(From luxo, to dislocate ) . Dislocatio; aberratio; eluxatio; emotio; elongatio; ecptoma; ecclysis; lygismos; delocatio; exarthrema; olis-thema; a luxation, or dislocation. A slight dislocation is termed diacinema; parathrema; an incomplete one, contortio or decllnatio. Dr. Cullen places it in the class locales., and order ectopia, which he defines a bone removed from its seat in the joints. To which may be added, "causing an impediment to voluntary motion:" a compound luxation is when a wound, fracture, or a violent contusion, attends.

Luxations from internal causes are thus distinguished: 1. The limb is so relaxed, that it may be easily moved in any direction. 2. A cavity about the joint, and a hollowness between the bones, may be felt with the fingers. 3. The dislocated bone, if replaced, soon escapes spontaneously, from the weakness of the ligament and muscles. 4. The dislocated limb is frequently longer than the sound one, and attended with neither pain, inflammation, nor convulsion. 5. It generally happens to the upper part of the femur, or humerus, and sometimes to the articulation of the foot with the tibia. When owing to an external injury, the diagnostics are uncertain, when the joint is swollen from a violent contusion or distortion. In such cases we must suspend our judgment; and could we decide until the inflammation and tumour were abated, attempts towards a reduction would be improper. The more readily to discover a luxation, it may be observed, that when the head of a bone is removed out of its place, the other and will be distorted in an opposite direction. A tu-our is also generally observable where the dislocated part of the bone is seated, and an hollowness from whence it receded; though, in a muscular part, the tumour and cavity are not easily perceived.

In consequence of a luxation, the symptoms differ as the parts affected are different: in general, there is an immobility, or a defective motion of the dislocated limb; a distraction of some muscles, and a relaxation of others; violent pain and inflammatory tension of the joint; a torpor of the subjacent parts; a compression of the neighbouring vessels, from whence an atrophy, gangrene, pain, oedematous. swellings, or convulsions, may ensue.

Compound luxations are more dangerous than compound fractures. Boerhaave observes, that the worst luxation is produced by a solution or a separation of the epiphysis from the body of the bone. In general, the prognostic should be cautious, but the difficulties and uncertainties are greater in proportion to the distance of the dislocated bone from its proper place; the figure of the luxated limb; the part in which the luxation is seated; the parts pressed, or intercepted; the pain, inflammation, or other violent symptoms.

It will be, obvious that a partial dislocation may be more easily reduced than a more complete one; and a fracture attending will render the cure more doubtful: indeed, if a fracture near the joint is accompanied will: a luxation, a stiff joint must be expected, if the limb can be saved. After a limb has been some time luxated, it forms a socket for itself, and its old cavitv i -usually filled with a fatty substance, but not with inspissated synovia, as has been asserted. The attempt is, in this case, hopeless, and generally unnecessary; for the limb, in its new position, retains some degree of motion, and is perhaps more serviceable than it would be after the inflammation which would arise from unsuccessful attempts. In delicate constitutions, and advanced periods of life, luxations are more easily reduced than in the young and strong, whose muscles resist very powerfully.

The object of the surgeon is to reduce the luxation, an operation called embole; and to retain the limb in its proper situation. If inflammation or tumour is considerable, they must be removed before a reduction is attempted. Mr. Pott justly observes, that the resistance of the muscles is the only cause of the difficulty of reducing luxations; that much force is never required, provided the muscles are relaxed by aproperposition of the limb; and that in recent cases, at least, the capsular ligament will rarely, if ever, impede. The extension should be gradual and continued, until the dislocated bone is on a level with the Cavity from whence it receded. If the head does not then spontaneously return, it must be assisted by pressure, employing the dislocated bone as a lever. Dr. Hunter seems to think that a rupture of the capsular ligament is a greater impediment to reduction than the contraction of the muscles. It cannot be denied, that, in violent luxations, this ligament is often broken; but this is by no means an universal consequence. Both recommend gentle extension, and to avoid violence.

When the external parts are violently bruised, general and topical bleeding, saturnine applications, etc. arc necessary. The limb must be laid in an easy posture, and the tumour allowed to subside before the real nature of the case can be understood, or any attempt made to reduce the displaced bone. The great impediment, we have said, is the strong power of the muscles, which not only resists the extension, but often throws the bone into a different cavity from that to which we wished to direct it. When a fracture accompanies dislocated bones, a firm callus must be allowed to form before the reduction is attempted; but, if the fracture be at a distance from the dislocation, or in very small bones, where the power of the muscles is inconsiderable, this precaution may be neglected.

After the luxation is reduced, leeches and saturnine applications should be employed, the pains moderated by opium, and fever diminished by cooling medicines, laxatives, and a low regimen in every respect. The most perfect tranquillity is absolutely necessary.

I.Calcisluxatioossis. Luxation of the heel bone. Whether luxated inward or outward, a cavity on one side, and a tumour on the other, discovers it; and the pain is severe. The treatment is the same as is directed when the bones of the hand are luxated.