Practical Plastic Surgery

Maxillary Abnormalities

The most common problems associated with the maxilla include maxillary sagittal hypo/hyperplasia, maxillary vertical hypo/hyperplasia and maxillary transverse hypo/hyperplasia. When evaluating a patient for maxillary surgery the surgeon must evaluate the following:

1.Vertical position of the maxilla

2.Sagittal position of the maxilla

3.Transverse width of the maxilla

Useful measurements include: PNS-Sella, maxillary tooth show, occlusal plane

angle, J point analysis, nasolabial angle, SNA and ANB. The LeFort I osteotomy is used to correct deformities of the maxilla in the vertical, sagittal and transverse planes. It is commonly employed to treat sagittal hypoplasia (small SNA), vertical maxillary excess (excess gingival show) and anterior open bite (large PNS-Sella).

Mandibular Abnormalities

Common problems associated with the mandible include mandibular sagittal hypoplasia and mandibular sagittal hyperplasia. Cephalometric measurements used to evaluate the mandibular position include SNB, ANB, gonial angle and mandibular length. SNB determines the relative position of the mandible to the cranial base, and ANB illustrates the position of the mandible as related to the maxilla. Large values of mandibular length are associated with mandibular prognathism. The patient with a long lower face height or open bite will often have a large gonial angle. The Class III patient often has a diagnosis of mandibular sagittal hyperplasia. Most often, the patient has a prominent lower jaw and chin and a long lower face height. The Class II patient typically has a diagnosis of mandibular sagittal hypoplasia. Most often, the patient has a small mandible, retrusive chin and obtuse

54cervicomandibular angle. Surgical treatment of the mandible for mandibular prognathism includes bilateral sagittal split osteotomy (BSSO) and vertical ramus osteotomy (VRO).

Cephalometric Analysis and Predictions

Computerized cephalometric analysis and predictions have become the standard in orthognathic surgery. Many popular software packages allow for incorporation and analysis of radiographic images. They enable the clinician to pinpoint angles on a digitized AP and lateral cephalogram and generate cephalometric calculations. These calculations can be adjusted for gender, race and age. Following cephalometric analysis, the software generates a cephalometric tracing based on the points and angles identified by the physician. The clinical photograph is overlaid and incorporated into the digitized radiograph. The digitized cephalometric data is used to generate diagnosis and treatment based on the measurements. Overall, the computerized cephalometric software program is a good tool in the rapid diagnosis of dentofacial deformity. It allows for the interface between digitized radiographs, cephalometric measurements and cephalometric predictions. Ultimately, the goal in cephalometric imaging is the incorporation of 3-D imaging and predictions.

Model Surgery

As discussed previously, othognathic surgery consists of mandibular surgery, maxillary surgery and double jaw procedures. Surgeons use model surgery to aid in

planning of the operation. Model surgery facilitates precise surgical movements. In general, the patient presents for diagnostic evaluation when the skeletal malformation is first identified. At that time, diagnostic records, radiographs, images and dental models are fabricated. This process is repeated immediately before the operation. Appropriate images, measurements, radiographs and models are generated prior to the operation. Specifically, dental casts are fabricated from dental impression and stone. A face-bow record of the patients Frankfort horizontal plane to occlusal plane is generated. The dental casts are articulated using a bite record in centric relation and these are mounted on an anatomic semiadjustable articulator. Reproducible vertical reference lines are placed at the midline, canine tip, mesiobuccal cusp of the first molar and posterior retromolar region. Horizontal reference lines are placed at 10 and 20 mm from the articulator mounting plate. The cast is separated from the mounting ring at 15 mm, centered between the two horizontal reference lines.

Next, model surgery is performed on the mandible, maxilla, or both by positioning the maxillary and mandibular arches into an ideal occlusal relationship. The horizontal and vertical reference lines keep the models in the appropriate vertical, anteroposterior and transverse relationship. A final surgical splint is fabricated using methyl methylacrylate resin. In the case of double jaw surgery, the maxilla is first positioned in the predicted horizontal and vertical position. A splint is fabricated using methylmethacrylate that preserves this “intermediate” maxillomandibular relationship. Next, the mandibular cast is moved into an ideal occlusal relationship with the maxilla, creating the final splint.

Pearls and Pitfalls

An inexperienced surgeon who takes a bite registration in centric occlusion rather than centric relation will end up with inaccurately mounted modes, inaccurate splints, and eventually a nonreproducible, unstable result with a malocclu- 54 sion intraoperatively.

The SN-FH correction must be taken into consideration in order to have an accurate cephalometric prediction and treatment plan. Most patients have a normal SN-FH and thus do not require any correction factors; however children with craniofacial anomalies often require close analysis of the corrected FH, otherwise the cephalometric analysis will not be accurate.

Suggested Reading

1.Ash M. Wheelers Dental Anatomy, Physiology and Occlusion. Philadelphia: Saunders, 2000.

2.Betts N, Turvey T. Orthognathic surgery. In: Fonseca R, ed. Oral and Maxillofacial Surgery. Philadelphia: Saunders, 2000.

3.Ferraro JW. Cephalometry and cephalometric analysis. In: Ferraro JW, ed. Fundamentals of Maxillofacial Surgery. New York: Springer, 1997.

4.Kaban LB, Troulis MJ. Pediatric Oral and Maxillofacial Surgery. Philadelphia: Saunders, 2004.

5.Peterson LJ, Ellis E, Hupp JR et al. Contemporary oral and maxillofacial surgery. St. Louis: Mosby, 1998.

6.Profitt WR, Thomas PM, Camilla-Tulloch JF. Contemporary orthodontics. St Louis, Mosby: 1986.

7.Proffit WR, White RP, Sarver DM. Contemporary treatment of dentofacial deformity. St. Louis. Mosby: 2002.

Table 55.2. Comparison of features between synostotic

Molding of the skull, or orthotic cranioplasty, is done with a helmet worn up to 23 hours a day for 2-4 months. It should begin around the age of 6 months and always before the age of 14 months. It is the recommended treatment for deformational plagiocephaly and can also be used as an adjunct to surgery.

Surgery

Since the most rapid phase of skull growth occurs within the first year of life (Fig 55.1), early treatment is required. Surgical intervention is most commonly performed between the ages of 3 to 12 months of age. There is some evidence that earlier intervention results in fewer learning disabilities and emotional problems in later years. However, these findings are disputed by those who believe that operating on infants with craniosynostosis will not have an effect on their future cognitive abilities. Regardless of the timing, surgical treatment must be tailored to the individual’s deformed structures.

Unilateral coronal synostosis is managed with unilateral or bilateral fronto-or- bital advancement. Bilateral coronal synostosis is managed with bilateral frontoorbital advancement. If there is evidence of brachycephaly, total calvarial reconstruction may be required. Sagittal synostosis is treated with strip craniectomies and partial-wedge osteotomies. If biparietal expansion is required, anterior and posterior parietal wedges may be required. Lambdoid synostosis is managed with excision of the lambdoid suture. Metopic synsotosis is treated with removal of the supraorbital bar, corticotomy and correction of the midline angle with bone grafts

Figure 55.1. The growth curve of the skull.

or miniplates. Kleeblattschadel is treated after life-threatening conditions are addressed (e.g., hydrocephalus, airway obstruction) with anterior calveriectomy and fronto-orbital advancement. Excess constricting bands of bone are removed.

Complications

As might be expected from the magnitude of the procedures, the complications

55can be devastating. Early complications specific to these procedures include: sagittal sinus tears with venous infarction, subdural hematoma, cerebral edema, excess vasopressin production (SIADH), nerve injuries, injury to the orbits, infections, elevated ICP and dural leaks. Late complications include: incomplete advancement, palpable hardware, alopecia, asymmetry, orbital deformities, pseudomeningocele and increased ICP.

Craniofacial Syndromes

Many craniofacial syndromes have been described in the literature. However, with a few exceptions, these are rare syndromes seen primarily in specialized centers. A discussion of the more commonly encountered craniofacial syndromes follows with an emphasis on the similarities and differences between them.

Apert Syndrome (Acrocephalosyndactyly)

•Autosomal dominant

•Bicoronal synostosis

•Hypertelorism or exorbitism

•Strabismus

•Maxillary hypoplasia

•Acne and coarse skin

•Large ear lobes

•Syndactyly of all fingers (mitten hands) and toes

•Variable mental retardation

•Brachydactyly with syndactyly

•Normal intelligence

Carpenter Syndrome

•Autosomal recessive

•Craniosynostosis

•Deafness

•Brachydactyly with syndactyly

•Polydactyly (preaxial)

•Mental retardation

Treacher-Collins Syndrome (Mandibulofacial dysostosis)

•Autosomal dominant

•Prominent eyelid abnormalities (e.g., pseudocoloboma and absence of lashes)

•Downward sloping palpebral fissures

•Poorly developed orbital rims

•Midface (zygomaticomaxillary) hypoplasia

•Macrostomia and resulting airway distress

•Cleft palate

Velocardiofacial Syndrome

•Autosomal dominant

•Cleft palate or submucus cleft

•Cardiac abnormalities

•Ectopic carotid arteries

•Malar flattening

•Prominent broad nose

•Epicanthal folds

•Vertical maxillary excess

•Retrognathia

•Developmentally delayed

Pierre Robin Sequence

•Retrognathia (occasionally described as retromicrogenia)

•Glossoptosis

•Airway obstruction

•Variable cleft palate

Although not a true craniofacial syndrome, Pierre Robin sequence is an impor-

tant constellation of findings. This condition can be life-threatening due to airway compromise. Initial treatment consists of prone positioning, while surgical management is reserved for more severe cases.

Pearls and Pitfalls

•Treatment of craniosynostosis and craniofacial syndromes requires a multidisciplinary team approach. Early involvement of the other relevant specialties (neurosurgery, otolaryngology, oral surgery, speech therapy, a prosthodon-

tist and a geneticist) is essential for achieving a good outcome.

55• Prevention of deformational plagiocephaly is quite simple. It consists of turning the infant’s head from side to side several times throughout the day, and placing the infant prone while he is awake and under observation by the caretaker.

•In any infant suspected of having a craniofacial abnormality, evaluation of the airway is the most important initial step in the work-up.

•Distraction osteogenesis of the facial skeleton is an alternative to bone grafting that offers excellent long-term outcomes. It should be considered whenever greater than 10-15 mm of advancement of the facial bones is required.

•Crouzon’s syndrome can be distinguished from Apert and Pfeiffer syndromes by the absence of hand abnormalities.

•Almost all of the craniofacial syndromes are transmitted via an autosomal dominant pattern with variable expression. An important exception is Carpenter syndrome.

•The FGFR is known to be mutated in the majority of the craniofacial syndromes involving craniosynostosis. Future therapeutic approaches may target these mutations.

Suggested Reading

1.Anderson FM, Geiger L. Craniosynostosis: A Survey of 204 cases. J Neurosurg 1965; 22:229.

2.Breugem CC, van R, Zeeman BJ. Retrospective study of nonsyndromic craniosynostosis treated over a 10-year perior. J Craniofac Surg 1999; 10:140.

3.Tessier P. The definitive plastic surgical treatment of the severe facial deformities of craniofacial dysostosis. Crouzon’s and Apert’s diseases. Plast Reconstr Surg 1971; 48:419.

4.Huang MH, Gruss JS, Clarren SK et al. The differential diagnosis of posterior plagiocephaly: True lambdoid synostosis versus positional molding. Plast Reconstr Surg 1996; 98:765.

5.Kapp-Simon KA. Mental development and learning disorders in children with single suture craniosynostosis. Cleft Palate Craniofac J 1998; 35:197.

6.Losken HW, Pollack IF. Craniosynostosis. In: Bentz ML, ed. Pediatric Plastic Surgery. 1st ed. Stamford: Appleton and Lange, 1998.

7.Marchac D, Renier D, Broumand S. Timing of treatment for craniosynostosis and faciocraniosynostosis: A 20-year experience. Br J Plast Surg 1994; 47:211.

8.Mulliken JB, Vander Woude Dl, Hansen M et al. Analysis of posterior plagiocephaly: Deformational versus synostotic. Plast Reconstr Surg 1999; 103:371.

9.Noetzel MJ et al. Hydrocephalus and mental retardation in craniosynostosis. J Pediatr 1985; 107:885.

10.Persing JA, Jane JA, Edgerton MT. Surgical treatment of craniosynostosis. In: Persing JA, Edgerton MT, Jane JA, eds. Scientific Foundation of Surgical Treatment of Craniosynostosis. Baltimore: Williams and Wilkins, 1989.

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•Type IIB. Similar to Type IIA, yet the condyle and glenoid fossa are not in the normal position and plane.

•Type III. The condyle and ramus are absent and there is no TMJ.

Other bones of the craniofacial skeleton can be hypoplastic as well. The maxilla

is reduced in the vertical plane, and contributes to the cant of the occlusion plane. The zygoma and zygomatic arch are often decreased in length and the arch may be entirely absent. The temporal and frontal bones are affected less; however the orbits are often reduced in all dimensions leading to microphthalmos.

Classification of Unilateral Craniofacial Microsomia

There are a number of classification schemes. The two that are common and easy to use are the OMENS classification (Table 56.1), and the system proposed by Munro and Lauritzen in 1985 (Table 56.2).

Treatment by Age

There is no uniform treatment plan that is appropriate for everyone. Children under the age of two with craniofacial microsomia do not usually undergo major reconstructive surgery. Preauricular skin tags or other cartilaginous remnants may be excised. Commissuroplasty can correct those patients with macrostomia at this young age.

After the age of two, distraction osteogenesis can correct mandibular ramus hypoplasia as seen in Pruzansky Type I and IIA. This will both lengthen the mandible and improve the function of the muscles of mastication. Bilateral cases can be treated with bilateral distraction, allowing closure of tracheostomies in many children.

At the age of four, children with Pruzansky Type III mandibular hypoplasia undergo costochondral rib-graft reconstruction of the mandible combined with a LeFort I osteotomy and sagittal split of the contralateral mandibular ramus. The zygomatic arch and glenoid fossa are also reconstructed using a rib graft and a cap of costo-

chondral cartilage, respectively. 56 After the age of six, and microtia repair may be performed and orthodontic

treatment initiated. Augmentation of the facial soft tissue with muscle flap transfers is also occasionally necessary at this age. Once skeletal maturity has been reached in the early teenage years, residual deficiencies should be addressed.

Teenagers who have not undergone any prior treatment will require alternative types of reconstruction. Interpositional bone grafts can be used to correct mild mandibular length deficiencies. More severe microsomia can be treated with combined LeFort I osteotomy, bilateral sagittal split of the mandible, and genioplasty. Micrognathia can be treated with bilateral mandibular advancement.

Table 56.1. The “OMENS” classification for craniofacial microsomia