In-Service Exam
Mandible - 2002





A 10-year-old boy has a laceration of the chin and pain in the jaw and ear after falling while ice skating. On examination, the maximal incisal opening is 10 mm, and the chin point is deviated to the left. There is an upward cant of the mandibular occlusion on the left with a right-sided lateral open bite.

These findings are most consistent with which of the following?

(A) Bilateral condylar fractures
(B) Bilateral temporomandibular joint dislocation
(C) Left-sided condylar fracture
(D) Left-sided mandibular body fracture
(E) Right-sided condylar fracture

The correct response is Option C.

The findings in this child are most consistent with a left-sided condylar fracture. It is necessary to exclude a diagnosis of condylar fracture in any child who sustains trauma to the chin. Indications for a diagnosis of condylar fracture include malocclusion, pain with range of motion of the temporomandibular joint, and preauricular pain. Lacerations of the external auditory canal may also be associated. Patients with unilateral condylar fractures exhibit loss of posterior ramus height unilaterally, resulting in premature contact of the maxillary and mandibular molars posteriorly and a contralateral lateral open bite. The mandibular occlusal plane will demonstrate an ipsilateral upward cant. The maximal incisal opening will be decreased, and the chin point and mandibular midline will be deviated ipsilaterally due to the unopposed action of the lateral pterygoid muscle on the contralateral side. Because this child has chin deviation and an upward cant on the left with a right-sided lateral open bite, a left-sided condylar fracture can be diagnosed.

A child with bilateral condylar fractures will have an anterior open bite resulting from premature contact of the mandibular and maxillary molars posteriorly. Ear pain and lacerations of the external auditory canal may also be present bilaterally.

Bilateral temporomandibular joint dislocation typically results in an open bite and severe limitation of jaw excursion, also known as "lock-jaw."

Although left-sided mandibular body fractures can be associated with limited mouth opening, a contralateral open bite and an ipsilateral upward occlusal cant are not typical of this type of fracture.

As mentioned above, a right-sided condylar fracture would manifest as a left-sided lateral open bite with chin deviation and an upward occlusal cant on the right.

References
1. Crawley WA, Sandel AJ. Fractures of the mandible. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:192-202.
2. Manson PN. Facial fractures. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:383-412.

A 24-year-old woman sustains facial injuries in a motor vehicle collision. On examination, there is tenderness in the preauricular region bilaterally, posterior facial height is decreased, and there is malocclusion with an anterior open bite. Panoramic radiographs show low subcondylar fractures of the mandible bilaterally. The mandibular condyles are seated within the glenoid fossa, and the proximal segment overrides the distal segment laterally.

Which of the following is the most appropriate management?

(A) Observation
(B) Intermaxillary fixation for two weeks followed by physical therapy
(C) Intermaxillary fixation for eight weeks followed by physical therapy
(D) Bilateral external fixation
(E) Open reduction and internal fixation

The correct response is Option E.

Because stable anatomic reduction of the fracture segments is crucial for management of this patient's injuries, open reduction and internal fixation should be performed via a preauricular approach. Accurate reduction of a subcondylar fracture is rarely achieved with closed reduction alone. In addition, the absence of internal fixation will lead to fracture instability secondary to the forces of the masseter, temporalis, and medial and lateral pterygoid muscles, ultimately resulting in decreased posterior facial height and abnormal condylar mechanics caused by displacement of the condylar head. The patient will be at greater risk for malocclusion and development of degenerative osteoarthritis. Therefore, accurate open reduction with rigid internal fixation is advocated to avoid any potential complications. With this approach, normal posterior facial height will be restored, and the risk for abnormal joint mechanics will be minimized. Endoscopically-assisted fracture reduction, with rigid fixation, is a new technique that shows promise because it combines the advantages of the open approach (ie, anatomic reduction and early motion) while minimizing external scarring and the risk for facial nerve injury.

Observation alone is inadequate fracture management and will result in malunion, nonunion, and/or the development of pseudarthrosis.

Although a short course of intermaxillary fixation (two to three weeks) followed by graduated opening of the mandible has traditionally been implemented in the management of subcondylar fractures, it does not address fracture malalignment or its potential complications. Prolonged intermaxillary fixation (six weeks or more) is associated with an increased risk for temporomandibular joint stiffness and a subsequent decrease in interincisal opening.

References
1. Crawley WA, Sandel AJ. Fractures of the mandible. In: Ferraro JW, ed. Fundamentals in Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:192-202.
2. Jacobovicz J, Lee C, Trabulsy PP. Endoscopic repair of mandibular subcondylar fractures. Plast Reconstr Surg. 1998;101:437-441.
3. Lee C, Mueller RV, Lee K, et al. Endoscopic subcondylar fracture repair: functional, aesthetic, and radiographic outcomes. Plast Reconstr Surg. 1998;102:1434-1443.
4. Lettieri S. Facial trauma. In: Achauer BM, Erikson E, Guyuron B, et al, eds. Plastic Surgery: Indications, Operations, and Outcomes. Saint Louis, Mo: Mosby Ð Year Book, Inc; 2000;2:923-940.
5. Zide MF, Kent JN. Indications for open reduction of mandibular condyle fractures. J Oral Maxillofac Surg. 1983;41:89-98.

In pediatric patients, abnormalities in mandibular growth are most closely associated with fractures involving which of the following regions of the mandible?

(A) Angle
(B) Body
(C) Condyle
(D) Ramus
(E) Symphysis

The correct response is Option C.

In children, abnormalities in mandibular growth are most closely associated with fractures involving the mandibular condyle. More than one-third of all facial fractures in children involve the mandible. The pediatric condyle, which is the primary growth center of the mandible, is immature, highly vascular, and covered with a thin sheath of periosteum. Any compressive or traumatic forces may cause the condyle to burst, rather than fracture, resulting in fragmentation of bone, hemarthrosis, and increased osteogenic potential. Ankylosis and growth disturbances are potential long-term complications. According to one study, 47% of children who sustained condylar fractures subsequently developed temporomandibular joint dysfunction or abnormalities of facial growth.

In order to maintain the height of the mandibular ramus and adequate function of the temporomandibular joint, appropriate management should include closed reduction and immobilization for five to eight days, followed by initiation of physical therapy.

References
1. McGuirt WF, Salisbury PL III. Mandibular fractures: their effect on growth and dentition. Arch Otolaryngol Head Neck Surg. 1987;113:257.
2. Posnick JC, Wells M, Pron GE. Pediatric facial fractures: evolving patterns of treatment. J Oral Maxillofac Surg. 1993;51:836.
3. Proffit WR, Vig KW, Turvey TA. Early fracture of the mandibular condyles: frequently an unsuspected cause of growth disturbances. Am J Orthod. 1980;78:1-24.
4. Rowe NL. Fractures of the jaws in children. J Oral Surg. 1969;27:497.