The mandible is located in the lower third of the face and is prominently positioned to be easily injured by blows. The mandible is a solid bone, but there are several anatomically weak areas where fractures can easily occur under direct or indirect violent blows. Since the mandible is the only large movable bone in the maxillofacial region and is involved in the composition of the temporomandibular joint, it has a greater impact on masticatory function after injury.
Surgical anatomy
The mandible is horseshoe shaped and consists of a curved mandibular body and bilateral mandibular ascending branches, with strong masticatory muscle attachments on the inside and outside of the ascending branches. The mandible has a thick bone cortex, but the mandibular joint, chin hole area, mandibular angle and condylar neck are the structural weaknesses of the mandible, which are the good sites for fracture. After the mandibular fracture, the fractured segment will be displaced by the pull of the masticatory muscles, resulting in occlusion disorder and masticatory dysfunction.
Fracture classification
1, according to the nature of fracture classification green branch fracture: bone fracture or cortical fracture fracture, but bone continuity intact; closed fracture: fracture surface soft tissue intact, the fracture is closed; open fracture: fracture surface soft tissue damage, with the fracture site; simple fracture: fracture single, no displacement or mild displacement; complex fracture: fracture multiple, with obvious displacement; comminuted fracture: fracture site bone fragmentation, often Fracture bone defect: the fracture is accompanied by bone defect and displacement.
2.Classification by fracture site
Condylar fracture, rostral fracture, ascending fracture, mandibular angle fracture, mandibular body fracture, chin/parachin fracture, and alveolar process fracture.
3.Classified by fracture line direction into favorable fracture and unfavorable fracture. The former refers to the fracture line direction and muscle involvement history. First, take an accurate history, and if the patient cannot cooperate, ask his or her family. The cause of injury, the size and number of striking objects and the size of the striking force should be clarified.
2.Clinical manifestations
(1) After acute symptoms and signs of mandibular fracture, there is pain, swelling, and subcutaneous bruising at the fracture site.
(2) Gingival tearing and bleeding around the fracture line in the mouth, and may be accompanied by loose, broken and displaced teeth.
(3) Displacement of the fracture segment and abnormal mobility A variety of factors can cause displacement of the fracture segment after a mandibular fracture, and the pulling of the masticatory muscles is the main factor causing displacement of the fracture segment. When the fracture is displaced, the fracture segment at both ends of the fracture site is abnormally dynamic, and the fracture site can be examined with bone rubbing sounds.
(4) Occlusal disorder After the mandibular fracture, the teeth are displaced with the displacement of the fracture segment and occlusal disorder occurs.
(5) Functional disorder mainly manifests as mouth opening restriction, which affects normal feeding and speech function, and the degree of mouth opening restriction depends on the fracture site and the severity of injury.
(6) Facial deformity can be caused by displacement of the fracture, among which the mandibular deviation deformity is more common.
(7) Sensory abnormalities can cause numbness of the lower lip and chin if the fracture damages the inferior alveolar nerve.
3. Imaging examination.
No matter what kind of examination method is chosen, the fracture should be examined from at least two different directions to avoid any missed diagnosis.
(1) Plain radiographs are generally chosen from the mandibular surface body layer film and the mandibular orthopantomogram, and when a condylar fracture is suspected, the mandibular opening posterior anterior film is chosen. In addition, the mandibular transverse occlusal film can well show the median mandibular fracture, and this film position can also assist in evaluating the fracture of the lingual bone plate of the chin, especially for oblique fractures.
(2) CT axial and coronal views combined with 3D reconstructed CT images can more accurately show mandibular fractures, especially
(2) CT axial and coronal views combined with 3D reconstructed CT images can more accurately demonstrate mandibular fractures, especially mandibular condyle fractures.
Fracture treatment
The goal of treatment of mandibular fractures is to anatomically reset the mandibular fracture and restore and maintain normal occlusion. The principles of treatment are correct repositioning and reliable fixation.
1. Closed repositioning and fixation
The methods of repositioning are.
(1) Manipulation for early simple linear fractures, the fracture segment is relatively loose and can be reset by manipulation under local anesthesia.
(2) Traction repositioning is a long intermaxillary traction repositioning, i.e. ligating the dental arch splint on the maxillary and mandibular dentition, and then traction with a rubber band to make the displaced fracture segment return to normal position based on occlusion. If the condylar fracture is accompanied by mandibular recession with anterior teeth opening, this method can be used for repositioning.
Methods of fixation.
(1) Monomandibular fixation, i.e., interdental or interosseous fixation on the mandible where the fracture occurs, is suitable for linear fractures without significant displacement. The most common method of fixation is monomandibular arch splinting.
(2) Intermaxillary fixation (traction) intermaxillary fixation is to ligate the dental arch splint on the maxillary and mandibular dental arches and then fix the maxilla and mandible together with a rubber band, using the intact dental arch of the maxilla as a basis to restore the occlusal relationship and thus restore the continuity of the mandible.
2. Incisional repositioning and internal fixation
(1) Mandibular mini-plate system fixation of mandibular chin, mandibular body and single fracture of mandibular angle mini-plate fixation is a single layer of cortical bone fixation, which will not damage the inferior alveolar canal, and the plate is easily bent into shape and placed according to the tensile stress trajectory.
(2) Mandibular fracture tension screw fixation tension screw fixation is to obtain maximum stability with minimum implants. It is mainly used clinically for mandibular body oblique section fractures, chin fractures, mandibular angle vertical section fractures, subcondylar neck fractures and free fracture block fixation.
(3) Extensive comminuted fractures occurring in the chin/para-chin and mandibular body reconstruction splints are mainly used to connect the bone segments on both sides of the fracture area, and small bone fragments within the fracture area can be connected with small or mini splints, or can be directly fixed with screws for penetration.
3. Treatment of teeth on the fracture line
Preserving the teeth on the fracture line can effectively help to reset and fix the fracture and prevent the misalignment of the fracture segment, and also help to restore the correct shape of the dental arch. Removing the teeth on the fracture line can cause damage to the bone tissue and interfere with the correct repositioning and fixation. Except for mandibular wisdom teeth, teeth with obvious infection, and teeth broken below the cervical part of the tooth, the teeth on the fracture line should be preserved as much as possible to facilitate the reset and fixation of the fracture and the later occlusal reconstruction.
4. Treatment of edentulous mandibular fractures
The treatment of edentulous mandibular fracture is more difficult, first of all, no teeth are available for simple intermaxillary fixation; at the same time, due to long-term toothlessness, the alveolar bone can be atrophied, the mandibular body becomes small, and the fracture segment is more easily displaced by the muscle pull during fracture. For older patients with systemic diseases, the original maxillary and mandibular full-mouth braces or plastic bracket splints can be used for perimandibular wire ligature fixation, but the stable braking is not reliable and can even cause compressive necrosis of soft tissues. In the case of displaced mandibular fractures with no teeth, open internal fixation should be done in general, and a plate nail system with strong fixation force should be selected for fixation.
5. Treatment of mandibular fractures in children
In the treatment of mandibular fractures in children, the following issues must be considered: ① The cortical bone of the mandible in children is thin, and incomplete fractures or green branch fractures are common, so it is best to use manual repositioning and simple braking methods. The dental and occlusal relationships of children are not yet stable, so the requirements for restoration of occlusal relationships are not as strict as those of adults, and the occlusal relationships will be restored by self-adjustment in the later process of establishment. (3) The mandible of children is in the process of growth and development, and any kind of surgical intervention on the fracture may affect the development of the jaws. The above reasons dictate that conservative treatment of mandibular fractures in children should be considered first. However, surgery should also be considered for significantly displaced mandibular fractures with incision and internal fixation, with the option of using absorbable plate nails for fixation.
6.Treatment of old mandibular fracture
It is suitable for simple “re-fracture” of old fractures that do not form bone and soft tissue defects after repositioning. Surgery is performed to chisel along the original fracture line as much as possible so that the fracture is correctly aligned. Bone grafting should also be considered for post-fracture bone defects.
Postoperative considerations
Postoperative antibiotics are recommended for 1-3 days depending on the surgery. Antibiotics can be chosen from penicillins, cephalosporin antibiotics, etc. If the postoperative occlusal relationship is poor, upper and lower jaw elastic traction may be considered for 1-2 weeks. If postoperative mouth opening restriction due to muscle damage exists, early mouth opening training is recommended to improve mouth opening. A postoperative review at 3 months with imaging is recommended to observe fracture healing. Patients should be reminded to eat a reasonable diet to restore occlusal function gradually.