1. There is no part of the scapula more liable to fractures than the
acromion. Being but slightly covered by the soft parts, this insulated
kind of appendix has not, in all positions of the humerus, a solid
point of support. A strong muscular force oftentimes acts on it with
great energy. Being large in front, it presents in that direction
a considerable surface to receive the action of external bodies.
Whence it follows, that if it is not oftentimes broken, this is to be
attributed, not so much to its natural disposition, as to the position
which it generally assumes in falls.
2. The fracture, which is almost always transverse, is sometimes at the
summit, and sometimes at the base of this apophysis, and is usually
produced by a violent shock from a body falling on the shoulder, by a
blow received on that part, &c.
3. But in whatever place it occurs, it greatly resembles a fracture of
the humeral extremity of the clavicle, of which the acromion appears
like a continuation. There is accordingly a strong analogy between the
phenomena, the consequences, and the modes of treating these two kinds
of fractures.
4. This accident is characterized, 1st, By a severe pain experienced
by the patient, at the place of the fracture. This pain is increased
by the elevation of the arm, which, generally hangs motionless down
along the side. 2dly, If the humerus be removed from the trunk, the
hand being at the same time placed on the acromion, the extremity of
this apophysis is felt sinking downward, creating thereby an evident
depression in the part. 3dly, Generally, the two fragments lose, of
their own accord, their relative position; and unless the precaution
about to be mentioned be used, their displacement becomes manifest,
being produced by the weight of the arm, and the contractions of the
deltoid muscle. 4thly, The head is inclined to the affected side.
§ II.