9. But whatever may be the causes or kind of the luxation, its
diagnosis is always easy. If it be forward, the direction of the stroke
which the shoulder has received, furnishes, at first, some ground of
suspicion. The accident is certainly known by the appearance of a hard
and unnatural protuberance in front of the sternum, and behind the
extremity of the sterno-cleido-mastoideus muscle, by the existence of
a sensible depression or hollow at the joint, and by the situation of
the shoulder, which is pushed further backward, and is less projecting
and more approximated to the trunk, than in its natural state. Add
to these, a difficulty in performing motions in a forward direction,
which, when somewhat forced, reduce, in proportion as they are
accomplished, the size of the protuberance formed by the displaced end.
The head is always inclined towards the side where the luxation exists;
an attitude which relieves the painful drawing or tension produced
in the sterno-mastoideus muscle, by the humeral extremity pushing it
forward.
10. A protuberance over the superior edge of the sternum, a difficulty
in raising the shoulder, the pain which results from attempting such
a motion, the diminution of the protuberance which it occasions,
the absence of the sternal extremity from its natural cavity, the
approximation of the shoulder to the thorax, and its depression and
diminished projection, compared to its usual state, afford evidence of
a luxation upwards.
11. A luxation inward or backward, would be characterized by a
projection of the shoulder exteriorly, by a difficulty in performing
motions in a backward direction, by the alarming effects, which, as
Petit remarks, the compression of the trachea would doubtless produce,
and by a depression or hollow at the joint, more perceptible here than
in the two preceding cases.
12. These appearances will be more or less striking, accordingly as
the membranes, lacerated or only distended, offer a greater or less
resistance.
§ IV.