5. When this obstacle to reduction has been removed, it is then very readily effected, and that without the process of conformation. Indeed that process is almost always unnecessary. For what purpose should it be employed? Is it to increase the effect of extension, and thus disengage the head of the bone from the place which it accidentally occupies? In this point of view, it is nothing but a very feeble force, added to a very powerful one, which receives from it, therefore, but little assistance: it is much better, if necessary, to augment the extending forces themselves. Is it to push the head of the bone into its cavity, after the extensions have dislodged it? It is to the muscles, and not to the efforts of the surgeon, that the performance of this office belongs. Indeed, the surgeon must act altogether in the dark in this respect, as he cannot possibly ascertain the precise point where the opening in the capsule exists: he may, therefore, even push the head of the bone against a sound part of the capsule, and thus himself create an obstacle to the reduction, which he is attempting to favour.
6. The muscles, on the other hand, by their contraction, naturally draw the head of the bone into its place, because the direction of their fibres is such as obliges them to do it. The great art of managing luxations, then, consists, in ascertaining clearly the obstacles that prevent reduction, in removing them, and, then, committing the rest to extension, and the powers of nature properly directed.
MEMOIR XII.
ON SPONTANEOUS LUXATIONS OF THE OS FEMORIS.
1. Our modern treatises on diseases are little else than fabrics artfully constructed of materials confusedly scattered through the writings of the ancients. Many of those materials oftentimes escape our notice, and we find them only, after practice has disclosed them to us, in the chambers of the sick. Thus, Hippocrates had an accurate knowledge of spontaneous luxations of the os femoris, and has even left an aphorism expressly on that subject. Yet this disease appeared to be unknown to the physicians who came after him, till John Louis Petit, having met with it in his practice, drew the attention of practitioners to it, by a memoir respecting it, published among those of the Academy of Sciences, in the year 1722.
2. The history of this affection, which was considered afterwards, ex professo, in his course on diseases of the bones, has been sanctioned by the assent of all practitioners, to whom it has since very frequently occurred, and who have generally admitted as Louis observes, the doctrine of Petit, respecting the cause on which it seems to depend.
3. Experience bears witness, that usually a fall on the great trochanter, more rarely on the knee, or the sole of the foot, precedes it, and has doubtless some share in producing it. But what is the nature of the primary affection which, rising immediately from this occasional cause, becomes the immediate cause of the luxation? Petit, and with him the practitioners of the present day, have conceived, that the different parts of the joint, being irritated and contused, pour out, in consequence of the injury received, a superabundant quantity of synovial fluid, which, not being absorbed with the same rapidity, accumulates in the articular cavity, distends the capsule, and, by degrees, forces the head of the os femoris from its natural cavity. Hence astringent and tonic remedies, with alum, spirit of wine, &c. are directed to be applied externally to the upper part of the diseased thigh.