Lateral Deviated Mandible - 謝明吉、姜厚任 顎顏面 美學 重建 專科診所-風華整形聯合診所
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Lateral Deviated Mandible

Lateral Deviated Mandible

Study of Bailey et al. (2001) indicated that 35% of patients underwent orthognathic surgery had lower facial asymmetry and concluded that lateral deviated mandible was the most possible cause. Trauma, congenital diseases or development abnormalities of craniofacial bones may lead to mandibular deviation.

Depends on the location and etiology, mandibular deviation can be divided into two groups:
(1) Condylar abnormality (Kawamoto HK,2009)
(2)Altered cranial base: Altered cranial base may result in malpositioned glenoid fossa. Condylar abnormality may result in mandibular hyper- or hypoplasia. These two types of mandibular deviation may occur simultaneously and lead to mandibular deviation.

Condylar Abnormality

Condylar Fracture

Condylar or subcondylar fracture occurs during childhood may cause development abnormalities of mandibular growth center leading to mandibular deviation. Childhood condylar fracture is one of the most commonly seen facial bone fracture, e.g. fall or traffic accidents lead to crashes on the chin.

In particular TMJ fracture in children can be easily overlook because there is no obvious wound (apart from the skin wound caused from crashes). Condylar fracture often results in ipsilateral mandibular hypoplasia. Proffit et al. found that 5-10% of mandibular deviation is related to condylar fracture (Proffit WR, 1980).



Condylar Hyperplasia

Condylar hyperplasia occurs most often during the adolescence, leading to unilateral (higher prevalence) bilateral mandibular overgrowth in horizontal direction. The etiology of condylar hyperplasia is not yet concluded. The possible causes include trauma, circulatory abnormalities, infections or arthritis that stimulate the growth of TMJ condyle (Pivar SJ,2006)。

Mandibular hyperplasia will result in facial asymmetry, deviation of mouth corner and cant in mandibular occlusal plane. Compensatory growth will occur afterwards and lead to cant in maxillary occlusal plane.  

Unilateral TMJ condylar hyperplasia (e.g. left TMJ) will compress the TMJ condyle on the other side (e.g. rightt TMJ) and therefore increase the risk of developing TMJ internal disc derangement and arthritis with pain and difficulty opening the mouth (Pivar SJ,2006)。



Hemifacial  Microsomia

Hemifacial microsomia is the second most common facial birth defect after cleft lip/palate (Kreiborg S, 1981) and its prevalence is about 1/5600. Hemifacial microsomia mainly affects the 1st and 2nd pharyngeal arches that develops in fetal life and consequently affects the development of maxilla, mandible, external and inner ear, masseter muscles and surrounding soft tissues (Cervelli V, 2008). The patients usually show little sign of abnormalities in the appearance or jawbones until the adolescence (Kjellberg H, 1998). Hemifacial microsomia can cause all levels of mandibular hypoplasia affecting mandibular ramus, condyle and glenoid fossa. Mandible has higher risk in developing bone deformity than maxilla and zygomatic bone.

Condylar Arthritis

The causes of TMJ arthritis include trauma, disc displacement, and autoimmune disease. Intra-articular inflammation will affect the soundness of synovial membrane and lead to condylar resorption and deformity.

Juvenile idiopathic arthritis or juvenile rheumatoid arthritis occurs in children less than 16 years old, which easily affects the growth of articular cartilage and causes retrognathia and cant occlusal plane

A mild degree of asymmetry is common in the faces; most cases are not very obvious and do not need treatment. However in the case of lateral deviated mandible resulting in facial asymmetry, it is easily recognized from the appearance because of its more protruding position. Besides lateral deviated mandible often combine with malocclusion and signs of TMJ disorders and therefor is in need of treatment.

Altered Cranial Base

Muscular Torticollis

Muscular torticollis is one of the most common congenital muscular abnormalities in children with an incidence of 0.3-1.3% in newborns (Clarren SK,1981). It often combines with various levels of sternocleidomastoid muscle fibrosis, facial hemihypo-plasia, plagiocephaly and scoliosis. The cause of congenital muscular torticollis is contracture of sternocleidomastoid muscle scar formed by trauma during intrauterine or delivery. About 62% of patients with muscular torticollis experienced dystocia, e.g. breech presentation, forcep delivery or cesarean section (Cheng JC,1994; Wolfort FG,1989; Stellwagen L,2008)。

Unbalanced forces in neck muscles will result in cranial base asymmetry and deformational plagiocephaly. In addition, facial asymmetry caused by facial muscle dystrophy and strabismus caused by visual axis deviation may occur. Moderate to severe muscular torticollis are often diagnosed and treated during childhood. Mild muscular torticollis however is easily overlooked. In this case the patient may miss the chance of early treatment and lead to deviation in facial anatomy (Kawamoto HK,2009)。



Unilateral  Coronal Craniosynostosis

Cranial bones refer to the bones that protect the brain and form the ventricles. Cranial bones are comprised of many bones including frontal bone, parietal bone, occipital bone and temporal bone- all bones connected to each other with the joints called cranial sutures. Normally the growth of the cranial bones or skull is toward the direction perpendicular to the cranial sutures. Premature fusion of cranial sutures will result in abnormal head shape as the frontal bones cannot grow and expend to hold the growing brain (Kane AA, 1996). The clinical signs include asymmetrical eyes, ears and jaws. 

Deformational Plagiocephaly

Deformational plagiocephaly is another common development defects in children. Its incidence has increased after the promotion of infant sleeping prone to prevent sudden infant death syndrome (SIDS) since 1992 (Kjellberg S,1998;Ronchezel MV,1995). Deformational plagiocephaly is often coupled with muscular torticollis. Same as muscular torticollis, the causes of deformational plagiocephaly are related to dystocia or intrauterine fetal constraint, resulting in asymmetrical growth of cranial bones and skull base and afterwards malposition of TMJ condyle and asymmetrical lower face (Kreiborg S,1981)。

Mandibular deviation is often related to condylar growth defects, in particular the hyper- or hypoplasia of mandible caused by TMJ trauma or diseases during childhood. Clinicians should carefully assess whether the underlying causes of mandibular deviation is endocranial or condylar abnormality. Only the correct diagnosis enables the clinician to develop appropriate treatment plan and maintain stable long-term treatment outcome.


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All Written Contents and Pictures Created by Dr. Adrian M. Hsieh and Dr. Scott H. Jiang





Results of surgery vary among patients. Please consult your doctor.