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The change in the angle of the mandible
05-09-2009
Mandibular fractures most often occur in the region of its angle. This fracture is more often direct, sometimes - as reflected, ie at some distance from the place of the applied force. Ignoring this fact is often the cause of diagnostic errors, especially at the turn without bias. For the displacement of fragments of considerable importance is the localization of the fracture gap. If it passes anterior to the chewing muscles and the medial pterygium, or more precisely - within only a quarter of the front of their plane, the displacement of fragments more often than significant. If the slot is located inside the fracture tendinous its case, formed in the place of attachment of these muscles, and it is not broken because of trauma, displacement of fragments less pronounced or absent. However, such fractures are extremely rare. Should be recalled that in the angle of fracture or passes between the second and third molars, or through the eighth hole of the tooth, which is usually located in the small fragments, or behind the third molar. The direction of the plane of the fracture in relation to the sagittal (longitudinal) axis of the body of the mandible is also essential to the nature of the displacement of bone fragments.
In transverse fracture in the frontal plane and the vertical plane of its outer and inner compact layer rarely break at the same level. Depending on whether a fracture of the plate is located anteriorly and how much distance between them in the anteroposterior direction, depends on severity of the fracture plane of the bevel, ie turning around its vertical axis. The greater the distance, the sharper the angle of the bevel, the more favorable conditions for the displacement of bone fragments, including the length. If the plane of fracture is located medially and posteriorly, ie fracture line outside the compact disc is located anterior to that of the inner (lingual) side, a small otlomok shifts upward under the influence of masticatory and temporal muscles, as well as several anterior (towards larger) under the influence of the surface fibers of masticatory muscles and part of the lateral muscles of pterygium while reducing it on the side of small and large fragments. This makes The occurrence of bone fragments to each other. In addition, the lower edge of the angle is shifted outwards, the front edge of the branches of a few turns orally (force the prevalence of chewing muscles on the medial pterygium).
If there is a small fragment of a third molar is his antagonist, otlomok shifted upward to contact the teeth. If there are no teeth, the mucous membrane of the alveolar process or pear-shaped area in contact with third upper molars, which creates the danger of dekubitalnoy ulcers. Its appearance is possible and on the mucous membrane of the alveolar process of maxilla, if there is no antagonist available on the small fragments of the eighth tooth.
In the absence of upper third molars small otlomok mandibular alveolar its part may be in contact with the alveolar bone of the upper jaw. The degree of displacement of fragments in this case up to be more significant. Big otlomok moves down and toward the fracture, crawled through a small slit through the slant fracture. At a large fragments will papulose-papulose contact molars and premolars on «healthy» side, the remaining teeth can not touch (oblique open bite).
In the case of the location of a fracture plane obliquely medially and anteriorly, ie fracture of the outer compact disc is located posteriorly, and internal - to front, the displacement of bone fragments will be different and more significant. In this situation, small otlomok shifted upwards, inwards and somewhat anteriorly. Value of bone fracture surface does not prevent pterygium lateral muscle on the side of small fragments significantly displace him inside. The front edge of the branches of a few turns inwards, and the lower edge of the angle - outwards. Big otlomok will move down and toward the fracture, but going down the fragments for each other will not.
Transverse fractures of the angle of the mandible are less common than fractures in which the plane of the fracture starts from the alveolar bone (between the second and third molars, or from the hole of the third molars), held at an angle to the sagittal axis, sinking downward and backward, or downward and anteriorly. In the first case, when the plane of the fracture on the alveolar bone located anterior to that of under the body of the mandible, ie has «anteroposterior» direction, the displacement of fragments is according to the rules set out above. The extent of his will also depend on the angle at which the fracture line crosses the longitudinal axis of the body of the mandible, on the degree of slant to it, and on whether the compact disc (external or internal) is located anterior to the line of fracture. In the second case, when the line is a fracture on the basis of body of the mandible is anteriorly relative to that of the eighth hole of the tooth (the crest of the alveolar - posteroanterior direction of the plane of fracture), the displacement of bone fragments may not occur, as may their relative retention in the correct position. However, this requires that the outer and inner compact discs on the fragments located on the same level in the anteroposterior direction, ie wound surface had a wide contact area. If the plane of the fracture will have oblique direction with respect to the sagittal (longitudinal) axis of the body of the mandible, ie deployed around the vertical axis may shift fragments toward each other: large - down, but small - up and inside (outside) depending on the direction of the bevel slot fracture (outwards or inwards). These patterns of displacement of fragments in more detail given in the beginning of the section.
Complaints of patients did not differ significantly from those in the localization of fracture in the lateral parts of the body of the jaw. Localized swelling in the lower section of parotid-masticatory area and due to the same factors as in the previous clinical observations. Palpated bone protrusion in the corner harder, because it can be masked by muscle-tendon sheath chewing muscles. Therefore, in the case of his absence must pay special attention to the definition of the most painful point on the base body of the mandible in the corner. It usually corresponds to the place of fracture. Symptom burden positive: the painful area coincides with palpable bone ribs or revealed a painful point in the angle of the mandible.
Limitation of opening the mouth is much more pronounced than at the turn in the lateral parts of the body. This is connected not only with increased morbidity when lowering the lower jaw, but also with the trauma of chewing muscles and the medial pterygium. Hemorrhage in the lower body of the arches of the mouth, if it is, is localized in the area of the second and third molars and extends to the pear-shaped area of tissue and Pterygopalatine mandibular crease.
Laceration of the mucous membrane is usually within the gums. It can reach transition folds, but rarely extends beyond the threshold of the lower body cavity. Often localized on the crest of the alveolar part between the second and third molar or wisdom tooth directly behind. In this area is sometimes possible to see the bare bone area of fracture jaw move up the smaller fragments. In other cases, the wound on the gums can be detected only by checking the mobility of fragments of symptom appearance transudate (less blood) from the wounds of soft tissues in that interdental spaces or the next tooth. Often this is accompanied by a characteristic «smack» audio.
At the turn of this localization is often possible to identify asynchronous movement of heads of the mandible: the amplitude of the displacement on the side of the fracture is less than the uninjured side. This is due to the fact that less otlomok (ie, a branch of the lower jaw) is practically out of the full impact of the functional muscle, lowering the lower jaw.
Individual muscle bundles of chewing and medial pterygoid muscles connect these fragments of soft tissue sarcomas «bridge». Therefore, movements in the temporomandibular joint on the side of the fracture saved, but the volume significantly limited. Possible relationship dentitions are shown above. On palpation the front edge of the branches of the mandible from the oral cavity can be clearly established its shift inwards and upwards.
On radiographs of the mandible in the lateral line is visible in the field of illumination angle (fracture line), determined by the degree of displacement of bone fragments in the vertical direction, on the radiograph in the direct projection can clarify the nature of the displacement of bone fragments inside or outwards
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