. Nerves from

other sources besides those of the axillary plexus traverse the axillary

space; such nerves, for example, as those named intercosto-humeral, seen

lying on the latissimus tendon, O, Plate 11. The vein named cephalic, S,

enters the axillary space at that cellular interval occurring between

the clavicular origin of the deltoid muscle, G, and the humeral

attachment of the pectoralis major, H, which interval marks the place of

incision for tying the axillary artery.



The general course of the main vessels through the axillary space would

be indicated with sufficient accuracy by a line drawn from the middle of

the clavicle, R R, Plate 11, to the inner border of the biceps muscle,

N. In this direction of the axillary vessels, the coracoid process, L*,

from which arises the tendon of the pectoralis minor muscle, L, is to be

taken as a sure guide to the place of the artery, b, which passes, in

general, close to the inner side of this bony process. Even in the

undissected body the coracoid process may be felt as a fixed resisting

point at that cellular interval between the clavicular attachments of

the deltoid and great pectoral muscles. Whatever necessity shall require

a ligature to be placed around the axillary in preference to the

subclavian artery, must, of course, be determined by the particular

case; but certain it is that the main artery, at the place B, a little

above the clavicle, will always be found freer and more isolated from

its accompanying nerves and vein, and also more easily reached, owing to

its comparatively superficial situation, than when this vessel has

become axillary. The incision required to be made, in order to reach the

axillary artery, b, from the forepart, through the skin, both pectoral

muscles, and different layers of fasciae, must be very deep, especially

in muscular, well-conditioned bodies; and even when the level of the

vessel is gained, it will be found much complicated by its own branches,

some of which overlie it, as also by the plexus of nerves, D, Plate 12,

which embraces it on all sides, while the large axillary vein, a, Plate

11, nearly conceals it in front. This vein in Plate 11 is drawn somewhat

apart from the artery.



Sometimes the axillary artery is double, in consequence of its high

division into brachial branches. But as this peculiarity of premature

division never takes place so high up as where the vessel, B, Plate 11,

overarches the first rib, F, this circumstance should also have some

weight with the operator.



When we view the relative position of the subclavian vessels, A B, Plate

11, to the clavicle, R, we can readily understand why a fracture of the

middle of this bone through that arch which it forms over the vessels,

should interfere with the free circulation of the blood which these

vessels supply to the arm. When the clavicle is severed at its middle,

the natural arch which the bone forms over the vessels and nerves is

lost, and the free moving broken ends of the bone will be acted on in

opposing directions by the various muscles attached to its sternal and

scapular extremities. The outer fragment follows more freely than the

inner piece the action of the muscles; but, most of all, the weight of

the unsupported shoulder and arm causes the displacement to which the

outer fragment is liable. The subclavius muscle, E, like the pronator

quadratus muscle of the forearm, serves rather to further the

displacement of the broken ends of the bone than to hold them in situ.



If the head of the humerus be dislocated forwards beneath L, Plate 11,

the coracoid attachment of the pectoralis minor muscle, it must press

out of their proper place and put tensely upon the stretch the axillary

vessels and plexus of nerves. So large and resistent a body as the head

of the humerus displaced forwards, and taking the natural position of

these vessels and nerves, will accordingly be attended with other

symptoms--such as obstructed circulation and pain or partial paralysis,

besides those physical signs by which we distinguish the presence of it

as a new body in its abnormal situation.



When the main vessels and nerves pass from the axillary space to the

inner side of the arm, they become comparatively superficial in this

latter situation. The inner border of the biceps muscle is taken as a

guide to the place of the brachial artery for the whole extent of its

course in the arm. In plate 11, the artery, b*, is seen in company with

the median nerve, which lies on its fore part, and with the veins called

comites winding round it and passing with it and the nerve beneath the

fascia which encases in a fold of itself all three structures in a

common sheath. Though the axillary vein is in close contact with the

axillary artery and nerves, yet the basilic vein, d*, the most

considerable of those vessels which form the axillary vein, is separated

from the brachial artery by the fascia. The basilic vein, however,

overlies the brachial artery to its inner side, and is most commonly

attended by the internal cutaneous nerve, seen lying upon it in Plate

11, as also by that other cutaneous branch of the brachial plexus, named

the nerve of Wrisberg. If a longitudinal incision in the course of the

brachial artery be made (avoiding the basilic vein) through the

integument down to the fascia of the arm, and the latter structure be

slit open on the director, the artery will be exposed, having the median

nerve lying on its outer side in the upper third of the arm, and passing

to its inner side towards the bend of the elbow, as at b*, Plate 12. The

superior and inferior profunda arteries, seen springing above and below

the point b, Plate 12, are those vessels of most importance which are

given off from the brachial artery, but the situation of their origin is

very various. The ulnar nerve, f, lies close to the inner side of the

main arterial trunk, as this latter leaves the axilla, but from this

place to the inner condyle, Q, behind which the ulnar nerve passes into

the forearm, the nerve and artery become gradually more and more

separated from each other in their descent. The musculo-spiral nerve, g,

winds under the brachial artery at the middle of the arm, but as this

nerve passes deep between the short and long heads of the triceps

muscle, P, and behind the humerus to gain the outer aspect of the limb,

a little care will suffice for avoiding the inclusion of it in the

ligature.



The brachial artery may be so effectually compressed by the fingers on

the tourniquet, against the humerus in any part of its course through

the arm, as to stop pulsation at the wrist.



The tourniquet is a less manageable and not more certain compressor of

the arterial trunk than is the hand of an intelligent assistant. At

every region of the course of an artery where the tourniquet is

applicable, a sufficient compression by the hand is also attainable with

greater ease to the patient; and the hand may compress the vessel at

certain regions where the tourniquet would be of little or no use, or

attended with inconvenience, as in the locality of the subclavian

artery, passing over the first rib, or the femoral artery, passing over

the pubic bone, or the carotid vessels in the neighbourhood of the

trachea, as they lie on the fore part of the cervical spinal column.





DESCRIPTION OF PLATES 11 & 12.



PLATE 11.



A. Subclavian vein, crossed by a branch of the brachial plexus given to

the subclavius muscle; a, the axillary vein; a *, the basilic vein,

having the internal cutaneous nerve lying on it.



B. Subclavian artery, lying on F, the first rib; b, the axillary artery;

b *, the brachial artery, accompanied by the median nerve and venae

comites.



C. Brachial plexus of nerves; c*, the median nerve.



D. Anterior scalenus muscle.



E. Subclavius muscle.



F F. First rib.



G. Clavicular attachment of the deltoid muscle.



H. Humeral attachment of the great pectoral muscle.



I. A layer of fascia, encasing the lesser pectoral muscle.



K. Thoracic half of the great pectoral muscle.



L. Coracoid attachment of the lesser pectoral muscle.



L*. Coracoid process of the scapula.



M. Coraco-brachialis muscle.



N. Biceps muscle.



O. Tendon of the latissimus dorsi muscle, crossed by the

intercosto-humeral nerves.



P. Teres major muscle, on which and O is seen lying Wrisberg's nerve.



Q. Brachial fascia, investing the triceps muscle. .



R R. Scapular and sternal ends of the clavicle.



S. Cephalic vein, coursing between the deltoid and pectoral muscles, to

enter at their cellular interval into the axillary vein beneath E, the

subclavius muscle.












PLATE 12.



A. Axillary vein, cut and tied; a, the basilic vein, cut.



B. Axillary artery; b, brachial artery, in the upper part of its course,

having h, the median nerve, lying rather to its outer side; b*, the

artery in the lower part of its course, with the median nerve to its

inner side.



C. Subclavius muscle.



C*. Clavicle.



D. Axillary plexus of nerves, of which d is a branch on the coracoid

border of the axillary artery; e, the musculo-cutaneous nerve, piercing

the coraco-brachialis muscle; f, the ulnar nerve; g, musculo-spiral

nerve; h, the median nerve; i, the circumflex nerve.



E. Humeral part of the great pectoral muscle.



F. Biceps muscle.



G. Coraco-brachialis muscle.



H. Thoracic half of the lesser pectoral muscle.



I. Thoracic half of the greater pectoral muscle.



K. Coracoid attachment of the lesser pectoral muscle.



K*. Coracoid process of the scapula.



L. Lymphatic glands.



M. Serratus magnus muscle.



N. Latissimus dorsi muscle.



O. Teres major muscle.



P. Long head of triceps muscle.



Q. Inner condyle of humerus.