LUXATION. 



it becomes flattened on that furface, by which it is in coHtaft 

 with a fubjacent bone, while this lail has a kind of depreflion 

 gradually made in it. In fome inftances the original cavity of 

 the joint diminifhes in depth, efpecially when the head of the 

 bone remains near its circumference. The mufcles, impeded 

 in their adlion, lofe their confidence, alTume a ligamentous 

 appearance, and even become attached to the ligaments by 

 a depofition of olTeous matter, and, in this manner, a bony 

 cafe is formed, which conilitutes, with the difplaced bone, 

 a new articulation. 



When a bone ij not reduced, the limb remains deformed, 

 and fcarccly any ufe can be made of it for fome months ; but 

 in time it approaches rather more to its natural direClion, and 

 when a new joint is formed, is yet capable of a confiderablc 

 latitude of motion. In general, however, in confequence 

 of the motion of the hmb being more or lefs obllrufted, 

 the mufcles fall away, and the limb has a weak and lefs 

 bulky appearance than that of its fellow. When a difloca- 

 tion in a child is left unreduced, this difference between the 

 fizeof the luxated limb and that of the found one, beconfes 

 very remarkable as the patient grows up to the adult 

 Hate. 



We (hall now treat of particular diflocations, and after- 

 wards conclude with fome obfervations on compound lux- 

 ations. 



Luxations of the lower Janv-hone, — When the mouth is 

 •widely opened, the condyles of the lower jaw advance for- 

 wards upon the enimentix articulares, and in this Hate may 

 be made to flip-under the zygomatic procefles by very flight 

 caufes. This bone is only liable to be luxated in this one 

 direction, whether one or both condyles efcape from the gle- 

 noid cavities of the temporal bones. Every luxation, except 

 that forwards, is rendered impofhble by the natural conforma- 

 tion of the parts. A diflocation backwards is oppoled by 

 the ofTeous portion of the auditory canal ; and luxations 

 laterally, to the right or left, are prevented by the i-efi fi- 

 ance arifing from the fpinous proceffes of the fphenoid 

 bone and the hgaments of the joint. But it muft be con- 

 feffed, that the principal flrength of the articulation of the 

 lower jaw does not depend upon thefe ligaments ; but rather 

 on the mufcles, and the pai-ticular conformation of the bones. 

 The very fhape of the lower jaw at once informs us, that 

 a blow on its fides muft be more likely to break it, by in- 

 creafing its curvature, than diflocate it. 



According to Boyer, luxations of the lower jaw cannot 

 happen in very young infants, on account of tlie body 

 and rami of this bone meeting at an obtufc angle, and, con- 

 fequently, the condyles and necks having nearly the fame 

 direction as the reft of the bone, fo that a luxation cannot 

 be caufed by any pofllble depreflion of the chin. Difloca- 

 tions of the jaw are feldom caufed by external violence ; 

 almoft always by exceffive yawning, or laughing. 



The condyles of the maxilla inferior, being thrown before 

 the tranfvcrfe roots of the zygomatic proceffes, comprefs the 

 deep-feated temporal nerves, and thofe going to the maffeters. 

 This faft affords a better explanation of the pains attending 

 a luxation of the jaw, than the tenlion and elongation of the 

 mafltter and other mufcles. 



Befides great pain, a more inflruftive fymptom of this 

 accident is the mouth being much open, and incapable of 

 being (hut. Thefe circumftances are more evident in recent 

 than old luxations of the jaw. An empty Ipace may be 

 felt before the ears in the natural lituation of the condyles. 

 The coronoid proccfs forms under the cheek bone an emi- 

 nence, which IS perceptible through the cheek, or by intro- 

 ducing a finger into the mouth. The checks and temples 

 are flattened by the lengthening of the temporal, mafTettr, 



Vol,. XXI. 



and buccinator mufcles. The falira flows in large quanfittef 

 from the mouth, the fecretion being augm.ented in confe- 

 quence of the exifting irritation. The arch formed by the 

 teeth of the lower jSw is placed anteriorly to that made by 

 thofe of ti.,- upper jaw. Laftly ; during the firfl days of 

 the luxation, the patient can neither fpeak nor fwallow. 



We have already adverted to one condyle being fome- 

 times diflocated, while the other remains in its proper 

 place. According to Mr. Hey, it is not always eafy to 

 know when this is the cafe. " One would expcft," fayj 

 this practical writer, " from a confideration of the flruftiire. 

 of the parts, and from the defcription given in fyftems 

 of furgcry, that the chin fhould be evidently turned towards 

 the oppolite fide ; but I have repeatedly feen the difeafe, 

 when I could difcern no alteration in the pofition of the chin. 

 The fymptom which I have found to be the beft guide in 

 this cafe, is a fmall hollow, which may be felt jult behind 

 the condyle that is diflocated, which does not fubfifl on 

 the found fide." Pract. Obferv. in Surgery, p. 32J, 

 edit. 2. 



When the luxation is recent, the above fymptoms enable 

 us to afcertain the nature of the accident with fufficient 

 eafe ; but when the diflocation has exifted feveral days or 

 weeks, the cafe becomes lefs flrongly marked. The lower 

 jaw has infcnfibly approached the upper one ; and the pati- 

 ent gradually recovers the faculty of fpeech and degluti- 

 tion ; but he flill ftammers, and drivels. 



Hippocrates pronounced luxations cf the jaw to be fatal, 

 unlefs reduced before the tenth day ; but furgeonshave no\r 

 found, that this fcntiment is not well founded, and it is 

 even fufpeiled, that Hippocrates might coiifound cafes of 

 locked jaw with thofe of diflocations. 



When the jaw has once been diflocated, the accident is 

 more prone to be produced again by flight caufes. Mr. Hey 

 mentions his having known two perfons in whom this dift 

 location frequently happened. Not only yawning, but even 

 opening the mouth incautioufly in eating, would caufe the 

 accident. P. 326, edit. 2. 



When a luxation of the jaw is to be reduced, the patient 

 fhould (it on a low ftool, with his head refling on the breafl 

 of an affillant. In this pofition of the patient, the furgeon's 

 hands are on a level with the mouth, which is advantageous, 

 becaufe he is not obliged to elevate them, and confequently 

 can act with greater force on the jaw. The furgeon, after 

 guarding his thumbs with hnen, or a thick pair of gloves, 

 is to introduce them into the mouth, and place them as far 

 back as poflible, on the great molares, at the fame time 

 bending under the chin the four fingers of each hand. 

 The jaw, being thus grafped, is to be moved in the manner 

 of a lever, the grinders being pnflied downwards and the 

 chin upwards. No fooner ace the condyles thus extricated 

 from under the zygomatic proceffes, than the mufcles dravr 

 them up into their proper places again, with con fiderable force 

 and fuddennefs. This takes place fo rapidly, that the 

 furgeon's thumbs would be in danger of injury, if he were 

 to negleft to move them quickly outwards, and place them 

 between the cheek and the jaws. 



After the reduftion, the four-tailed bandage for the lower 

 jaw is to be applied, as in cafes in which this bone is 

 broken. (Sec Plate V.) In the plate jult referred to, 

 however, it is proper to mention, that the centre of the 

 bandage fhould have been placed exaftly on the chin, an 

 effential circumftancc, as this is the point farthcfl from the 

 centre of motion, and confequently that where the bandage 

 can operate with the moll power in keeping trlie bone motion- 

 lefs. During the firil days, the patient fhould only b» 

 allowed liquid food, or fuch as requires no maltication. 



4 (^ Whw 



