Orthognathic surgery

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Orthognathic surgery
Osteotomies of the jaws:

1. LeFort I 2. Bilateral Sagittal Split 3. Genioplasty 4. IMDO 5. GenioPaully 6. Custom PEEK 7. SARME 8. Custom BIMAX

9. Super BIMAX
ICD-9-CM76.6

Orthognathic surgery (

orthodontic dental bite problems that cannot be treated easily with braces, as well as the broad range of facial imbalances, disharmonies, asymmetries, and malproportions where correction may be considered to improve facial aesthetics [1]
and self-esteem.

The origins of orthognathic surgery belong in oral surgery, and the basic operations related to the surgical removal of impacted or displaced teeth – especially where indicated by orthodontics to enhance dental treatments of malocclusion and dental crowding. One of the first published cases of orthognathic surgery was the one from Dr. Simon P. Hullihen in 1849.

Originally coined by Harold Hargis, it was more widely popularised first in Germany and then most famously by Hugo Obwegeser who developed the bilateral sagittal split osteotomy (BSSO). This surgery is also used to treat congenital conditions such as

cleft palate.[2] Typically surgery is performed via the mouth, where jaw bone is cut, moved, modified, and realigned to correct malocclusion or dentofacial deformity
. The word "osteotomy" means the division of bone by means of a surgical cut.

The "jaw osteotomy", either to the upper jaw or lower jaw (and usually both) allows (typically) an oral and maxillofacial surgeon to surgically align an arch of teeth, or the segment of a dental arch with its associated jawbone, relative to other segments of the dental arches. Working with orthodontists, the coordination of dental arches has primarily been directed to create a working occlusion. As such, orthognathic surgery is seen a secondary procedure supporting a more fundamental orthodontic objective.

It is only recently, and especially with the evolution of oral and maxillofacial surgery in establishing itself as a primary medical specialty – as opposed to its long term status as a dental speciality – that orthognathic surgery has increasingly emerged as a primary treatment for obstructive sleep apnoea, as well as for primary facial proportionality or symmetry correction.

The primary use of surgery to correct jaw disproportion or malocclusion is rare in most countries due to private health insurance and public hospital funding and health access issues. A small number of mostly heavily socialist funded countries report that jaw correction procedures occur in some form or other in about 5% of a general population, but this figure would be at the extreme end of service

deformities like maxillary prognathisms, mandibular prognathisms, open bites, difficulty chewing, difficulty swallowing, temporomandibular joint dysfunction
pains, excessive wear of the teeth, and receding chins.

Increasingly, as people are more able to self-fund surgery, 3D facial diagnostic and design systems have emerged, as well as new operations that enable for a broad range of jaw correction procedures that have become readily accessible; in particularly in private maxillofacial surgical practice. These procedures include IMDO, SARME, GenioPaully, custom BIMAX, and custom PEEK procedures. These procedures are replacing the traditional role of certain orthognathic surgery operations that have for decades served wholly and primarily orthodontic or dental purposes.[6] Another development in the field is the new index called the index of orthognathic functional treatment need (IOFTN) that detects patients with the greatest need for orthognathic surgery as a part of their comprehensive treatment.[7] IOFTN has been validated internationally and detected over 90% of patients with greatest need for orthognathic surgery.[8]

Medical uses

It is estimated that nearly 5% of the UK or US population present with dentofacial deformities that are not amenable to orthodontic treatment requiring orthognathic surgery as a part of their definitive treatment.[9][4][5] Orthognathic surgery can be used to correct:

  • Gross jaw discrepancies (anteroposterior, vertical, or transverse discrepancies)[10]
  • Skeletofacial discrepancies associated with documented sleep apnea, airway defects, and soft tissue discrepancies
  • Skeletofacial discrepancies associated with documented temporomandibular joint pathology

A disproportionately grown upper or lower jaw causes dentofacial deformities. Chewing becomes problematic, and may also cause pain due to straining of the jaw muscle and bone. Deformities range from

underbites, or a receding chin.[citation needed] The deformities listed above can be perfected by an osteotomy surgery of either the maxilla or mandible (whichever the deformity calls for), which is performed by an oral surgeon who is specialized in the working with both the upper and lower jaws.[12] Orthognathic surgery is also available as a very successful treatment (90–100%) for obstructive sleep apnea.[13]

Cleft lip and palate

Orthognathic surgery is a well established and widely used treatment option for insufficient growth of the

orofacial cleft.[14] There is some debate regarding the timing of orthognathic procedures, to maximise the potential for natural growth of the facial skeleton.[15] Patient reported aesthetic outcomes of orthognathic surgery for cleft lip and palate appear to be of overall satisfaction,[16][17] despite complications that may arise. A potentially significant long-term outcome of orthognathic surgery is impaired maxillary growth, due to scar tissue formation.[18] A 2013 systematic review comparing traditional orthognathic surgery with maxillary distraction osteogenesis found that the evidence was of low quality; it appeared that both procedures might be effective, but suggested distraction osteogenesis might reduce the incidence of long-term relapse.[19] The most common causes of cleft lip and palate are genetic and environmental factors. Clefts are known to occur due to folic acid deficiency, iron and iodine deficiency[20]

Risks

Although infrequent, there can be complications such as bleeding, swelling, infection, nausea and vomiting.[21] Infection rates of up to 7% are reported after orthognathic surgery; antibiotic prophylaxis reduces the risk of surgical site infections when the antibiotics are given during surgery and continued for longer than a day after the operation.[22]

There can also be some post operative facial numbness due to nerve damage.[23] Diagnostics for nerve damage consist of: brush-stroke directional discrimination (BSD), touch detection threshold (TD), warm/cold (W/C) and sharp/blunt discrimination (S/B), electrophysiological tests (mental nerve blink reflex (BR), nerve conduction study (NCS), and cold (CDT) and warm (WDT) detection thresholds.[24] The inferior alveolar nerve, which is a branch of the mandibular nerve, must be identified during surgery and worked around carefully in order to minimize nerve damage. The numbness may be either temporary, or more rarely, permanent.[25] Recovery from the nerve damage typically occurs within three months after repair.

Surgery

Orthognathic surgery is performed by maxillofacial or an

craniofacial
anomalies. Careful coordination between the surgeon and orthodontist is essential to ensure that the teeth will fit correctly after the surgery.

Planning

Planning for the surgery usually involves input from a multidisciplinary team, including oral and maxillofacial surgeons, orthodontists, and occasionally a speech and language therapist. Although it depends on the reason for surgery, working with a speech and language therapist in advance can help minimize potential relapse. The surgery usually results in a noticeable change in the patient's face; a psychological assessment is occasionally required to assess patient's need for surgery and its predicted effect on the patient. Radiographs and photographs are taken to help in the planning. There is also advanced software that can predict the shape of the patient's face after surgery,[26][27][28][29][30] which is useful for the planning and also explaining the surgery to the patient and the patient's family.[31] Great care needs to be taken during the planning phase to maximize airway patency.

Orthodontics are a critical component of orthognathic surgery. Traditionally the presurgical orthodontic phase can take as long as one year and undertaken with conventional metal braces.[32] However, these days new approaches and paradigms exist including surgery-first [33] And using clear aligner orthodontia (like Invisalign)[34][35]

Sagittal split osteotomy

Oral palate unit

This procedure is used to correct

mandibular prognathism
(over and under bite). First, a
vertical
cut is made extending inferior to the body of the mandible, to the inferior border of the mandible. All cuts are made into the middle of the bone, where bone marrow is present. Then, a chisel is inserted into the pre existing cuts and tapped gently in all areas to split the mandible of the left and right side. From here, the mandible can be moved either forwards or backwards. If sliding backwards, the distal segment must be trimmed to provide room in order to slide the mandible backwards. Lastly, the jaw is stabilized using stabilizing screws that are inserted extra-orally. The jaw is then wired shut for approximately 4–5 weeks.[36]

Anatomy of oral cavity and adjacent structures

Genioplasty osteotomy (intra-oral)

This procedure is used for the advancement (movement forward) or retraction (movement backwards) of the chin. First, incisions are made from the

mandible. Then, soft tissue of the mandible is detached from the bone; done by stripping attaching tissues. A horizontal incision is then made inferior to the first bicuspids, bilaterally, where bone cuts (osteotomies) are made vertically inferior, extending to the inferior border of the mandible, thereby detaching the bony segments of the mandible. The bony segments are stabilized with titanium plates; no fixation (binding of the jaw) necessary. If advancement is indicated for the chin, there are inert products available to implant onto the mandible, utilizing titanium screws, bypassing bone cuts.[37][38]

GenioPaully

This is a modified box osteotomy of the chin, designed to deliberately grab the paired

obstructive sleep apnoea
.

Rapid palatal expansion osteotomy

When a patient has a constricted (oval shape)

palatal
expansion. This consists of the surgeon making horizontal cuts on the lateral board of the maxilla, extending anterally to the inferior border of the
orthopedic appliance attached to the maxilla teeth, bilaterally, extending over the palate with an attachment so the surgeon may use a hex-like screw to place into the device to push from anterior to posterior to start spreading the bony segments.[36]
The expansion of the maxilla may take up to eight weeks with the surgeon advancing the expander hex lock, sideways (← →), once a week.

Post operation

After orthognathic surgery, patients are often required to adhere to an all-liquid diet for a time. Weight loss due to lack of appetite and the liquid diet is common. Normal recovery time can range from a few weeks for minor surgery, to up to a year for more complicated surgery. For some surgeries, pain may be minimal due to minor nerve damage and lack of feeling. Doctors will prescribe pain medication and prophylactic antibiotics to the patient. There is often a large amount of swelling around the jaw area, and in some cases bruising. Most of the swelling will disappear in the first few weeks, but some may remain for a few months.

Recovery

All dentofacial osteotomies require an initial healing time of 2–6 weeks with secondary healing (complete bony union and bone remodeling) taking an additional 2–4 months. The jaw is sometimes immobilized (movement restricted by wires or elastics) for approximately 1–4 weeks. However, the jaw will still require two to three months for proper healing. Lastly, if screws were inserted in the jaw, bone will typically grow over them during the two to three month healing period. Patients also may not drive or operate vehicles or large machinery during the consumption of painkillers, which are typically taken for six to eight days after the surgery, depending on the pain experienced. Immediately after surgery, patients must adhere to certain infection preventing instructions such as daily cleaning, and the consumption of

antibiotics. Cleaning of the mouth should always be done regardless of surgery to ensure healthy, strong teeth. Patients are able to return to work 2–6 weeks after the surgery, but must follow the specific rules for recovery for ~8 weeks.[39]

History

temporomandibular joint disorder
(TMJ).

Prior to 1991, some patients undergoing a dentofacial osteotomy still had

third molar extraction at the same time highly increases the chances of infection development.[41]

Advances in the surgical techniques allow surgeons to perform the surgery under

sedate patients, hospitalizing them shortly after the surgery for a 2–3 day recovery, specifically from the anesthesia. Advancements allow surgeons to expand the use of an osteotomy on more parts of the jaws with faster recovery time, less pain, and no hospitalization, making the surgery more effective with respect to time and recovery.[42]
The procedure, which is strictly used for a mandibular (jaw) deformity and mobilization, has advanced from similar, very effective procedures performed since 1985. The original mandible and maxilla osteotomy procedure still remains almost unchanged, as it is the simplest and still the most effective for dentofacial deformity correction.

See also

References

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