2. Fractures of the rotula may, in general, assume any direction,
transverse, longitudinal, or oblique: but the first kind occurs in
practice much more frequently than the others; and so great indeed
is the disproportion, that it has almost exclusively attracted the
attention of authors, in the numerous forms of apparatus invented to
retain the fragments.
3. A shattering of the bone, the effect of a violent blow; a contusion;
an echymosis; an effusion of blood into the adjacent soft parts; one
or more wounds of the soft parts, with or without an opening into the
joint; a swelling, the degree of which varies greatly, according to the
state of the fracture, and the disposition of the subject, but which is
constantly present; a double division of the bone, one of which, being
longitudinal, forms an angle with the other, which is transverse; and a
concomitant fracture of the condyls of the os femoris, or of the tibia:
such are the varieties and complications, of which the fracture under
consideration is susceptible.
4. But this fracture may be produced in two modes. 1st, by the
action of external bodies: 2dly, by that of the extensor muscles.
The first mode of division takes place in falls on the knee, or when
a body in motion strikes against it, and, in this case, there is no
counter-stroke, the rotula being too small for such an occurrence,
and always sustaining the fracture where it receives the blow. In the
second, the fall is only subsequent to the fracture, and, as Camper
has well observed, is most frequently the effect of it. For instance,
the line of gravity of the body is, by some cause, removed behind it;
the anterior muscles contract themselves to bring it forward again;
the extensors act on the rotula; it is broken, and a fall ensues.
Again, the leg is suddenly thrown into a state of violent extension;
the extensors act with great force; a fracture is the consequence,
and the patient falls. A soldier once fractured his rotula in kicking
at his serjeant; thus the olecranon, in like manner, has been broken
by throwing a stone. A man, in the Hotel-Dieu, fractured the rotula
of each knee, in the operating room, by means of convulsive motions,
produced by the operation of lithotomy.
5. The action of external bodies, can alone produce a longitudinal
fracture, as when a person falls on a sharp projecting piece of timber:
but this may also produce a transverse fracture. On the other hand,
muscular action can never give rise to any but the latter kind, since
the direction of this fracture is at a right angle with that of the
extensors. A fracture resulting from the action of external bodies, is
oftentimes accompanied by a wound, a contusion, or a shattering of the
part (2); a fracture, arising from muscular action, is always simple,
except as to a swelling around the joint. The latter cause may, instead
of fracturing the rotula, rupture the common tendon of the muscles,
or, what is more common, the inferior ligament. Desault has seen many
examples of this: Petit has also observed several, and Sabatier has
sometimes met with them. External violence seldom produces this double
accident.
§ III.