I. ABNORMAL CONDITIONS, TILE RESULT OF ACCIDENT.
Fractures and Imrations. — Simple frac tures of the bones of the hand are seldom followed by any notable deformity ; but lux ations of these bones require from us some attention here.
Lunation of the bones qf the carpus.—The bones of the carpus are united to each other so solidly, and their movements seem so limited, that, without experience, we should be dis posed to pronounce luxation of any of these bones impossible; nevertheless, the head of the os magnum may be dislocated from the cavity formed for it by the scaphoid and semi lunar bones. The first range of the bones of the carpus is articulated with the bones of the second range in such a manner that slight gliding movements of flexion and extension of the hand are permitted, which augment a little the movements of flexion and extension of the hand upon the forearm, and add some what, as Cruveilhier says, to the grace of the movements of this portion of the upper ex treinity. In flexion, the head of the os mag num, which is somewhat inclined backwards, raises up the thin capsule which surrounds its articulation, and, if this movement be carried very far, the capsule and accessory fibres which support the bone posteriorly are broken, and the os magnum escapes from the cavity in which it is naturally placed ; the dislocation cannot be called complete, yet the os magnum passes somewhat the level of the posterior surface of the other bones of the carpus. The accident is more common in women than in men, no doubt because the ligaments are weaker and the bones enjoy greater motion in the former than in the latter; the luxation backwards of the os magnum, the only one which can occur, is always the result of a forced and violent flexion of the wrist, such, for example, as a fall on the back of the hand would produce.
We recognize the luxation of the os mag num by the history of the accident, and by the deformity produced. We perceive a hard cir cumscribed tumour which has suddenly ap peared on the back of the hand in the situation which corresponds to the head of the bone. This tumour becomes more prominent when the hand is flexed, and diminishes when it is extended ; we can make it disappear entirely by a slight compression. This luxatinn causes but little inconvenience, but the head of the os magnum always remains more salient when the hand is flexed, and forms a tumour more or less marked according to the extent of the displacement.
We can easily reduce this luxation by extending the hand, or by exercising a slight pressure on the head of the os magnum ; but, although it is easy to make the bone resume its position in the cavity formed for it by the scaphoid and semilunar bones, it is very dif ficult to maintain it there, and the inconve nience and deformity resulting from the luxation are so trivial that few persons will submit with patience to the means usually recommended.
Luxation of the bones of the metacarpus. Luxation of the metacarpal bone of the thumb. The carpal head of the metacarpal bone of the thumb, notwithstanding the range of motion it enjoys, is rarely dislocated. Sir A. Cooper, in his extensive experience, has seen but one spe cies of this accident, viz. luxation of the meta carpal bone of the thumb upon the os trapezium, inwards. " in the cases I have seen of this accident," says Sir Astley, " the metacarpal bone has been thrown inwards between the tra pezium and the root of the metacarpal bone of the forefinger; it forms a protuberance towards the palm of the hand; the thumb is bent back wards, and cannot be brought towards the little finger : considerable pain and swelling are pro duced by this accident." Luxation of the carpal head of the meta carpal bone of the thumb backwards. Some surgeons seem to doubt that the metacarpal bone of the thumb is capable of being dis located in any other direction than that in wards; but the following case is given on the highly respectable authority of the experienced Boyer. Madame De la p_____ luxated the metacarpal bone of her left thumb backwards on the dorsum of the trapezium by falling on the external or radial border of her hand ; the luxation was at first mistaken. When Boyer saw it six months after the accident, the su perior extremity of the metacarpal bone of the thumb formed posteriorly a very remarkable prominence on the trapezium, and this bone and the phalanges of the thumb were inclined towards the palm of the hand. On pressing posteriorly on the prominence formed by the superior extremity of the dislocated bone, it could be made to resume its natural place and the prominence disappeared ; so long as the pressure was continued, the bone retained its place and the thumb enjoyed its natural powers of flexion and extension ; but as soon as the pressure was remitted, the bone became dis placed anew, and the movements of the thumb impossible. The lady was unwilling to sub mit to any treatment, and the condition of the joint remained unaltered. These luxations of the metacarpal bone of the thumb, whether backwards or inwards, must be rare, as the causes which are calculated to produce them must act through the first phalanx of the thumb, which, it is manifest, will be much more dis posed to yield than the metacarpal bone.