Orthognathic Surgery

Orthognathic surgery relates to the correction of facial deformities by surgical means. They are elective operations and are carried out widely across OMFS departments. The main indications for these operations are obstructive sleep apnoea and the correction of a skeletal base discrepancy.
In terms of skeletal base discrepancies and their surgical corrections this is usually planned in conjunction with the orthodontic team. These patients usually have been wearing fixed appliances for at least 12 months. The necessity for surgical correction arises from the fact that the skeletal base discrepancy is too severe for correction by orthodontic means only.
The scope for movements of the maxilla and mandible is vast surgically. It is possible for advancements/retrusions/impactions and rotational movements. The two main operations you will come across are the Le Fort 1 osteotomy and the bilateral sagittal split osteotomy (BSSO). If the patient requires movement of upper and lower jaws this operation is referred to as a “bimax” which involves a Le Fort 1 osteotomy and a BSSO.
We will briefly discuss each procedure, however only an overview will be provided and it is recommended to do further reading to develop your understanding.

Le Fort 1 Osteotomy

A LeFort I osteotomy separates the segment of the maxilla which is tooth bearing from the superior aspect of the maxilla. This is done to achieve maximum mobility of the segment to correct deformities.
An incision is made through the buccal sulcus and a mucoperiosteal flap is raised to expose the lateral maxilla. The osteotomy lines are marked bilaterally and a horizontal osteotomy cut is made at the level of the nasal floor avoiding the apices of the teeth. The nasal septum is separated from the palate and the lateral nasal wall is also separated. Subsequently the maxilla is down fractured.
At this point the tooth bearing segment of the maxilla is fixed to the mandible using MMF and a wafer/splint can used to ensure the correct occlusal relationship is achieved. Once the surgeons are happy with the maxilla-mandibular relationship, the maxilla is fixed using mini-plates.

Bilateral sagittal split osteotomy (BSSO)

This procedure is used to correct mandibular deformities which can involve advancing the mandible, retruding it or correcting an asymmetry.
A transoral approach is used meaning the incision is made in the mandibular vestibule and extended posteriorly up the external oblique ridge.
Two osteotomy cuts are made; the first is through the lingual cortex from the anterior aspect of the ramus posterior to the lingula. The second cut is made in the sagittal plane through the buccal cortex around the first mandibular molar.
The split is now performed which separates the mandible into the tooth bearing anterior segment and the posterior ramus and condyle.
Similar to the LeFort I osteotomy the mandible is fixed to maxilla using wires and a splint can be placed to achieve the desired occlusal relationship. Once the surgeons are happy with the occlusal relationship, the mandible is fixed in position using mini-plates and screws or bicortical screws.

Genioplasty

This procedure targets deformities of the chin that affect facial aesthetics. It is most commonly a cosmetic procedure as opposed to being medically necessitated.
With regards to the relevant anatomy, the main muscle involved is the mentalis which elevates and protrudes the lower lip. The motor nerve supply comes from the marginal mandibular nerve of the facial nerve. The mental nerve supplies sensation to the overlying skin of the chin and lower lip, labial gingivae of the anterior teeth. With regards to the blood supply, the region is served by the mental and inferior alveolar arteries as well as the labial branches of the facial artery.
In terms of the procedure a transoral approach is taken to the chin. There are a number of incisions that can be made such as a vestibular approach or a sulcular incision. Care must be taken to avoid the mental nerve.
A mucosal flap is raised to expose the mentalis muscle which is then dissected and a mucoperiosteal flap is raised to expose the chin.
Osteotomy lines are then marked and subsequently the bony cuts are made. Internal fixation is performed ordinarily using miniplates.
Note a number of cuts can be made depending on how you wish to change the shape of the chin and a range of movements can be performed. For example, with this procedure it is possible to reduce/increase the height of chin and retrude/protrude the chin.

Regenerative techniques and bone grafting

Bone grafting and regenerative techniques are implemented within OMFS to reconstruct bony defects. Therefore it is worth being aware of procedures such as iliac crest grafts.

Iliac Crest

Iliac crest is the most common extra-oral donor site for bone grafting as a large quantity of bone can he harvested.
A full thickness bone graft can be taken consisting of two thick cortices with cancellous bone and is commonly used to reconstruct congenital defects such as alveolar clefts. Analgesic catheters are commonly used for post-operative pain management following a bone graft as severe post-operative pain can cause delays in discharge and overall recovery. Therefore one technique used involves continuous administration of LA via a catheter placed in the iliac crest wound known as an analgesic catheter. Levobupivacaine is often the anaesthetic of choice.
Complications to be aware of are post-operative pain, gait disturbances, haematoma formation, scar, iliac fractures and herniation of abdominal contents.

Distraction osteogenesis

This method is used to generate new bone by gradual separation of bone segments. A distractor device is placed at the osteotomy sites and can be activated to increase separation and can also be deactivated to allow new bone to mature. Note intra and extra-oral devices can be used. Generally the main indications in OMFS for this technique are hemi-mandibular microsomia and secondary reconstruction in head and neck cancer.
One of the main advantages of this technique is the surrounding soft tissues grow with bone formation as well as avoiding issues with donor site morbidity. The downsides to this procedure are that it is a very specialized technique and not all departments perform distraction osteogenesis. Also bear in mind a general anaesthetic is required to insert the device and a separate anaesthetic at a later date to remove it, with possible plating [5].

Management on the ward

Orthognathic procedures are extremely painful post-operatively for patients and the surgical sites are very inflamed. Therefore in some units, steroids are prescribed for a short period post-operatively however steroid prescribing can be controversial and this should directed by a senior.
To help with the inflammation, patients often receive cooling devices such as hilotherms. A hilotherms is a temperature controlled device designed to relive pain and reduce inflammation post-operatively. The device is fitted over the patients face and cooling water is passed through it. It is worth knowing how to apply and adjust the device. Ensure the patient is prescribed antibiotics post-operatively too.
For patients who have undergone orthognathic surgery, post-operative radiographs may be taken prior to discharge to verify correct positioning.
It is also recommended to obtain a FBC and U&E’s the day after surgery to check the patient’s Hb and that there are no electrolyte disturbances.
Epistaxis after le Fort 1 osteotomies can be common. The management of these range from simple nasal packings to return to theatre for vessel ligation. If a patient develops epistaxis on the ward, you should contact your senior. Elastics are usually fitted to the patient’s fixed appliances to stabilise jaw movements. Ordinarily, the patient is shown how to insert the elastics and given a kit to take home. A soft diet is advised for 6 weeks and they are prescribed a strict oral hygiene regime to for aid healing of the intra-oral wounds. These patients are also reviewed on an outpatient basis regularly to monitor healing and occlusion.

Discharge summary/TTO

The following things should be on the TTO:
1) Follow-up appointment
2) Chlorhexidine mouthwash
3) Oral antibiotics
4) Pain relief – codeine, paracetamol
5) Post-operative instructions – diet (may include supplementation), oral hygiene

References