20. On looking into the causes of that displacement (15 ... 18), so
common in fractures of the clavicle, it appears that in almost every
case, the external extremity of the humeral fragment is drawn, by a
double power, downward, inward, and forward. Hence it follows, 1st.
That the resistance opposed to this power, by the means used for
the purpose of reduction, and the retentive apparatus subsequently
employed, ought to be directed upward, backward, and outward,
these directions being the reverse of those in which the powers of
displacement act: 2dly. That, in as much as these powers, viz. the
weight of the parts and the action of the muscles, are in constant
operation, and, besides, as the motions of the arm are continually
disturbing the fragments of the bone, the apparatus ought to be equally
constant in its action, and should keep up, without any remission, the
effect produced, at first, by the means of reduction. This principle is
applicable to every case, and ought to be the standard of comparison,
for determining the advantages or disadvantages of different bandages,
and processes for the reduction of fractures of the clavicle.
21. But we are not to suppose, that these processes have heretofore
manifested an exact application of this rule. Hippocrates directed
to press the arm close to the ribs, and at the same time to push it
upwards, in such a manner, as to make the shoulder appear as sharp
and pointed as possible. Hence his precept, to lay the patient down
on his back, the back being supported by some projecting body, and
then to press the shoulders backward; hence again, when the humeral
fragment is drawn inward, his advice to press the elbow close to the
breast. This twofold expedient was attended with great difficulties,
even under the direction of the father of medicine. Celsus only copied
Hippocrates, adding nothing whatever to his mode of practice. Paul of
Egina, more judicious in this case, conceived, that for the purpose
of forcing the shoulder outward, and rendering it, agreeably to the
idea of Hippocrates, very projecting and sharp, it would be advisable
to place the fulcrum or point of support, not in the middle of the
back, but under the arm-pit. A woollen ball was employed by him for
this purpose, a practice which would, at once, have carried the art
near to perfection, if, after being employed to reduce the fragments,
this process had been continued for the purpose of retaining them in
apposition.
22. No new method distinguished the surgery of the Arabians. It is
necessary to come down to the time of Guy of Chauliac, before we
meet with the method which is almost universally adopted at present,
and which consists in placing between the shoulders, the knee of an
assistant, whose hands are to be employed in drawing them forcibly
backwards. But it is evident that this is only doing, while the patient
is in an erect position, what Hippocrates did, after having laid him
with his back on a projecting body. Here, then, the art seems to
have degenerated, after the time of Paul of Egina: and, indeed, on
comparing this process with the general principles already established
(20), it will be immediately perceived, that the powers of replacement
do not here act in an opposite direction to those of displacement.
Hence the difficulties of reduction, the time spent in the operation,
and the sufferings by which it was sure to be accompanied. The
fragments were brought together, it is true; but it was only by varying
the movements, and changing their direction, that the point of contact
was ultimately found.
23. Desault conceived, in the year 1768, that to reduce, in the most
effectual manner, a fracture of the clavicle, it was necessary not only
to push the shoulder backward and upward, as was commonly done, but,
above all, to force it outward, and that the power destined to draw it
in this latter direction, ought to act horizontally, according to the
course of the clavicle, in the same way, as, in an oblique fracture of
the thigh or leg, the extension for replacing the fragments is made in
the direction of the bone.
24. As the union of the humerus to the clavicle, by means of the
scapula, communicates to the one the movements of the other, it is
easy, by placing the ball used by Paul of Egina, under the arm-pit, to
convert the arm into a lever of the first kind.[2]
[2] That form of lever, where the weight to be raised or the
resistance to be overcome, is at one end, the force at the other,
and the fulcrum or prop between them. This form is well represented
by the handle of a pump, where the piston is the weight or
resistance, the hand of the drawer of water the force, and the iron
pin, on which the handle works, the fulcrum or prop.