6. In longitudinal fractures the diagnosis is always accompanied with
more or less difficulty, because the extensor muscles, drawing by
their contractions the two fragments equally upwards, and the inferior
ligament holding them equally down, tend to keep them in apposition,
and to prevent them from separating. Sometimes also the ligamentous
production which covers the rotula, remains entire and serves to keep
the fragments together. It will be necessary, therefore, should the
existence of such a fracture be suspected, to move the two sides of the
rotula in opposite directions, by pressing them to the right and to the
left, in order to arrive at certainty on the subject. Should a wound
exist, as is oftentimes the case (5) the diagnosis is less difficult.
7. If the division be transverse, the diagnosis becomes then as
plain and easy, as it is difficult and obscure in cases where it is
longitudinal. In such a case, a considerable separation or space
exists between the two fragments, sensible to the touch, when the
hand is placed on the knee. In this separation, the fragments are not
displaced by the same means. The superior fragment being attached to
the extensors, is drawn upwards with great force by these muscles, the
action of which the rotula no longer resists. The lower fragment, on
the other hand, being attached only to the inferior ligament, is not
moved by any muscle, and cannot be displaced in any other way than by
the motions of the leg with which it is still connected.
8. Hence it follows, 1st, that, in a state of extension, the separation
is the least possible, because it is then produced on the part of
the superior fragment only; 2dly, that in a state of flexion it is
greatest, because then both fragments concur alike in producing it;
3dly, that it may be increased or diminished by varying the degrees of
flexion.
9. This fracture is further characterized by the following
circumstances, namely, a practicability of moving the fragments
transversely in opposite directions, and of producing, by that means,
some degree of crepitation, provided they be first brought close
together; by the pain which accompanies these motions; by the swelling
common to every kind of fracture of the rotula, and which, if very
great, may involve the other signs in more or less uncertainty; by
a difficulty of standing; and an almost entire loss of the power
of walking, in consequence of the extensors being no longer able to
communicate motion to the leg, unless when the fracture exists very low
down, near to the inferior ligament.
10. The touch will always discover in what part of the bone the
fracture is situated, which, if it be oblique, will partake more
or less of the characters of the longitudinal or the transverse,
accordingly as it approaches to the one or the other.
§ IV.