2. These fractures, like those of the condyls of the os femoris, are
rarely the effect of a counter-stroke. They are almost always produced
by the immediate action of external bodies; such, for instance, as a
fall on the joint of the arm; the wheel of a carriage passing over this
part, &c. &c.
3. Whatever may be their cause, they generally occur in such a manner,
that a longitudinal division separates the condyls from each other,
and, extending upwards to a greater or less distance, is terminated by
another transverse or oblique division, which passes through the whole
thickness of the body of the bone, so that there are three fragments,
and two fractures.
4. Sometimes the division is simple; in which case, being directed
outwards or inwards, it crosses the lower end of the humerus, obliquely
from above downwards, and terminating at the joint, separates but one
of the condyls from the body of the bone, leaving the other adhering to
it.
5. In the first case (3), there is more deformity at the broken
extremity of the humerus; and the mobility is also greater. If the
fingers, placed before or behind, press on the limb in the direction
of the longitudinal fracture, the two condyls will be separated from
each other, the one yielding in an outward, and the other in an inward
direction, leaving a fissure or opening between them. The part at the
same time expands in breadth. Thus, the two condyls of the os femoris,
are seen to separate from each other when in a similar fracture,
pressure is made on the rotula. The fore-arm is almost constantly in
a state of pronation. When we take hold of one of the condyls in each
hand, and endeavour to make them move in opposite directions, they can
be brought alternately forward or backward: and, if their surfaces
touch, a manifest crepitation is heard.
6. In the second case (4), the condyls cannot be so easily separated
from each other; but it is always practicable by taking hold of that
one which is divided from the body of the bone, and moving it from
before backward, to produce a crepitation, which is a sufficient proof
that a fracture exists. In a case where the external condyl was alone
separated, Desault found the limb in a constant state of supination, a
position to be attributed, without doubt, to the muscles attached to
this condyl.
7. An acute pain, the almost inevitable effect of the flexion or
extension of the fore-arm, the habitual semi-flexion of the limb, a
tumefaction of it sometimes supervening, and a swelling more or less
considerable, around the joint, are symptoms which accompany both modes
of division (3 and 4). The fracture may further be rendered complicated
by means of wounds, splinters, &c. when the blow has been very severe,
or when a pointed fragment has made its way through the surrounding
soft parts, &c.
§ II.