27. Luxations of the fore-arm have, oftentimes, a great disposition
to occur anew, after having been reduced, whether they be recent, or
of long standing. Extension readily dislodges the olecranon and the
radius, and replaces them perfectly in their natural situation; but if
any thing interrupt them, the displacement is sometimes immediately
renewed: suppose the parts even remaining in contact, the slightest
motion may derange this contact, and give rise to a necessity for a
new reduction, more difficult, oftentimes, than the first. Hence it is
always prudent to employ a retentive apparatus for some time.
28. But, on what principle and for what purpose ought it to be applied?
The motions communicated to the fore-arm by external bodies, but, more
particularly, the action of the muscles inserted in the bones that have
been reduced, are here the causes of their displacement. Hence, 1st,
to render the limb immoveable; 2dly, to push the articular ends of
the bones in a direction opposite to that in which they are drawn by
the muscles, and have a tendency to be displaced: such is the twofold
indication of the bandage; an indication not fulfilled by the kind of
bandage and the sling which Petit proposed, and which leave the arm
free to move, and the muscles free to act.
29. Desault employed the following apparatus: 1st, The arm and fore-arm
are first covered by oblique turns of a roller, intended both to
protect them from the impression of splints, and to diminish the power
and action of the muscles, by the pressure made on them: 2dly, Behind
the olecranon is to be placed a thick compress, designed to retain
it downwards, and which must be secured by a strong splint, situated
behind, and curved at the elbow, to accommodate it to the flexion of
the fore-arm: 3dly, On the sides are placed two other splints, chiefly
necessary in lateral luxations: 4thly, The whole is to be secured by
the remaining part of the roller, by which the arm and fore-arm are
already covered.
In this bandage, the immobility of the arm is secured by the splints,
while the olecranon is pushed by the compress, in a direction the
reverse of that of its displacement. But these circumstances constitute
the double indication that was to be fulfilled (28).
30. The period at which these means may be dispensed with, is
undetermined. It belongs to the surgeon to examine and ascertain,
when the natural connexions of the joint are sufficiently confirmed.
Then motions, at first gentle, are to be impressed on the limb;
being afterwards gradually increased, they remove by degrees that
stiffness, which usually follows a dislocation, particularly an old
one. But if it has existed too long, to give the limb motion, is then
the only resource: the new attachments or adhesions, contracted by
the articulating surfaces in their displaced state, render reduction
impracticable. We must then confine ourselves merely to increasing the
extent of the motions, which the displaced fore-arm is yet capable of
performing.
31. There is, in general, all other things being favourable, a hope of
accomplishing the reduction, till the end of the second month after the
accident. Desault succeeded in it, at even a later period. What trouble
or hardship is it, at last, to try extension? Should no other end be
gained, but merely to bring the bones nearer to their natural cavities
or situations, even without actually replacing them, this will aid
their movements, the extent of which is inversely proportioned to their
distance from these cavities.