Orthognathic Surgery for Craniofacial Deformities

Orthognathic surgery is a specialized field focused on correcting dentofacial deformities through surgical movement of the tooth-bearing segments of the maxilla and mandible. While some occlusal discrepancies can be resolved with orthodontics alone, many craniofacial anomalies and severe malocclusions necessitate orthognathic surgery. This comprehensive guide explores the history, patient selection, surgical techniques, and outcomes of orthognathic surgery for craniofacial deformities, providing a valuable resource for students seeking to understand this complex area.

Understanding Orthognathic Surgery for Craniofacial Deformities

Orthognathic surgery aims to establish an ideal dental occlusion, ensuring the jaws are positioned to optimize both facial form and function. It's particularly crucial for children with cleft lip and palate and those with certain craniofacial anomalies, who are more prone to developing malocclusion.

Approximately 2.5% of the general population may require surgical correction for occlusal issues. However, this number rises significantly to 25-30% for patients who underwent early surgical correction of cleft lip and palate, often needing orthognathic surgery for severe midface retrusion.

A Glimpse into the History of Orthognathic Surgery

The history of orthognathic surgery spans two centuries, marked by significant innovations. Early advancements focused on mandibular surgery, with the first osteotomy reported in 1846 by Hullihan. Pioneer surgeons like Blair and Kostecka published early large series addressing mandibulofacial disproportion.

These initial procedures were performed in a seated dental chair under simple ether sedation, with blind osteotomies using a Gigli saw taking as little as 15 minutes. The field was revolutionized by Hugo Obwegeser, an Austrian-born dentist credited with modernizing orthognathic surgery and introducing it to the US.

Obwegeser's contributions include the sagittal split osteotomy for mandibular advancement and the intraoral approach to osseous genioplasty. His demonstration in 1965 that the maxilla could be completely mobilized, reliably, and stably repositioned in one procedure, led to the widespread appeal of modern orthognathic surgery.

Patient Selection and Preoperative Evaluation

Identifying the right candidate for orthognathic surgery is crucial for successful outcomes and patient satisfaction. This involves a thorough evaluation, often coordinated by a specialized cleft/craniofacial team.

The Cleft and Craniofacial Team

Optimal surgical outcomes are best achieved through presurgical planning with a multidisciplinary team. This team typically includes plastic surgeons, orthodontists, otorhinolaryngologists, dentists, geneticists, and speech pathologists. Speech pathologists, for instance, assess velopharyngeal mechanisms and predict how maxillary advancement might affect speech nasality.

Orthodontists play a critical role, conducting a comprehensive workup that includes occlusal characteristics, facial skeleton age, and the need for presurgical orthodontics or palatal expansion. Surgical intervention is usually delayed until skeletal maturity is reached to prevent the need for revision surgery due to continued growth.

Comprehensive History and Physical Examination

A detailed medical, dental, and surgical history is essential. Systemic diseases like juvenile rheumatoid arthritis, diabetes, and scleroderma can influence treatment planning. Evaluation includes assessing jaw asymmetries from syndromic, traumatic, postsurgical, or neoplastic causes.

Key aspects of physical examination:

• Frontal facial evaluation: Assesses vertical facial thirds (richion to glabella, glabella to subnasale, subnasale to menton) and horizontal facial fifths. The degree of incisor show at rest is critical (2–3 mm for males, 5–6 mm for females).
• Lip incompetence or mentalis strain: Often indicates vertical maxillary excess.
• Projection of inferior orbital rims, malar eminence, and piriform areas: Often deficient in cleft patients, indicating maxillary advancement, or prominent, suggesting posterior repositioning.
• Alar base width: Assessed preoperatively as surgery can alter it, accentuating cleft nasal deformities.
• Asymmetries: Documented for maxilla and mandible, noting deviation from the facial midline.
• Profile evaluation: Focuses on the projection of the forehead, malar region, maxilla, mandible, nose, chin, and neck. Experienced clinicians can often determine the deformity's origin (maxilla, mandible, or both) clinically.

Intraoral Examination

Good oral hygiene and periodontal health are critical for successful treatment. Any retained deciduous teeth or unerupted adult teeth are noted. Occlusal classification, incisor overlap, and overjet are quantified. The transverse dimension of the maxilla is assessed, especially in cleft patients who often have transverse growth restriction.

Mandibular third molars must be extracted six months prior to a sagittal split osteotomy. Any missing teeth or periapical pathology, as well as signs of temporomandibular joint dysfunction, should be addressed before orthognathic surgery.

Cephalometric and Dental Evaluation

Cephalometric analysis uses lateral cephalometric radiographs to plan skeletal movements and predict soft-tissue profile changes. Computer-aided analysis is increasingly replacing traditional hand tracing. This allows independent relation of the maxilla and mandible to a stable reference, the cranial base, to determine which jaw contributes to a deformity.

Key cephalometric measurements:

• Sella–nasion–subspinale (SNA): Indicates anteroposterior position of the maxilla relative to the cranial base.
• Sella–nasion–supramentale (SNB): Indicates mandibular position relative to the cranial base.

Dental compensation describes how teeth tilt to minimize malocclusion. For example, in an overbite (Class II), upper incisors may retrocline and lower incisors proclinate. This masks the true skeletal discrepancy. Presurgical orthodontics will decompensate the occlusion, exaggerating the malocclusion but allowing for maximized skeletal movements. If surgery is not desired, further dental compensation can camouflage the deformity.

Mounted dental casts are essential for preoperative model surgery and surgical splint fabrication. They help evaluate occlusion before and after articulation, and distinguish between absolute and relative transverse maxillary deficiency.

Model Surgery and 3D CT Modeling

Model surgery reproduces jaw movements on articulated dental models, guiding the fabrication of intraoperative occlusal splints. For isolated mandibular surgery, casts can be hand-articulated. For isolated maxillary or two-jaw surgery, a face bow relates the maxillary model to the cranium on an articulator.

3D CT modeling with CAD/CAM technology offers improved accuracy in diagnosis and treatment. Cone beam CT scans provide comparable image quality with less radiation. This technology allows simulated jaw and chin movements in any dimension, facilitates surgical splint fabrication, and enhances the prediction of soft-tissue effects, saving surgeon time.

Developing a Treatment Plan for Optimal Aesthetics

The goal of treatment planning is to achieve a Class I occlusion while optimizing the soft-tissue features of the face. It's not about normalizing every measurement, but rather focusing on the aesthetic success of the soft-tissue envelope.

Historically, skeletal movements that expanded the face were less stable, favoring posterior and superior (contractile) movements. However, with rigid fixation systems, skeletal expansion has become predictable. The aim is to expand or maintain preoperative facial volume, minimizing signs of premature aging.

If a superior or posterior movement of one jaw is planned, it should ideally be neutralized by an advancement or inferior movement of the other jaw or chin to avoid facial contraction. Slight facial disproportion from skeletal expansion can be aesthetically pleasing.

Treatment and Surgical Techniques in Orthognathic Surgery

Several general principles apply to jaw surgery, emphasizing patient safety and predictable outcomes.

General principles:

• Blood loss management: Head elevation, hypotensive anesthesia, blood donation, and preoperative erythropoietin are used to reduce blood loss, especially in pediatric patients.
• Infection prevention: Antimicrobial rinses and a short course of antibiotics minimize intraoral bacterial count.
• Swelling reduction: Topical and intravenous steroids, ice, and head elevation reduce postoperative edema.
• Occlusion control: Surgical splints maintain desired occlusion when it doesn't match maximal intercuspal position. Guiding elastics assist patient adaptation postoperatively.
• Stability of movements: Mandibular advancement and superior maxillary positioning are generally stable. Posterior mandibular positioning and inferior maxillary positioning are less stable. Transverse maxillary expansion is the least stable.
• Rigid fixation: Improves predictability in two-jaw surgery, reducing relapse rates.

Pertinent Anatomy for Jaw Surgery

Understanding the anatomy is critical to avoid complications. Key structures include:

• Maxilla: Associated with the descending palatine artery, infraorbital nerve, tooth roots, and internal maxillary artery.
• Mandible: Important structures include the mental nerve, inferior alveolar nerve, and tooth apices. The inferior alveolar nerve runs below tooth roots and exits through the mental foramen.

Le Fort I Osteotomy: Maxillary Surgery

This procedure involves mobilizing the maxilla. A nasal endotracheal tube is secured, and vertical maxillary position is recorded. An incision is made in the maxillary vestibule, and subperiosteal dissection exposes the maxilla.

Key steps:

• Nasal mucosa reflection and release of septum and lateral nasal wall.
• Transverse osteotomy made from the piriform aperture laterally, descending posteriorly to the last maxillary molar, at least 5 mm above tooth apices.
• Maxilla is downfractured using manual pressure or Rowe disimpaction forceps.
• Descending palatine arteries may be clipped. The splint positions the maxilla in occlusion with the mandible.
• Maxillomandibular fixation (MMF) is applied, and the maxilla is secured with L-shaped plates.
• Alar cinch can be performed to normalize alar base width; V-Y closure helps alleviate lip shortening.
• High Le Fort I osteotomy can increase cheek projection.

Surgically Assisted Rapid Palatal Expansion (SARPE)

SARPE is used for transverse maxillary constriction, common in cleft palate or syndromic craniosynostosis patients. An orthodontist places a palatal expander pre-procedure. A Le Fort I osteotomy mobilizes the maxilla, followed by a midline split between the central incisors to the posterior nasal spine.

Separation is verified by activating the device, widening the maxilla until gingival blanching occurs, then relaxing turns to avoid ischemia. SARPE offers the best stability for maxillary expansion in young adults and older patients.

Bilateral Sagittal Split Osteotomy: Mandibular Surgery

This technique corrects mandibular prognathism or retrognathia. A mucosal incision is made from the mid-ramus to the second molar. Subperiosteal dissection exposes the lateral mandible and anterior coronoid process.

Key steps:

• J-stripper releases pterygomasseteric sling attachments.
• Mandibular nerve is identified and protected.
• Lindemann side-cutting burr makes a cut on the medial ramus, parallel to the occlusal plane.
• Fissure burr or reciprocating saw makes an osteotomy from the mid-ramus along the external oblique ridge to the inferior border.
• Segments are gently separated; the inferior alveolar nerve is identified and protected.
• Distal segment (tooth-bearing) is placed into occlusion and secured with wire loops or a surgical splint.
• Proximal segments (condylar) are seated in the glenoid fossa and secured with three lag screws.
• MMF is released, and occlusion verified. If malocclusion occurs, screws are removed and replaced until proper condyle seating.

Intraoral Vertical Ramus Osteotomy

An alternative for correcting mandibular prognathism or asymmetry. An incision and subperiosteal dissection expose the lateral ramus. An oscillating saw makes a vertical cut from the sigmoid notch to the inferior border of the mandible, posterior to the mandibular foramen.

The distal segment is moved into occlusion, with proximal segments remaining lateral. Rigid fixation is difficult, so a single wire or no fixation is used, and the patient remains in MMF for six weeks. This approach avoids an external scar.

Genioplasty: Chin Surgery

A genioplasty is a powerful adjunct to mandibular movements, offsetting soft-tissue collapse from posterior mandibular repositioning or augmenting anterior movement. It can also correct minor mandibular asymmetries when performed asymmetrically.

Key steps:

• Incision made from canine to canine, 5 mm below the mucogingival junction.
• Mentalis muscle is transected, preserving enough cuff for reapproximation to prevent a "witch's chin" deformity.
• Mental nerves are identified and protected.
• Transverse osteotomy is made approximately 3 mm below the mental foramina to protect nerves and canine roots.
• Mobilized segment is fixed into desired position with plates and screws. Mentalis muscle is repaired, and mucosa closed.

Two-Jaw Surgery: Combined Maxillary and Mandibular Procedures

This procedure involves osteotomizing both jaws and precisely securing them as determined by the treatment plan. Proper planning and splint fabrication are crucial for precise placement.

Sequence:

1. Mandibular bony cuts are started but not completed.
2. Maxillary osteotomy is performed, and maxilla is positioned using an intermediate splint.
3. Splint is used to wire teeth into MMF, indexing the new maxillary position to the preoperative mandible.
4. Maxilla is plated into position, MMF released, and intermediate splint removed.
5. Mandibular osteotomies are completed, and distal segment is placed into desired occlusion using a final splint (or maximum intercuspal position if suitable).
6. Wire loops secure occlusion, and rigid fixation is completed.

Cleft Surgery Modifications

Orthognathic surgery in cleft lip/palate patients requires important modifications to maintain blood supply and assist in fistula closure.

• Unilateral cleft lip: Standard maxillary incision, with alveolar dissection for bone grafting or fistula closure. Le Fort osteotomy allows compression of maxillary segments to close pre-existing fistulas, ensuring tension-free soft-tissue closure.
• Bilateral cleft: Care is taken to avoid incisions across the premaxilla to preserve its blood supply (from vomer and buccal mucosa). The incision stops just lateral to the alveolar cleft on each side. Premaxillary osteotomy is made from a posterior approach, avoiding buccal mucosa violation.
• Fistula repair: If present, can be corrected by two-layer mucosal closure and bone grafting into alveolar defects. Maxillary segments can be compressed if wide fistulas exist.

Treating Specific Dentofacial Deformities

Orthognathic surgery addresses various common dentofacial problems, each with tailored approaches.

• Skeletal Class II Malocclusion (Mandibular Retrognathia): Often associated with conditions like Treacher–Collins syndrome. Best treated by mandibular advancement, an expansile movement that enhances facial form. Bimaxillary advancement may be considered if the maxilla is also slightly deficient.
• Skeletal Class III Malocclusion (Underbite): Treated by advancing the maxilla, posteriorly positioning the mandible, or combining both. Consider separate contributions of mandible and chin. Advancement genioplasty may counteract skeletal contraction from mandibular setback.
• Maxillary Constriction: Narrow maxilla in transverse dimension. In patients up to 15 years, orthodontists can use palatal expanders. For older patients, SARPE is preferred. If other maxillary movements are needed, a two-piece (or multipiece) Le Fort I osteotomy can achieve transverse expansion.
• Apertognathia (Anterior Open Bite): Caused by premature contact of posterior molars, seen in craniosynostoses like Apert or Crouzon syndromes. Recommended treatment is posterior impaction of the maxilla, which allows counterclockwise mandibular autorotation to close the open bite. Incisor show typically remains unaffected.
• Vertical Maxillary Excess (Long-Face Syndrome): Associated with lip incompetence, mentalis strain, and excessive gingival show. Treatment involves impacting the maxilla to achieve proper incisor show. Mandibular autorotation occurs, rotating the chin anteriorly. Anterior repositioning of jaws may be considered to neutralize skeletal contraction. Genioplasty might be needed to re-establish proper chin position.
• Short Lower Face: Marked by insufficient incisor show or a short distance between subnasale and pogonion. Treatment aims to establish proper incisor show by inferiorly positioning the maxilla. Clockwise mandibular rotation may lead to posterior chin positioning, potentially requiring an advancement genioplasty.
• Distraction Osteogenesis (DO): A technique for reliable, large advancements with low relapse rates. It uses osteoinductive properties of tension and stress across an osteotomy to rapidly expand mandibular or maxillary segments, allowing soft tissue to relax. DO is often technically easier and faster than traditional orthognathic surgery, offering precise control in various vectors.

Postoperative Care and Outcomes in Orthognathic Surgery

Postoperative care is paramount for a successful outcome, focusing on oral hygiene, swelling reduction, and diet.

Postoperative care regimen:

• Oral hygiene: Regular tooth brushing and chlorhexidine mouth rinses minimize infection risk, supported by a short course of antibiotics.
• Swelling reduction: Ice, head elevation, and anti-inflammatory medication (e.g., Solu-Medrol) improve patient comfort.
• Diet: A soft diet for at least the first three weeks helps reduce malunion or hardware failure risk.
• Guiding elastics: Usually employed for the first 2–3 weeks to help patients adapt to the new occlusion.

Outcomes, Prognosis, and Complications

Accurate assessment of outcomes is essential, using tools like 3D CT scanning, volumetric analyses, and patient satisfaction questionnaires. With reasoned expectations, orthognathic surgery can lead to high levels of functional and aesthetic satisfaction.

Effect on speech and velopharyngeal function:

• Maxillary movement can alter velopharyngeal function due to the intricate attachment of palatal musculature to the maxilla. Studies show maxillary advancement can lead to a decline in competent velopharyngeal function and an increase in hypernasality.
• Articulation defects may improve, though not always statistically significant.
• Preoperative assessment, including nasopharyngoscopy, can help predict postoperative speech and velopharyngeal function.

Relapse and Stability:

• Relapse, especially in cleft patients, can be influenced by primary soft tissue deficiencies and prior scarring.
• Studies show mean horizontal relapse of 24.1% of advancement, recommending a 2-mm overcorrection for inferior positioning.
• Surgical rotation often results in relapse. Overcorrection may mitigate this.
• Bilateral cleft patients are more prone to relapse due to increased scarring and missing teeth. Previous alveolar bone grafting shows no clear association with relapse rates.
• No significant difference in relapse rates between maxillary surgery alone and two-jaw surgery.

Potential complications:

• Improper jaw positioning: Noted by malocclusion or unaesthetic results, often due to improper condyle seating during mandibular osteotomy fixation. This requires removal and reapplication of fixation.
• Unfavorable mandibular split: Reduced by extracting mandibular third molars six months prior. Excessive force should be avoided. If it occurs, segments can be plated to re-establish anatomy.
• Bleeding: Most commonly from the descending palatine artery in the maxilla, managed with packing or hemoclips. Bone wax helps with bony edges.
• Nerve damage: Rare, but can affect the infraorbital, inferior alveolar, and mental nerves. Transaction may require coaptation. Approximately 70% of patients experience some immediate paresthesia, with permanent changes in about 25%.
• Nonunion or malunion: Rare. Malunion may require re-osteotomy. Nonunion requires secondary bone grafting.

Secondary Procedures

While uncommon with careful planning, secondary procedures may be needed. Orthognathic surgery rarely resolves all preoperative dentofacial deformities. Maxillary and mandibular movements can highlight features previously de-emphasized by malocclusion. Procedures like rhinoplasty, fat grafting, or malar augmentation may help restore facial harmony.

Underlying issues related to primary cleft or craniofacial disorders may persist, requiring additional surgeries like bone grafting or vestibuloplasty. Osseointegrated implants should only be utilized after jaw surgery and postoperative orthodontics have determined final tooth positions.

Frequently Asked Questions (FAQ) about Orthognathic Surgery

What is orthognathic surgery and who needs it?

Orthognathic surgery involves surgical repositioning of the maxilla (upper jaw) and mandible (lower jaw) to correct severe dentofacial deformities that cannot be treated with orthodontics alone. It's often needed for patients with significant malocclusion, jaw asymmetries, or craniofacial anomalies like cleft lip and palate, aiming to improve both bite function and facial aesthetics.

How long is the recovery period for orthognathic surgery?

Immediately after surgery, patients typically maintain a soft diet for at least three weeks. Postoperative care includes diligent oral hygiene, managing swelling with ice and medication, and using guiding elastics to help adapt to the new bite. Full recovery, including the resolution of swelling and nerve sensation, can take several months to a year, though most patients resume normal activities much sooner.

Are there any risks or complications associated with orthognathic surgery?

Like any major surgery, orthognathic surgery carries risks. Potential complications include bleeding, nerve damage (leading to temporary or permanent numbness), infection, malunion or nonunion of bones, and relapse of jaw positions. However, with careful planning, advanced techniques, and a skilled surgical team, the likelihood of serious complications is low, and patient satisfaction rates are generally high.

When is the best time to perform orthognathic surgery for younger patients?

For younger patients, orthognathic surgery is ideally performed after the facial skeleton has reached maturity. This is typically in the late teens, as intervening before growth is complete can increase the likelihood of needing revision surgery due to continued postoperative growth and changes in jaw development.