Lateral augmentation by osteotomy

This procedure provides lateral augmentation to the face by using a sagittal split osteotomy with lateral positioning of the proximal segment.

It is possible to carry out augmentation purely with a sagittal split on one side with interpositioning augmentation using a block bone graft.

Surgical approach to the mandible is transoral approach to the angle.

Minimal planning is required. It is only necessary to determine that there is sufficient bone stock to perform the osteotomies.

Orthodontic appliances or arch bars are necessary to control the occlusion during the procedure.

Planning is based purely on what is considered desirable and possible for the augmentation to achieve maximal symmetry. 3D planning software may be helpful.

If any screws or other fixation devices are present in this part of the mandible from previous surgery, these should now be removed. An Obwegeser-Dal Pont type sagittal split osteotomy is performed.

It should be remembered that previous surgery will have been performed in this area and the bone quality and quantity may be deficient.

The procedure starts with three corticotomies.

The first cut is made through the lingual cortex just above the mandibular foramen parallel to the occlusion. The corticotomy is extended from the anterior to the posterior borders of the ramus.

The second corticotomy is made through the buccal cortex in a vertical direction at the level of the first or second molar.

The third corticotomy connects the first two osteotomy lines along the anterior border of the ascending ramus.

The final split is completed with a thin osteotome, splitting the entire ascending ramus from the anterior to the posterior border of the ramus.

After MMF is established, a cortico cancellous block of iliac crest bone graft of predetermined size is inserted between the proximal and distal fragments. Bicortical screws are placed between the proximal and distal fragments, incorporating the bone graft.

After completion of osteosynthesis the MMF is removed and the final occlusion is verified.

It is also possible to carry out this procedure in combination with bimaxillary orthognathic surgery in which both the mandible and the maxilla are widened by additional midline osteotomies.

If MMF screws or Temporary Anchoring Devices (TADs) are used intraoperatively, they are removed at the end of surgery if not further needed for elastic traction. If a final splint was used, it may be fixed to the orthodontic devices (brackets) of the upper jaw to assure the planned occlusion and to serve as guidance for the neuromuscular adaption during functional training for about 2 weeks postoperatively.

To reduce swelling, the application of ice-packs or cooling devices during the early post-operative phase is advice. Intravenous steroids should also be continued for a short period postoperatively for the same purpose.

Antibiotic prophylaxis is continued for 1-5 days depending on the nature, complexity, and duration of the surgical procedure.

Especially in two-jaw surgery, the airway control is of major importance. An individual decision has to be taken if the patient can be extubated or should remain intubated until it is clear that safe airway can be established.

Early post-operative x-rays are obtained to verify correct segment position. Additional postoperative imaging is performed as needed.

Regular follow up examinations to monitor healing and the postoperative occlusion are required. If an occlusal problem is present in the early postoperative phase, the surgeon must determine its etiology. If the malocclusion is secondary to surgical edema or muscle detachment/disorders, training elastics may be beneficial. The elastics are only used for guidance, because active motion of the mandible is desirable. Patients should be instructed how to place and remove the elastics using a hand mirror. If the malocclusion is secondary to a bone problem due to inadequate fragment positioning, displaced or failed hardware, or condylar displacement during surgery, elastic training will be of no benefit. The patient must be rescheduled for revision surgery.

At each appointment, the surgeon must evaluate the patient's ability to perform adequate oral hygiene and wound care and should provide additional instructions if necessary.

Postoperatively, patients will have to follow three basic instructions:

1. Diet
In orthognathic surgery the internal fixation devices usually do not allow for full functional load. A soft diet should be used up to 6 weeks, starting with liquids for the first 3-4 days. Elastics can be removed during eating.

2. Oral hygiene
Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. The presence of orthodontic appliances, the splint, and elastics makes this a more difficult task. A small soft toothbrush with toothpaste should be used.Any elastics are usually removed for oral hygiene procedures. Additionally, antiseptic rinses can be used in the early postoperative period. An oral irrigator (eg, Waterpik) is a very useful tool to help . If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions to prevent wound dehiscence in the early postoperative phase.

3. Functional training/physiotherapy
The patient is instructed how to perform functional training (opening and excursive exercises) as soon as possible. The progress should be monitored by the surgeon. If available and needed, a physiotherapist can support the functional rehabilitation. An undisturbed mouth opening of minimum 35 mm interincisal jaw opening should be attained by 4 weeks postoperatively.

In case of undisturbed healing, the postoperative orthodontic treatment can usually start 2 to 6 weeks after surgery depending on the case.