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Flashcards in Orthognathic and TMJ Deck (13):

Which of the following terms best describes the temporomandibular joint?
A) Ellipsoid (condyloid)
B) Gliding (arthrodial)
C) Hinge-sliding (ginglymoarthrodial)
D) Pivot (trochoid)
E) Saddle (ephippial)

C) Hinge-sliding (ginglymoarthrodial)

The temporomandibular joint is classified as a ginglymoarthrodial joint since it has both hinge and sliding components during jaw opening. These functions take place in the two separate compartments in the joint, upper and lower, that are effectively separated by an articular disc. During the first 20 mm of jaw opening, the condyle rotates in the lower compartment (space between condylar head and articular disc) in a nearly pure hinge motion. For further opening to take place, the condyle translates (or shifts) forward with the articular disc through the upper compartment (space between the articular disc and the joint surface). The other options describe other joint configurations. Examples of each are: saddle, thumb basilar joint; pivot, atlas-axis (C1-2 neck); gliding, tarsal bones in the foot; ellipsoid, radiocarpal articulation.


A 22-year-old woman comes to the office because she is unhappy with the appearance of the lower third of her face. On examination, she has a class II occlusion. Lateral cephalometric evaluation shows an SNA angle of 82 degrees (N 80-84), an SNB angle of 75 degrees (N 78-80), and an ANB angle of 7 degrees. Cranial base anatomy shows no abnormalities. Which of the following orthognathic procedures is most appropriate in this patient?
A) LeFort I maxillary advancement
B) LeFort I maxillary advancement with mandibular setback
C) Maxillary impaction
D) Sagittal split mandibular osteotomy with advancement
E) Sliding genioplasty

D) Sagittal split mandibular osteotomy with advancement

This patient has a skeletal class II deformity with a retrognathic mandible and normal maxillary projection. The SNA angle of 82 degrees (N 80-84) indicates a normally positioned maxilla relative to the cranial base, while the SNB angle of 75 degrees (N 78-80) indicates a retrognathic mandible relative to the cranial base. The ANB angle confirms the class II deformity (>4 degrees). A mandibular sagittal split osteotomy with advancement will correct this deformity.

Maxillary impaction is used to treat vertical maxillary excess.

LeFort I maxillary advancement will worsen this patient’s deformity.


Which of the following cephalometric landmarks is included in the Frankfort horizontal plane?
A) Nasion
B) Pogonion
C) Point B
D) Porion
E) Sella turcica

D) Porion

The two cephalometric planes used most frequently in lateral cephalograms to describe and evaluate the cranial base are the Sella-nasion plane and the Frankfort horizontal plane. The Frankfort horizontal plane is defined by a line from the superior edge of the external auditory meatus (porion) to the inferior orbital meatus (orbitale). The SNA and SNB are angles used to describe the position of the maxilla and mandible, respectively. The SN refers to a line from the sella turcica to the nasion, while point A is on the maxilla and point B is on the mandible. The pogonion refers to the chin point.


A 22-year-old woman comes to the office for evaluation of an abnormal bite. On physical examination, she has an anterior open bite, and the upper teeth are not exposed with the lips in repose. Cephalometric analysis shows a nasion (N) to anterior nasal spine (ANS) distance of 45 mm (N 52–57 mm), an ANS to menton (Me) distance of 63 mm (N 63–68 mm), and an N-ANS:ANS-Me ratio of 1:1.4 (N 1:1.2). All other measurements are within the reference ranges. Which of the following is the most appropriate surgical procedure for correction of this patient’s deformity?
A) Le Fort I maxillary osteotomy with downward repositioning
B) Le Fort II osteotomy with maxillary advancement
C) Naso-orbito-maxillary osteotomy
D) Perinasal osteotomy
E) Sagittal split osteotomy with mandibular setback

A) Le Fort I maxillary osteotomy with downward repositioning

Le Fort I osteotomy with downward repositioning effectively lengthens the maxilla in cases of isolated vertical maxillary hypoplasia. The maxilla is repositioned vertically in its entirety or rotated downward, depending on whether or not the hypoplasia extends to the posterior maxilla. The goal is to close the anterior open bite and to restore facial height, allowing 3 to 4 mm of upper incisor to show with lips in repose.

Perinasal osteotomy is a procedure designed to lengthen the skeletal framework of the nose. It lengthens and increases nasal projection. It is therefore a suitable procedure for patients with nasomaxillary hypoplasia and a foreshortened nose, but with normal dental occlusion and facial height. It does not correct maxillary height or change the dental relationships.

Naso-orbito-maxillary osteotomy is a step beyond perinasal osteotomy, in that it corrects both the foreshortened and retruded nasal framework and maxillary hypoplasia horizontally and vertically. The entire osteotomized segment includes the central section of the maxilla from nasion to teeth, and from one internal orbital rim to the other. It can therefore close an anterior open bite when vertical maxillary insufficiency is a component of the deformity in addition to a retruded nasomaxillary complex. However, it would most likely shift the occlusion into class II if there were not also a horizontal deficiency of the maxilla. Therefore, it is not an appropriate procedure for the patient in the vignette because it would alter the naso-orbital region unnecessarily, and possibly cause a new deformity or abnormal relationship in this otherwise isolated vertical maxillary deficiency. The indications for a or a naso-orbito-maxillary osteotomy would overlap those for a Le Fort II osteotomy.

Le Fort II osteotomy is indicated for nasomaxillary hypoplasia with a recessed maxilla and class III malocclusion. This is frequently noted in patients with a history of cleft lip and palate. The same discussion used for the naso-orbito-maxillary osteotomy would apply here as well.
Sagittal split osteotomy is a procedure that modifies the mandible, permitting setback or advancement of the mandibular dentition when the cause of the malocclusion is mandibular hypoplasia or overdevelopment. It has no effect on the maxilla.


Which of the following is the most common cause of temporomandibular joint ankylosis?
A) Bruxism
B) Congenital anomaly
C) Infection
D) Radiation
E) Trauma

E) Trauma

The most common cause of temporomandibular joint (TMJ) ankylosis is trauma. It usually occurs after untreated or inadequately treated mandibular fractures. Damage to the articular surface of the TMJ is the most common factor seen. In children, this can lead to growth disturbances ultimately requiring orthognathic surgery. Otherwise, joint replacement and repair may be indicated in adults. In the antibiotic era, infection is a rare cause. Congenital anomalies, bruxism, and radiation are less common.


A 16-year-old boy who successfully underwent Le Fort III advancement with bone grafting 6 years ago because of severe maxillomandibular disharmony comes to the office due to severe malocclusion. Physical examination shows an Angle class III malocclusion and severe mid face deficiency. Which of the following is the most likely explanation for the reappearance of this patient's condition?
A) Age during original surgery
B) Discrepancy in the growth rate of the operated mid face and the mandible
C) Lack of bony stability in the first postoperative year
D) Poor follow-up
E) Poorly performed orthognathic surgery

B) Discrepancy in the growth rate of the operated mid face and the mandible

A recent article showed for the first time that children who underwent Le Fort III advancement had recurrence of their initial pathology due to minimal mid face sagittal growth, but with normal mandibular growth. This study displayed this, despite excellent early advancement and bony stability up to 1 year. After 5 years, the lack of mid face growth ultimately relegates these patients to at least another advancement surgery. Definitive orthognathic surgery is required following the completion of skeletal growth to improve maxillomandibular relationships and to achieve optimal occlusion. In multiple studies, the average age of children undergoing Le Fort III osteotomies was close to age 6 years and age was not an independent factor for recidivism. Finally, studies of distraction after a Le Fort III osteotomy show better advancement and may help to minimize the recurrence of pathology.


A 16-year-old girl with facial asymmetry secondary to hemifacial microsomia comes to the office for evaluation of orthognathic surgery. Which of the following procedures puts her at the highest risk for perioperative bleeding?
A) Bilateral sagittal split osteotomy
B) Distraction osteogenesis
C) Le Fort I osteotomy
D) Mandibular vertical ramus osteotomy
E) Osseous genioplasty

C) Le Fort I osteotomy

Significant hemorrhage is uncommon in orthognathic surgery, but when it occurs, it is most likely secondary to the maxillary osteotomies. The vessels at risk with the maxillary osteotomy include the greater palatine vessels, maxillary artery, and pterygoid plexus. The incidence of significant hemorrhage with mandible osteotomies is rare. The vessels at risk include the inferior alveolar artery, facial artery, retromandibular vein, and the pterygoid venous vein. Distraction osteogenesis is associated with lower risk for bleeding than any of the open procedures.


A 41-year-old man comes to the emergency department because he is unable to close his mouth after yawning. He reports pain in the jaw. Which of the following is the most appropriate initial treatment?
A ) Arthroplasty
B ) Closed reduction during sedation
C ) Eminectomy
D ) Injection of botulinum toxin type A
E ) Intra-articular sclerosing

B ) Closed reduction during sedation

This patient has an acute anterior dislocation of his temporomandibular joint. Anterior dislocations are usually secondary to an interruption in the normal sequence of muscle action when the mouth closes from extreme opening. The masseter and temporalis muscles elevate the mandible before the lateral pterygoid muscle relaxes resulting in the mandibular condyle being pulled anterior to the bony eminence and out of the temporal fossa. Spasm of the masseter, temporalis, and pterygoid muscles causes trismus and keeps the condyle from returning into the glenoid fossa. Dislocations can be both unilateral and bilateral.

The most appropriate initial treatment is attempted closed reduction. Local anesthesia or sedation can help relax the muscles that are in spasm. Reduction involves downward and posterior movement of the mandible.

All other choices are options that have been tried with variable success to prevent chronic, recurrent temporomandibular joint dislocation. Arthroplasty or eminoplasty refers to augmentation of the articular eminence with a bone graft or an alloplastic material, or even titanium hardware. In contrast to the eminectomy, an eminoplasty seeks to confine the condyle to the glenoid fossa.

Eminectomy involves reducing or removing the articular eminence, which is the anterior wall of the glenoid fossa, surgically so that spontaneous reduction is possible.

Injection of botulinum toxin type A has been suggested as a treatment. The theoretic mechanism of action is relaxation of the masseter and temporalis muscles, allowing spontaneous reduction.

Intra-articular injection of a sclerosing agent, such as alcohol, usually followed by a period of interdental fixation has been described but has fallen out of favor due to lack of proven long-term efficacy. It was thought to be a noninvasive way of preventing the mandible from opening excessively wide and allowing dislocation of the condyle from the glenoid fossa by inducing fibrosis of the temporomandibular joint.


A 50-year-old man is evaluated for a 6-month history of clicking of the left temporomandibular joint and pain with joint movement. Physical examination shows an interincisal opening of 20 mm and recurrent locking in the open position; no signs of infection or ankylosis are noted. Which of the following is the most appropriate treatment?
A ) Botulinum toxin type A injection
B ) Intracapsular disk repositioning and reduction of the articular eminence
C ) Removal of disk and placement of an interpositional temporalis fascia flap
D ) Temporomandibular joint replacement
E ) Observation

B ) Intracapsular disk repositioning and reduction of the articular eminence

Surgical reduction of the articular eminence is indicated for patients who have symptomatic open locking of the mandible. Surgical options for symptomatic patients and secondary functional limitations with internal joint abnormalities on MRI include: intracapsular disk repositioning; discectomy; and an interpositional temporalis fascia flap. Botulinum toxin type A is not an approved use in this clinical setting. Discectomy is appropriate as a salvage procedure. Temporomandibular joint replacement is rarely warranted unless signs of infection, as part of cancer resection, or severe ankylosis are noted. Conservative management is appropriate in cases with no functional abnormalities.


A 12-year-old girl is evaluated because of a 1-year history of progressive mandibular retrognathia and bilateral temporomandibular joint pain. There is no history of trauma. Examination shows slightly decreased interincisal opening without chin point deviation and an Angle class II malocclusion with an anterior open bite. Which of the following is the most likely cause of this patient?s symptoms?
A ) Bruxism
B ) Condylar hyperplasia
C ) Infection
D ) Myofascial pain syndrome
E ) Rheumatoid arthritis

E ) Rheumatoid arthritis

Disorders that can affect the temporomandibular joint (TMJ) include ankylosis, arthritis, trauma, dislocation, congenital and developmental anomalies, and neoplasms. Rheumatoid arthritis (RA) can cause tenderness, swelling, and decreased motion in any joint, including the TMJ. The TMJ can be affected in up to 33% of patients with RA. Chronic inflammation can, eventually, result in articular erosions, joint destruction, and ankylosis. When RA develops in childhood or early adolescence (juvenile idiopathetic arthritis), erosion of the condyles can lead to progressive mandibular retrognathism and anterior open bite.

Bruxism is grinding of the teeth and can lead to progressive dental wear, myofascial pain, and TMJ derangement. It does not affect the facial profile. Condylar hyperplasia is overgrowth of the condyle. It is most commonly unilateral, painless, and can lead to chin point deviation. Infection can cause tenderness and, ultimately, degeneration of the TMJ. However, infection is rarely bilateral and there are usually concurrent systemic symptoms. Myofascial pain syndrome is a common cause of pain in the TMJ region. It is more common in girls and is considered a localized form of fibromyalgia in the head and neck. It usually is unilateral and does not typically lead to joint degeneration or alterations in occlusion.


A 7-year-old boy with Pfeiffer syndrome is brought to the office because of snoring that has worsened progressively for the past 6 months. Treatment with tonsillectomy and adenoidectomy failed to correct the obstruction. Physical examination shows moderate proptosis, Angle class III malocclusion, and inadequate malar projection. Nasendoscopy shows pharyngeal obstruction by the soft palate. Which of the following is the most appropriate management?
A ) Le Fort I osteotomy and advancement
B ) Le Fort II osteotomy and advancement
C ) Le Fort III osteotomy and advancement
D ) Mandibular setback with glossopexy and tongue-lip adhesion
E ) Mandibular setback with vertical ramus osteotomies

C ) Le Fort III osteotomy and advancement

In a patient with Pfeiffer syndrome who is found to have worsening nasopharyngeal airway obstruction, mid face advancement is indicated to obviate a tracheostomy. Until the adult dentition has erupted, a Le Fort I osteotomy is contraindicated to avoid injuring the developing teeth in the maxilla. A Le Fort II osteotomy will fail to advance the deficient malar processes. A mandibular setback, by any means, will worsen the airway.


A 13-year-old boy who underwent repair of left unilateral cleft lip and palate is brought to the office because he is dissatisfied with his “underbite.” He reports no other symptoms. Cephalometric analysis shows an SNA angle of 76 degrees (N = 81 ± 3) and an SNB angle of 81 degrees (N = 79 ± 3). A negative overjet of 5 mm is noted. Which of the following is the most appropriate management?
A ) Bimaxillary advancement
B ) Le Fort I advancement of the maxilla with internal fixation
C ) Le Fort I osteotomy and distraction
D ) Mandibular setback
E ) Orthodontics and follow-up in 1 year

E ) Orthodontics and follow-up in 1 year

At 13 years of age, the facial skeletal growth is not complete. Therefore, the patient should wait until his facial skeletal growth is complete, usually at age 18 for boys. Meanwhile, he should follow up regularly with his craniofacial team. The Angle class III malocclusion is not uncommonly seen in patients after cleft palate repair. The scarring from bony dissection in the palate repair restricts maxillary growth. However, unless there are severe symptoms (such as respiratory compromise), the definitive orthognathic surgery is deferred until skeletal maturation. When skeletal maturation is complete, a Le Fort I osteotomy with immediate fixation, or distraction osteogenesis (DO), can be done. DO is reserved for those cases where the advancement is calculated to exceed 10 mm. His SNB angle is within normal limits, therefore a setback is not indicated, nor is bimaxillary surgery.


A 34-year-old woman comes to the office because she would like to improve the appearance of her face. She recently completed orthodontic therapy with lingual braces. When she smiles, no upper incisal show is noted. Occlusion is Angle class I. Which of the following is the most appropriate management?
A ) Cosmetic dental laminates
B ) Horizontal excision of the upper lip
C ) Mandibular osteotomy and advancement of the mandible with a genioplasty
D ) Maxillary osteotomy with vertical lengthening of the maxilla
E ) Vertical shortening of the upper lip using a scar hidden under the nostril

D ) Maxillary osteotomy with vertical lengthening of the maxilla

This case describes an adult with vertical maxillary deficiency resulting in inadequate upper incisal show. This is corrected with a maxillary osteotomy and vertical lengthening while maintaining the occlusive relationship. Excision of the upper lip is not the best solution of the patient described with vertical maxillary deficiency. A mandibular advancement should not be recommended as cephalometric evaluation is noted to be normal. Shortening the upper lip is not recommended for vertical maxillary deficiency.