THE FACE. 67 



Dislocation occurs when the mouth has been widely opened and the condyles 

 are forward on the articular eminences. Some sudden jar accompanied by contrac- 

 tion mainly of the external pterygoid muscle causes the condyle to slip forward just 

 in front of the articular eminences. The internal pterygoids and the superficial fibres 

 of the masseter muscles aid in producing the luxation. As the condyle leaves 

 the articulation to jump forward, it will be noted that it does so by an extensive 

 movement, which is one of rotation on a transverse axis passing across in the 

 region of the mandibular foramina. The condyle once out of its socket is kept 

 out by the contraction of the temporal, masseter, and internal and external pterygoid 

 muscles. 



Reduction of Dislocation of the Lower Jaw. In reducing the dislocation, 

 the condyles must be depressed and pushed back. This can be done by one of two 

 ways: viz., the thumbs of the surgeon, being protected by wrapping with a towel or 

 bandage, are placed on the last molar teeth, and the jaw firmly grasped with the 

 fingers beneath it. The back part of the jaw is then pressed downward, the chin 

 tilted upward, and the condyles slid back into place. 



Small fragment into which 

 was inserted the geniohyoid 

 and geniohyoglos!>us muscles 



FIG. 77. Fracture of the mandible through the symphysis (author's sketch). 



The other method is to place two corks, one on each side, or a piece of wood, 

 transversely, between the last molar teeth, then raise the chin and push it backward. 



The undetached lateral ligaments are put on the stretch when the condyle is 

 luxated forward. Lewis A. Stimson believes that in attempting reduction the jaw 

 should first be opened wider to relax these and then pushed back, but we are 

 not prepared to admit that so doing does relax these ligaments. He has, however, 

 shown that the interarticular cartilage may become displaced and, by filling up the 

 articular cavity, prevent a proper reduction. In rare instances the catching of the 

 coronoid process beneath the malar bone may hinder replacement. 



Fractures of the Lower Jaw (Mandible). Fractures of the lower jaw 

 almost never occur through the symphysis; this is on account of its being the thickest 

 and strongest part of the bone. When a fracture of the anterior portion of the jaw 

 detaches a median piece a most dangerous condition is produced. The piece, if 

 sufficiently loosened by the injury, is drawn back into the throat, carrying the tongue 

 with it and tending to suffocate the patient. Such a case is "recorded by A. L. 

 Peirson (review by Geo. W. Norris, Amer. Jour. Med. Sciences, 1841, N. S. vol. i, 

 p. 1 86). A man was run over by a wheel which passed over his jaw, fracturing it 

 on each side and forcing the piece into his mouth. The piece was drawn backward 

 and nearly caused death from suffocation. 



