43. We meet here with the same appearances and state of things, which
constantly occur in fractures of the rotula. The triceps extensor,
finding no longer in the continuity or sound state of the ulna, a
resistance to its contractions, draws upwards the short fragment to
which it adheres, produces between it and the lower one an interval
more or less perceptible, and gives rise to the greater part of the
other characteristic signs of the affection: these are, 1st, An
interval or space between the fragments, corresponding to the posterior
part of the articulation. This interval may be increased at pleasure,
by increasing the flexion of the fore-arm, or by making the patient
contract the triceps muscle, and may be again diminished, by bringing
the arm into a state of extension: 2dly, An inability in the patient to
extend the fore-arm spontaneously, which is the necessary result of the
separation of the triceps from the ulna: 3dly, A constant semiflexion
or half-bent state of the fore-arm, produced by the contractions of
the biceps and brachialis internus muscles, to which no antagonists
are now opposed: 4thly, An elevation, more or less perceptible, of
the olecranon above the condyls, which, on the contrary, rise above
it, when, in a natural state of the parts, the fore-arm is half-bent:
5thly, A facility of moving the upper fragment in every direction,
without communicating any motion to the ulna; 6thly, A peculiar
sensation experienced by the patient, to whom it seems, when he makes
an effort to extend the fore-arm, as if some body or substance were
detached or broken off from his elbow, and carried upwards. The patient
may realize the justness of this sign, by comparing it with what he
feels on attempting to extend the opposite fore-arm, placed in the same
position.
44. If to these signs be added the circumstances which accompany
the accident, the severe pain that is always felt, the crack which
is sometimes heard by the patient, and the possibility of producing
a perceptible crepitation, by rubbing the fragments in contrary
directions, after having first brought them together, it will be
difficult to be mistaken respecting the existence of the fracture,
which indeed the swelling of the part alone can conceal from the
practitioner, if, as sometimes happens, it be considerable. But then,
being soon dispersed, either spontaneously, or by the action of
discutients, it leaves the accident unmasked, accompanied by the signs
just enumerated.
45. To the swelling is oftentimes added, an echymosis more or less
considerable, when the accident has been produced by a fall on the
elbow. But by this, no change is effected in the essential characters,
which are always sufficient to distinguish a fracture from a luxation
backwards, with which it has been sometimes confounded, as appears from
many examples recorded in different works.
§ XV.