Rotational osteotomies including inverted L-osteotomy

The majority of end stage reconstructions in HMF require bimaxillary orthognathic surgery. Of course there are exceptions which can be managed with more limited procedures.

The challenges are surgery on a patient who has usually been operated on many times previously with consequent presence of scar tissue and with often severely deformed asymmetric bone structures. In addition, the rotational movements required commonly stretch the enveloping soft tissues to their limit.

Most of the techniques are identical to those described under orthognathic surgery and can be found in that section. In this area we will only comment on the special considerations which have to be made for HFM cases.

Planning of these cases is best carried out in 3D using a combination of proprietary software into which a CT scan is imported, virtual model planning of procedures and commonly physical model planning as well using a stereolithographic rapid prototyped skeletal model.

The surgical technique is as for a conventional Le Fort I maxillary osteotomy. The correction must take into account the pitch, roll and yaw deformities found in these patients.

The maxilla usually has to be rotated so that the maxillary dental midline is placed coincident with the facial midline (yaw). Vertically, the cant is corrected via differential impaction right to left (roll). Sagittaly, the occlusal plane is also leveled via differential impaction antero-posteriorly on the facial center (pitch).

The osteotomized maxilla is stabilized to the upper facial skeleton with miniplates. Cortico cancellous bone grafts can be used to fill any gaps resulting from any inferior repositioning of the maxillary segment.

Bilateral sagittal split osteotomies split are used to correct the mandibular deformity except when the surgical movement results in significant lengthening of the ramus or when a sagittal split osteotomy is challenging due to previous surgery. In such cases an Inverted L osteotomy with or without an interpositional bone graft is indicated.

Any residual fixation material from previous operations has to be removed.

It is unusual for the mandibular ramus to require lengthening on the non-affected side. Therefore it is almost always possible to carry out a sagittal split osteotomy on that side.

Although an inverted L-osteotomy can be carried out intraorally, an external approach is often utilized to allow for the placement and fixation of the bone graft.

The procedure is a genioplasty osteotomy as described in the orthognathic surgery section. Modifications of the traditional procedure in this patient population included asymmetric movement of the distal segment with possible bone grafting.

In some cases delaying the genioplasty is advisable to allow for the true evaluation of the chin symmetry once the major rotational osteotomies have been performed.

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.