What Is a Mandibular Fracture?

The mandible is horseshoe-shaped and consists of a curved mandible and bilateral ascending branches of the lower jaw. Strong chewing muscles are attached to the inside and outside of the ascending branch. The mandibular cortex is thick, but the mandibular mandibular midline joint, the sacral foramen region, the mandibular angle, and the sacral neck are structurally weak areas of the mandible, which are the most common sites for fractures. After a mandible fracture, the fracture segment is in the masticatory muscles. Displacement occurs under the pull of, resulting in occlusal disorder and chewing dysfunction. ^[1]

An King Kong	(Deputy Chief Physician)	Department of Maxillofacial Surgery, Peking University Stomatological Hospital
Zhang Yi	(Chief physician)	Department of Maxillofacial Surgery, Peking University Stomatological Hospital

The mandible is located 1/3 below the plane, and it is prone to injury. The mandible bone is solid, but there are several areas of weak anatomy. Fractures in these areas are easy to occur under direct or indirect violence. Because the mandible is the only active large bone in the maxillofacial region and participates in the formation of the temporomandibular joint, the chewing function is greatly affected after injury.

Western Medicine Name: Mandible fracture
Affiliated Department: Department of Physiology-Stomatology

Disease site: Maxillofacial
The main symptoms: Pain, swelling, subcutaneous blotches
Main cause: Motor vehicle accident

Mandibular fracture surgical anatomy

The mandible is horseshoe-shaped and consists of a curved mandible and bilateral ascending branches of the lower jaw. Strong chewing muscles are attached to the inside and outside of the ascending branch. The mandibular cortex is thick, but the mandibular mandibular midline joint, the sacral foramen region, the mandibular angle, and the sacral neck are structurally weak areas of the mandible, which are the most common sites for fractures. After a mandible fracture, the fracture segment is in the masticatory muscle Displacement occurs under the pull of, resulting in occlusal disorder and chewing dysfunction. ^[1]

Mandible fracture fracture classification

1. Classification according to the nature of the fracture: green branch fracture: osteotomy or cortical fracture, but bone continuity is intact; closed fracture: the soft surface of the fracture surface is intact and the fracture is closed; Connected; simple fracture: single fracture, no displacement or slight displacement; complex fracture: multiple fractures, with obvious displacement; comminuted fracture: bone fragmentation at the fracture site, often accompanied by displacement; bone defect: fracture With bone defect and displacement.

2. Classification by fracture site: Condylar fracture, coracoid fracture, ascending branch fracture, mandibular angle fracture, mandibular fracture, condylar / paracondylar fracture, alveolar fracture.

3. Classified according to the fracture line direction: divided into favorable fractures and unfavorable fractures. The former means that the direction of the fracture line is perpendicular to the direction of the muscle stretch; the latter means that the direction of the fracture line is parallel to the direction of the muscle stretch. ^[2]

Causes of mandibular fractures

Motor vehicle accidents are the main cause of injury.

Mandibular fracture fracture diagnosis

Ask a detailed medical history, understand the cause of the injury, conduct a comprehensive and detailed oral and maxillofacial examination, and combine with imaging examination to make a clear diagnosis.

Medical history

First, the medical history must be accurately collected. If the patient cannot cooperate, ask his family. It is necessary to clarify the cause of injury, the size and number of striking objects, and the size of the striking force. ^[3]

Clinical manifestations

(1) Acute symptoms and signs: After fracture of the mandible, pain, swelling and subcutaneous bruising appear at the fracture site.

(2) Gum tears and tooth damage: Gum tears and bleeding around the fracture line in the mouth can also be accompanied by tooth looseness, breakage, displacement, etc.

(3) Fracture displacement and abnormal mobility: A variety of factors can lead to fracture displacement after mandibular fracture, and the pulling of the masticatory muscle is the main factor that causes fracture displacement. When the fracture is displaced, the abnormal movement of the fracture segment at both ends of the fracture site may cause bone fricatives at the fracture site.

(4) Occlusal disorders: After mandibular fractures, teeth are displaced with the displacement of fractured segments, and occlusal disorders occur.

(5) Dysfunction: Mainly manifested as restricted mouth opening, which affects normal eating and language functions. The degree of mouth opening restriction depends on the fracture site and the severity of the injury.

(6) Facial deformity: After the fracture is displaced, it can cause facial deformity, and the mandibular deviation is more common.

(7) Paresthesia: When the lower alveolar nerve is damaged by a fracture, it can cause numbness of the lower lip and palate.

3. Imaging examination

Regardless of the method chosen, the fracture should be examined from at least two different directions to avoid missed diagnosis.

(1) Plain film: Generally select the mandibular surface tomography film and the mandibular orthotopic film. When the condylar fracture is suspected, choose the anterior posterior mandibular opening. In addition, the mandibular transverse occlusal film can show the median fracture of the mandible. The position can also help evaluate the fracture of the lingual bone plate of the palate, especially for oblique fractures.

(2) CT: Axial and coronal combined with 3D reconstructed CT images can more accurately show mandibular fractures, especially mandibular condylar fractures. ^[1] ^[2]

Mandible fracture fracture treatment

The goal of mandibular fracture treatment is to anatomically reduce mandibular fracture and restore and maintain normal occlusion. The principle of treatment is correct reduction and reliable fixation.

Closed reduction and fixation of mandible fracture

1. The reset methods are:

(1) Manipulative reduction For early simple linear fractures, the fractured section is relatively loose, and can be reduced under local anesthesia.

(2) Traction reduction It is common to see intermaxillary traction reduction, that is, ligating the dental arch splint on the maxillary and maxillary dentition, and then using a rubber band to traction, based on the occlusion, to return the displaced fracture segment to the normal position. For patients with condylar fractures and mandibular anterior teeth opening and closing, this method can be used for reduction.

2. Fixed method:

(1) Single-jaw fixation is the interdental or inter-bone fixation on the fractured mandible, which is suitable for linear fractures without obvious displacement. At present, the most commonly used fixation method is single-jaw arch splint fixation.

(2) Intermaxillary fixation (traction) Intermaxillary fixation is ligating the arch splint on the maxillary dental arch, and then fixing the upper and lower jaw bones with rubber bands, using the intact dental arch as a basis to restore the occlusal relationship Thereby restoring the continuity of the mandible.

Mandibular fracture open reduction and internal fixation

(1) Mandibular miniplate system fixes single fracture of mandibular condyle, mandibular body and mandibular angle: The small plate is fixed as a single layer of cortical bone, which will not damage the alveolar canal, and the plate is easy to bend and shape. Stress trace placement.

(2) Mandibular fracture lag screw fixation: lag screw fixation achieves maximum stability with the smallest implant. Clinically, it is mainly used for mandibular oblique fractures, patellar fractures, vertical fractures of the mandibular angle, subcondylar fractures, and free fracture block fixation.

(3) Extensive comminuted fractures that occur in the palate / condylar and mandibular bodies: reconstruction bone plates are mainly used to connect the bone segments on both sides of the fracture area. Small bone fragments in the fracture area can be connected with small or micro bone plates, or Directly fix it with screws.

Management of teeth on mandible fracture fracture line

In addition to retaining the teeth on the fracture line, in addition to effectively helping the reduction and fixation of the fracture, preventing misalignment of the fracture segment, it is also conducive to the correct restoration of the dental arch shape. Extraction of teeth that can be retained on the fracture line can cause bone tissue damage and interfere with proper reduction and fixation. Except for mandibular wisdom teeth, teeth with obvious infection, and broken teeth below the neck of the teeth, the teeth on the fracture line should be kept as far as possible to facilitate the reduction and fixation of the fracture and the subsequent occlusal reconstruction.

Treatment of mandibular fractures

The treatment of toothless mandible fractures is difficult. First of all, toothless can be used for simple intermaxillary fixation. At the same time, due to long-term tooth loss, alveolar bone atrophy, the mandible body becomes small, and muscles are pulled during the fracture. Fractured sections are more easily displaced. For older patients with systemic systemic diseases, the original maxillary or maxillary bracket or plastic bracket splint can be used for peri-maxillary ligature ligation and fixation, but stable braking is not reliable, and it can even cause compression necrosis of soft tissue. In the case of obvious toothless mandibular fractures, open reduction and internal fixation should generally be performed when systemic conditions allow, and a plate nail system with a strong retention force should be selected for fixation.

Treatment of mandible fractures in children with mandible fractures

In the treatment of children's mandible fractures, the following issues must be considered: The cortical bone of children's mandibles is thin, and is usually incomplete fractures or green branch fractures. It is best to use manual reduction and simple braking methods. The dentition and occlusal relationship of children are not stable, so the requirements for restoration of occlusal relationship are not as strict as adults. The occlusal relationship is adjusted and restored by itself during the later stage of occlusion. The mandible of the child is in the process of growth and development. Any form of surgical intervention on the fracture may affect the development of the jaw. The above reasons determine that children with mandibular fractures should first consider conservative treatment. However, for mandibular fractures with obvious displacement, surgery should also be considered, and internal fixation by incision and reduction can be considered. The use of absorbable plate nails can be considered for fixation.

Treatment of old mandible fractures

It is suitable for simple re-fracture reduction of old fractures that will not form bone and soft tissue defects after reduction. Surgery should be performed along the original fracture line as far as possible so that the fractures can be correctly aligned. Bone grafts should also be considered after bone fractures. ^[3]

Precautions after mandibular fracture

Antibiotics are recommended for 1-3 days after surgery. Antibiotics can be selected from penicillins and cephalosporins. The postoperative occlusion relationship is not good, and elastic traction of the upper and lower jaws can be considered for 1-2 weeks. If there is limited mouth opening due to muscle injury after surgery, it is recommended to perform mouth opening training early to improve mouth opening. A follow-up review is recommended after 3 months, and imaging examination is performed to observe the fracture healing. Patients should be reminded to eat properly and gradually restore occlusal function. ^[1] ^[2]