Orthognathic surgery


Orthognathic surgery, also known as corrective jaw surgery or simply jaw surgery, is surgery designed to correct conditions of the jaw and lower face related to structure, growth, airway issues including sleep apnea, TMJ disorders, malocclusion problems primarily arising from skeletal disharmonies, and other 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 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. This surgery is also used to treat congenital conditions such as cleft palate. 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 allows 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 presenting with dentofacial 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. Another development in the field is the new index called the index of orthognathic functional treatment need that detects patients with the greatest need for orthognathic surgery as a part of their comprehensive treatment. IOFTN has been validated internationally and detected over 90% of patients with greatest need for orthognathic surgery.

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. Orthognathic surgery can be used to correct:
  • Gross jaw discrepancies
  • 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 micrognathia, which is when the mandible does not grow far forward enough, and when the mandible grows too much, causing an under bite; all of which are uncomfortable. Also, a total maxilla osteotomy is used to treat the "long face syndrome", known as the skeptical open bite, idiopathic long face, hyper divergent face, total maxillary alveolar hyperplasia, and vertical maxillary excess. Prior to surgery, surgeons should take x-rays of the patient's jaw to determine the deformity, and to make a plan of procedures. Mandible osteotomies, or corrective jaw surgeries, benefit individuals who have difficulty chewing, swallowing, TMJ pains, excessive wear of the teeth, open bites, overbites, underbites, or a receding chin. The deformities listed above can be perfected by an osteotomy surgery of either the maxilla or mandible, which is performed by an oral surgeon who is specialized in the working with both the upper and lower jaws. Orthognathic surgery is also available as a very successful treatment for obstructive sleep apnea.
;Cleft lip and palate
Orthognathic surgery is a well established and widely used treatment option for insufficient growth of the maxilla in patients with an orofacial cleft. There is some debate regarding the timing of orthognathic procedures, to maximise the potential for natural growth of the facial skeleton. Patient reported aesthetic outcomes of orthognathic surgery for cleft lip and palate appear to be of overall satisfaction, despite complications that may arise. A potentially significant long-term outcome of orthognathic surgery is impaired maxillary growth, due to scar tissue formation. 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. 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

Risks

Although infrequent, there can be complications such as bleeding, swelling, infection, nausea and vomiting. 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.
There can also be some post operative facial numbness due to nerve damage. Diagnostics for nerve damage consist of: brush-stroke directional discrimination, touch detection threshold, warm/cold and sharp/blunt discrimination, electrophysiological tests, nerve conduction study, and cold and warm detection thresholds. 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. Recovery from the nerve damage typically occurs within three months after repair. Some 3D movements are considered riskier than other ones, such as maxillary impaction.

Surgery

Orthognathic surgery is performed by maxillofacial or an oral surgeon or a plastic surgeon in collaboration with an orthodontist. It often includes braces before and after surgery, and retainers after the final removal of braces. Orthognathic surgery is often needed after reconstruction of cleft palate or other major 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, which is useful for the planning and also explaining the surgery to the patient and the patient's family. 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. However, these days new approaches and paradigms exist including surgery-first and using clear aligner orthodontia

Sagittal split osteotomy

This procedure is used to correct mandible retrusion and mandibular prognathism.
First, a horizontal cut is made on the inner side of the ramus mandibulae, extending anterally to the anterior portion of the ascending ramus. The cut is then made inferiorly on the ascending ramus to the descending ramus, extending to the lateral border of the mandible in the area between the first and second molar. At this time, 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.