13. To reduce a luxation, is, in general, to make the bone re-enter
its cavity, by retracing, or returning along, the same route which
it followed in escaping from it. Now, in a forward luxation, the
displacement is from behind forward, in an upward one from below
upward, in an inward or backward one from before backward, but, in each
of the three, it is more particularly from without inward. In the first
case, therefore it is backward, in the second, forward, in the third
downward, but, in each of the three, more particularly outward, that
the powers for producing extension must be directed.
14. Hence the method generally employed by most practitioners,
recommended by almost every author who has written on the subject,
adopted by Petit, Duverney, Heister, &c. and which consists in
placing the knee between the shoulders of the patient, as a point of
resistance, by the aid of which the shoulders may be drawn backward,
fulfils only half of the indication of cure; because at the time
that the humeral extremity is drawn backward, it is not directed
sufficiently outward.
Hence a difficulty of replacing the bone sometimes occurs, a difficulty
always removed, when, pursuant to the method employed by Desault in
fractures of the clavicle (see Desault’s method), the arm is made to
serve as a lever of the first kind, to carry backward and outward, the
head of the bone, which is displaced in the opposite directions, when
the luxation is forward. This method possesses the advantage, not
only of giving the powers of extension a proper direction, but also of
increasing them to a degree even beyond what is necessary for effecting
a reduction, by removing them further from the resisting force. Hence
it is unnecessary to adopt any particular measures for restoring and
preserving the form of the part, as the extension is alone sufficient
for that purpose.
These principles, evidently applicable in effecting a reduction, are
still more strikingly so in the means destined for retaining it. Let
us apply what I have just said, to a case of dislocation in a forward
direction. It will be easy to transfer it afterwards to the other kinds
of luxation.
§ V.