Mandible OMF Flashcards
A 46-year-old man comes to the office because he has pain in the jaw and trismus after being involved in a motor vehicle collision two days ago. Radiographs show a mandibular fracture. In adults, the normal range of vertical mandibular opening is closest to which of the following?
(A) 11 to 20 mm
(B) 21 to 30 mm
(C) 31 to 40 mm
(D) 41 to 50 mm
(E) 51 to 60 mm
The correct response is Option D.
In adults, the vertical mandibular opening measured from maxillary incisal edge to mandibular incisal edge (interincisal distance) typically ranges from 40 to 50 mm. In addition, normal range of motion of the mandible includes lateral jaw excursion (measured at the midline incisor) to 10 mm on each side.
Decreased mandibular opening may indicate dysfunction of the temporomandibular joint (TMJ) or surrounding soft tissues. Patients who may potentially have internal derangement of the TMJ also may experience painless clicking when opening the mouth.
A 27-year-old man is admitted to the emergency department after being injured in an altercation. Physical examination shows objective malocclusion with a left-sided crossbite and right-sided open bite. A CT scan is shown. Which of the following muscles is most likely responsible for these radiographic and physical examination findings?
A) Genioglossus
B) Lateral pterygoid
C) Masseter
D) Medial pterygoid
E) Mylohyoid
The correct response is Option B.
The patient described has typical radiographic and physical exam findings of a right subcondylar mandibular fracture.
Anteromedial displacement of the condylar segment out of the glenoid fossa occurs secondary to pull from the lateral pterygoid muscle, which normally functions in anterior translation of the condyle across the articular eminence of the temporal bone during wide mouth opening. This leads to loss of height of the mandibular ramus and a premature occlusion on the fracture side. This causes the typical findings of condylar/subcondylar fractures: ipsilateral crossbite and contralateral open bite.
The masseter and medial pterygoid form the pterygomasseteric sling, which attaches from the skull base and zygoma to the inferior mandibular border, and is responsible for fracture displacement after angle and body fractures. The mylohyoid and genioglossus muscles run along the floor of the mouth and can contribute to fracture displacement in the body and parasymphyseal region.
A 45-year-old woman with a history of metastatic breast cancer previously treated with zoledronate is evaluated because of an area of exposed necrotic mandibular bone measuring 1 × 1 cm. She has no pain, and there is no clinical evidence of infection. Panoramic x-ray study (Panorex) shows no evidence of fracture. Which of the following is the most appropriate next step in management?
A) Aggressive debridement and prophylactic titanium plate placement
B) Antiseptic mouth rinses and observation
C) Dental extraction and intravenous antibiotics
D) Segmental mandibulectomy and osteocutaneous free flap reconstruction
E) Superficial debridement and oral antibiotics
The correct response is Option B.
This patient has osteonecrosis of the jaw secondary to bisphosphonate medication used to treat her bony cancer metastases. The mandible is more commonly affected than the maxilla. The appropriate next step in management is to begin antiseptic mouth rinses in addition to stressing good dental hygiene. Asymptomatic bone exposure can be followed for progression, and early cases appear to often resolve spontaneously when the bisphosphonates are discontinued.
Ruggiero et al. proposed a three-stage classification system and treatment algorithm for bisphosphonate-related osteonecrosis of the jaw based on clinical features. In Stage 1, there is exposed and necrotic bone that is otherwise asymptomatic, as in the patient described above. In Stage 2, there is exposed and necrotic bone with pain and clinical evidence of infection. Antiseptic mouth rinses, oral antibiotics, and superficial debridement are recommended for this stage. Stage 3 includes all the features of Stage 2 and one or more of the following: pathologic fracture, extraoral fistula, and osteolysis extending to the inferior mandibular border. Stage 3 patients require surgical debridement or resection in addition to antiseptic mouth rinses and oral antibiotics. Dental extraction of infected, unsalvageable teeth should be performed, but extractions may also result in further nonhealing wounds and bone exposure. Segmental mandibulectomy is usually followed by immediate reconstruction with osseous or osteocutaneous free flap reconstruction. The role for prophylactic titanium plating of the jaws to prevent pathologic fracture has not been studied.
Which of the following terms best describes the type of occlusion in which the upper central incisor lies anterior to the lower central incisor in the sagittal plane?
(A) Buccal crossbite
(B) Lingual crossbite
(C) Open bite
(D) Overbite
(E) Overjet
The correct response is Option E.
Overjet is a horizontal measurement that refers to the distance between the incisal aspect of the maxillary incisors and the incisal aspect of the mandibular incisors with the teeth in centric occlusion. When the upper central incisor lies anterior to the lower central incisor in the sagittal plane, this is known as overjet.
Overbite is a vertical measurement referring to the distance between the maxillary incisor edge and the mandibular incisor edge with the teeth in centric occlusion. An overbite or deep bite is one in which the upper central incisor overrides the lower central significantly in the vertical dimension.
Buccal and lingual crossbite refer to the positioning of the mandibular molars with respect to the maxillary molars in the transverse plane.
Open bite occurs when the maxillary and mandibular teeth fail to contact. This can occur at any point in the dentition.
A 22-year-old man sustains a left subcondylar fracture of the mandible during a motor vehicle collision. On CT scan, the condyle is displaced medially and anteriorly. This displacement is most likely caused by tension from which of the following muscles?
(A) Medial pterygoid
(B) Lateral pterygoid
(C) Masseter
(D) Mylohyoid
(E) Temporalis
The correct response is Option B.
The inferior belly of the lateral pterygoid originates from the lateral pterygoid plate and inserts onto the scaphoid fossa of the condyle and joint capsule. The superior belly of the lateral pterygoid muscle originates from the sphenoid and inserts on the temporomandibular joint. The effect of the lateral pterygoid muscle is to displace the condyle medially and anteriorly in fractures of the condylar neck. It also tends to displace the meniscus anteriorly. The muscles inserting directly on the mandible exert significant forces on fracture fragments. An understanding of their direction of pull and insertions is important in the proper reduction and fixation of mandibular fractures. All the muscles of mastication serve to elevate and protrude the mandible. The elevators include the masseter, medial pterygoid, and temporalis. The temporalis inserts onto the coronoid process and the superior aspect of the external oblique line. The masseter inserts onto the lateral aspect of the mandibular angle while the medial pterygoid inserts on the medial aspect of the mandibular angle. None of these muscles directly affect the condyle. The mylohyoid muscle inserts on the body of the mandible, displacing segmental body fractures medially.
A 25-year-old man with a fracture of the mandibular angle is evaluated for open reduction and internal fixation. Which of the following is the most appropriate location for placement of internal fixation when using the Champy technique in this patient?
A) External oblique ridge
B) Lingula
C) Mandibular notch
D) Mental tubercle
E) Mylohyoid line
The correct response is Option A.
This technique for internal fixation of mandibular angle fractures was first described by Michelet in 1972, and biomechanical studies by Champy et al were published in 1976. In his original paper, Champy advocated placement of an internal fixation miniplate along the external oblique line of the mandible. By contouring the plate to this line, rigid fixation is achieved in two planes, taking advantage of the force vectors along the angle of the mandible to help compress the fracture site.
Mylohyoid line is not appropriate because the mylohyoid line is located along the lingual surface of the mandibular body and is not used routinely as a location for plate fixation for mandibular fractures.
Lingula is not appropriate because the lingula is located along the lingual surface of the mandibular ramus, and is the location where the mandibular nerve (V3) enters the mandible. Plate fixation should be avoided in this area because of the difficulty of exposure and the risk for damaging the mandibular nerve.
Mental tubercle is not appropriate because the mental tubercle is not an appropriate place to apply internal fixation when utilizing the Champy technique.
Mandibular notch is not appropriate because it is located between the mandibular condyle and the coronoid process and is not an appropriate place to apply internal fixation when utilizing the Champy technique.
In planning open reduction and internal fixation in a patient with a low subcondylar neck fracture, which of the following extraoral incisions provides the safest and most versatile exposure to the fracture site?
(A) Postauricular
(B) Preauricular
(C) Retromandibular
(D) Submandibular
The correct response is Option C.
The retromandibular incision provides the safest and most versatile exposure for open reduction and internal fixation of submandibular fractures. When compared with the subcondylar and preauricular incisions, there is significantly less injury to the marginal mandibular, temporal, and zygomatic branches of the facial nerve.
The retromandibular incision allows access superiorly to the coronoid notch and inferiorly to the angle of the mandible. The addition of a transfacial trocar to this approach facilitates access to higher level subcondylar fractures as well. The preauricular, postauricular, and submandibular incisions provide a more limited view of low subcondylar fractures.
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.
Simultaneous ipsilateral contractions of which of the following muscles produce the side-to-side grinding movements of the mandible?
(A) Masseter and lateral pterygoid
(B) Masseter and medial pterygoid
(C) Masseter and temporalis
(D) Medial and lateral pterygoid
(E) Medial pterygoid and temporalis
The correct response is Option D.
Simultaneous contractions of the medial and lateral pterygoid muscles largely produce the side-to-side grinding and chewing movements of the mandible. Both pairs of medial and lateral pterygoid muscles have two heads. The heads of the medial pterygoids originate from the medial surface of the lateral pterygoid plate and the tuberosity of the maxilla and insert into the medial surface of the mandibular angle and ramus. These muscles act to elevate the
mandible. The heads of the lateral pterygoids originate from the lateral surface of the lateral pterygoid plate and the infratemporal surface of the greater wing of the sphenoid and insert into the neck of the mandibular condyle and articular disk. These muscles act to protrude the mandible forward and open the mouth. When the ipsilateral medial and lateral pterygoid muscles work together, rotation occurs around the vertical axis of the contralateral condyle. Grinding and chewing movements occur when both sides alternate this action in rhythmic fashion. Simultaneous action of all four pterygoid muscles results in protrusion of the mandible.
The masseter muscle arises from the lower border and medial surface of the zygomatic arch and attaches to the lateral aspect of the mandibular ramus. It functions primarily to elevate the mandible to occlude the teeth. The temporalis muscle originates in the temporal fossa of the cranium and attaches to the coronoid process of the mandible. Although its primary function is elevation of the mandible, it can also retract the mandible because of the action of the posterior muscle fibers. Both the masseter and temporalis muscles contribute only minimally to the side-to-side grinding movements of the mandible.
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.
A 12-year-old boy is brought to the emergency department after he fell while riding his bike and landed on the chin. Panorex radiographs show a minimally displaced fracture of the high right condylar neck and an open left parasymphyseal fracture. Which of the following is the most effective management?
(A) Observation with serial radiographs and restriction to soft diet
(B) Intermaxillary fixation with infraorbital and circummandibular wires for four weeks
(C) Intermaxillary fixation with arch bars for four weeks
(D) Open reduction with internal fixation of the parasymphyseal fracture and arch bars for two weeks
(E) Open reduction with internal fixation of both the parasymphyseal fracture and the fracture of the high condylar neck
The correct response is Option D.
Observation alone is inadequate management of the parasymphyseal fracture. This child presents in the late phase of the mixed dentition and should have enough adult dentition in place to secure the arch bars. Wires to reduce the fractures will not provide as much stability as arch bars. This technique, however, is useful in the child who does not yet have enough adult dentition to secure the arch bars.
Immobilization for a short period (i.e., two weeks) is the appropriate management of the condylar neck fracture. This will help to allow the fractures to become stable enough to maintain the reduction once movement is instituted. Early movement helps to decrease the risk of ankylosis of the temporal mandibular joint. Extended immobilization to allow for healing of the parasymphyseal fracture will increase the risk of ankylosis of the temporomandibular joint. Open reduction and internal fixation (ORIF) of the parasymphyseal fracture will ensure an anatomic reduction of a stable skeletal unit. This, in turn, will decrease the risk of infection and nonunion.
ORIF of the condylar neck fracture is not indicated because the fracture is minimally displaced. Conservative management of these fractures is well accepted and has stood the test of time. Open reduction would incur the risks of injury of the facial nerve.
A 16-year-old boy is evaluated for multiple fractures to the mandible after crashing his ATV into a tree. Which of the following modalities best takes advantage of load-bearing osteosynthesis in the management of this patient’s fractures?
A) Bicortical border plate for a mandibular parasymphyseal fracture
B) Champy plate fixation for a mandibular angle fracture
C) Lag screw fixation for a displaced fracture of the mandibular symphysis
D) Locking reconstruction plate for a comminuted mandibular body fracture
E) Maxillomandibular fixation for a minimally displaced mandibular subcondylar fracture
The correct response is Option D.
Load-bearing osteosynthesis differs from load-sharing osteosynthesis in that the fracture plate assumes all of the load of the given bone rather than distributing the load among the plate and the bone.
Examples of load-sharing osteosynthesis include lag screw fixation, maxillomandibular fixation, nonlocking mandibular border plate, and monocortical miniplate (Champy principle) fixation.
An example of load-bearing fixation is a mandibular locking reconstruction plate for a comminuted fracture.
A 33-year-old woman is brought to the emergency department after sustaining injuries in a motor vehicle collision. The patient notes pain on opening her mouth. Physical examination shows bilateral facial swelling and loss of posterior facial height. An anterior open bite is also noted. Which of the following additional findings on physical examination is most likely to suggest a bilateral subcondylar fracture in this patient?
A) Bilateral facial numbness
B) Bilateral mastoid ecchymosis
C) Blood in the external auditory canal
D) Clear fluid in the external auditory canal
E) Preauricular pain
The correct response is Option E.
Bilateral subcondylar fractures result in premature occlusion of the posterior teeth along with an anterior open bite, loss of posterior facial height, and bilateral facial swelling with pain on mouth opening. These findings occur because the subcondylar fracture interrupts the integrity of the vertical buttress. The lateral pterygoid muscles displace the condylar necks medially and anteriorly, allowing the unopposed vertical action of the temporalis and masseter muscles to shorten the posterior facial height. Swelling bilaterally would be expected in this fracture, and opening would displace the fracture line, causing pain.
Bilateral facial numbness suggests a fracture of the ramus or body as the inferior alveolar nerve traverses these areas. Blood in the external auditory canal suggests a fracture more proximal than subcondylar. Bilateral mastoid ecchymosis and/or clear fluid in the external auditory canal suggest a skull base fracture.
A 26-year-old man comes to the office because he has pain in the mandible seven days after undergoing open reduction and internal fixation of a fracture of the mandible. Physical examination shows infection in the submandibular space. Which of the following teeth are the most likely source of this infection?
(A) Mandibular canines
(B) Mandibular central incisors
(C) Mandibular first and second premolars
(D) Mandibular second and third molars
(E) Maxillary second and third molars
The correct response is Option D.
The submandibular space is located inferolateral to the mylohyoid muscle and superior to the hyoid bone. The contents of the submandibular space include the submandibular gland, lymph nodes, the facial vein and artery, and the inferior loop of the hypoglossal (XII) nerve. Anteriorly, the submandibular space communicates with the submental space and posteriorly with the pharyngeal space. The sublingual space is located superomedial to the mylohyoid muscle. Involvement of the submandibular space is produced principally by infections of the second and third mandibular molars because of the more superior position of the mylohyoid ridge on the mandible posteriorly, which places the root apices of the second and third molars beneath the mylohyoid muscle. Infections of the maxillary molars, when they extend through the buccal cortical plates above the attachments of the buccinator muscle, can present as infections of the buccal space. Infections from the anterior mandibular teeth (anterior to the second molar) usually drain above the mylohyoid muscle into the sublingual space.
The application of a locking reconstruction plate to a comminuted mandibular fracture is LEAST likely to cause which of the following?
(A) Decreased bone resorption
(B) More difficulty in contouring the plate
(C) Hardware failure
(D) Hardware-related infection
(E) Malocclusion
The correct response is Option E.
Use of a locking reconstruction bone plate has been shown to decrease postoperative malocclusion after a comminuted fracture of the mandible. A conventional (nonlocking) bone plate requires precise adaptation of the plate to the underlying bone. Without intimate contact, the bone is drawn toward the plate when the screws are tightened, altering the position of the osseous segments and the occlusal relationship. However, a locking bone plate does not require intimate contact of plate to bone because the bony segments are secured by screws that are locked to the plate. This makes it less likely for screw insertion to alter the reduction and, ultimately, the occlusion.
Cortical compression, blood supply disruption, and associated bone resorption occur less frequently with locking plates than with standard reconstruction plates. Difficulty in plate contouring is less likely to occur with locking plates because they require less precise bending than do conventional plates, which depend on intimate bony contact for stability. No increase in hardware failure has been noted with locking plates. In fact, screws in locking plates are less likely to become loose than those in standard reconstruction plates. The rate of hardware-related infection with locking plates is similar to the rate with standard reconstruction plates.
A 12-year-old boy is brought to the emergency department after he fell while riding his bike and landed on the chin. Panorex radiographs show a minimally displaced fracture of the high right condylar neck and an open left parasymphyseal fracture. Which of the following is the most effective management?
(A) Observation with serial radiographs and restriction to soft diet
(B) Intermaxillary fixation with infraorbital and circummandibular wires for four weeks
(C) Intermaxillary fixation with arch bars for four weeks
(D) Open reduction with internal fixation of the parasymphyseal fracture and arch bars for two weeks
(E) Open reduction with internal fixation of both the parasymphyseal fracture and the fracture of the high condylar neck
The correct response is Option D.
Observation alone is inadequate management of the parasymphyseal fracture. This child presents in the late phase of the mixed dentition and should have enough adult dentition in place to secure the arch bars. Wires to reduce the fractures will not provide as much stability as arch bars. This technique, however, is useful in the child who does not yet have enough adult dentition to secure the arch bars.
Immobilization for a short period (i.e., two weeks) is the appropriate management of the condylar neck fracture. This will help to allow the fractures to become stable enough to maintain the reduction once movement is instituted. Early movement helps to decrease the risk of ankylosis of the temporal mandibular joint. Extended immobilization to allow for healing of the parasymphyseal fracture will increase the risk of ankylosis of the temporomandibular joint. Open reduction and internal fixation (ORIF) of the parasymphyseal fracture will ensure an anatomic reduction of a stable skeletal unit. This, in turn, will decrease the risk of infection and nonunion.
ORIF of the condylar neck fracture is not indicated because the fracture is minimally displaced. Conservative management of these fractures is well accepted and has stood the test of time. Open reduction would incur the risks of injury of the facial nerve.
A 22-year-old man is evaluated because of a painless, firm, unilateral enlarging mass of the body of the mandible. He denies trauma to the area and he has excellent oral hygiene. His dentist performed fine needle biopsy that showed multinucleated giant cells. CT scan shows a radiolucent bone lesion with an expanded cortex. Which of the following is the most appropriate next step in management?
A) Incisional biopsy
B) Partial mandibulectomy with free margins
C) Radiation therapy
D) Resection and curettage
E) Sclerotherapy
The correct response is Option D.
This patient has an aneurysmal bone cyst (ABC). These lesions may be related to giant cell granulomas. These lesions are most common in the long bones with 1.9% of them being reported in the mandible.
The correct answer is resection and curettage. In a study of 120 ABC cases, resection and curettage was reported to have a 91.8% success rate (recurrence occurred in 11 out of 120 cases). Incomplete resection is hypothesized to be a cause of recurrence. Recurrence was not related to histopathologic parameters.
Pathologically, these lesions are a pseudocyst comprised of multinucleated giant cells, woven trabecular bone with caverns, and sinusoids lacking endothelium. Recurrence can be treated with repeat excision curettage, open packing, or block resection. These lesions are quite vascular and typically bleed until resected, so expeditious removal is recommended (transfusion with packed red blood cells has been reported in the literature).
Incisional biopsy would be diagnostic but is not recommended for these lesions given their vascularity and the surgeon’s inability to control the bleeding.
Sclerotherapy is recommended for vascular malformations such as arteriovenous malformations, venous malformations, or lymphatic malformations. This lesion would not be responsive to this type of therapy.
Partial mandibulectomy with free margins is the preferred treatment for lesions like ameloblastomas. Given the efficacy of excision and curettage, mandibulectomy is not the recommended first line treatment for this diagnosis. It can be employed in recurrences (although as stated above, less aggressive interventions are typically employed first).
A patient has an infection at the surgical site one week after undergoing open reduction and internal fixation of a fracture of the mandibular body using an inferior border reconstruction plate and a tension band. Occlusion is normal. The infection site is surgically drained; intraoperative exploration shows that the plates and screws are stable with no evidence of loosening.
Which of the following is the most appropriate management of the hardware?
(A) Maintenance of current stabilization without removal of the hardware
(B) Removal of all plates and immediate application of intermaxillary fixation
(C) Removal of all plates and immediate application of two miniplates
(D) Removal of all plates and immediate placement of an external fixator
(E) Removal of all plates and placement of new plates when the infection has subsided
The correct response is Option A.
Infections following open reduction and internal fixation of mandibular fractures typically result from failure of fixation devices, for example, loosening of the screws. In addition to operative drainage of the infection and antibiotic therapy, appropriate management in the majority of these situations includes removal and replacement of the hardware with intermaxillary or external fixation for stabilization of the fracture.
In this patient, the plates continue to provide stable fixation of the fracture. Because of this, the current stabilization should be maintained without removal of the hardware, and the patient should undergo operative drainage of the infection and administration of antibiotics.
A 22-year-old man sustains a transverse, noncomminuted fracture of the right mandibular angle when he is struck in the face during a fistfight. Which of the following interventions best adheres to Champy’s principle for management of this fracture?
(A) Dynamic compression plate with bicortical screws on the inferior edge of the mandible and a superior tension band
(B) Dynamic compression plate with bicortical screws and a mandibular arch bar
(C) Lag screw
(D) Miniplate with monocortical screws along the external oblique ridge
(E) Reconstruction plate with bicortical screws
The correct response is Option D.
Champy’s principles for fracture management call for placement of miniplates along the lines of tension in the mandible at the site of the fracture. Because compression is not necessary, the miniplates can be anchored with monocortical screws. Based on the muscular forces pulling on the mandible, Champy determined that, anterior to the canine tooth, two miniplates are needed to control the rotational forces of the genial and digastric muscles; posterior to the canine tooth, just one miniplate is required.
In a 10-year review examining various methods for treating fractures of the mandibular angle, Ellis concluded that use of a single 2.0-mm noncompression miniplate was associated with fewer complications than a double-plate system (one using two compression or noncompression plates) or a reconstruction plate.
A 26-year-old man presents to the emergency department because of jaw pain and malocclusion. He has normal dentition. CT scan shows an isolated, noncomminuted left-sided angle fracture of the mandible. Which of the following treatment methods is likely to have the lowest complication rate?
A) Closed reduction with arch bars
B) Open reduction through an intraoral approach with one miniplate
C) Open reduction through an intraoral approach with two miniplates
D) Open reduction through a submandibular incision with a 2.7-mm reconstructive plate
The correct response is Option B.
Treatment options for mandibular fractures are varied and include closed reduction and external fixation with intermaxillary fixation, as well as open reduction and internal fixation through either intraoral or extraoral approaches. Internal fixation strategies include non-rigid fixation with wire osteosynthesis, internal fixation with single or multiple miniplates, compression plate fixation, and locking reconstruction plates.
Intermaxillary fixation represents the historic standard for treating mandible fractures. Closed treatment of fractures with interdental fixation alone or combined with non-rigid internal fixation does not stabilize movement of the proximal segment in unstable and/or unfavorable angle fractures and results in an approximately 17% risk for infection or malunion.
Comparative studies and recent meta-analyses have demonstrated the lowest complication rates when treating isolated, noncomminuted mandibular angle fractures via open reduction and internal fixation with a single noncompression miniplate.
The addition of a second plate results in increased soft tissue and infection complications, likely because of the increased need for periosteal stripping and devascularization of the fractured segments.
Open reduction and fixation through an extraoral approach with a locking reconstruction plate results in slightly higher, but comparable, risk for complication. This treatment mandates a visible scar and carries increased risk for facial nerve injury. This treatment is indicated in comminuted fractures, fractures with loss of bone stock, and atrophic mandibles, but it is unnecessary in a patient with intact dentition and a noncomminuted, isolated fracture.
A 35-year-old woman is unhappy with the appearance of her “square face,” especially at the bottom jaw “near the corners,” and she wishes to have a smoother mandible contour permanently. Which of the following is the most appropriate treatment?
A) Alloplastic implant
B) Autologous fat grafting
C) Hyaluronic acid dermal filler
D) Mandible angle and body contouring
E) Suction lipectomy
The correct response is Option D.
Mandible contouring surgery, frequently called mandible angle reduction, is a bony procedure to decrease the angular contours in a “square face” or bottom jaw with “sharp corners.” The term “mandible angle” reduction is a misnomer, as usually both the mandible angle and the mandible body need to be gracefully contoured or resected to result in an aesthetically pleasing, rounder face.
Although fillers, fat grafting, and implants are used in the face, they are not usually used for mandible contouring. Suction lipectomy for a patient with a square jaw would not be successful.
A 26-year-old man comes to the office because he has pain in the mandible seven days after undergoing open reduction and internal fixation of a fracture of the mandible. Physical examination shows infection in the submandibular space. Which of the following teeth are the most likely source of this infection?
(A) Mandibular canines
(B) Mandibular central incisors
(C) Mandibular first and second premolars
(D) Mandibular second and third molars
(E) Maxillary second and third molars
The correct response is Option D.
The submandibular space is located inferolateral to the mylohyoid muscle and superior to the hyoid bone. The contents of the submandibular space include the submandibular gland, lymph nodes, the facial vein and artery, and the inferior loop of the hypoglossal (XII) nerve. Anteriorly, the submandibular space communicates with the submental space and posteriorly with the pharyngeal space. The sublingual space is located superomedial to the mylohyoid muscle. Involvement of the submandibular space is produced principally by infections of the second and third mandibular molars because of the more superior position of the mylohyoid ridge on the mandible posteriorly, which places the root apices of the second and third molars beneath the mylohyoid muscle. Infections of the maxillary molars, when they extend through the buccal cortical plates above the attachments of the buccinator muscle, can present as infections of the buccal space. Infections from the anterior mandibular teeth (anterior to the second molar) usually drain above the mylohyoid muscle into the sublingual space.
An 18-year-old man is evaluated for a mandibular fracture sustained in a motor vehicle collision. CT scan shows displaced left parasymphyseal and right mandibular body fractures. Resorbable plate fixation is planned. Compared with titanium implants, the use of resorbable fixation to treat this fracture is associated with which of the following?
A) Decreased postoperative pain
B) Decreased risk for malunion
C) Increased overall cost
D) Increased risk for infection
E) Lower hardware profile
The correct response is Option C.
Bioresorbable fixation is now widely employed in craniomaxillofacial surgery. While this technology has theoretical advantages in the treatment of craniosynostosis (e.g., obviates concerns of intracranial implant migration), the benefits of orthognathic surgery and the management of facial trauma are dubious. For mandibular fractures, several studies have found no statistical differences in overall or specific complication rates, including the need for plate removal, postoperative infection, malreduction/malocclusion, postoperative pain, or loss of fixation. Rigorous comparisons are lacking, but a recent comprehensive review of the reported studies demonstrated a trend toward increased complications using resorbable fixation to treat facial fractures. The only consistent difference is the cost of the implants, which is considerably higher for the resorbable systems.
A 20-year-old man comes to the office for consultation regarding malocclusion. On physical examination, the mandibular incisors are anterior to the maxillary incisors. The mesial buccal cusp of the maxillary first molar lies distal to the buccal groove of the mandibular first molar. These findings are characteristic of which of the following Angle classifications?
(A) Angle class I
(B) Angle class II, division I
(C) Angle class II, division II
(D) Angle class III
The correct response is Option D.
Angle class I, or normal occlusion, is characterized as having the mesial buccal cusp of the upper first molar occluding in the buccal groove of the mandibular first molar. In Angle class II, both divisions I and II, the mandibular dentition is distal to its class I position. Class II, division 1 is lingually inclined, and Class II, division 2 is labially inclined. In Angle class III malocclusion, the mandibular molar is anterior to its normal position with the maxillary molar.
A 31-year-old man presents with a posterior fracture to the body of the mandible involving the alveolus of the first molar sustained during an assault. Open reduction and internal fixation of the fracture is performed. Intraoperatively, the position of the mandibular first molar in the fracture prevents an adequate reduction, and it must be extracted. Removal of how many intact tooth roots is most likely to indicate complete extraction of the mandibular molar in this patient?
A) One
B) Two
C) Three
D) Four
The correct response is Option B.
Anatomy of the mandibular first molar is relatively consistent in that the vast majority will have two roots. Knowledge of the number of roots is important in the setting of extraction to ensure complete removal. If either the injury or the reduction of the mandible fracture had caused a fracture of the tooth root itself, then complete removal of the fractured root would involve either exploration at the time of open reduction and internal fixation or postoperative referral to an oral surgeon. A retained tooth root would place the patient at high risk for abscess formation that could require additional treatment.
1 root: Incisors, canines, mandibular premolars, and maxillary second premolars usually have one root.
2 roots: Maxillary first premolars and mandibular molars usually have two roots.
3 roots: Maxillary molars usually have three roots.
In a 27-year-old man who has sustained bilateral parasymphyseal fractures, which of the following muscles exerts a distractive force on the anterior fracture segment?
(A) Geniohyoid
(B) Lateral pterygoid
(C) Masseter
(D) Medial pterygoid
(E) Posterior belly of the digastric muscle
The correct response is Option A.
Both anterior and posterior muscles exert forces on the mandible. The anterior muscles consist of the geniohyoid, genioglossus, mylohyoid, and digastric muscles. The muscles from this group exert primary distractive forces on the anterior fracture segment of a parasymphyseal fracture, displacing the fracture segment downward, posteriorly, and medially. The geniohyoid muscle originates from the mental spine of the inner anterior mandible and inserts on the hyoid bone. It acts to depress and retract the mandible.
The masseter, temporalis, and medial and lateral pterygoids comprise the posterior muscles. These muscles do not exert any force on the anterior segment of a parasymphyseal fracture.
The digastric muscle has an anterior and a posterior belly. The posterior belly originates on the medial aspect of the mastoid and courses forward and inferiorly as a tendon, passing through a fascial sling on the hyoid to transition into the anterior belly, which inserts into the digastric fossa of the mandible. The posterior belly of the digastric muscle primarily functions to elevate the hyoid and exhibits only a secondary effect on the anterior mandible. In contrast, the anterior belly of the digastric muscle exerts force on the anterior fracture segment.
Removal of a tooth in a fracture line of the mandible is indicated in a patient with which of the following conditions?
(A) Cavities in the tooth
(B) Fracture of the root of the tooth
(C) Loose tooth
(D) Multiple fractures of the mandible
(E) Periodontal disease
The correct response is Option B.
Indications for removal of teeth in mandibular fractures include fracture of the root of the tooth, severe loosening of the tooth in presence of chronic periodontal disease, extensive periodontal injury and broken alveolar walls, and displacement of teeth from their alveolar socket. Periodontal disease alone is not an indication for tooth removal. Multiple fractures of the mandible are also not an indication for tooth removal because the teeth usually are needed for intermaxillary fixation prior to open reduction and internal fixation of the fractures. History of caries would warrant a referral to a dentist to ascertain whether any intervention would be required but would not necessitate removal of that tooth at the time of fracture management. Loose tooth is seen in most cases of mandibular fracture but is addressed by proper alignment and reduction of all fractures.
A man presents to the emergency room with a complicated mandibular third molar infection. He has limited range of motion of the jaw (trismus) and point tenderness above the zygomatic arch. The infection is most likely in which of the following anatomic spaces?
A) Buccal
B) Prevertebral
C) Pterygomandibular
D) Submasseteric
E) Temporal
The correct response is Option E.
There are four separate compartments that comprise the masticator space, including masseteric or submasseteric space, pterygomandibular space, deep temporal space, and superficial temporal space. The submasseteric space is bordered by the masseter muscle and ascending ramus of the mandible. The pterygomandibular space is formed by the medial pterygoid muscle and ascending ramus. The superficial temporal space is formed by the temporalis fascia and temporalis muscle. The deep temporal space is formed by the temporalis muscle and calvarium. These four spaces function as “subspaces” of the masticator space, but they can all become involved rapidly once one compartment is affected. The submasseteric and superficial temporal spaces are separated by the zygomatic arch. The pterygomandibular and deep temporal spaces are separated by the lateral pterygoid muscle.
An infection in the prevertebral space would not present with the signs and symptoms of tenderness above the zygomatic arch, and would be more likely to present with neck rigidity or dysphagia.
A 21-year-old man sustains blunt trauma to the face while playing football. On examination, he has unilateral pain and facial swelling; he is unable to open his mouth. Radiographs show a nondisplaced coronoid fracture. Which of the following is the most appropriate initial step in management?
(A) Coronoidectomy
(B) Maxillomandibular fixation
(C) Endoscopic reduction and fixation
(D) Open reduction and rigid internal fixation
(E) Open reduction and wire fixation
The correct response is Option B.
In this 21-year-old man who has an isolated nondisplaced fracture of the coronoid process, the most appropriate management is short-term maxillomandibular fixation. The tendons of the temporalis muscle act as splints for the fracture fragments, allowing osseous union to occur spontaneously. Because ankylosis may develop between the coronoid process and the zygomatic arch if immobilization is prolonged, fixation should only be applied for one to two weeks. Following removal of fixation, physical therapy may be required to re-establish the normal vertical dimension of the face.
In rare patients who have displaced fracture fragments that obstruct normal mandibular motion, partial coronoidectomy may be performed. Endoscopic approaches to the temporomandibular joint are reserved for intra-articular injuries such as meniscal tears. Rigid or wire fixation is not required because of the expected osseous union associated with this type of fracture.
A 66-year-old man comes for a follow-up examination 7 months after resection of a T4 N1 M0 squamous cell carcinoma in the region of the retromolar trigone, including alveolectomy, followed by soft-tissue reconstruction with a platysma flap. Postoperatively, he received radiation therapy to the primary tumor site (6 Gy) and to the neck bilaterally (64 Gy). He completed radiation therapy 5 months ago. Examination today shows a malodorous, tender area of exposed, soft bone at the operative site. A panoramic x-ray study (Panorex) is shown. Multiple biopsies are negative for recurrent carcinoma. Which of the following is the most appropriate management?
A ) Long-term intravenous antibiotic therapy
B ) Open reduction and internal fixation
C ) Segmental resection and vascularized tissue transfer
D ) Sequestrectomy
The correct response is Option C.
The patient described has osteoradionecrosis of the mandible, a complication that occurs in up to 40% of patients receiving adjuvant radiation therapy for head and neck malignancies caused by hypoxia, hypovascularity, hypocellularity, and impaired collagen synthesis. The traditional definition is an area of exposed, irradiated bone that is nonhealing over 3 months. Treatment depends on the severity of the disease. Debridement and antibiotic therapy, plus or minus
hyperbaric oxygen therapy, with soft-tissue reconstruction as needed, may be curative in up to 90% of cases of osteoradionecrosis limited to the alveolar ridge or mandible superior to the alveolar canal. When more extensive destruction of the mandible is present, or when there is a pathologic fracture, as seen in the scenario described, resection of all the necrotic bone and soft tissue is indicated, followed by reconstruction with vascularized bone and soft tissue. Successful healing occurs in up to 80 to 90% of patients with more extensive disease when treated in this way. Local flaps are of limited use for soft-tissue coverage because of the radiation.
A 6 year old boy is evaluated because of severe pain on opening his mouth. One week ago, he hit his chin in a fall. Physical examination shows chin deviation to the right and premature contact of the molar region on the right. Facial radiographs are ordered. The most likely cause of these findings is fracture of which of the following segments of the mandible?
(A) Angle
(B) Body
(C) Condyle
(D) Ramus
(E) Symphysis
The correct response is Option C.
Mandibular condyle fractures are the most common facial fractures seen in children. In a recent review of more than 1250 pediatric maxillofacial fractures, condylar injuries constituted 34.9% of all mandible fractures; however, the angle (17.7%), body (14.9%), ramus (8%), and symphysis (9%) are also important sites of potential mandible fracture.
The application of a locking reconstruction plate to a comminuted mandibular fracture is LEAST likely to cause which of the following?
(A) Decreased bone resorption
(B) More difficulty in contouring the plate
(C) Hardware failure
(D) Hardware-related infection
(E) Malocclusion
The correct response is Option E.
Use of a locking reconstruction bone plate has been shown to decrease postoperative malocclusion after a comminuted fracture of the mandible. A conventional (nonlocking) bone plate requires precise adaptation of the plate to the underlying bone. Without intimate contact, the bone is drawn toward the plate when the screws are tightened, altering the position of the osseous segments and the occlusal relationship. However, a locking bone plate does not require intimate contact of plate to bone because the bony segments are secured by screws that are locked to the plate. This makes it less likely for screw insertion to alter the reduction and, ultimately, the occlusion.
Cortical compression, blood supply disruption, and associated bone resorption occur less frequently with locking plates than with standard reconstruction plates. Difficulty in plate contouring is less likely to occur with locking plates because they require less precise bending than do conventional plates, which depend on intimate bony contact for stability. No increase in hardware failure has been noted with locking plates. In fact, screws in locking plates are less likely to become loose than those in standard reconstruction plates. The rate of hardware-related infection with locking plates is similar to the rate with standard reconstruction plates.
Which of the following muscles controls depression and protrusion of the mandible?
(A) Buccinator
(B) Digastric
(C) Lateral pterygoid
(D) Masseter
(E) Temporalis
The correct response is Option C.
The muscles of mastication are involved in the process of biting and chewing. These are all inserted upon the mandible and innervated by the mandibular division of the trigeminal (V) nerve. The lateral pterygoid muscle originates from the greater wing of the sphenoid, the inferotemporal crest, and the lateral pterygoid plate and inserts on the neck of the mandibular condyle and articular disc of the temporomandibular joint. Its action is to depress, protrude, and move the mandible from side to side. The masseter muscle originates from the zygomatic arch and inserts on the mandibular angle, ramus, and condyle. Its action is to close the jaw. The medial pterygoid muscle originates on the medial aspect of the lateral pterygoid plate of the sphenoid in the tuberosity of the maxilla. It inserts on the medial surface of the ramus of the mandible and acts to close the jaw. The temporalis muscle originates from the temporal fascia and entire temporal fossa. It inserts on the coronoid process and the anterior border of the ramus of the mandible and acts to close and retract the jaw. The buccinator muscle is innervated by the facial nerve (VII). Although this muscle aids in mastication by compressing the cheek, thus holding food under the teeth, it is not considered a muscle of mastication.
Which of the following nerves supplies sensory innervation to the buccal mucosa?
(A) Trigeminal (V) nerve
(B) Facial (VII) nerve
(C) Glossopharyngeal (IX) nerve
(D) Vagus (X) nerve
(E) Lingual nerve
The correct response is Option A.
The buccal branch of the trigeminal (V) nerve provides sensation to the buccal mucosa. It is important for the surgeon to know the anatomy of this nerve branch to plan and perform neurotized free flap reconstruction and reinnervation of the intraoral cavity.
The buccal branch of the facial (VII) nerve innervates the muscles surrounding the buccal mucosa.
The glossopharyngeal (IX) and vagus (X) nerves do not provide sensory innervation to the intraoral mucosa.
The lingual nerve provides sensation to a portion of the tongue.
A 4-year-old girl is brought to the emergency department for evaluation of mandibular fractures 12 hours after being kicked in the face by a horse. Physical examination shows an anterior open bite and bilateral crossbites. CT scans are shown. Which of the following is the most appropriate management at this time?
A) Closed reduction of all mandibular fractures and maxillomandibular fixation
B) Open reduction and internal fixation of all mandibular fractures
C) Open reduction and internal fixation of the parasymphysial and condylar fractures, closed reduction of the ramal fracture, and maxillomandibular fixation
D) Open reduction and internal fixation of the parasymphysial fracture, closed reduction of the condylar and ramal fractures, and maxillomandibular fixation
E) Observation only
The correct response is Option D.
In comparison to adult fractures, pediatric fractures are treated more conservatively due to the stage of mixed dentition, the elasticity of the craniofacial skeleton, and the potential for remodeling of the bone and fracture site with growth. Consideration must be given to the effects of invasive surgery on growth of the jaw. Many surgeons believe that conservative management prevents further growth disturbance.
Given the extent of fractures and displacement of the parasymphysial fracture, observation alone is not an option. Closed reduction of all of the fractures followed by maxillomandibular fixation (MMF) will not yield a stable result due to the unfavorable forces displacing the right hemi mandible. Open reduction and internal fixation (ORIF) of all fractures is not possible due to the intracapsular nature of the condylar fracture. The fragments are too small to internally fixate. ORIF of the displaced parasymphysial fracture and closed reduction of the condylar and ramal fractures is the most appropriate management. The occlusion is restored, and bone anchor screws are used to obtain MMF. Due to the child’s dentition, arch bars are not an option. MMF can be accomplished with a custom splint and drop wires with circummandibular wires or with bone anchor screws. Care needs to be taken to place the screws to avoid the dentition. MMF is typically removed at 3 to 4 weeks in this age group to prevent any ankylosis of the temporomandibular joint. If a titanium plate is used to fixate the parasymphysial fracture, removal of this 2 to 3 months following surgery is also recommended to prevent any growth restriction and embedding of the plate.
Which of the following provides the most significant blood supply to the mandibular condylar head?
A) Articular disk
B) Capsule of the temporomandibular joint
C) Deep branch of the superficial temporal artery
D) Facial artery
E) Medullary branch of the inferior alveolar artery
The correct response is Option E.
Concerning the condyle itself, its blood supply is mostly derived from three sources. A branch of the inferior alveolar artery courses upward through the neck of the condylar process, where it anastomoses liberally with vessels from the attached musculature. Another major contributor to the condyle and its articular surface derives from the temporomandibular joint (TMJ) capsule, with its lush vascular plexus. A large supply of blood also comes from branches of the lateral pterygoid muscle through its attachment at the pterygoid fovea. Of these three sources, the medullary blood supply from a branch of the inferior alveolar artery was found to be the most important source in monkeys and, presumably, in man. Fracture of the subcondylar or neck region of the condylar process could therefore disrupt the main vascular supply to the condyle.
There is another ramification of the loss of medullary blood supply from fracture of the condylar process. Surgical access to the condylar process in order to perform open reduction and internal fixation requires exposure and dissection of some of the soft tissues from the condylar process to permit manipulation and attachment of fixation devices. Therefore, surgery further diminishes the blood supply to a segment of bone that has already been severely compromised. If maintenance of blood supply to the condyle is important, the best choice is a surgical approach that can minimize the amount of soft-tissue stripping from the fractured condylar process and maintain, as much as possible, the attachment of the TMJ capsule and the lateral pterygoid muscle. Thus, if the preauricular approach is chosen, one should not enter the capsule of the joint as one might for an intra-articular surgery. Doing so can disrupt the already compromised blood supply to the condyle.
A 16-year-old girl is brought to the emergency department after sustaining fractures to the mandible in a rollover motor vehicle collision. She is intubated during the primary survey because of her critical airway. A CT scan is shown. Which of the following is the most appropriate treatment of this fracture pattern?
A) Maxillomandibular fixation only
B) Observation and soft diet
C) Open reduction and internal fixation of both the right body and the left angle fractures
D) Open reduction and internal fixation of the right body fracture only
E) Secondary mandible reconstruction after 6 weeks
The correct response is Option C.
This CT scan shows right–body and left–angle fractures, both with clinically significant displacement. Modern facial fracture management dictates early primary reduction and repair; therefore observation and soft diet without surgery is incorrect, as is avoiding disturbance of the mandible and allowing 6 weeks of bone healing.
Since she has reached the age of skeletal maturity permanent titanium hardware is an accepted modality of treatment; therefore it is incorrect to avoid hardware and rely on non-reduced maxillomandibular fixation. In addition, an angle fracture cannot typically be treated with maxillomandibular fixation alone, but requires a Champy plate or more rigid fixation. Open reduction and internal fixation of the right–body fracture, without repairing the left angle is incorrect, as Champy lines do not preclude the need for fixation. Open reduction and internal fixation of both the right body and the left angle fractures is correct, as both fractures need to be reduced, and then fixated, for the best chance of restoring occlusion.
A 32-year-old man comes to the emergency department because he has had jaw pain and difficulty closing his mouth after he was punched in the face 30 minutes ago. A panoramic radiograph (Panorex) of the lower face is shown. Which of the following clinical findings is consistent with this fracture pattern?
A ) Anterior crossbite
B ) Fracture of tooth No. 31
C ) Maxillary occlusal cant
D ) Paresthesia of right upper lip
E ) Posterior open bite on the left
The correct response is Option E.
A right mandibular angle fracture is shown. Foreshortening of the height on the right from the fracture and powerful influence of the masseter will likely result in posterior open bite on the contralateral side.
Anterior crossbite occurs in maxillary hypoplasia and prognathism conditions and is not a result of the fracture in the patient described.
Tooth No. 32 is fractured in the Panorex shown. Standard numbering of the dentition of the maxillary dental arch from right to left is No. 1 to No. 16. The mandibular dental arch from left to right is No. 17 through No. 32.
Maxillary occlusal cant occurs congenitally or with maxillary fracture.
Paresthesias of the upper lip are not associated with mandibular fracture through the inferior alveolar nerve. This fracture would be consistent with paresthesia of the right lower lip.
A 63-year-old woman is admitted to the hospital with a fracture to the left mandibular angle that she sustained in a motor vehicle collision. Open reduction and internal fixation is planned via a submandibular (Risdon) incision. The region between which of the following planes of dissection is most appropriate for approaching the fracture and avoiding injury to the marginal mandibular branch of the facial nerve?
A) Carotid sheath and the posterior belly of the digastric muscle
B) Platysma and the superficial (investing) layer of the deep cervical fascia
C) Skin and the platysma
D) Submandibular gland and the carotid sheath
E) Superficial (investing) layer of the deep cervical fascia and the submandibular gland
The correct response is Option E.
The submandibular approach to the mandibular body/ramus is an important surgical approach to address a number of facial fractures. An understanding of the anatomy of the submandibular region is crucial to performing this approach with minimal complications.
The marginal mandibular nerve leaves branches off the facial nerve trunk during its intraparotid course. One to three branches usually exit the inferior border of the parotid gland before changing course to travel along the mandibular border toward the symphysis. In almost all cases, the marginal mandibular nerve travels superficial to or within the investing layer of the deep cervical fascia as it courses anteriorly.
In several cadaveric studies, the nerve consistently coursed within 1 cm below the mandibular border posterior to the facial vessels, and above the mandibular border anterior to the facial vessels.
The submandibular approach to facial fractures involves incising the skin 2 cm below the mandibular border, dividing the platysma and dissecting deep to the investing fascia, just above the submandibular gland . Once in this plane, the course of dissection is carried superiorly toward the mandibular border.
A 5-year-old child has malocclusion and limited opening of the mouth after falling from playground equipment. A CT scan is shown. Which of the following is the most likely long-term sequela of this patient’s injury?
(A) Bimaxillary prognathism
(B) Mandibular hypoplasia
(C) Mandibular prognathism
(D) Maxillary hypoplasia
(E) Maxillary prognathism
The correct response is Option B.
This child is at increased risk for mandibular hypoplasia. The condyle serves as a growth center for the mandible and contributes primarily to vertical growth. The condylar cartilage is a site of secondary passive growth dependent on forces acting on it, notably the medial and lateral pterygoid muscles. Pediatric condylar fractures generally remodel and do not often cause growth disturbance. However, the thin, localized functional matrix of the condyle may disallow normal mandibular growth after it has been injured and may result in unilateral or bilateral hypoplasia depending on the injury. Pediatric mandibular fractures are frequently treated conservatively via closed reduction and short periods of maxillomandibular fixation.
A 19-year-old man presents to the emergency department with malocclusion sustained during an assault. Examination shows isolated mandibular subcondylar fracture. A photograph is shown. Which of the following is the most likely location of the mandibular fracture?
A) Left
B) Right
C) Bilateral
D) Not possible to determine with information provided
The correct response is Option A.
Posterior mandibular fractures, such as those of the subcondylar subunit, cause foreshortening of the vertical height of the mandible and early contact of the molar teeth on the ipsilateral side of the fracture. This results in an open bite on the anterior contralateral side of the fracture as demonstrated in the picture (right open bite).
A displaced right subcondylar fracture usually presents with a left open bite.
The malocclusion pattern from bilateral subcondylar fractures is more difficult to predict. If displaced, they may present with an anterior open bite, caused by early contact of the molar teeth on both sides of the face.
A 40-year-old woman is referred for treatment after being found to have an idiopathic fracture on panoramic radiograph (Panorex), performed because of severe pain following a dental procedure. She has been treated for osteopenia related to multiple myeloma. A CT is shown. On evaluation, the patient has chronic pain and exposed intraoral bone. Which of the following is the most likely diagnosis?
A ) Bisphosphonate-related osteonecrosis
B ) Breast cancer metastasis
C ) Infectious osteomyelitis
D ) Myeloma-induced changes to the mandible
E ) Old unhealed fracture from trauma
The correct response is Option A.
Bisphosphonate-related osteonecrosis (BRON) is an increasingly reported diagnosis for patients being treated with bisphosphonates for bone loss from Paget disease, osteoporosis, and bone-related cancer. Bisphosphonates are clinically important for the treatment of hypercalcemia of malignancy and can reduce cancer-induced bone pain. The two bisphosphonates approved by the FDA for use in patients with cancer involving bone are pamidronate and zoledronic acid. Because of the high frequency of skeletal involvement in advanced cancers, bisphosphonates are routinely prescribed in the practice of medical oncology, and the incidence in these patients for BRON ranges between 1% and 10%. Because of the common use of these drugs in multiple myeloma, there have been many case reports of patients with BRON. Other diseases with a similar presentation include intraoral conditions including periodontal disease, gingivitis, or mucositis; temporomandibular joint disease; sinusitis; periapical pathology caused by a carious infection; osteoradionecrosis; neuralgia-inducing cavitational osteonecrosis; odontogenic infections leading to osteomyelitis; herpes zoster infection €“associated osteonecrosis; benign sequestration of the lingual plate; or HIV-associated necrotizing ulcerative periodontitis.
For established pathology, there is little need for diagnostic imaging techniques because the presence of exposed bone and associated symptoms such as pain, swelling, paresthesia, suppuration, and soft-tissue ulceration can be detected without them. However, early identification of BRON, although more challenging, is potentially important for patient care and prevention of disease. A Panorex or CT combined with clinical history, examination, and biopsy are adequate.
Recommendations for patients with established BRON include oral antimicrobial rinses, such as 0.12% chlorhexidine digluconate. Systemic antibiotic therapy may be prescribed if there is evidence of infection. Establishing and maintaining an €œinfection-free € oral environment is especially important for patients with multiple myeloma who are being considered for stem cell transplantation. Surgical treatment should be conservative or delayed. Removal of sharp bone edges is recommended to prevent trauma to adjacent soft tissues. Loose segments of bony sequestra should be removed without exposing uninvolved bone. Segmental jaw resection may be required for symptomatic patients with large segments of necrotic bone or pathologic fracture, and with this, the potential need for vascularized tissue. No published data have established that stopping bisphosphonates will promote resolution of BRON. Although some have advocated hyperbaric oxygen therapy, the efficacy of this approach has not been established.
There have been many case reports of breast cancer metastatic to the mandible; it must be considered in any woman with severe changes to this bone. Multiple myeloma is most frequently seen in vertebrae and secondarily in long bones. Its presence in the jaw is extremely rare, and when it is seen, it is usually in the mandibular angle and ramus.
A 2-month-old male infant is brought to the office because of mid face hypoplasia, craniosynostosis, and bilateral hand and foot anomalies. A photograph of the left foot is shown. This patient most likely has which of the following syndromes?
A) Apert
B) Crouzon
C) Goldenhar
D) Nager
E) Treacher Collins
The correct response is Option A.
The patient described has Apert syndrome. This autosomal dominant syndrome is characterized by bicoronal craniosynostosis that leads to turribrachycephaly, mid face hypoplasia, and complex hand and feet syndactyly. Patients with Crouzon syndrome, an autosomal dominant disorder, typically have craniosynostosis involving the coronal, sagittal, and lambdoid sutures, as well as turribrachycephaly. Other findings include mid face hypoplasia, exorbitism, and proptosis. The extremities are normal.
Goldenhar syndrome, or oculoauriculovertebral dysplasia, involves asymmetry of the hard and soft tissues of the face. This condition is most commonly unilateral but may be seen bilaterally in some patients. Manifestations of this syndrome include hypoplasia involving the mandible and underlying soft tissues of the face, epibulbar dermoids, and varied degrees of microtia on the affected side. Most patients have associated vertebral abnormalities. Nager syndrome, or acrofacial dysostosis, is an autosomal recessive disorder characterized by craniofacial and upper extremity abnormalities. Patients with Nager syndrome have hypoplasia of the orbits, zygoma, maxilla, mandible, and soft palate. Auricular defects may also be present. Hypoplasia or agenesis occurs in the radius, thumbs, and metacarpals. Some patients may have radioulnar synostosis and elbow joint deformities. Patients with Treacher Collins syndrome, or mandibular dysostosis, have hypoplasia of the zygoma, maxilla, and mandible, downward slanting of the palpebral fissures, colobomas of the lower eyelids, absence of eyelashes, and auricular defects.
A 22-year-old woman is brought to the emergency department after being hit by a car where she was intubated at the scene. A maxillofacial CT scan performed on admission shows a non-displaced right mandibular parasymphaseal fracture. She is extubated later that day after being cleared by trauma. Upon reevaluation the next morning, significant malocclusion with a step-off between the right mandibular cuspid and lateral incisor is noted. She has a right-sided open bite. Which of the following mechanisms most likely explains the change in physical examination findings after extubation?
A) Delayed disruption of the periodontal ligament
B) Differential pull of muscles on the mandible
C) Dissipation of post-traumatic edema
D) Fibrinolysis of the fracture hematoma
E) Refracture of the parasymphysis
The correct response is Option B.
This patient has a right mandibular parasymphyseal fracture that is in an unfavorable orientation. The right temporalis and pterygomasseteric sling will work naturally to close the mandible while the floor of mouth musculature, including the mylohyoid, work to open the mandible at the level of the symphysis. Because of the orientation of the fracture, these forces distract the fracture, causing it to become more displaced. When this patient was first examined, the paralytic agent she received when she was intubated at the scene inhibited those distraction forces and kept her in appropriate occlusion. However, upon extubation, she fell out of occlusion as those muscle groups separated the fracture. While hematoma fibrinolysis and edema reduction occur after mandible fractures, they are not likely to result in displacement of the fracture. The periodontal ligament has no role in fracture displacement.
A 25-year-old man is brought to the emergency department 2 hours after being punched in the left side of the face. Physical examination shows swelling on the left side of the face. The panoramic x-ray study (Panorex) shown was obtained. Which of the following is the most appropriate management?
A) Extraction of all components of the third left mandibular molar and maxillomandibular fixation (MMF) for 2 weeks
B) Extraction of all components of the third left mandibular molar and MMF for 6 weeks
C) Extraction of all components of the third left mandibular molar, MMF, and open reduction and internal fixation (ORIF)
D) Ligating the third left mandibular molar to the adjacent tooth for stability, MMF, and ORIF
E) Preservation of the third molar, MMF, and ORIF
The correct response is Option C.
The x-ray study shows a fracture of the root, thus the tooth and root must be removed. Indications for extraction of a tooth in the line of a fracture include the need for MMF to regain the patient’s occlusion. The left parasymphyseal and comminuted left angle fractures can be managed in a number of ways, but the parasymphyseal fracture requires open reduction and internal fixation to prevent lateral displacement of the left mandibular body by the masseter muscle.
A 56-year-old woman with type 1 diabetes mellitus has a six-month history of a slowly enlarging, painless mass in the mandible. She is edentulous. Physical examination shows a 4-cm mass on both the buccal and lingual portions of the alveolus with intact mucosa. A panoramic radiograph (Panorex) is shown. Biopsy confirms ameloblastoma. Which of the following is the most definitive management?
A ) Conservative segmental resection of the mandible, followed by nonvascularized iliac crest cortical bone grafting
B ) Curettage and cancellous bone grafting
C ) Segmental resection of the mandible with wide margins and cervical lymph node dissection, followed by vascularized free fibular bone grafting
D ) Segmental resection of the mandible with wide margins and cervical lymph node
dissection, followed by vascularized free fibular bone grafting and adjuvant radiation
therapy
E ) Segmental resection of the mandible with wide margins, followed by vascularized free fibular bone grafting
The correct response is Option E.
The history and radiographic findings in the patient described are most consistent with multicystic ameloblastoma. This odontogenic tumor commonly presents as a painless enlarging mass in the mandible or, less commonly, in the maxilla. The typical radiographic finding is a multilocular lucency with preservation of the cortex, though the cortex may be thinned. There are subcategories including peripheral (extraosseous) and central (intraosseous), which may be unicystic or multicystic, as in the radiograph shown. Extraosseous lesions may have no radiographic findings. This tumor goes beyond the boundaries seen on radiograph.
Wide resection is necessary for multicystic lesions to prevent recurrence. The sizeable defect resulting from wide resection in the patient described would be best treated with vascularized bone graft, especially in light of her diabetes.
Curettage or conservative resection of this tumor would result in recurrence in 50% of patients. Conservative resection may have higher cure rates for unicystic lesions. The lack of mucosal ulceration or cortical bone erosion in a lesion this size point away from a malignancy; therefore, cervical lymph node dissection and adjuvant radiation therapy would not be indicated.
A 22-year-old man is scheduled to undergo surgery to correct a displaced symphyseal fracture of the mandible using a vestibular approach. To avoid injury to the mental nerve, the mental foramen is best identified in which of the following locations?
A) Anterior to the first premolar
B) Inferior to the lateral incisor
C) Inferior to the lower canine tooth
D) Inferior to the second molar r
E) Inferior to the second premolar
The correct response is Option E.
The vestibular approach to the mandible is useful for a number of mandibular procedures. The most important neurovascular structure of significance in the region of the symphysis is the mental neurovascular bundle.
The mental nerve is the terminal branch of the inferior alveolar nerve. It gives sensation to the skin and mucosa of the lower lip, skin of the chin, and facial gingiva of the anterior teeth. It is important to preserve this nerve during the surgical dissection in this approach.
The mental nerve exits the mental foramen usually inferior to or slightly anterior to the second premolar tooth.
A 32-year-old man undergoes open reduction and internal fixation of a fracture in the left body of the mandible. A six-hole dynamic compression plate is chosen for the inferior mandibular border. The first screw is placed bicortically through a plate hole immediately adjacent to the line of fracture. To obtain maximum compression at the fracture line using the spherical gliding principle, the most appropriate next step is to drill for a second screw at which of the following locations (A–E)?
The correct response is Option A.
To obtain maximum compression at the fracture line using the spherical gliding principle, the most appropriate next step is to drill for a second screw eccentrically, away from the line of fracture, through a plate hole located across the fracture line.
Concentric or neutral drilling occurs in the center of a plate hole, while eccentric drilling occurs in the periphery (corner) of the plate hole (either away or closer to the line of fracture).
The figure above illustrates the spherical gliding principle in a dynamic compression plate. The special geometry of the plate hole—together with eccentric, away from the fracture line, placement of the screw that has a spherically shaped head—allows interfragmentary compression in an axial direction when the screw is driven fully into the plate hole. For appropriate fracture compression to occur, the head of the screw that was placed first must be well seated into the plate hole, stabilizing the plate against the underlying bony segment.
Drilling concentrically (neutrally) through a plate hole located across the fracture line would cause no axial movement of the underlying bone fragments upon tightening of the screw against the plate, generating no further compression at the fracture line.
Drilling eccentrically, closer to the line of fracture, through a plate hole located across the fracture line would increase the fracture gap upon tightening of the screw against the plate.
Placement of a second screw in a plate hole located on the same side of the first screw (in relation to the line of fracture) would have no effect over the fracture line. Also, after eccentric (away from the line of fracture) placement of one screw on each side of the fracture, the remaining screws should be placed concentrically.
