Luxations of the lower extremity of the ulna.
— There are two species of this luxation of the.lower extremity of the ulna. In one, the ulna escapes from the sigmoid cavity of the radius in passing backwards ; in the other, it is by the anterior part of the articulation that the displacement occurs. Luxation of the inferior extremity of the ulna backwards is the more frequent of the two ; that forwards must be rare, says Boyer, for I have seen but one example of it, and Dupuytren mentions that he has met with but two. Sir A. Cooper refers to only one case of dislocation of the lower extremity of the ulna. In this case the bone was thrown backwards.
Luxation of the lower extremity of the ulna at the wrist-joint, backwards. — Desault has published the history of a washerwoman who had a luxation of the inferior extremity of the ulna backwards, in consequence of the violent and sudden pronation in which the wrist had been forced into while she was in the act of wringing clothes.
In this luxation, backwards, the forearm and hand are in a state of forced pronation, and the two bones are strongly crossed, forming with each other a very acute angle of decus sation ; the inferior part of the forearm is much narrower than in the normal state ; the forearm, the hand, and the fingers, are main tained in a state of moderate flexion, but fixed ; the tendons of the flexor muscles of the finger are, as it were, matted together into a single fasciculus, displaced inwards, and form a sensible saliency upon the ulnar border of the radius.
What strikes one most, in looking at the back part of the wrist, is the very manifest projection on the dorsum of the region, formed by the lower extremity of the ulna, which rises so much above the level of the back of the hand.
Luxation forwards. — Desault, Boyer, and Dupuytren have each adverted to this dislo cation, in which we observe an oblique cross ing of the bones of the forearm ; the fingers are semiflexed, and there is a remarkable narrowness of the inferior part of the limb. The forearm and hand are fixed into a state of supination, the saliency of the ulna is per ceived in front, the tendons of the flexor muscles are pushed outwards towards the radius, and the inferior part of the ulna, instead of being parallel to that of the radius, as in the normal state, is oblique from above downwards, from within outwards, and from behind forwards.
Boyer gives the following remarkable ex ample of this accident. In 1791, a woman of a strong constitution, and of a spare, though muscular frame, while in a state of intoxica tion, looking at two persons playing "domino" in a cafe, in Paris, foolishly ventured some advice to the players, who besought her not to interrupt them. She, however, thought proper to persist in giving her gratuitous advice, until at last one of the players, a strong and vigorous man, got up in a very angry mood, seized her violently by the right hand and endeavoured to push her out of the room. In this movement her hand and fore arm were carried suddenly into a state of preternatural supination. Immediately the woman experienced the most acute pain, and cried out that her wrist was broken. The pain, the deformity, and the impossi bility she experienced of executing the or dinary movements of the forearm, made her fear that she was most seriously injured' "I was called in," says Boyer, "instantly, and I found the patient complaining of most acute suffering, having the forearm flexed, the hand fixed in a forced state of supination. The least alert to communicate a movement of pronation caused the patient the most acute aggravation of her sufferings. The ulna formed a very sensible prominence anteriorly, and this bone, instead of being parallel to the radius, formed with it an acute angle, crossing its direction somewhat, and passing down wards, forwards, and outwards." All these symptoms taken together left no doubt on the mind of Boyer, but that the case he had to deal with was one of luxation forwards of the lower extremity of the ulna. It was not until after having tried thrice unsuccessfully that at length he succeeded in reducing the dislocation.