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The mechanism of fractures of the mandible
05-09-2009
There are four variants of the mechanism of fracture of the mandible: bend, shear, compression, separation. The lower jaw, having an arched shape, when a mechanical force is experiencing stress of bone tissue in the most crooked, or the most delicate of areas. Established in the limits of the lower jaw are the foundation and condylar neck of the appendix, angle, area openings and canine chin, chin department. It is in these most «weak» ground breaking lower jaw as a result of its inflection. Are possible different clinical variants of mandibular fractures.
Well in the strikes on the chin in his large square in front to back the greatest stress occurs in the zone of condylar processes. Chance of indirect fracture in the neck with one side or both sides, but not at the bottom of it. This is due to the fact that in the anteroposterior direction of condylar neck of the appendix is 3 times thinner than its base.
▲ If the force is applied to a small area of lateral part of the body of the mandible, can direct change in the place of its applications: most of the angle of the jaw (bone thinned in the area of the hole of the third molars), chin hole (zone of premolars is one of the thin sections of the lower jaw) in the field of the canine (bone weakened by the deep recess of the canine).
▲ If the force is applied to a small area of the lateral branch of the Department of the jaw (in the frontal plane), can direct condylar fracture of the base the process, since its thickness is much smaller than in the neck area.
▲ In the event of an impact on a broad area of lateral part of the body of the mandible possible indirect fracture on the opposite side of the force exerted on the angle and base condylar the process, are less likely - his neck.
▲ If the force is applied to a wide area of the angle of the mandible on one side, ie asymmetric, there will be a direct change in the angle and indirect - in the lateral portion chin department body of the mandible.
Thus, in the case of the inflection line fracture of the mandible was more frequently at the site of application of force on a narrow area, and indirect, if the force is applied at large
Square jaw.
Shift mechanism is realized in the case when the force is applied to sections of the mandible, which had no support, and it shifts (shifts) with respect to its other sites of support. Because of the shift is a longitudinal fracture of the actual branches of the mandible, if a force directed upwards, is attached to the base of the mandible anterior to its angle on the narrow section (in the projection of coronoid process). Anterior branch of the lower jaw moves up towards the rear, which has support in the articular cavity. The implementation of this mechanism is possible in the absence of molars and premolya-ditch on the lower jaw, or their antagonists on the side of the fracture, the complete absence of teeth on the upper and lower jaw, at the time of the attack at the victim's mouth was half open. Shift mechanism takes place in fractures of the body of the mandible. If the force is applied to the base of the jaw from the bottom up in the area devoid of teeth, it is without support, could move up on the sites of teeth and, consequently, support.
The mechanism of compression can occur if the two active toward each other forces are applied on a broad basis. In striking a blow from the bottom up along the lower edge of the angle of the mandible of a broad-area branch of the mandible, fixed in the glenoid cavity, is subjected to compression and bone ravine break. Gap with the fracture is located in the central regions of the branches of the mandible in the transverse direction.
The mechanism of separation can occur in cases where under the influence of force applied downward to the chin, lower jaw moves down. Thus there is a sharp reflex contraction of masticatory muscles. Powerful temporal muscle, attached to, insufficient coronoid process in a large area, separates him from the branches of the jaw. The reality of such a mechanism fracture coronoid process did not recognize all the authors.
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Articles for theme "fracture of the jaw":
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05-09-2009
There are numerous classification neognestrelnyh fractures of the mandible. Conveniently enough for practical purposes is, in our opinion, the classification proposed by BD Kabakov, and VA Malyshev.
Classification of fractures of the mandible on BD Kabakov and VA Malyshev
A. For localization.
I. Fractures body of the mandible:
• the presence of the tooth in the fracture gap;
• in the absence of teeth in the fracture gap.
II. Fractures of the branches of the jaw:
• own branch;
• coronoid process;
• condylar sprouts: base, neck, head.
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03-09-2009
When combined craniocerebral trauma (CoN ™) as a result of mechanical impact damage occur simultaneously, the facial skeleton, bones of the cranial trauma and brain. Possible closed craniocerebral trauma (CCT), without damage to the bones of the skull, combined with fractures of the face. Fractures of facial bones, combined with head injury is diagnosed in 6.3% [Fraerman AP, YE Gelman, 1977], or 7,5% of victims [Lebedev VV, 1980]. Enough high frequency of craniofacial injuries caused not only by their anatomical proximity, but also the fact that some of the facial bones of the skeleton are involved in the formation of the skull base.
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03-09-2009
In practice, the surgeon-dentist found unilateral or sagittal fractures of the upper jaw. They tend to occur when the injuring object has sharp edges and the force is applied downward in an oblique direction, mainly at the side of a single department or zone of the upper jaw of the upper lip with one hand. It breaks down the body of the upper jaw with a wing-offshoot sphenoid bone of the party or without it. In the area of the anterior and infratemporal walls (tuber) of the upper jaw fracture line passes above the bottom of the maxillary sinus, and in the hard palate - lateral of the median suture.
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03-09-2009
Assume that the left is fractured along the middle and the right - the bottom type. Fracture line runs from the junction point of the frontal sprouts upper jaw with the nasal part of frontal bone on the left, extends on the inner wall of the orbit and beyond - in accordance with a fracture in Le Fort II, but with only one left. Nasal septum is broken at different levels depending on the transmission line fracture of nasal bones. The right line of the fracture begins at the pear-shaped holes, and further extends the type characteristic of a fracture in Le Fort III (ris.
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03-09-2009
For convenience of presentation, suppose that the left fissure fracture runs along the upper type, and the right - on average. The line is a fracture in the frontal connections sprouts upper jaw with the nasal part of frontal bone. Left it extends characteristic of Le Fort I (ris.3.12), and the right - for the Le Fort II (see the relevant section, as outlined above). Patients may complain of pain in the upper jaw, with the increasing interdigitation or attempted biting or chewing food, improper closing of the teeth, foreign body sensation in the throat, choke and retch, insufficient opening of the mouth, double vision.
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