SURGERY. 
758 
In the dislocation downwards, the arm is lengthened, 
the elbow separated from the side, and the forearm is ex¬ 
tended in consequence of the tension of the triceps muscle; 
the arm cannot be put near the body, nor the forearm be 
bent without pain; the acromion projects more than natural; 
a vacancy is distinguishable under this process; the fulness 
of the shoulder is lost, the deltoid muscle not being now 
duly supported by the head of the bone; the arm cannot 
be raised to a level with the acromion; and, lastly, the 
swelling caused by the head of the bone may be plainly 
felt in the axilla. 
The dislocation into the axilla is usually the consequence 
of external violence, combined with a powerful sudden con¬ 
traction of the pectoralis major, latissimus dorsi, and teres 
major muscles. The accident frequently happens from falls, 
in which the elbow strikes against the ground, while sepa¬ 
rated from the side of the trunk. When a person falls side¬ 
ways, he naturally puts out his arm in order to hinder his 
head from striking the ground. In this situation, the weight 
of the body is upon the shoulder-joint; and, as, at the same 
instant, the pectoralis major, latissimus dorsi, and teres 
major, act strongly and pull the arm forcibly towards the 
chest, they make the head of the humerus slip out of its cavity, 
because the elbow rests upon the ground as a fixed point, 
while the upper end of the bone is the moveable one. 
On many occasions, however, the head of the humerus 
is dislocated downwards, not exactly in the foregoing manner, 
in which the elbow is fixed against the ground, or some 
other surface with which it comes into contact in the fall: 
thus, an ostler, in putting on a bridle, often has his arm 
dislocated by the horse suddenly throwing up its head, and 
striking the under part of the elbow, while raised from the 
side of the body. In this last instance, the lower end of the 
humerus is violently thrown up, and its head propelled 
down into the axilla, the movement being like that of a 
lever. 
In the dislocation downwards, the tendon of the subsca- 
pularis is ruptured. The tendons of the supra and infra-spi- 
natus muscles may likewise be torn from the bone, and with 
them a shell of the head of the humerus may be detached. 
Writers do not agree in their accounts of what becomes of 
the long head of the biceps. 
The dislocation next in frequency to that downwards, 
is the case, in which the head of the humerus breaks 
through the internal, portion of the capsular ligament, 
and passes immediately under the great pectoral muscle, 
constituting the luxation inwards. Thus, when the arm 
is raised so as to form nearly a right angle with the trunk, 
and the elbow is inclined backwards, a fall on the side may 
drive the head of the humerus through the inner part of 
the capsular ligament. In this kind of accident, the re¬ 
sistance of the ground operates very obliquely upon the 
elbow, and, consequently, a great part of the violence is 
lost. 
In the dislocation inwards, the length of the limb is not 
much altered, and, if changed at all, it is somewhat dimi¬ 
nished. The forearm is not fixed in the half-bent position, 
because the muscles are less stretched, than in the luxation 
downwards. The direction of the arm is downwards and 
backwards. The flatness of the shoulder, and the depression 
formed by the glenoid cavity, are not very obvious, ex¬ 
cepting towards the back of the joint. The head of the hu¬ 
merus seems to be as much under the coracoid process, as in 
the axilla, and that it is situated more towards the median 
line, than the-neck of the scapula, is quite manifest. The 
movement, in which the elbow is carried forwards, is 
attended with the greatest difficulty, and that, in which 
the limb is inclined in the opposite direction, the least 
painful. 
Many surgical authors believe, that the head of the hume¬ 
rus cannot be dislocated backwards. But, a few cases, in 
which the head of the humerus was dislocated backwards, 
under the spine of the scapula, may now be found in the 
records of the profession. Thus, M. Fizeau has detailed one 
rare instance, which was also witnessed by Professor Boyer. 
In the case here alluded to, the bone, after its reduction, was 
observed to have a remarkable tendency to slip out of its 
place again: and, in one case dissected by Delpech, the 
head of the bone lay under the infraspinatus muscle, in im¬ 
mediate contact with the scapula. 
Paralysis of the arm is sometimes the consequence of a 
dislocation downwards, or inwards, and is supposed to pro¬ 
ceed from injury done to the axillary-plexus of nerves by the 
head of the humerus. This paralytic affection may remain 
for ever incurable, may get well spontaneously, or yield to 
stimulating liniments, blisters, issues, or the moxa. A still 
more frequent ill effect of luxations of the shoulder is para¬ 
lysis of the deltoid muscle; an infirmity ascribed by some 
writers to laceration of the circumflex nerve. 
To reduce these dislocations, the trunk is usually fixed by 
means of a sheet, or table cloth, put round the chest, and the 
ends of which are either held by one or more assistants, or 
fastened to a post, or any other immoveable point. The 
scapula may be kept back by a napkin folded longitudinally, 
placed over the shoulder and tied to the sheet. 
Whether the extension be made at the wrist, or at the 
lower end of the humerus, the soft parts should be protected 
from the effects of the pressure with flannel, or a few turns 
of a wet calico roller, over which the longitudinally folded 
table-cloth or sheet, or the quilted leather of the multiplied 
pulley employed for making the extension, may be placed. 
When the dislocation is downwards, the extension should 
be made directly outwards, and the arm afterwards inclined 
downwards, and a little forwards, until it touches the side. 
The surgeon must be careful to guide the movement, by 
which the assistants change the direction of the extension ; 
and, in proportion as the wrist is inclined downwards, he is 
to press with his abdomen on the external side of the elbow, 
while, with both his hands applied to the inner and upper 
part of the humerus, he inclines the head of the bone up¬ 
wards and a little backwards. The success of these manoeu¬ 
vres will depend in a great measure upon the extension and 
counter-extension being well proportioned to each other, 
and regulated so as to promote the movements, which it is 
the duty of the surgeon to communicate to the limb during 
the operation. 
When the dislocation is inwards, Boyer recommends the 
extension to be made horizontally outwards and a little back¬ 
wards; and the limb is afterwards to be inclined forwards 
and downwards, until it is brought obliquely over the front 
of the chest. But, previously to the arrival of the member in 
the last position, the operator is to press with one of his hands 
upon the back of the elbow, and with the other, upon the 
front and upper part of the humerus, in order to push the 
head of the bone outwards, and direct it into the glenoid 
cavity of the scapula. 
Were the case originally a dislocation downwards, or in¬ 
wards, but the head of the bone now in a state of conse¬ 
cutive, or secondary displacement inwards, or upwards, the 
aim of the surgeon should be first to bring the head of the 
humerus down into the axilla, and then to guide it over the 
lower part of the brim of the glenoid cavity, where the cap¬ 
sular ligament was torn at the moment of the accident. 
Whether the extending force to be applied to the wrist, 
or just above the elbow, the position and inclination of the 
humerus during the operation should be the same. In short, 
while the extension and counter-extension are kept up by 
the assistants, the limb, or the humerus itsejf, is to be employ¬ 
ed by the surgeon as a lever for moving the head of the bone 
gradually towards the glenoid cavity. In Boyer’s account, 
we see, that this principle is acted upon, the elbow and wrist 
being inclined in particular directions, while the surgeon 
forms with his hands a kind of fulcrum, or active resistance 
at the upper part of the humerus. When the extension has 
been performed in a certain degree, many surgeons make a 
still more efficient fulcrum by directing one of the assistants 
to draw up the upper portion of the humerus with a towel 
placed under the member just on the outside of the axilla. 
Others execute the same purpose by letting the ends of the 
towel, or table-cloth, be fastened over the back part of their 
necks. 
