PARTICULAR DISLOCATIONS.
Lowerjaw. This bone can only be lux ated forwards, when the condyloid pro cesses advance beyond the eminentin arti culares. In this case the mouth remains open, and cannot be shut; there is pain ; impaired and almost destroyed articula tion and deglutition, &c. One or both condyles may be displaced. To reduce it, the thumbs, well covered, should be intro duced as far backward as possible along the grinding teeth. The surgeon then elevates the front of the bone with his fingers, and the palms of his hands, while he depresses the condyles with his thumbs ; and the latter prominences are thus forced back into the glenoid cavities of the temporal bones.
Dislocations of the head and vertebrae are probably imaginary occurrences, as we know hitherto of no well-attested ex ample of their occurrence.
The os humeri is probably luxated more frequently than any other bone. It may be displaced downwards, forwards, and backwards. In all these cases a vacancy is distinguishable under the acromion, in consequence of the absence .of the head of the humerus from the glenoid cavity of the scapula. The head of the bone forms a preternatural tumour in some situations. The elbow cannot be carried close to the chest, nor can the limb be elevated, without extreme pain, to a line with the acromion. Great pain is caused by the pressure of the head of the bone hi its unnatural position, particularly when it lies in the axilla. Our object is to dislodge the head of the os brachii from its unnatural situation, in order to bring it on a level with the glenoid cavity of the scapula. To accomplish this pur pose, extension must be made ; that is, the limb must be drawn forcibly outwards ; and the bone itself should be made to operate as a lever, which can be best of by the surgeon's knee placed tinder it towards the head, while he depres ses the elbow at the proper time, so as to raise the head towards the glenoid cavity. The patient's body should be fixed, by placing a broad towel round the chest, and tying it to some immoveable point. The extension should be gradual, and kept up unremittingly, which can be best effected by means of pullies. The elbow should be bent, and the extending power applied just above the condyles of the humerus. When the surgeon finds that the head of the bone is drawn out of its unnatural position, he may allow the extension to be remitted, and depress the elbow. The arm should afterwards be kept quietly in a sling, a piece of soap plaster, and a spica bandage, being appli ed to the shoulder.
Elboa.. Dislocations at this joint are very difficult to discover, from the swell ing, which comes on so quickly. The radius may be displaced forwards ; and here the flexion of the elbow is almost entirely destroyed. The ulna may at the same time be driven backwards : it may also be pushed inwards, so as to occupy the place of the radius. All these are easily
reduced, when they are ascertained. Leeches and cold washes should be em ployed afterwards.
Wrist; The distortion consequent on a displacement of the carpus is so consid erable, that the nature of the case is ren dered immediately obvious. The reduc tion is easy ; and after it has been accom plished, the hand and fore-arm should be bound on a splint, and supported by a sling.
Thigh. The os femoris may be dis placed downwards and inwards, So that the head rests on the obturator foramen ; upwards and outwards, when the head is towards the sacro-ischiatic foramen, and the trochanter forwards ; and upwards and forwards, so that the head rests upon the os pubis. In the first case, the toes are turned out, and the limb elongated. In the second, the limb is shortened, the foot turned inwards, and the buttock more prominent. Great pain is excited by attempting to move the limb in all cases of luxation, and a vacuity is dis cernible in the natural situation of the head of the bone. The patient should be placed on the side opposite to the acci dent, and his pelvis should be fixed by means of a sheet passed under the perine um. Extension may be made by fixing a broad towel, or the gullies, just above the condyles. When the head of the bone is on the dorsum ilii, the extension is to be continued until it has been brought to the acetabulum, into which the surgeon must guide it. In the dislo cation on the obturator foramen, we should make a lever of Abe bone, by pass ing a towel under the thigh, near the tro chanter, and elevating it after a slight extension has been made, the condyles being at the same time depressed.
'The patella may be dislocated either in wards or outwards. Its reduction is very easy, when the muscles• inserted into it have been relaxed.
The knee hardly admits of complete luxation, without such injury of the parts as would render the loss of the limb ne cessary. The nature of the accident must be obvious from the altered figure of the parts, and replacement is perfectly easy. Inflammation must be guarded a gainst afterwards.
The ankle may be dislocated outwards, the fibula being at the same time broken. This is generally a compound luxation ; the extremity of the tibia, when displaced from the astragulus, very often penetrat ing the integuments. Formerly this_ac cident was considered as a cause of am putation; and many practitioners have been in the habit of sawing off the pro jecting portion. Yet by replacing the bone, closing the wound, keeping the parts quiet, &c. the injury has been often recovered. Luxation may also oc cur in the opposite direction, and for wards. The latter is very difficult to re tain in place, as the muscles of the calf are so apt to move the foot.