Show Summary Details
Page of

Orthognathic surgery 

Orthognathic surgery
Chapter:
Orthognathic surgery
Author(s):

Johno Breeze

, Sat Parmer

, and Niall McLeod

DOI:
10.1093/med/9780198814306.003.0002
Page of

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2020. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

date: 01 June 2020

Viva 2.1 High angle class 2 skeletal relationship

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. How would you manage this patient?

  3. 3. What are your orthodontic objectives?

  4. 4. What is the importance of not decompensating the incisors too much?

  5. 5. What are your surgical objectives?

  6. 6. What are the possible complications of orthognathic surgery?

  7. 7. How would you counsel the patient in terms of potential relapse and is there anything that can be done to affect this?

  8. 8. How would you compare stability, migration, and relapse?

Answers

  1. 1. This image demonstrates a male in his twenties. Key features are:

    • High angle class 2 skeletal relationship.

    • Increased lower facial height.

    • Class 2 division 1 incisal relationship, with an anterior open bite.

    • Short upper lip.

    • Average nasolabial angle.

    • Satisfactory upper incisor show at rest.

    • Incompetent lips at rest.

    • Retrogenic mandible with reduced chin–throat length.

  2. 2. Management of this patient comprises:

    • History and examination: focusing on contributing factors (tongue thrust, thumb-sucking), previous orthodontic treatment, and risk factors for relapse.

    • Investigations: radiographs (OPG (orthopantomogram) and lateral cephalogram), articulated study models.

    • Joint orthognathic planning clinic.

    • Orthodontic followed by surgical treatment.

  3. 3. The orthodontic objectives are to: align, level, co-ordinate, decompensate incisors, and relieve crowding.

  4. 4. You should not decompensate the incisors too much because:

    • Lip support is required, and the incisors will be surgically retroclined when performing a posterior impaction of the maxilla to address the anterior open bite.

    • A negative overjet is required to enable larger surgical movements, e.g. a pre-treatment overjet of –5 mm will enable a 7 mm antero-posterior surgical movement.

  5. 5. The surgical objectives are to impact the maxilla (posterior impaction) and advance the mandible. An additional genioplasty may be required.

  6. 6. Complications of orthognathic surgery comprise:

    • Immediate: haemorrhage, bad split.

    • Early: pain, malocclusion, swelling (compromised airway), fixation failure.

    • Late: temporomandibular joint (TMJ) dysfunction, negative effects on speech, relapse, nasal changes.

  7. 7. An element of relapse generally occurs. The orthodontic and surgical planning should ensure that the prescribed movements have the best predicted stability in order to diminish the degree of any dental and skeletal relapse. Mandibular advancements >10 mm are one of the least stable movements as demonstrated by Profitt. Distraction osteogenesis can be used instead of a bilateral sagittal split osteotomy (BSSO), but its effect upon relapse and stability is contentious.

  8. 8. Stability, migration, and relapse are important definitions when describing changes following orthognathic surgery:

    • Stability: maintenance of the achieved post-operative result in the long term. Post-surgical change may be classified as relapse or migration.

    • Migration: continued movement in the direction of the initial move.

    • Relapse: movement towards the pre-operative position and may be skeletal or dental in origin. Pre-surgical orthodontics aims to build in relapse.

Proffit WR, et al. Orthognathic surgery: a hierarchy of stability. Int J Adult Orthodont Orthognath Surg 1996;11:191–204.

Viva 2.2 Craniofacial hyperplasia

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What are the potential causes of a mandibular asymmetry?

  3. 3. In this case what is the likely diagnosis?

  4. 4. How does this differ from hemimandibular elongation?

  5. 5. How would you assess the patient?

  6. 6. When would you perform a radio-isotope scan?

  7. 7. Explain briefly what a single positron emission computed tomography (SPECT) scan is.

  8. 8. The scan demonstrates an area of increased uptake at the condyle. How would you manage this?

  9. 9. How should the maxillary cant be treated?

Answers

  1. 1. This is an OPG radiograph of a child in the mixed dentition. Measurements demonstrate an increased height of the ramus on one side. The condylar head is also enlarged, there is an occlusal cant but no obvious deviation of the midline.

  2. 2. Potential causes of a mandibular asymmetry include congenital and acquired:

    • Congenital: craniofacial macrosomia, Parry–Romberg disease, fibrous dysplasia, neurofibromatosis.

    • Overgrowth of mandible: hemimandibular hyperplasia, hemimandibular elongation.

    • Lack of growth of mandible: condylar hypoplasia secondary to trauma or infection.

  3. 3. The most likely diagnosis in this case is hemimandibular hyperplasia as the whole of the hemimandible is enlarged in all three dimensions.

  4. 4. Clinical features of hemimandibular elongation include deviation of the midline and lengthening of the condylar neck, due to localized overgrowth of the condyle.

  5. 5. Assessment of the patient with mandibular asymmetry comprises:

    • History: progression, previous orthodontic or surgical interventions, risk factors for ankylosis such as trauma or middle ear infections.

    • Examination: upper to lower dental centre lines, dental centre lines to facial midline and chin point, temporomandibular joint deviation and function, lateral open bite, stigmata of congenital conditions.

    • Investigations: clinical photographs and serial study models to monitor progression; consideration for a radio-isotope scan.

  6. 6. In a child of this age, SPECT radio-isotope scan is indicated if there is evidence of progression after a period of monitoring.

  7. 7. A SPECT scan is undertaken in the nuclear medicine department. A radiolabelled isotope (such as technetium-99m) is injected intravenously, which is detected by a gamma camera in higher amounts within areas of increased bone turnover.

  8. 8. A patient with increased bone turnover at the condyle is generally treated by a high condylar shave (although many clinicians are reluctant to do this at such a young age). Following a period of monitoring to ensure that no further progression occurs, the patient has definitive orthognathic surgery if required.

  9. 9. The maxillary cant should be treated by bodily impaction on one side, the amount to be determined by tooth show and pupillary level. If midfacial height is a problem, distraction or bone grafting should be considered. In a young child, interceptive orthodontics may play a role in prevention of cant formation.

Ferguson JW. Definitive surgical correction of the deformity resulting from hemimandibular hyperplasia. J Craniomaxillofac Surg 2005; 33: 150–7.

Viva 2.3 Low-angle class 2 skeletal relationship

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. Identify the name of each labelled point on this lateral cephalogram and how it is determined.

  3. 3. How do you measure anterior vertical facial proportions and what is the norm?

  4. 4. How do you measure the maxillary mandibular plane angle and what is the Caucasian norm?

  5. 5. What do you understand by the SNA and SNB angles and what values would you expect them to be?

  6. 6. If the ANB angle in this patient is 7°, the overjet 6 mm, and the maxillomandibular plane angle is 20°, what is the skeletal diagnosis?

  7. 7. What is the most likely surgical treatment going to be for this patient, if the SNA, upper anterior facial height (UAFH), and incisor show are all normal?

  8. 8. Do you extract third molars prior to a BSSO?

Answers

  1. 1. This is a lateral cephalogram demonstrating a patient with a low angle class 2 skeletal relationship and several labelled cephalometric points.

  2. 2. The following cephalometric points can be identified in this image:

    1. (A) Sella: the centre of the sella turcica.

    2. (B) Nasion: most anterior point of the fronto-nasal suture.

    3. (C) Orbitale: the most inferior anterior point on margin of orbit.

    4. (D) Porion: the uppermost point on bony external auditory meatus.

    5. (E) Anterior nasal spine (ANS): the most anterior point (the tip) of the hard palate.

    6. (F) Posterior nasal spine (PNS): the most posterior point of the bony hard palate.

    7. (G) Pogonion: the most prominent point on the contour of the chin in sagittal plane.

    8. (H) Gonion: a projected point on the mandible of a bisected angle between a line along the lower mandibular border and a line down the posterior ramus border.

    9. (I) Menton: the most inferior point on the mandibular symphysis.

    10. (J) A point: the position of deepest concavity on the anterior profile of the maxilla.

    11. (K) B point: the position of deepest concavity on anterior profile of mandibular symphysis.

  3. 3. Total anterior face height (TAFH) comprises upper anterior facial height (UAFH, nasion to ANS) plus lower anterior facial height (LAFH, ANS to menton). LAFH/TAFH should be approximately 50–55%.

  4. 4. The maxillary mandibular plane angle (MMPA) relates anterior vertical facial height to posterior vertical facial height, with a Caucasian range of 27° ± 5.

  5. 5. The SNA and SNB angles relate the anteroposterior positions of the maxilla and mandible, respectively, to the cranial base. An Eastman cephalometric analysis describes average values of 81° and 78° to these angles, respectively.

  6. 6. This patient has a low angle class 2 skeletal relationship.

  7. 7. The patient would most likely proceed to an advancement BSSO, incorporating a ‘three-point’ landing to increase vertical facial height.

  8. 8. Many clinicians extract third molar teeth six months prior to BSSO, stating that this is less likely to produce an unfavourable mandibular split, although strong evidence to support this is lacking. Other authors, such as Precious et al., have demonstrated that the incidence of a bad split is no higher when third molars are extracted at the time of surgery.

Precious DS. Removal of third molars with sagittal split osteotomies: the case for. J Oral Maxillofac Surg 2004; 62: 1144–6.

Viva 2.4 Anterior open bite

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What is a normal overbite?

  3. 3. What is the aetiology of this condition?

  4. 4. How would you assess the patient?

  5. 5. What are the orthodontic treatment options and their limitations?

  6. 6. What would be your surgery of choice and why?

  7. 7. What other surgical options are there?

  8. 8. What are the causes of relapse following anterior open bite closure?

Answers

  1. 1. This is a clinical image of an anterior open bite (AOB), affecting the anterior teeth.

  2. 2. A normal overbite demonstrates vertical overlap of one-third of the crown height, equating to ~3 mm.

  3. 3. The aetiology of this condition can be broadly divided into:

    • Skeletal: congenital (vertical maxillary excess or short mandibular ramus), condylar resorption (idiopathic or traumatic), Le Fort 1 fracture.

    • Dental: tongue thrusting, thumb sucking, macroglossia.

  4. 4. Assessment of a patient with an AOB comprises:

    • History: progression, TMJ pain.

    • Examination: increased lower anterior face height (LAFH), vertical maxillary excess (VME), lip incompetence, teeth affected by AOB (anterior and/or posterior), macroglossia, thumb sucking, proclined lower incisors (tongue thrust).

    • Investigations: study models, photographs (to demonstrate if progressive).

    • Imaging: OPG (for condylar resorption), SPECT (evidence of active resorption).

  5. 5. Standard orthodontics may be all that is required if assessment demonstrates aetiology is principally due to dental inclination. Temporary Anchorage Devices have been used to treat AOBs up to 4–5 mm by intruding posterior teeth.

  6. 6. The most common choice for surgery in the UK is a differential Le Fort 1 impaction osteotomy with autorotation of the mandible, following dental arch alignment. Autorotation may make the chin more prominent necessitating a set-back mandibular osteotomy. Differential impaction is one of the most stable procedures in the ‘hierarchy of stability’. A differential Le Fort 1 impaction can cause undesirable effects on upper lip position, alar base, and alteration of dental display.

  7. 7. Alternative surgical options include maxillary segmental osteotomy or mandibular surgery alone. Segmental osteotomies are indicated where there is localized protrusion of the anterior maxilla on otherwise well con-ordinated arches. Mandibular surgery alone is principally indicated in Class II patients with retrogenia and an acceptable maxillary position, and a maximum of 5 mm open bite. Disadvantage of mandibular surgery alone is relapse. If there is congenital or acquired absence of condyles, alloplastic TMJ replacement with repositioning of the mandible is the most reliable option.

  8. 8. Causes of relapse following AOB closure include:

    • Habits: tongue thrust, thumb-sucking.

    • Growth pattern.

    • Type of surgical procedure (hierarchy of stability).

    • Fixation type: rigid fixation (less relapse) versus wire fixation (more relapse).

Reyneke J, et al. Anterior open bite correction by Le Fort I or bilateral sagittal split osteotomy. Oral Maxillofac Surg Clin North Am 2007; 19: 321–38.

Proffit WR, Turvey TA, Phillips C. Orthognathic surgery: a hierarchy of stability. Int J Adult Orthodon Orthognath Surg 1996; 11: 191–204.

Viva 2.5 Bleeding following Le Fort 1 osteotomy

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. Do you know of any variations to the cuts of the Le Fort 1?

  3. 3. What is the arterial supply of the down-fractured maxilla?

  4. 4. What is the effect of cauterizing the greater palatine vessels?

  5. 5. Which structures are at risk of bleeding in the Le Fort 1 osteotomy?

  6. 6. As you complete your maxillary cuts there is profuse bleeding. What would you do?

  7. 7. Describe how you would tie off the external carotid artery.

Answers

  1. 1. This is an intra-operative photograph showing the cuts of a Le Fort 1 osteotomy.

  2. 2. Variations to standard Le Fort 1 cuts are described, attempting to reduce paranasal flattening and include winged, stepped, and high variations. A Kufner (quadrangular) osteotomy is a high osteotomy, involving the infraorbital rim, but beneath the nasal bones. Other variations include inferior angulation of the cut at the tuberosity, so that the fracture is beneath the pterygo-maxillary junction and pterygo-maxillary disjunction is not required.

  3. 3. The arterial supply of the down-fractured maxilla is comprised of the greater palatine (a terminal branch of the maxillary artery) and ascending pharyngeal arteries, as well as the mucosal anastomotic network.

  4. 4. Cauterizing the greater palatine vessels has minimal effects to the maxillary perfusion of a single-piece Le Fort 1 osteotomy.

  5. 5. The structures at risk of bleeding in the Le Fort 1 osteotomy are: the greater palatine artery, the maxillary artery, the nasopalatine artery, and the pterygoid venous plexus.

  6. 6. Management of a significant bleed in a Le Fort 1 osteotomy comprises:

    • Inform the anaesthetist and ask for hypotensive anaesthesia with patient head up.

    • Ask the anaesthetist to give intravenous tranexamic acid, fluids via a large-bore intravenous access, and to ensure that the crossmatch for blood is completed.

    • Complete the maxillary down-fracture.

    • Use suction to visualize the point of bleeding and cauterize with bipolar diathermy if possible.

    • Pack the maxilla tightly with Surgicel®, cover with warm gauze and replace the maxilla, applying pressure manually or by placing bite blocks.

    • Wait 10 min before inspecting for bleeding again.

    • If there is still bleeding then repeat packing with Surgicel® and warm gauze and wait a further 10 min.

    • If there is still bleeding then contact an interventional radiologist for potential embolization.

    • The alternative is to clamp the external carotid artery on the bleeding side.

    • If that does not arrest bleeding then clamp the external carotid on the other side.

  7. 7. To tie off the external carotid:

    • Position the patient with neck extended and rotated contralaterally.

    • Make a 5 cm incision along the anterior border of sternomastoid.

    • Dissect down through fat, platysma, and deep cervical fascia.

    • Retract sternocleidomastoid posteriorly.

    • Open up the carotid sheath, follow the common carotid artery superiorly to the bifurcation, and identify the external carotid by its multiple branches.

Dodson TB, et al. Maxillary perfusion during Le Fort I osteotomy after ligation of the descending palatine artery. J Oral Maxillofac Surg 1997; 55: 51–5.

Kufner J. Four year experience with major maxillary osteotomies for retrusion. J Oral Surg 1971; 29: 549.

Viva 2.6 Unwanted mandibular split

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What causes a bad split, and how common is this?

  3. 3. What types of bad split can occur?

  4. 4. Describe how you would proceed if you had a bad split on the second side of a BSSO in a bimaxillary osteotomy where you have completed the maxillary movements.

  5. 5. What are the potential complications of a BSSO?

  6. 6. What statistics regarding potential nerve damage will you give your patient when consenting?

Answers

  1. 1. This is an OPG radiograph demonstrating cuts consistent with a BSSO and Le Fort 1 maxillary osteotomy. The plate on the right side is longer than on the left. The right ramus appears to have a fracture line across it.

  2. 2. A bad split describes an unwanted fracture that does not propagate along the planned cuts. The incidence is 0.5–5%. It is caused by incomplete cuts through the cortical bone, abnormal bony anatomy (thin mandible and/or thick cortex), or inappropriate direction or force of splitting.

  3. 3. A bad split most commonly represent an unwanted buccal or lingual plate fracture, or less commonly separation of the condylar unit from the body of the mandible. For buccal plate fractures a longer fixation plate may be all that is required, whereas for lingual plate fractures bicortical screws may no longer be possible. For slightly larger fractures in mandibular advancement, sufficient bone overlap must be ensured to permit bone healing. Alternatively, the condylar unit and body may not be separated, and a further split would be required to achieve the planned mandibular position, and standard fixation may not be achievable.

  4. 4. Confirm the position of the fracture by extending access and moving each fragment horizontally and vertically to know which fragment the condyle is on. Consider whether a split can be undertaken, and the mandible positioned satisfactorily with enough contact between the fragments to allow healing. Modified skeletal fixation may be possible, but intermaxillary fixation for six weeks may be required. If a further, satisfactory, split is not clearly feasible then repositioning the bad split and re-fixing the contralateral side in the original position is the best option. Leave for at least six months before re-trying. Having not moved the mandible, one must assess whether the occlusion is stable with the maxilla having been moved, and, if not, the maxilla will have to be restored to its original position. Undertaking a condylotomy has been described to allow movement of the mandible, but the condylar head will often be pulled antero-medially. This then requires reduction and fixation to a condyle fracture, which might be difficult with a mandibular advancement where there may be minimal contact between the condyle and the remainder of the mandible.

  5. 5. Potential complications of a BSSO include:

    • Immediate: damage to the inferior alveolar and lingual nerves, damage to teeth, bleeding from facial artery.

    • Early: malocclusion.

    • Late: TMJ dysfunction, relapse, condylar resorption.

  6. 6. Incidences of potential nerve damage during mandibular osteotomy include:

    • Temporary alteration in inferior alveolar nerve sensation: 50% per nerve.

    • Permanent alteration in inferior alveolar nerve sensation: 20% per nerve.

    • Permanent alteration in lingual nerve sensation: 2%.

McLeod NMH, Bowe DC. Nerve injury associated with orthognathic surgery; Part 2: Inferior alveolar nerve. Br J Oral Maxillofac Surg 2016; 54: 366–71.

Viva 2.7 High angle class 3 skeletal relationship

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What are the potential causes of this skeletal relationship?

  3. 3. How would you manage this patient?

  4. 4. What are the orthodontic objectives?

  5. 5. What are the surgical objectives?

  6. 6. What changes to appearance of soft tissues do you expect with a maxillary advancement?

  7. 7. What methods do you know of addressing any negative changes to the nose?

Answers

  1. 1. This is a series of orthodontic photographs of a male patient in their twenties that appears to be pre-orthognathic surgery. Key features include:

    • General: non-syndromic and symmetrical.

    • Lateral: high angle skeletal class 3, increased lower anterior face height, paranasal hollowing.

    • Frontal: increased incisor show, anterior open bite, incompetent lips at rest, short lip length, broad nasal base, increased naso-labial angle.

    • Intra-oral: class 3 incisal relationship, reverse overjet, slightly retroclined upper incisors, and retroclined lower incisors.

    • Summary: this is a high angle skeletal class 3, with a class 3 incisor relationship and anterior open bite.

  2. 2. Potential causes of this class 3 skeletal relationship include one or more of the following: hypoplastic maxilla in the antero-posterior and transverse dimensions, vertical maxillary excess (VME), and a hyperplastic mandible.

  3. 3. Patients should be assessed with a history, examination, imaging, and study casts. Patients should be managed in a joint orthognathic clinic with an orthodontist, an oral and maxillofacial surgeon, and in some cases (such as congenital hypodontia) a restorative dentist.

  4. 4. Orthodontic objectives comprise the following:

    • Relief of crowding.

    • Decompensate: retrocline upper incisors and procline lower incisors to optimize surgical movements.

    • Align: rotate teeth, extractions, expansion.

    • Level: reduce the curve of Spee.

    • Co-ordination: of upper and lower arches to achieve an occlusion with satisfactory overjet and overbite.

  5. 5. In the UK the vertical dimension would be treated by differential posterior impaction of the maxilla to close the anterior open bite (AOB) with impaction anteriorly to correct incisal show. The horizontal dimension would be treated by a maxillary advancement and a mandibular setback using a 2/3:1/3 ratio.

  6. 6. At the Le Fort 1 level, soft tissue to hard tissue movement is approximately 1:3. Soft tissue changes following maxillary advancement include an upturned nasal tip, decreased nasolabial angle, widening of the alar base.

  7. 7. Methods of addressing these negative changes to the nose post osteotomy include:

    • Alar cinch suture to prevent widening of alar base, recognizing that the evidence suggests this may only be temporary and limiting the maxillary advancement and impaction.

    • Trimming of nasal septum, or reduction the floor of the nose to prevent buckling.

    • V to Y closure to evert the lip and increase vermillion show.

    • Separation of the anterior nasal spine, which is kept attached to the nose to prevent upturning of the nasal tip, and trimming the anterior nasal spine.

Howley et al. Use of the alar base cinch suture in Le Fort I osteotomy: is it effective? Br J Oral Maxillofac Surg 2011; 49: 127–30.

Viva 2.8 Obstructive sleep apnoea

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What do you understand by the term obstructive sleep apnoea (OSA)?

  3. 3. What are the potential consequences of OSA?

  4. 4. What are the risk factors for OSA?

  5. 5. This patient has been referred by his GP for orthognathic surgery for snoring. How would you assess the patient?

  6. 6. What is polysomnography?

  7. 7. What non-surgical treatment is available?

  8. 8. What surgical treatment options are there?

  9. 9. What does the orthognathic surgery involve?

Answers

  1. 1. This is a mandibular advancement device, which is used to treat snoring. It protrudes the mandible, bringing with it the tongue and increasing the posterior pharyngeal space.

  2. 2. OSA is characterized by multiple episodes of pharyngeal airway collapse during sleep. It results in partial or complete temporary cessation of breathing.

  3. 3. Potential consequences of OSA include hypertension, daytime sleepiness, reduced concentration, cardiovascular disease, and type 2 diabetes mellitus.

  4. 4. Most patients with OSA have no underlying craniofacial abnormality. Risk factors for OSA include obesity, male sex, alcohol, smoking, small mandibles (including syndromic), and enlarged adenoids or tonsils.

  5. 5. Assessment of patient for orthognathic surgery to treat snoring comprises:

    • History: risk factors, daytime sleeping, snoring.

    • Orthognathic examination: retrognathia.

    • Nasendoscopy: tonsils, soft palate, tongue base.

    • Lateral cephalogram: mandible, hyoid, and soft palate retrusion.

    • Special tests required for assessment include polysomnography, apnoea/hypo-apnoea index (AHI), and Epworth sleepiness score questionnaires.

  6. 6. Polysomnography is an overnight sleep study. It uses an electroencephalogram, electrocardiogram, and electromyogram.

  7. 7. Non-surgical treatment options include avoidance of alcohol, weight loss, continuous positive airway pressure devices, and protrusive mandibular splints.

  8. 8. Surgical treatment that has been described to treat OSA includes uvulopalatopharyngoplasty, hyoid advancement, midline glossectomy, and orthognathic surgery. Although many case series have demonstrated positive outcomes, a Cochrane review demonstrated insufficient evidence to support the widespread use of surgical treatment.

  9. 9. Orthognathic surgery to treat OSA involves advancement of the mandible ± maxilla ± genioplasty. This results in antero-posterior and lateral expansion of airway. The degree of necessary advancement is debated, with a suggestion of 10 mm being required to reduce AHI.

Vigneron A, et al. Maxillomandibular advancement for obstructive sleep apnoea syndrome treatment: long-term results. J Craniomaxillofac Surg 2017; 45: 183–91.

Viva 2.9 Transverse maxillary deficiency

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What else would you expect to see with a narrow palate?

  3. 3. What is the difference between a cross bite and scissor bite?

  4. 4. What are broad treatment options for a narrow palate?

  5. 5. What are the orthodontic options?

  6. 6. What are the surgical options?

  7. 7. What different types of appliance are available for surgically assisted rapid palatal expansion (SARPE)?

  8. 8. What are the advantages of a SARPE for transverse palatal expansion?

  9. 9. What are the disadvantages of SARPE?

  10. 10. How does a SARPE differ from a Le Fort 1 osteotomy?

  11. 11. What rate of movement is generally used?

  12. 12. What you do if performing SARPE and it starts to bleed uncontrollably?

Answers

  1. 1. This is a clinical image of a narrow V-shaped palate reflecting a transverse maxillary deficiency with anterior segment crowding.

  2. 2. A narrow palate is often found with a cross bite or scissor bite.

  3. 3. In a cross bite, the buccal cusps of the maxillary molars lie in the opposing central fossa of the mandibular molars. In a scissor bite the buccal cusps of the maxillary molars touch only the lingual surface of the mandibular molars.

  4. 4. Treatment options for a narrow palate depend upon the patient’s age and include orthodontics only, surgery only, and orthodontics in conjunction with surgery.

  5. 5. Orthodontic options comprise:

    • A removable appliance.

    • Arch wire expansion (limited to a 4–5 mm and tips teeth).

    • A quad helix or removable palatal expander (if the suture is not closed i.e. age <16 years).

  6. 6. Surgical options for transverse expansion of the palate comprise surgically assisted rapid palatal expansion (SARPE) or a segmental osteotomy.

  7. 7. The different types of appliance available for SARPE are tooth-borne versus bone-borne. The former provides more stability and less tipping of the teeth, but is more complex to fit, and it cannot be simply repositioned if it becomes loose.

  8. 8. The advantages of a SARPE for transverse palatal expansion are that there is less need for extraction and that large movements are possible (up to 15 mm in some cases). Orthodontics is also associated with more tipping of the buccal segments and less true expansion of the palatal arch.

  9. 9. The disadvantages of SARPE are the requirement for a second procedure and the risk of damage to teeth.

  10. 10. A SARPE differs from a Le Fort 1 osteotomy in the following ways:

    • Pre-operatively: space is required between the central incisors for the vertical cut.

    • Intra-operatively: standard Le Fort I horizontal cuts are performed but without down-fracture.

    • Post-operatively: the patient will need to turn a distraction key on the device.

  11. 11. Intra-operatively the distractor is opened until the incisors start to move apart. The patient then moves the distractor by 0.5 mm twice a day. Many clinicians over-distract by 2 mm to account for relapse.

  12. 12. Patients should be consented prior to SARPE that if it starts to bleed uncontrollably after making the cuts, then the down-fracture must be completed.

Starch-Jensen T, et al. Transverse expansion and stability after segmental Le Fort I osteotomy versus surgically assisted rapid maxillary expansion: a systematic review. J Oral Maxillofac Res 2016; 7: e1.

Viva 2.10 Segmental osteotomy

Orthognathic surgery

Questions

  1. 1. Describe what you can see.

  2. 2. What do you understand by the term subapical osteotomy?

  3. 3. What are the indications for subapical segmental mandibular osteotomy?

  4. 4. What are the risks of performing an anterior subapical segmental osteotomy to close an anterior open bite (AOB)?

  5. 5. What are the other alternatives for closure of an AOB?

  6. 6. Do you know of any variations to a subapical osteotomy?

  7. 7. What other broad types of segmental osteotomy are there?

  8. 8. What are broad surgical approaches to anterior maxillary segmental osteotomies?

Answers

  1. 1. This is an intra-operative image demonstrating a sawcut in the mandible, consistent with an anterior subapical segmental mandibular osteotomy.

  2. 2. A subapical osteotomy uses a horizontal bone cut below the apices of the teeth.

  3. 3. The main indications for a segmental osteotomy include:

    • Superior movement: closure of an AOB, usually in combination with a bone graft.

    • Posterior movement: to treat a class 3 skeletal relationship. Space needs to be made in the arch for the vertical saw cut usually through extraction of a premolar tooth either prior to, or at the time of, surgery.

  4. 4. Potential complications of subapical segmental osteotomy comprise:

    • Immediate: haemorrhage (primarily from the sublingual tissue that may be difficult to manage).

    • Early: devitalization of teeth or the bony fragment (the lingual mucosa is the only blood supply).

    • Late: relapse (even with a bone graft this is an unstable procedure).

  5. 5. Alternatives for AOB closure include differential maxillary impaction or ramus osteotomy (bilateral sagittal split osteotomy or a vertical subsigmoid osteotomy).

  6. 6. A Kole procedure is an anterior subapical osteotomy in conjunction with a genioplasty. The gap created by the upward movement of the lower labial segment is closed by using the wedge of bone removed from the genioplasty. It is also used to close an AOB but also results in a large decrease in lower anterior facial height.

  7. 7. Other types of segmental osteotomy include:

    • Mandibular: subapical osteotomy.

    • Maxillary: vertical (anterior and posterior segmental), transverse (surgically assisted rapid palatal expansion: SARPE).

  8. 8. There are three broad eponymous surgical approaches to anterior maxillary segmental osteotomies:

    • Wunderer: vascular supply from buccal pedicle using a transpalatal incision in combination with buccal vertical incisions.

    • Wassmund: vertical incisions only are used, with subperiosteal tunnelling and no labial or palatal flaps.

    • Epker: a vestibular incision is used with the vascular supply from the palatal pedicle.

Epker BN. Vascular considerations in orthognathic surgery. II. Maxillary osteotomies. Oral Surg Oral Med Oral Pathol 1984; 57: 473–8.