28. The diagnosis of luxations of the humerus, presents in general, but
few difficulties.
Whatever may be the mode or seat of the displacement, there always
exists, as Hippocrates has observed, a manifest depression under the
acromion, which exhibits a prominence more perceptible than in its
natural state. The motions of the part are almost all accompanied with
pain; the greater part of them are impracticable; all of them very much
confined. The arm cannot move, without a synchronous motion of the
shoulder, because, the articulation being no longer able to exercise
its functions, these two parts constitute, so to speak, but one body.
29. Besides these signs, which characterize generally every species
of luxation of the humerus, each species is marked by certain others
peculiar to itself. If the displacement be downward, the arm is a
little longer than in its natural state; it can be moved gently
outwards; but an acute pain is the inevitable consequence of moving
it forward or backward. The elbow is more or less removed from the
axis of the body, by the action of the deltoid, the long portion of
the biceps, and the supra-spinatus muscles, which, being unnaturally
stretched, contract themselves and tend to carry the bone outward. The
pains which result from this position, force the patient, in order to
relieve them, to lean towards the affected side, to keep the fore-arm
half-bent, the elbow resting on the hip, so that the arm, finding a
place of support, may be freed from the painful movements, and from
the disagreeable sensation produced by its own weight. From this
attitude alone, was Desault in the habit of discovering luxations in
a downward direction, and was rarely mistaken in his diagnosis. It is
thus, that, in a fracture of the clavicle, the inclined position of the
patient is oftentimes, at first sight, characteristic of the nature of
his complaint. Beneath the hollow of the arm-pit there always exists
a protuberance more or less perceptible, formed by the head of the
humerus.
30. To the general signs of luxations of the humerus (28), that in an
inward direction adds the following: the elbow, being separated from
the trunk of the body, is carried a little backward; the humerus seems
to direct itself towards the middle of the clavicle; motions backward
are not very painful, while those in a forward direction are extremely
so; under the pectoralis major a manifest protuberance exists; the arm
is but little longer than in a natural state; the attitude is the same
as in the preceding case.
31. Should a luxation in an outward direction occur, it would be
particularly characterized by a hard tumour under the spine of the
scapula, by the direction of the elbow forward, by its separation from
the trunk, and by a little increase in the length of the arm.
A protuberance behind the clavicle, an obvious shortening of the arm,
together with its direction, would plainly disclose a luxation upwards.
32. The signs discriminative of the nature of luxations of the humerus,
are not always accompanied by the same degree of certainty as those
that announce merely its existence. Thus, nothing is more difficult
than to determine when a luxation inward is primitive, and when it is
consecutive, the same phenomena being common to both. Nothing but an
exact history of the disease, stating the order in which the phenomena
have succeeded each other, can throw light on this point, which is the
more interesting and important, as, according to the one or the other
state of things, the processes of reduction ought to vary. In the first
case, the head re-enters its natural cavity by a short route; whereas,
in the second, it arrives there by a much longer one.
If, as Petit pretended, there exist luxations backward, sometimes
primitive, and sometimes consecutive, the same remark may be applied to
them with equal propriety.
33. Certain signs, common to luxations of the humerus, fractures of its
neck, and dislocations of the scapulary extremity of the clavicle,
might here create some uncertainty, if in the one, the absence of a
tumour under the arm-pit, and of a depression under the acromion,
did not prevent a mistake, which Hippocrates declared to be easily
committed, into which, according to Galen, the masters of the art of
wrestling fell, and which Pare cautions us to avoid; and if, in the
other, the appearances proper to a fracture, did not prevent a mistake
which would be serious in its consequences, and which sometimes results
from the direction of the humerus, and the kind of protuberance formed
in the arm-pit, by the end of the inferior fragment. (_See Fracture of
the neck of the humerus_).
§ V.