In-Service Exam
Orthognathic, TMJ, Chin - 2003





Which of the following soft-tissue changes is most common in patients who have undergone Le Fort I maxillary advancement?

(A) Decreased incisor show
(B) Increased nasolabial angle
(C) Lengthening of the upper lip
(D) Narrowing of the alar base

The correct response is Option B.

In patients who have undergone Le Fort I maxillary advancement, characteristic soft-tissue changes in the nose include an increased nasolabial angle and widened alar base. In addition, the upper lip is shortened and incisal show is increased. These changes vary depending on the degree of maxillary advancement and the proclination of the maxillary incisors. Alar cinch sutures can be used to minimize excess widening of the alar base, while excess shortening of the upper lip may be prevented by performing V-Y advancement during closure.

References
1. Betts NJ, Fonseca RJ. Soft tissue changes associated with orthognathic surgery. In: Modern Practice in Orthognathic and Reconstructive Surgery. Philadelphia, Pa: WB Saunders Co; 1992:2170-2209.
2. Carlotti AE, Aschaffenburg PH, Schendel SA. Facial changes associated with surgical advancement of the lip and maxilla. J Oral Maxillofac Surg. 1986;44:593-596.

Alloplastic chin augmentation is most appropriate for a patient with which of the following findings?

The correct response is Option D.

Because the indications for alloplastic chin augmentation are limited, the surgeon should carefully consider the skeletal deficiencies of each patient before considering this procedure. Alloplastic augmentation is most appropriate for a patient who has a minimal sagittal deficiency of the lower face, a shallow labiomental fold, and symmetry and normal height of the lower face.

Alloplastic chin implants are not appropriate for patients with chin asymmetry. Because a chin implant is always placed over the anterior symphysis, it cannot be used to correct abnormalities in facial height. Chin implantation will further accentuate any preexisting deep labiomental folds, resulting in an unnatural, "operated" appearance. Osseous genioplasties are more appropriate instead in those patients who require adjustments in the height of the lower face, or in patients who have a deep labiomental fold and require genial advancement. The vertical height of the chin can be elongated during advancement of the chin to prevent further deepening of the labiomental fold.

References
1. Guyuron B. Genioplasty. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:250-269.
2. Rosen HM. Chin surgery. In: Rosen HM, ed. Aesthetic Perspectives in Jaw Surgery. New York, NY: Springer-Verlag; 1999:248-249.

PHOTO

The photograph shown above is of a 15-year-old girl who has midface hypoplasia. Which of the following best describes this patient's occlusion?

(A) Angle class I
(B) Angle class II, division 1
(C) Angle class II, division 2
(D) Angle class III

The correct response is Option D.

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. Malocclusions can occur as a result of dental dysplasia, skeletal dysplasia, or a combination of both.
The findings shown in the photograph are consistent with Angle class III malocclusion, or mesio-occlusion. In this patient, the mesiobuccal cusp of the maxillary first molar lies distal or posterior to the buccal groove of the mandibular first molar and in the buccal groove of the lower second molar, resulting in the prognathic profile. With this type of malocclusion, the maxillary teeth are typically positioned end-to-end or in a cross-bite pattern. Angle class III malocclusion is also common in patients with cleft palate.

In patients with class I occlusion (neutral occlusion), the mesiobuccal cusp of the maxillary first molar lies in the buccal groove of the mandibular first molar. There is a minimal degree of overjet and overbite.

Angle class II malocclusion, or distal occlusion, is defined as the mesiobuccal cusp of the maxillary first molar being located 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, resulting in significant overjet, while in class II, division 2, the incisors are lingually inclined, producing a retrognathic appearance.

References
1. Baird WL, Wornom IL, Jurkiewicz MJ. Maxillofacial trauma. In: Jurkiewicz JM, Krizek TJ, Mathes SJ, et al, eds. Plastic Surgery: Principles and Practice. Philadelphia, Pa: Mosby Ð Year Book, Inc; 1990;1:231-270.
2. Ferraro JW. Oral anatomy. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York, NY: Springer-Verlag, 1997:127-157.

A 37-year-old woman is undergoing evaluation because of intermittent clicking of the right temporomandibular joint (TMJ). She has no pain or crepitus of the joint. Interincisal opening is 40 mm. MRI shows a nonreducing articular disk within the right TMJ. Which of the following is the most appropriate management?

(A) Observation
(B) Intracapsular repositioning of the disk
(C) Intracapsular repositioning of the disk and reduction of the articular eminence
(D) Removal of the disk and placement of an interpositional temporalis fascia flap

The correct response is Option A.

Conservative management is most appropriate for this patient who has episodic clicking, no pain, and a normal interincisal opening distance. Operative correction is indicated only for internal derangement of the temporomandibular joint associated with congenital anomalies, neoplasia, previous trauma to the joint, chronic pain, or trismus resulting in functional limitation.

Intracapsular repositioning of the disk, removal of the disk, and placement of a temporalis fascia flap are options for those patients with internal derangement who are surgical candidates. Surgical reduction of the articular eminence, or eminectomy, is indicated in patients who have symptomatic open locking of the mandible.

References
1. Bays RA. Surgery for internal derangement. In: Bays RA, Quinn PD, eds. Oral and Maxillofacial Surgery. Philadelphia, Pa: WB Saunders Co; 2000:275-300.
2. Feinberg S, Larsen P. Reconstruction of the temporomandibular joint with pedicled temporalis muscle flaps. In: Bell WH, ed. Modern Practice in Orthognathic and Reconstructive Surgery. Philadelphia, Pa: WB Saunders Co; 1992:733.

In an 18-year-old man with Angle class III malocclusion, cephalometric analysis shows a decreased SNA angle and a normal SNB angle. Which of the following is the most likely cause of these findings?

(A) Mandibular prognathism
(B) Mandibular retrognathism
(C) Maxillary retrusion
(D) Vertical maxillary excess

PHOTO

Reproduced with permission of McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:1198.

The correct response is Option C.

Maxillary retrusion is the most common cause of a decreased SNA (sella-nasion-point A) angle combined with a normal SNB (sella-nasion-point B) angle. The SNA angle measures the position of point A (anterior maxilla) relative to the anterior cranial base (SN); a normal SNA angle is defined as 82 degrees  3 degrees. Patients with maxillary protrusion have an increased SNA angle, while patients with maxillary retrusion have a decreased SNA angle. In contrast, the SNB angle measures the position of point B (anterior mandible) relative to the anterior cranial base (SN); a normal SNB angle is defined as 80 degrees  3 degrees. It is increased in patients with mandibular protrusion and decreased in patients with mandibular retrusion.
This patient has Angle class III malocclusion, in which the mandible is abnormally protrusive relative to the maxilla, or the maxilla is retrusive relative to the mandible. This patient has a decreased SNA angle and a normal SNB angle, as stated above; therefore, the mandibular position is normal while the maxillary position is deficient.

References
1. Ferraro JW. Cephalometry and cephalometric analysis. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:233-245.
2. Schendel SA. Cephalometrics and orthognathic surgery. In: Bell WH, ed. Modern Practice in Orthognathic and Reconstructive Surgery. Philadelphia, Pa: WB Saunders Co; 1992;1:85-99.

Which of the following is the optimal amount of incisor show at rest?

(A) 0 to 1 mm
(B) 2 to 3 mm
(C) 4 to 5 mm
(D) 6 to 7 mm

The correct response is Option B.

At rest, the upper lips should be parted slightly and 2 to 3 mm of upper central incisors should be visible beneath the lower border of the upper lip. Only 1 to 2 mm of gingiva should be visible during a full smile. Patients with vertical maxillary deficiency typically have no incisor show at rest, resulting in a "prematurely aged" appearance. Patients with vertical maxillary excess often exhibit a "gummy" smile that occurs as a result of excessive gingival show.

References
1. Betts NJ, Fonseca RJ. Soft tissue changes associated with orthognathic surgery. In: Modern Practice in Orthognathic and Reconstructive Surgery. Philadelphia, Pa: WB Saunders Co; 1992:2170-2209.
2. Robertson B, Crawley W. Orthognathic surgery. In: Evans GR, ed. Operative Plastic Surgery. New York, NY: McGraw-Hill, Inc; 2000:585-593.

A 27-year-old woman desires surgical correction because she has an edentulous appearance. Physical examination shows decreased height in the lower third of the face and absence of maxillary incisor show. Cephalometric analysis shows an acute mandibular plane angle.

Which of the following operative procedures is most appropriate?

(A) Genioplasty
(B) Le Fort I osteotomy with inferior repositioning
(C) Le Fort I osteotomy with maxillary impaction
(D) Le Fort III osteotomy
(E) Bilateral sagittal split osteotomy of the mandible

The correct response is Option B.

This patient has findings consistent with vertical maxillary deficiency, or short face syndrome. Affected patients have a vertical decrease in facial height and absence of maxillary show, resulting in an edentulous appearance. The upper lip appears short and flat; the bite is deep, and the chin protrudes excessively. The alar bases are wide. The mandibular plane angle is acute.

Appropriate management of vertical maxillary deficiency is Le Fort I osteotomy with inferior repositioning of the maxilla. Bone grafts can be interposed to stabilize the mandible during downward movements and prevent recurrence of the deformity.

Genioplasty can be performed as an adjuvant to Le Fort I osteotomy to improve the aesthetic appearance of the chin but will not effectively increase maxillary height if performed alone.

Le Fort I osteotomy with maxillary impaction is performed to shorten the face in patients with vertical maxillary excess.

Le Fort III osteotomy is not indicated for patients with deformities limited to the lower third of the face.

Bilateral sagittal split osteotomy can be combined with downfracture of the maxilla to improve facial projection but will not improve midface height when performed alone.

References
1. McCarthy JG, Kawamoto HK, Grayson BH, et al. Surgery of the jaws. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:1188-1474.
2. Schendel SA. Orthognathic surgery. In: Achauer BM, Erikson E, Guyuron B, et al, eds. Plastic Surgery: Indications, Operations, and Outcomes. Saint Louis, Mo: Mosby Ð Year Book, Inc; 2000;2:871-895.
3. Schendel SA. Vertical maxillary deformities. In: Ferraro JW, ed. Fundamentals in Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:284-286.

During unilateral distraction osteogenesis of the mandible in a 5-year-old child, which of the following is the most appropriate technique to optimize the resulting bone formation?

(A) Acute intraoperative distraction of 5 mm
(B) Nonrigid pin fixation of the bone segments
(C) Resection of periosseous soft tissues
(D) Low-energy corticotomy
(E) Wide subperiosteal dissection

The correct response is Option D.

In experimental studies of limb lengthening involving the long bones, minimal disruption of the central medullary bone has been shown to be a core principle of distraction osteogenesis. This can be accomplished using a low-energy corticotomy that divides only the bone cortex, thus optimizing the resultant bone formation.

Acute intraoperative distraction of 5 mm or more is likely to result in early disruption of the medullary bone and impairment of the central callus. Fibrous union has been demonstrated following acute intraoperative distraction in animal models.

Because increased fixator stability has been shown to improve the quality of regenerated bone, nonrigid pin fixation of bone segments is discouraged because it would impair resultant bone formation.

Enhanced bone formation has been shown to result from preservation of the periosseous and intraosseous soft tissues. Several authors have advocated against resecting soft tissue because the vascularity of the periosseous soft tissue is thought to be critical to bone regeneration.

Wide subperiosteal undermining is also thought to be detrimental to bone regeneration.

References
1. Aronson J. Experimental and clinical experience with distraction osteogenesis. Cleft Palate Craniofac J. 1994;31:473-482.
2. Aronson J. Mechanical induction of osteogenesis: the importance of pin rigidity. J Ped Orthop. 1988;8:396-401.
3. Gosain AK. Distraction osteogenesis of the craniofacial skeleton. Plast Reconstr Surg. 2000;107:278-280.
4. Ilizarov GA. The tension-stress effect on the genesis and growth of tissues. Clin Orthop. 1989;238:249-281.

A 10-year-old boy is scheduled to undergo Le Fort III osteotomy with distraction osteogenesis for advancement of the midface. Which of the following is an advantage of using a rigid external distraction device rather than an internal distraction device in this patient?

(A) Decreased operative morbidity
(B) Decreased risk for relapse following midface advancement
(C) Greater degree of advancement
(D) More rapid rates of distraction
(E) Need for fewer subsequent operative procedures

The correct response is Option E.

Distraction osteogenesis with external or internal distraction devices can be performed to lengthen the midface gradually in children with craniosynostosis, cleft lip and palate, hemifacial microsomia, and midface hypoplasia. Midface osteotomies must be performed in order to initiate distraction regardless of the type of device. The rigid external distraction (RED) device is most commonly used externally. Distraction with this device, rather than with an internally implanted device, is advantageous primarily because it can be removed in the office and a second operative procedure is not necessary. In contrast, an additional operative procedure is required in a patient who has an implanted internal device to expose and remove the hardware. Resorbable internal devices have been introduced recently, which may decrease the extent of operative dissection required for removal. However, a second operative procedure is still necessary to remove the metallic distraction foot plate attached to the resorbable hardware.

There are no differences in the degree of operative morbidity at the time of osteotomy with either the internal or external distraction device. However, operative morbidity following midface osteotomy for distraction osteogenesis is lower than that seen with midface osteotomy using conventional bone grafting and rigid fixation techniques. Distraction techniques using either internal or external devices do not have the potential for morbidity associated with bone graft harvest sites.

The potential for relapse of the advanced midface segment is no different with either technique following removal of the distraction device and an adequate period of consolidation.

There are no data to indicate that the results achieved with either type of device differ substantially. There is also no difference in the rate of distraction or the amount of distraction that can be achieved with either technique. Both techniques require a period of bone consolidation after distraction has been completed.

References
1. Cohen SR, Holmes RE, Amis P, et al. Internal craniofacial distraction with biodegradable devices: early stabilization and protected bone regeneration. J Craniofac Surg. 2000;11:354-366.
2. Cohen SR. Midface distraction. Sem Orthodont. 1999;5:52-58.
3. Gosain AK. Distraction osteogenesis of the craniofacial skeleton. Plast Reconstr Surg. 2001;107:278-280.
4. Polley JW, Figueroa AA. Management of severe maxillary deficiency in childhood and adolescence through distraction osteogenesis with an external, adjustable, rigid distraction device. J Craniofac Surg. 1997;8:181-185.

A 16-year-old girl who has hypoplasia of the chin and a prominent hump on the nasal dorsum is scheduled to undergo rhinoplasty and osseous genioplasty. In this patient, nerve injury during osseous genioplasty is most likely to result in which of the following complications?

(A) Inability to depress the lower lip
(B) Inability to elevate the lower lip
(C) Numbness of the ipsilateral tongue
(D) Numbness of the lower lip
(E) Oral incompetence

PHOTO

The inferior alveolar neurovascular bundle dips inferiorly and anteriorly before exiting the mental foramen. In designing the genioplasty, the surgeon must take this factor into consideration to prevent severance of the neurovascular bundle within the canal. The undesirable approach is shown to demonstrate what not to do.

Reproduced with permission of Kaban LB, Pogrel MA, Perrott DH, eds. Complications in Oral and Maxillofacial Surgery. Philadelphia, Pa: Elsevier Science; 1997:209.

The correct response is Option D.

This 16-year-old girl who is undergoing genioplasty is at greatest risk for injury to the mental nerve, which will result in numbness of the lower lip. The mental nerve is a sensory portion of the inferior alveolar nerve and is located distally. It should be routinely identified and preserved during surgery. Patients who have damage to the mental nerve, either from injury during genioplasty or an inferior alveolar nerve block, often inadvertently bite the lip because of the loss of sensation.

An inability to depress the lower lip during facial animation occurs as a result of injury to the facial nerve. Injury to branches of the facial nerve is most likely to result in an inability to depress or elevate the lower lip and oral incompetence. Injury to the lingual nerve would result in numbness of the tongue.

References
1. Clemente CD, ed. Anatomy: A Regional Atlas of the Human Body. 4th ed. Baltimore, Md: Williams & Wilkins; 1997:730, 735-736, 748-750, 866.
2. Kaban LB, Pogrel MA, Perrott DH, eds. Complications in Oral and Maxillofacial Surgery. Philadelphia, Pa: WB Saunders Co; 1997:209.
3. McCarthy JG, Kawamoto H, Grayson BH, et al. Surgery of the jaws. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:1305-1333.

PHOTO

The lateral cephalogram shown above is from a 16-year-old boy who desires occlusal correction. He underwent bilateral cleft lip and palate repair in infancy and pharyngeal flap transfer in early childhood. Examination shows Angle class III malocclusion with 12 mm of negative overjet; the SNB angle is within an acceptable range.

Which of the following is the most appropriate management?

(A) Le Fort I maxillary advancement
(B) Le Fort I maxillary advancement and genioplasty
(C) Maxillary distraction osteogenesis
(D) Maxillary and mandibular distraction osteogenesis
(E) Maxillary distraction osteogenesis and bilateral sagittal split-ramus osteotomy with mandibular setback

The correct response is Option C.

In patients who have severe deficiencies of the midface occurring secondary to cleft lip and palate, traditional orthognathic and orthodontic approaches are often ineffective. This patient with a bilateral cleft lip and palate has 12 mm of negative overjet following pharyngeal reconstruction with a posterior pharyngeal flap. These factors, as well as other complications seen in similar patients, including absence of maxillary and alveolar bone, scarring, and residual fistulas, can make reconstruction problematic and predispose these patients to surgical relapse. Therefore, newer procedures such as maxillary distraction osteogenesis are most appropriate for correction of the midface deficiency. This technique will expand the soft tissues and bones of the midface and palate in a single-stage procedure, correcting the malocclusion and leaving the mandible untouched.

Le Fort I maxillary advancement of more than 10 mm is a technically challenging, unpredictable procedure that would not correct this patient's malocclusion. In addition, the posterior pharyngeal flap would have to be taken down before surgery, and a certain amount of relapse would be seen.

Although it is technically possible, a combined Le Fort I maxillary advancement and genioplasty procedure is not the first choice for this patient because the mandible and SNB angle are normal. For the same reason, mandibular distraction and/or setback are not necessary. Skeletal reduction procedures, such as the bilateral sagittal split-ramus osteotomy, are not recommended when maxillary distraction is available.

References
1. Molina F, Ortiz Monasterio F, Paz Aguilar M, et al. Maxillary distraction: aesthetic and functional benefits in cleft lip-palate and prognathic patients during mixed dentition. Plast Reconstr Surg. 1998;101:951.
2. Polley JW, Figueroa AA. Rigid external distraction: its application in cleft maxillary deformities. Plast Reconstr Surg. 1998;102:1360.

A 25-year-old woman seeks surgical correction of a "gummy" smile. On physical examination, she has lip incompetence, 5 mm of incisor show at rest, evidence of mentalis muscle strain, and Angle class II malocclusion. She has a long, narrow nose, a retruded chin, and excessive vertical height in the lower third of the face.

Which of the following is the most appropriate surgical correction?

(A) Anterior segmental maxillary osteotomy with impaction
(B) Le Fort I osteotomy with inferior repositioning and genioplasty
(C) Le Fort I osteotomy with maxillary impaction and genioplasty
(D) Le Fort III osteotomy
(E) Sagittal split osteotomy and genioplasty

The correct response is Option C.

This patient has findings consistent with vertical maxillary excess, including increased height in the lower third of the face and a narrow nose. Patients with this condition frequently have constriction of the alar base and an obtuse nasolabial angle. There is lip incompetence and incisor show at rest; the lip-to-tooth ratio is greater than 3 mm. Mentalis muscle strain occurs as the patient attempts to obtain lip competence. This chin is retruded and vertically long; occlusion is frequently Angle class II. The mandible is typically retrognathic; this may be true retrognathism or may result from backward autorotation of the jaw.

Following application of orthodontic appliances to eliminate any dental compensation, the most appropriate operative management is Le Fort I osteotomy with maxillary impaction. Genioplasty may also be performed in patients with persistent retrusion of the chin.

Anterior segmental maxillary osteotomy will not completely correct the long face deformity. Le Fort I osteotomy with inferior repositioning will increase the length of the lower face and thus worsen the deformity. A Le Fort III osteotomy, which entails detachment of the entire midface from the base of the skull, is inappropriate for the treatment of vertical maxillary excess. Sagittal split osteotomy is performed for correction of mandibular deficiencies, not maxillary excess.

References
1. McCarthy JG, Kawamoto HK, Grayson BH, et al. Surgery of the jaws. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:1188-1474.
2. Schendel SA. Orthognathic surgery. In: Achauer BM, Erikson E, Guyuron B, et al, eds. Plastic Surgery: Indications, Operations, and Outcomes. Saint Louis, Mo: Mosby Ð Year Book, Inc; 2000;2:871-895.
3. Schendel SA. Vertical maxillary deformities. In: Ferraro JW, ed. Fundamentals in Maxillofacial Surgery. New York, NY: Springer-Verlag; 1997:284-286.

Which of the following structures is NOT involved in a Le Fort II advancement osteotomy?

(A) Lateral orbital wall
(B) Medial orbital walls
(C) Nasofrontal junction
(D) Orbital floor
(E) Pterygoid plates

PHOTO

Le Fort II osteotomy. A: The line for the midface osteotomy in this illustration is drawn behind the lacrimal fossae, which will advance the medial canthal tendon complex. The osteotomy may be performed in front of the lacrimal fossae, thereby avoiding the medial canthal attachment but possibly placing the nasolacrimal duct in jeopardy. In addition, a horizontal mandibular osteotomy is depicted. B: Mobilization is followed by rigid fixation and bone grafting (C).

Reproduced with permission of Aston SJ, Beasley RW, Thorne CH, eds. Grabb & Smith's Plastic Surgery. 5th ed. Philadelphia, Pa: Lippincott-Raven; 1997:326.

The correct response is Option A.

The Le Fort classification is used to identify the pattern of midface fractures. Identification of the lines of fracture is useful in planning osteotomies for patients requiring midface advancement.

Le Fort I midface advancement involves placement of the osteotomy at a level above the apices of the teeth. The entire alveolar processes of the maxilla, vault of the palate, and pterygoid processes are included in a single block. The osteotomy extends transversely across the base of the maxillary sinuses and the floor of the piriform aperture.
The Le Fort II osteotomy begins above the level of the apices of the teeth laterally and extends through the pterygoid plates in a manner similar to the Le Fort I osteotomy, leaving a central maxillary segment undisturbed. The osteotomy procedure includes portions of the medial orbital wall, orbital floor, and nasofrontal junction. Patients undergoing Le Fort II midface advancement are at increased risk for injury to the ethmoid area and the lacrimal system. The lateral orbital wall is unaffected.

Le Fort III osteotomy extends through the zygomaticofrontal suture and the nasofrontal suture and across the floor of the orbits. The entire midface is completely detached from the base of the skull.

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; 1997:295-304, 326.
2. Jackson IT, Munro IR, Salyer KE, et al. Orthognathic surgery. In: Atlas of Craniomaxillofacial Surgery. Saint Louis, Mo: CV Mosby Co; 1982:83.
3. Manson PN. Facial injuries. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;2:935-937.
4. McCarthy JG, Epstein FS, Wood-Smith D. Craniosynostosis. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;6:3038.

Which of the following is the most appropriate initial step in the management of a patient being evaluated for chin implantation?

(A) Cephalometric analysis
(B) Determination of the patient's occlusion
(C) Evaluation of bite mechanics
(D) Panoramic radiograph

The correct response is Option B.

Dental occlusion must be adequately assessed in any patient who is being considered for chin implantation. If occlusion is normal, orthognathic surgery is not necessary. However, if Angle class III malocclusion is the underlying cause of the retrognathia, chin implantation is not appropriate because it does not address the underlying malformation.

If the patient is shown to have malocclusion, cephalometric analysis, evaluation of bite mechanics, and a panoramic radiograph may be required.

References
1. Choe KS, Stucki-McCormick SU. Chin augmentation. Facial Plast Surg. 2000;16:45-54.
2. Cohen SR. Genioplasty. In: Achauer BM, Erikson E, Guyuron B, et al, eds. Plastic Surgery: Indications, Operations, and Outcomes. Saint Louis, Mo: Mosby Ð Year Book, Inc; 2000;5:2563-2582.

PHOTO

A 43-year-old woman has noticeable strain of the labial and mentalis muscles, lip incompetence, and excess vertical facial height 15 years after undergoing chin implantation. A photograph is shown above. Physical examination shows asymmetry over the lateral aspect of the bone-implant junction. CT scan shows mild bony resorption in the affected area.

Which of the following is the most appropriate management?

(A) Reassurance
(B) Injection of collagen into the chin
(C) Removal of the implant
(D) Removal of the implant and bone grafting of the chin
(E) Removal of the implant, bone grafting of the chin, and sliding genioplasty

The correct response is Option E.

The lateral contour irregularity seen in this patient is caused by bony resorption that, over time, will worsen at the junction of the alloplastic implant and menton. The most appropriate management includes removal of the chin implant, which is causing the resorption. However, this procedure alone will result in a decrease in vertical and horizontal facial height that is greater than what this patient had before implantation. Therefore, sliding genioplasty should be performed concomitantly. This technique will effectively treat the microgenia and can be used to decrease vertical height and correct labial incompetence. Bone grafting may also be required to compensate for any laterally resorbed bone.

As implied above, reassurance only will result in further worsening of this patient's problem. Collagen injection is a temporary measure that will not reverse the effects of bony resorption.

References
1. Barnett MP. Labial incompetence: a marker for progressive bone resorption in Silastic chin augmentation. Plast Reconstr Surg. 1997;100:553-554.
2. Wider TM, Spiro SA, Wolfe SA. Simultaneous osseous genioplasty and meloplasty. Plast Reconstr Surg. 1997;99:1273-1287.
3. Zide BM, Pfeifer TM, Longaker MT. Chin surgery: I: augmentation Ñ the allures and the alerts. Plast Reconstr Surg. 1999;104:1843-1862.