What Is a Mandibular Angle?

The angle of mandible is formed by the intersection of the posterior edge of the mandibular branch and the lower edge of the mandible. The angle is related to the age and chewing force. The bone surface in the inner and outer regions of the mandibular angle is rough, with external chewing muscles attached, internal pterygoid muscles attached, and styloid process mandibular ligaments attached. The mandibular angle is one of the bony anatomical signs on the maxillofacial surface. Often used.

The angle of mandible is formed by the intersection of the posterior edge of the mandibular branch and the lower edge of the mandible. The angle is related to the age and chewing force. The bone surface in the inner and outer regions of the mandibular angle is rough, with external chewing muscles attached, internal pterygoid muscles attached, and styloid process mandibular ligaments attached. The mandibular angle is one of the bony anatomical signs on the maxillofacial surface. Often used.

Chinese name

Mandibular angle

Foreign name

angle of mandible

Types of

Angular structure

Make up

Mandibular branch and mandible of the mandible

Shape

bilateral symmetry

Change method

Plastic surgery

Function

Race and region

Mandibular angle auxiliary structure

The main blood vessels in the mandibular angle area: The facial artery starts from the anterior wall of the external carotid artery, passes through the styloid process of the hyoid muscle and the digastric muscle, the deep side of the abdomen and the hypoglossal nerve, to the subcondylar triangle, and passes through the facial nerve groove above the submandibular gland Later, to the front edge where the masseter muscle is attached, around the lower edge of the mandible to the face. Studies have reported that the facial veins accompany the facial arteries at the lower edge of the mandible. 80% of the facial arteries are located in front of the facial vein, and 20% of the facial arteries are located deep in the facial vein. The facial vein runs in the submandibular area and merges with the anterior branch of the posterior mandibular vein to form a common facial vein. At the lower edge of the mandible, the facial arteries and veins are superficial, with the superficial facial mandibular branches, platysma, and skin on the superficial surface; the deep side is close to the periosteum of the mandible.

The posterior mandibular vein is formed by the confluence of the superficial temporal vein and the maxillary vein at the back of the mandible neck, penetrates into the parotid gland, and descends on the superficial surface of the external carotid artery in front of the external ear hilar. The posterior mandibular vein and the facial nerve or its main branch are nearly cruciform. There is rarely parotid tissue separation between them, and they are more directly attached. The posterior mandibular vein is almost parallel to the posterior edge of the ascending branch of the mandible. Here the tube wall is thinner and the diameter is thicker. Only the periosteum or thin parotid tissue is attached to the posterior edge of the ascending branch of the mandible. After penetrating the lower pole of the parotid gland, it was divided into two branches of 16 sides (80%). The anterior branch was injected into the facial vein forward and backward, and the posterior branch and posterior ear vein merged into the external jugular vein. Four sides (20%) merged directly into the external jugular vein with the posterior auricular vein regardless of the anterior and posterior branches. The relationship between the posterior mandibular vein and the angle of the mandible is divided into two types: Tightly combined type: The arc structure formed by the posterior mandibular vein and its branches is closely attached to the mandible, and the distance from the nearest 8 sides is 40%; Loosely combined Type: The arc-shaped structure formed by the posterior mandibular vein and its branches is 60% away from the mandibular angle with 12 sides. The more the mandibular angle protrudes, the closer the posterior mandibular vein is to the mandibular angle. The distance between the posterior mandibular vein and the posterior edge of the ascending branch of the mandible, and the angle of the mandible were (3.00 ± 0.56) mm (12.20 ± 1.09) mm.

The main nerves in the mandibular angle area: 1 to 2 of the mandibular limb of the facial nerve, mostly 1 branch. After initiation from the cervical and facial trunk of the facial nerve, they all pass above the mandibular angle and at the posterior edge of the masseter muscle. The movement of the mandibular limb branch from the parotid gland is generally walking in the masseter muscle fascia, crossing the facial artery at the anterior edge of the masseter muscle. This position is relatively constant, and there is no case where it does not cross the facial artery; the last branch dominates the broad neck Muscles, lower horn muscles, lower lip muscles, diaphragm muscles. The distance from the position of the mandibular margin to the parotid gland is (10.36 ± 0.41) mm. The positional relationship between the position of the mandibular margin and the lower margin of the mandible can be divided into three cases: walking parallel to the lower margin of the mandible and away from the mandible The lower edge (6.84 ± 0.70) mm, with 12 sides accounting for 60%. It is almost parallel to the facial artery at the anterior edge of the masseter muscle. The lower edge of the mandible is approximately flat, which is equivalent to walking in the groove between the lower edge of the mandible and the submandibular gland. 30% on the side, crossing diagonally with the facial artery at the leading edge of the masseter muscle; walking below the lower edge of the mandible in an arcuate shape, with a minimum of 1.2cm, with 10% on both sides, facing diagonally upward with the front edge of the masseter muscle Arteries cross. The intersection of the mandibular limb of the facial nerve and the facial artery can be divided into three types: the mandibular limb is located on the 16 sides of the superficial facial arteries, accounting for 80%; the mandibular limb is on the deep side, 2% accounting for 10%; the mandibular limbs are divided into two meridians The superficial or deep surface clamps or embraces the external maxillary artery, and then synthesizes one branch, with 10% on both sides. Observation also found that there was an anastomosis between the mandibular limb branch of the facial nerve and the inferior buccal branch of the facial nerve, which accounted for 20% of the four sides. The distance between the position of the mandibular limb of the facial nerve spanning the facial artery and the lower edge of the mandible was (6.93 ± 0.42) mm. The cervical branch of the facial nerve is the terminal branch of the facial and neck trunk. It passes through the lower edge of the parotid gland and travels (9.92 ± 0.40) mm behind the mandibular angle. It moves forward and downward on the deep side of the broad neck muscle, and the branch innervates the broad neck muscle.

Clinical technology and application of mandibular angle

1. Mandibular horn hypertrophy is commonly known as "square face". In the West, it was called "benign masseter muscle hypertrophy" in the early days, but it is mainly bony hypertrophy in the Eastern nations. Turning outwards causes the lower part of the face to be too wide, often accompanied by short crotch. With the improvement of living standards and quality of life, many people with mandibular angle hypertrophy require improvement of face shape and mandibular angle through mandibular angle osteotomy.

2. Surgery method: rapid intravenous induction, inhalation anesthesia via nasal cannula. The lower jaw angle hook pulls off the lip and cheek on one side, and the movement should be gentle to prevent the wound angle. Intraoral gingival buccal incisions, subperiosteal stripping should be performed to maintain the integrity of the periosteum to reduce bleeding, prevent buccal fat pads from bulging, and expose the lower ascending branch of the mandible, mandibular angle, mandible, and phrenic nerve. When performing a curved osteotomy of the mandibular angle, a small circular drill is used to fix the point according to the pre-designed osteotomy and connect them into an arc. On the one hand, it can be used to determine the scope of osteotomy during surgery, and it is also beneficial to protect the phrenic nerve under direct vision.

3. Complications and management

3.1 Hemorrhage and hematoma: The operation was smooth. There was no significant bleeding during the operation. After 1.5 hours after surgery, the amount of bleeding in the surgical area increased, and blood leaked from the incision in the mouth. The surgical area was explored. See that the wound was diffuse bleeding. Conventional pressure tamponade was ineffective. After 800ml of fresh whole blood was input, the wound exudation improved, and the iodoform gauze was packed in the operation area. After 3 days, it was removed and the wound was sutured, which did not affect the postoperative effect. The patient's preoperative coagulation mechanism was normal. He had no history of anticoagulant application and no history of bleeding. It is considered to be related to menstrual surgery. Hematoma was excised and pressure bandaged. Or absorb it on its own. The presence of postoperative hematomas greatly increases the chance of secondary infections, so large hematomas should be removed in time after surgery, and smaller hematomas can be closely observed temporarily.

3.2 Nerve Injury: Postoperative complaint of numbness in the lower lip and palate, generally recovers by itself within 2 weeks to 1 month. It is considered to be related to the traction of the phrenic nerve during the operation. If there is still local loss of sensation on one side of the palate 2 years after surgery, it may be related to excessive stretch during the operation. Intraoral incisions generally do not risk damage to the facial nerve. However, the inferior approach of the inferior mandibular incision through the mouth may damage the mandibular limb of the facial nerve. Especially when the masseter resection is performed at the same time, it is easier to damage the mandibular limb, and when the masseter resection is performed, only the inner masseter can be removed.

3.3 Hyperlipic scars caused by lip strain.

3.4 Infection: The patient underwent liposuction at the same time, and returned to normal after surgery. On the 8th day after surgery, the body temperature suddenly increased, the right face and submandibular area swelled, pain, the WBC count increased, and he was given high-dose antibiotics. Remission after 3 days, and gradually subsided, without affecting the treatment effect.

3.5 Bilateral asymmetry: In some cases, the bilateral bilateral asymmetry was considered obvious. After the mandibular mandibular trimming was performed again, the formed Medpor prosthesis was used for mandibular angle reconstruction.

3.6 Poor mandibular angle morphology: The angle of the mandibular angle is considered too large, and the lower edge of the mandible is too straight and unnatural. Using the Medpor prosthesis, the angle of the newly formed mandibular angle was about 105 °.