In-Service Exam
Orthognathic, TMJ, Chin - 2002





A 22-year-old man desires aesthetic enhancement of the chin. Examination of the chin shows horizontal (sagittal) deficiency and vertical excess. Which of the following surgical procedures should be performed in this patient?

(A) Alloplastic chin augmentation
(B) Interpositional genioplasty
(C) Jumping genioplasty
(D) Reduction genioplasty

The correct response is Option C.

A jumping genioplasty can performed to correct both horizontal (sagittal) deficiency and vertical excess. Preoperative evaluation of patients with chin abnormalities should involve analysis of the horizontal and vertical (ie, superoinferior) dimensions; chin symmetry should also be noted. Patients can have a combination of deficiency and/or excess in both the horizontal and vertical dimensions. In order to correct the findings seen in this patient, horizontal osteotomy is performed first, and then the caudal mandibular osteotomized segment is placed in front of the mandible.

Alloplastic augmentation is typically reserved for older persons with minimal pure horizontal chin deficiencies, and osseous genioplasties are performed in younger patients with more pronounced anomalies. Interpositional genioplasty, which is indicated for correction of vertical deficiency alone, is accomplished by performing a horizontal osteotomy with interpositional grafting using bone or a bone substitute. Reduction genioplasty, which involves wedge ostectomy followed by securing of the caudal segment to the mandible, is used for correction of vertical excess alone.

References
1. Guyuron B. Genioplasty. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:250-269.
2. McCarthy JG, Ruff GL, Zide BM. A surgical system for the correction of bony chin deformity. Clin Plast Surg. 1991;18:139-152.

A 16-year-old boy is scheduled to undergo maxillary advancement for correction of a 10-mm negative overjet of the maxillary incisors. Which of the following additional findings is associated with the greatest risk for the development of velopharyngeal incompetence?

(A) Class III malocclusion secondary to mandibular prognathism
(B) Maxillary-mandibular disharmony secondary to craniofacial microsomia
(C) Midface hypoplasia secondary to Crouzon syndrome
(D) Midface hypoplasia secondary to repaired cleft palate

The correct response is Option D.

Patients with midface hypoplasia secondary to repaired cleft palate are at increased risk for development of velopharyngeal incompetence, especially following maxillary (Le Fort I) advancement of greater than 10 mm. In a study of 70 patients who underwent Le Fort I advancement, the incidence of velopharyngeal incompetence was increased in those patients who had previously undergone cleft palate repair. This was particularly true in patients who, on preoperative examination, exhibited evidence of nasal air emission, nasal resonance, borderline velopharyngeal incompetence, or a combination of these findings.

In patients with Angle class III malocclusion secondary to mandibular prognathism, maxillary advancement is not the treatment of choice; instead, the skeletal anomaly is more appropriately addressed by performing mandibular setback. This procedure should not increase the patient's risk for development of velopharyngeal incompetence.

Patients undergoing maxillary advancement for management of other conditions, such as craniofacial microsomia or Crouzon syndrome, are at much lower risk for development of velopharyngeal incompetence than those patients with a repaired cleft palate.

References
1. McCarthy JG, Coccaro PJ, Schwartz MD. Velopharyngeal function following maxillary advancement. Plast Reconstr Surg. 1979;64:180-189.
2. McCarthy JG, Kawamoto H, Grayson BH, et al. Surgery of the jaws. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:1379.

In a 5-year-old child, the optimal latency period for mandibular distraction is approximately how many weeks?

(A) 1
(B) 2
(C) 3
(D) 4
(E) 8
The correct response is Option A.

The latency period is defined as that time following the osteotomy procedure during which the cut bone surfaces begin to become bridged by initial fracture healing, just prior to initiation of distraction. Although recommendations regarding the optimal latency period for mandibular distraction have been controversial, current clinical protocols typically describe a latency period of five to seven days. However, some studies have questioned the necessity of a latency period. In experimental studies involving adult canines, premature consolidation of the tibial bone surfaces was noted following latency periods of either 14 days or 21 days. Because latency periods of 14 days or longer have been theorized to result in premature bony union, such lengthy periods are contraindicated in distraction osteogenesis. After active distraction is complete, the bone segments are held in rigid fixation until new bone mineralization occurs. This is known as the period of consolidation, which according to clinical protocols typically lasts for eight weeks.

References
1. Aronson J. Experimental and clinical experience with distraction osteogenesis. Cleft Palate Craniofac J. 1994;31:473-482.
2. Aronson J, Shen X. Experimental healing of distraction osteogenesis comparing metaphyseal with diaphyseal sites. Clin Orthop. 1994;301:25-30.
3. Gosain AK. Distraction osteogenesis of the craniofacial skeleton. Plast Reconstr Surg. 2001;107:278-280.

A 32-year-old man is undergoing evaluation because he has temporal headaches and a sensation of "sand in the jaw" when he eats. He sustained trauma to the face while playing football in college. On current physical examination, there is reciprocal clicking and transient locking of the jaw during opening and closing movements. MRI shows anterior malpositioning of the meniscus and posterosuperior displacement of the condyle.

These findings are most consistent with which of the following?

(A) Ankylosis of the temporomandibular joint
(B) Avascular necrosis of the condylar head of the mandible
(C) Dislocation of the temporomandibular joint
(D) Internal derangement of the temporomandibular joint
(E) Myofascial pain dysfunction syndrome

The correct response is Option D.

The findings in this patient are most consistent with internal derangement of the temporomandibular joint (TMJ), which is defined as an abnormal relationship between the articular disk and mandibular condyle. This condition is typically associated with anterior displacement of the meniscus and often with posterosuperior malpositioning of the condyle. The retromeniscal pad may be damaged and/or disrupted. Affected patients usually have preauricular pain and clicking of the joint, as well as other, less specific symptoms such as headache and aching pain in the ear or neck. A history of trauma or previous orthodontic treatment may be associated.

Ankylosis of the TMJ can result from trauma, infection, juvenile rheumatoid arthritis, or other conditions. In patients with TMJ ankylosis, destruction of the articular disk and joint elements occurs, resulting in fibrosis, narrowing of the joint space, and bony fusion.

Although avascular necrosis is rarely seen within the mandibular condyle, it may occur as a result of trauma or devascularization at the time of TMJ surgery. Affected patients have pain and limited jaw motion; MRI will show devascularization of the condyle.

Acute TMJ dislocation occurs following anterior extension of the condyle beyond the eminence; this condition occurs as a result of joint hypermobility secondary to either trauma or an excessively large mouth opening. Although spontaneous relocation typically follows, manual reduction under anesthesia may be required.

Patients with myofascial pain dysfunction have short, sudden episodes of aching pain in the jaw associated with stress; this condition is often referred to as masticatory muscle spasm secondary to bruxism. Malocclusion associated with long-term microtrauma to the joint (as seen in patients with bruxism) is thought to result in spasm of the lateral pterygoid or deep posterior masseter muscle, which is then further aggravated by episodes of anxiety and stress.

References
1. Bessette RW, Jacobs JS. Temporomandibular joint dysfunction. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:335-347.
2. Mendes D, Jacobs JS. Traumatic deformities and reconstruction of the temporomandibular joint. In: Cohen M, ed. Mastery of Plastic and Reconstructive Surgery. Boston, Mass: Little, Brown & Co; 1994;2:1220-1228.

A 25-year-old woman seeks surgical correction of a "gummy" smile. On examination, she has lip incompetence and full incisal show with the lips in repose and 3 mm of gingival show with animation. There is Angle class II malocclusion and a horizontal chin deficiency. These findings are most consistent with which of the following?

(A) Gingival alveolar hypertrophy
(B) Mandibular prognathism
(C) Mandibular retrognathism
(D) Vertical maxillary deficiency
(E) Vertical maxillary excess
The correct response is Option E.

This patient's gummy smile is a manifestation of vertical maxillary excess. A gummy smile is defined as greater than 4 mm of incisal show with the lips in repose and greater than 2 mm of gingival show with animation. Patients with vertical maxillary excess, also known as the "long face" syndrome, have lip incompetence, an excessive interlabial gap, and mentalis muscle strain associated with attempts to overcome the labial incompetence. The chin is retruded and the mandible appears retrognathic secondary to a backward, or inferoposterior, high-angle clockwise mandibular rotation. The width of the inter-alar base is excessively narrow, and the nasolabial angle is open and obtuse. Appropriate management in this patient includes preoperative orthodontics followed by maxillary Le Fort I osteotomy and impaction, which will allow for autorotation and correction of the retrognathic appearance.

Gingival alveolar hypertrophy can result in excessive show of the teeth and gingiva but would not be responsible for all of the findings seen in this patient.

Mandibular prognathism is characterized by Angle class III malocclusion, effacement of the labiomental fold, and prominence of the lower third of the face. Several techniques may be considered depending on facial aesthetics, including mandibular setback, maxillary advancement, or a combination of both.

Patients with mandibular retrognathism have protrusion of the anterior teeth, associated lip incompetence, and a deep labiomental crease with eversion of the lower lip. There is Angle class II malocclusion; the lower third of the face may appear foreshortened. Mandibular advancement is recommended; genioplasty may also be required concomitantly.

Vertical maxillary deficiency manifests as a lack of maxillary incisor show, leading to an edentulous appearance. Affected patients have a concave facial profile with an "overclosed" appearance to the mandible. Other characteristics include excessive chin projection, an acute nasolabial angle, and an excessively wide inter-alar base. Appropriate management is Le Fort I osteotomy with interpositional grafting.

References
1. McCarthy JG, Kawamoto H, Grayson B, et al. Surgery of the jaws. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:1188-1474.
2. Schendel SA. Vertical maxillary deformities. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:284-286.

A 17-year-old boy is referred for orthognathic surgery. On intraoral examination, the mesiobuccal cusp of the maxillary first molar is positioned distal to the buccal groove of the mandibular first molar. Which of the following best describes this occlusal relationship?

(A) Angle class I
(B) Angle class II
(C) Angle class III
(D) Overbite
(E) Overjet

The correct response is Option C.

Occlusion describes the relationship between the upper and lower teeth and is critical for planning reconstructive surgery of the jaws. The Angle classification of occlusion is based on the relationship of the mesiobuccal cusp of the maxillary first molar to the mandibular first molar when viewed in the sagittal plane. In this patient, the mesiobuccal cusp of the maxillary first molar lies distal (posterior) to the buccal groove of the mandibular first molar and instead is located in the buccal groove of the lower second molar, which is Angle class III malocclusion.

In patients with class I (normal) occlusion, the mesiobuccal cusp of the maxillary first molar lies in the buccal groove of the mandibular first molar. Angle class II malocclusion is defined as the mesiobuccal cusp of the maxillary first molar located mesial (anterior) to the buccal groove of the mandibular first molar. This classification of malocclusion has two divisions; in class II, division 1, the lateral incisors are flared labially, while in class II, division 2, the incisors are lingually inclined.

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. Overjet is a horizontal measurement referring 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.

References
1. Ferraro JW. Oral anatomy. In: Ferraro JW, ed. Fundamentals in Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:127-157.
2. Wolfe SA, Spiro SA, Wider TM. Surgery of the jaws. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:321-333.

Which of the following is the most common etiology of ankylosis of the temporomandibular joint?

(A) Autoimmune
(B) Congenital
(C) Infectious
(D) Neoplastic
(E) Trauma

The correct response is Option E.

Intra-articular (true) ankylosis of the temporomandibular joint (TMJ) most frequently occurs as a result of trauma. In patients with true ankylosis, destruction of the articular disk and joint elements occurs, leading to fibrosis, narrowing of the joint space, and ultimately bony fusion.

Abnormalities of bone, cartilage, and/or soft tissue have also been shown to cause TMJ ankylosis.

Other causes of TMJ ankylosis, such as congenital abnormalities, idiopathic occurrences, infection, and juvenile rheumatoid arthritis, have been documented but are less common than trauma. Neoplasms of the TMJ are extremely rare.

References
1. Bessette RW, Jacobs JS. TMJ dysfunction. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:335-347.
2. Posnick JC, Goldstein JA. Surgical management of temporomandibular joint ankylosis in the pediatric population. Plast Reconstr Surg. 1993;91:791-798.
3. Zins JE, Smith JD, James DR. Surgical correction of temporomandibular joint ankylosis. Clin Plast Surg. 1989;16:725-732.

When obtaining lateral cephalograms, which of the following represents a commonly used cranial base plane?

(A) Long axis of the maxillary incisor plane
(B) Nasion-to-point A plane
(C) Occlusal plane
(D) Palatal plane
(E) Sella-nasion plane

The correct response is Option E.

A cephalogram is a radiograph obtained from a standard distance (typically 60 inches) with the head placed in a mechanical device. The lateral cephalogram is most effective for demonstrating both occlusion and relationships between the maxilla, mandible, and base of the skull.

A typical cephalometric plane connects three or more cephalometric points. The most commonly used cranial base planes are the sella-nasion, basion-nasion, and Frankfort horizontal planes. Commonly used maxillary planes include the long axis of the maxillary incisor plane; the nasion-to-point A plane; the occlusal plane, which extends between the mesial cusp of the maxillary molar through the point that bisects the overbite; and the palatal plane, which joins the anterior nasal spine to the posterior nasal spine.

References
1. Wolfe SA, Spiro SA, Wider TM. Surgery of the jaws. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:321.
2. Zide B, Grayson B, McCarthy JG. Cephalometric analysis: part I. Plast Reconstr Surg. 1981;68:816.
3. Zide B, Grayson B, McCarthy JG. Cephalometric analysis for upper and lower midface surgery: part II. Plast Reconstr Surg. 1981;68:961.

Which of the following sites is osteotomized in the Le Fort III osteotomy but NOT in the monobloc advancement osteotomy?

(A) Frontozygomatic suture
(B) Inferior orbital fissure
(C) Lamina papyracea
(D) Pterygomaxillary fissure
(E) Zygomatic arch

Reproduced with permission of Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:301-302.
The correct response is Option A.

Although the Le Fort III osteotomy, as shown in the first illustration on page 36, is most often used for correction of midface hypoplasia in patients with craniosynostosis, the monobloc advancement osteotomy is now gaining acceptance. In the Le Fort III procedure, the osteotomies pass through the nasofrontal junction first, then laterally across the medial orbital wall (lamina papyracea) and onto the orbital floor, continuing into the inferior orbital fissure. The lateral orbital wall is cut through the frontozygomatic suture and separated from the cranium; it continues inferiorly and posteriorly, where a pterygomaxillary disjunction is performed. After the zygomatic arch is cut, the advancement can be performed.

In the monobloc advancement, shown in the second illustration on page 36, the osteotomy lines are similar to the Le Fort III osteotomy, but the nasofrontal junction and frontozygomatic suture are not osteotomized. An advantage of the monobloc procedure is simultaneous correction of the supraorbital and midface deformities. However, this technique is associated with higher rates of infection and cerebrospinal fluid leakage, which is most likely due to direct communication between the cranial and nasal cavities.

References
1. Bartlett SP, Mackay GJ. Craniosynostosis syndromes. In: Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:295.
2. Gillies H, Harrison SH. Operative correction by osteotomy of recessed malar maxillary compound in a case of oxycephaly. Br J Plast Surg. 1951;3:123.
3. McCarthy JG, Epstein FJ, Wood-Smith D, et al. Craniosynostosis. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:3028.
4. Ortiz-Monasterio F, del Campo AF, Carrillo A. Advancement of the orbits and the midface in one piece, combined with frontal repositioning, for the correction of Crouzon's deformities. Plast Reconstr Surg. 1978;61:507.