Mandibular Osteotomies

Most facial gender affirmation surgeries are performed on individuals transitioning from male to female. The reason for this is simply because testosterone therapy usually results in satisfactory development of secondary sex characteristics to obviate facial surgery.

For masculinization, fat transfer and implants focus on the lower part of the face, whereas feminization is more often directed to the upper part of the face. Feminization focuses on the hairline, the brow ridge, and the bossing of the frontal bone. Other surgeries for feminization might include procedures like rhinoplasty, surgery to the eyes, the upper lip, a tracheal shave, hair removal, chin surgery, and reduction of the angle of the mandible.

Most of these surgeries are performed under general anesthesia, meaning the patient will be put to sleep completely. Jaw surgery is considered generally safe and is performed when orthodontics alone do not solve the problems that patients experience. When the gum inside the mouth is cut, dissolvable stitches are usually used. Small incisions inside the mouth are more common to minimize visible scars, and most patients experience only moderate pain following a mandibular osteotomy.

WPATH recommendations for Facial Surgery

There are no official recommendations laid down by WPATH regarding facial surgery for the purpose of gender affirmation. However, most surgeons will require a minimum period for hormone therapy and a mental health evaluation. There are very important reasons for these requirements for surgeons, and they are usually employed to enhance the final results of the surgery and to ensure the patient can cope with the implications of surgery that will change the appearance of the face.

All transgender patients, but more specifically transgender women, should expect to remain on hormone replacement therapy for at least 12 months before the surgery is attempted. Since hormone therapy will make significant changes to the thickness of the skin and hair growth. Mental health evaluations reduce the risk of depression and stress disorders following facial surgery.

Contraindications to Facial Surgery

There are no specific contraindications that are unique to transgender individuals, so any contraindication will be the same for anyone undergoing facial surgery. These are heart and lung diseases, bleeding disorders, history of complications related to anesthetics, history of poor wound healing, malnutrition, or other known comorbidities that can negatively affect the outcome for the patient.

Transgender patients should be treated like any other patient, which includes a concern for the psychological health of the patient, especially with facial surgery. Depression and anxiety following such a surgery are normal, so a history of such problems is a cause for concern as it can result in more severe reactions than someone without such a history. Patients may be required to undergo some counseling in preparation for facial surgery.

There are some general considerations that surgeons make before attempting jaw surgery. It is essential that your teeth fit following surgery. Maxillary and mandibular sizes vary between patients, but everyone generally has the same amount of teeth. This means that some people have more room for teeth than others. A mandibular osteotomy will almost always involve the removal of some teeth, and it is essential that a surgeon can fit your teeth into your new jaws.

The type of operation you require will also play a part, not only in your recovery but also in your surgery plan. To gain access to the surgical field, the surgeon needs to open your mouth very wide in a controlled manner so as not to cause irreparable damage to the ligaments and muscles at the back of the mouth. Mandibular setback procedures are different from mandibular advancement procedures, which are different from maxillary advancement. Some will affect your lower jaw and lower teeth; others will affect the upper jaw and upper teeth. No matter what jaw surgery you need, it is essential to discuss the surgery plan and possible setbacks with your surgeon well before the procedure.

The Role of Hormone Replacement Therapy

Before attempting any invasive surgery, it is advised that patients spend at least one full year on treatment. This is so that all possible changes from HRT be complete before further changes are made surgically. This way, the final result is what is seen after surgery, and further changes due to HRT will not interfere with the final product.

It is also not uncommon for a surgeon to require transgender individuals to stop hormone therapy for two weeks before surgery. This is to reduce the risk of HRT-associated complications such as thromboembolism. This will be even more prominent if the patient is also a known smoker. Wound healing issues are common among smokers, especially when they are also on estrogen therapy.

As you can imagine, any wound healing problems on or near the face can lead to unsightly scarring, which is most definitely something that your surgeon will be trying to actively avoid.

Preparing for Surgery

The preparation stage of facial surgery involves quite a lot of expectation management. The surgeon will spend a lot of time assessing the goals of the patient and establishing whether the existing anatomy will support the changes that the patient wants. The surgeon must manage the expectations of the patient just so that you do not go into a surgery without fully understanding what you are signing up for and what kind of final results you can expect.

Before any such major surgery, there is quite some time devoted to taking the patient's history, both medical and psychiatric. Specific attention is paid to areas that are usually problematic, such as sensitivity to anesthesia or a history of clotting difficulties. In the case of clotting problems and HRT, some patients also need to travel, and this can further increase the risks of thromboembolism. This is another reason why surgeons request a two-week pause from HRT.

Please note, however, that this pause is not likely to have lasting effects on your HRT schedule, and you will be able to return to your normal HRT schedule as soon as the surgeon is happy with your healing progress.

Mandibular Osteotomy

Mandibular osteotomy is actually a blanket term for any procedure that involves the removal of pieces of the jaw bone.

Mandibular Angle Reduction

The most common mandibular osteotomy type of surgery for transgender individuals is the Mandibular Angle Reduction. It is commonly used to feminize the face. Before attempting surgery, some surgeons might suggest botox treatments; in rare cases, this causes enough change for a satisfactory result without surgical intervention. If a patient still wants to proceed with surgery, then a surgical treatment plan will be discussed with the patient.

This type of facial surgery is difficult and highly technical to perform. It requires symmetry and has several access constraints. Most of the cuts are made within the mouth to avoid scarring on the skin. Cutting through the skin on the face or neck also carries a high risk of nerve damage.

That being said, the traditional intraoral approach has severe visualization limitations for the surgeon, which makes it more difficult to achieve symmetry. If the surgeon chooses an extraoral approach (outside of your mouth, usually through the neck), it is usually done via a Blair incision and then will also involve a neck or facelift surgery. The masseter muscle needs to be exposed through an incising to the musculoaponeurotic system.

This part is done with extreme care because, in some people, the facial nerve overlaps the area that is incised. There are also important arteries crisscrossing the inferior and anterior border of the mandible. A nerve stimulator can be used as a measure to prevent iatrogenic injury.

Once the masseter is exposed, it can be isolated so that a reciprocating saw can be used to perform the osteotomy. The pterygoid muscle is then also lifted from the bone so that the bone fragment can be removed.

The intraoral approach is much better, and most surgeons will prefer it. Incisions are made in the mouth, which involves opening the mouth widely. This means that you can also expect some pain further back in the jaw joint area. Care should be taken to preserve enough gingival (gum) tissue to close after the procedure is complete. Smaller tendons and muscles are moved and elevated to expose the bone and allow the bone to be removed. Sometimes an endoscope is used for better visualization.

While performing the actual osteotomy, the surgeon should take care to avoid harming the inferior alveolar nerve. Many of these nerves are identified on a CT scan that is done prior to surgery.

Bilateral Sagittal Split Osteotomy

This is one of the oldest and most fundamental forms of jaw surgery to address dentofacial abnormalities. While it has been around since the 1800s, it only became popular after revisions were made in the 1960s and 70s. The procedure was made safer and ensured less relapse. It is used to address several types of malocclusions.

While this jaw surgery does involve a bilateral sagittal split, it is not a bimaxillary orthognathic surgery as it involves the mandible, not the upper jaw.

Anterior Segmental Maxillary Osteotomy

This procedure is used to correct things like a frontal open bite. It involves repositioning of the premaxilla and is only performed if orthodontics alone did not achieve the desired results.

On the buccal side of the maxilla, a mucosal incision is made. Care is taken to ensure that this incision is made above the incisor roots. The incision is bilaterally extended to the far sides of the bicuspid. Most commonly, a small saw and a chisel are used to do this due to the concern for damage to the roots of the teeth.

In many cases, the first bicuspid will be removed before surgery. A greenstick fracture is made by incising transversely along the palate after a wedge-shaped osteotomy. The goal is direct access to the anterior lateral maxillary walls, the nasal floor, the piriform aperture, and the septum.

Complications can arise from this surgery, including fistulas, loss of vitality of the teeth, other damage to the teeth, damage to the maxillary sinus, septal deviation, or unwanted nasolabial aesthetics. The most common complication involves the gingiva retracting in the early phases of healing.

Posterior maxillary segmental osteotomy

This surgery involves a lot of technical difficulties. A cut is made at the buccal vestibular section above the root of the apices on the posterior maxilla. This surgery is usually used for a bilateral or unilateral posterior open bite.

A cut is made horizontally from the second molar to the canine in the buccal vestibule. Most surgeons prefer to remove the molar a few months before the surgery. If extraction is needed, then an interdental vertical osteotomy or posterior vertical osteotomy can be done through extraction sites without moving the palate. The dentoalveolar complex is then separated and moved to the new position. A parasagittal palatal incision is made without the interdental incision following the buccal vestibular incision.

Because this method is so complex, it is rarely used for a posterior maxillary deficiency. This procedure is indicated for maxillary hyperplasia, or distal replacement of the posterior maxillary alveolar fragment so that there is enough space for proper growth of an impacted bicuspid or canine posterior open bite, scissor bite, and anterior correction of an open bite due to bilateral impaction of the parts at the back.

Complications usually include relapse, loss of teeth vitality, periodontal defects, or necrosis of segments.

Horseshoe osteotomy

This surgery is most often used to address midface hypoplasia. In this specific surgery, the hard palate is not cut and remains in its original position. It cuts the maxilla into three pieces without disturbing the central nasal position.

What makes this specifically difficult is that bone contacts must be aligned in multiple places. It is rare to see this specific procedure performed today as there are newer forms of orthognathic surgery that are more effective.

Vertical ramus osteotomy

This is one of the few osteotomies that are sometimes performed extraorally.

When there is mandibular excess an osteotomy is performed in the ramus of the mandible. It is most often used for asymmetry correction of the mandible. A submandibular incision is made to expose the lateral aspect of the ramus.

Genioplasty

Genioplasty is the medical word for chin surgery and is an important part of mandibular osteotomy as it has a dramatic effect on the overall appearance of the face.

There are three dimensions that reduction or augmentation can be performed by: Sagittally, Transversely, and Vertically. While the surgery can be performed in isolation, it is often combined with other mandibular or maxillary osteotomy.

A transoral incision is made in the mucosa from one canine to the other. Enough gingiva should be left over to support suturing. The surgeon then exposes the mental muscles and dissects them to get to the bone. The periosteum is then cut. The inferior anterior border needs to be left alone so that the blood circulation remains intact. The periosteal attachment is released, though. The midline between the mental bilateral foramen is the reference point.

The resection begins below the roots and will differ depending on the kind of deviation and the degree of deviation. If necessary the angulation can be changed posteriorly. It changes the vertical dimensions of the anterior mandible. It is important that the osteotomy ends 7-8mm below the mental foramen, this way, you will not injure the mental nerves. The mental nerve can be found around 5mm underneath the mental foramen. Bone can be added or removed to this gap as needed.

Segmentation of the symphysis area will alter the transverse dimension of the chin. If this is part of the surgery plan, then parallel vertical osteotomies are done to the midline laterally. Suturing of the wound needs to happen in two layers. Before closing, the surgeon must make sure that mental muscles are in the right place.

Chin‐wing osteotomy

This type of chin surgery was used to address aesthetic issues on the lower face. It can involve the whole mandible base or the anterior part of the base.

The incision is always made intraorally and involves the whole border of the lower jaw from the mandibular ramus to the opposite side underneath the dental arch. The mucoperiosteum is raised to match the cortex. The surgeon needs to ensure new blood flow to the mandible. The position of the nerve bundle near the mental foramen needs to be identified in advance of the surgery and needs to be handled with extreme care.

Because the osteotomy is performed from the buccal cortex, the inferior mandibular nerve should not be placed buccally. Angulation is then sloping from the superior position to the inferior position below this nerve canal. This is followed by a horizontal bicortical mandibular cut. The anterior mandible can be cut into one or two pieces. Mobilization needs to be done with extreme care so that the mandible is not fractured.

It would be very dangerous for the bone to break close to the mental foramen. You can change the base of the mandible with this method, and you can adjust the chin prominence sagitally and transversely without making any changes to the mandible that bears the teeth. You can also do this without influencing the Temporomandibular joint.

Lateral body osteotomy of the mandible

This procedure is popular for some instances of mandibular prognathism. It is especially suitable when the first or second premolars will be extracted or are already missing. When this method is used, the need for prosthetic reparation is obviated. It is also the preferred method to correct mandibular dental arch asymmetry, negative overjet caused by excess mandible growth in anterior dentoalveolar region, or an anterior open bite.

This method allows for repositioning of the anterior part of the mandible in any direction. It is suitable for either an alveolar, block or segmental osteotomy.

The first premolars are removed, and then a transoral circumvestibular incision is made. The inferior anterior border needs to be left alone to preserve the soft tissue contour, and the blood circulation is not disturbed, but the periosteal attachment is released. Distal to a second premolar, an incision is made. In order to ensure sufficient access, the flap is extended behind the second premolar. It is important not to strip too much soft tissue. This will expose enough of the subapical area for the removal of the bone. Two vertical cuts are made where the first premolars were extracted to connect the horizontally placed subapical 5mm above the tooth roots. This horizontal cut ends around 2-3mm from the mental foramen. The inferior alveolar neurovascular bundle should be avoided with a vertical incision with an anterior step osteotomy.

Ideally, premolar teeth and bone are removed. While extraction sites are closed, the anterior segment is repositioned posteriorly, following down fracture and separation. If extraction is not part of the surgical plan, then the anterior part can just be moved upwards, so the anterior open bite is closed. A bone graft is put into the gap. To avoid periodontal problems, excessive interdental bone needs to be kept.

Anterior subapical osteotomy

There are a few indications for this type of surgery:

• There is negative overjet in the anterior dentoalveolar process of the mandible.
• There is a negative curve of Spee
• There is asymmetry in the mandibular dental arch – the position of the chin should be satisfactory

This type of surgery can be used to move the anterior section of the jaw in any direction.

Posterior subapical osteotomy

This orthognathic surgery can be used to correct movement of the posterior teeth beyond their normal planes or stiffness in the jaw.

An incision is made inside the mouth at the anterior border of the vertical ramus all the way to the canine area. This incision follows the margins of the teeth. Connected horizontally are two vertical, oblique incisions. While the periosteal attachment is released, the inferior border is left alone so that the soft tissue contour does not change. The neurovascular bundle needs to be identified and protected.

Inverted L and C ramus osteotomies

These procedures are indicated for horizontal mandibular deficiencies and can be done extraorally if need be. The cut is a lot like the bilateral vertical ramus osteotomy. You start 2cm below the mandible's inferior edge and cut 6cm. Dissection through layers of soft tissues is done carefully to expose the entire ramus.

A verticle osteotomy is performed behind the lower jaw foramen in order to lessen the risk of nerve damage. It starts where the lower jaw begins and is horizontally connected above the lower jaw foramen just underneath the sigmoid notch.

For mandibular setback surgery, the proximal segment is put laterally. Rigid fixation can be used to keep it in place with small plates. A bone graft can be done if necessary.

What can I expect after surgery?

The first few days after surgery will be the hardest, but that being said, these surgeries are not particularly painful, despite what one might expect. In the vast majority of cases, only regular painkillers are needed for around a week.

You will need to keep an eye on your healing to make sure that there is no infection. In the hospital, you will receive intravenous antibiotics, but you will also be sent home with an additional course of antibiotics. It is vital that you complete this course as prescribed.

When you wake up from surgery, your face will feel tight due to the swelling. You will not be able to open your mouth widely and your jaws will be stiff. It is also normal for your nose to be blocked and your throat to feel uncomfortable. This only lasts for the first few days after surgery.

On the second or third day after surgery, the bruising and swelling are at its worst. You might need to consider sleeping propped upright during this time. While the majority of swelling will be gone within two weeks, there might be some subtle swelling that will linger for several months. It is unlikely to be severe enough for anyone but you and your family to notice.

Some incisions are only a few millimetres long and might require only a single stitch, but with surgery on the jaws, there are many different possibilities, and it is important that you know what to expect in advance.

It is best to maintain excellent oral hygiene, even with the back teeth, which are often forgotten during recovery in order to avoid infection. Jaw surgery can seem like a very drastic step, but the recovery goes by fairly quickly. Whether you are considering jaw surgery for jaw problems or for gender confirmation, it can be very helpful to discuss your options with medical professionals directly.

Will I be able to eat after surgery?

For the first two days, you will be on a liquid diet only, but after that, you should be able to manage soft foods and then gradually build up to your normal intake within a few weeks. In addition to any pain medications, cold compresses can also help with post-surgical discomfort.

How long is the hospital stay?

It is difficult to say for sure as it may be different between patients, but patients spend a night or two in hospital following surgery if there are no complications. Usually, X-rays of your jaw will determine whether you can go home or not. If you have an intermaxillary fixation or similar fixation, it might be necessary, in later years, to have it removed.

How much work will I miss?

This will depend on the kind of work you do and how your recovery progresses. We recommend that most people take around three weeks off, but this might need to be extended. Remember that jaw surgery is very invasive, and for two days following general anesthetic, you will not be able to drive to work with heavy machinery.

What are the most common complications?

While complications are rare and do not affect the majority of people who undergo jaw surgery, it is important to know what the possible complications are so that you can seek medical help before it reaches its generally worst point.

Numbness

Parts of your face and mouth will be numb and feel tight after surgery. This numbness can take several weeks to dissipate completely. This is not necessarily a bad thing, but you should be aware that it is a possibility.

Bleeding

Very slight bleeding soon after the surgery is normal. The bleeding might come from the cuts in the mouth or from the nose, and this can last for about a week. But this bleeding is very minor and can be better described as oozing. Any real bleeding is pretty unusual, and if you cannot stop it yourself, then you should seek medical advice.

Infection

Your jaw will be held in its new position with plates and screws, and these plates and screws can become infected. This tends to happen several months after the surgery and often requires the plates and screws to be removed. Surface infections soon after surgery are uncommon, but if they occur, you should contact your surgeon immediately.

Adjusting the Bite

After surgery, you will have orthodontic braces, which are used, with the help of elastic bands, to guide your jaws into their new position. If the surgeon finds that the bite is not quite right, a small second surgery is performed to reposition the small metal plates and screws to get the position of the bite just right.

Glossary

Gingival – Related to the gums

Maxillary surgery – Upper jaw surgery

Mandibular Surgery – Lower jaw surgery

Osteotomy – Removal of bone

Advancement – Bringing something forward

Interior – On the inside

Inferior – Below/Lower

Posterior – Behind/Back

Malocclusions – Bite abnormalities of the lower or upper jaw.

For example, a maxillary advancement refers to bringing the upper jaw forward, whereas a mandibular setback involves pushing the lower jaw backward.

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