Some adult and adolescent cleft patients will present with skeletal deformities such as maxillary retrognathia or vertical deficiency and will benefit from corrective surgery at the Le Fort I level.
The indications for using distraction osteogenesis in cleft patients are large anterior and inferior advancements of the maxilla outside of the physiological envelope of conventional Le Fort I osteotomies.
This section describes a method of carrying out Le Fort I osteotomies in patients with repaired clefts of the palate using distraction osteogenesis.
The potential advantages of this alternative approach are:
To make it easier to advance the maxilla
To make it easier and safer to make large advancements
To avoid bone grafts and internal plate fixation
To achieve more stable results
To produce less harm to velo-pharyngeal function
Distraction osteogenesis (DO) in these cases can be carried out using internal or external devices. This section describes the use of an internal device which can achieve advancements of up to 25mm.
The challenge of internal devices is that no adjustment of the vector of distraction is possible once the device has been inserted. Consequently detailed planning of distractor position is recommended preoperatively together with some means by which the plan can be transferred to the patient at surgery.
2. Planning and preparation
The Le Fort I osteotomy can be planned with commercially available 2D- and 3D-software. Whereas the 2D-software gives a good idea of the advancement required, it does not allow placement and adjustment of a distractor. By contrast 3D-software using either CT or cone beam CT, allows both. Since some distractor footplates are difficult to bend in situ at surgery and the vector can be critical, it is often helpful to have a 3D-facial bone model on which the distractor can be adapted and the maxillary movement trialed.
A cephalometric tracing of the patient is imported into a 2D-orthognathic surgery software program.
A 2D-plan of the desired position of the advanced maxilla is produced.
A CT-scan is imported into a 3D-orthognatic surgery planning program. Simulated Le Fort I osteotomies can be performed, one option being chosen. A virtual distractor is selected and placed over the maxilla. The osteotomy is completed on screen and the distractor activated to achieve the desired vector for the maxillary advancement.
Distractor adaptation on 3D physical model
A stereolithographic model is produced from the above CT data. The osteotomy and the distractor are replicated on the model and the maxillary movement trialed. Once again the vector of the distractors can be adjusted.
Production of surgical guide
Once the precise distractor position has been confirmed a guide can be produced to enable that position to be transferred precisely to surgery.
A periosteal elevator is inserted between the nasal mucosa and the lateral wall of the nose on one side. A curved retractor is inserted behind the maxillary tuberosity. A further instrument is used to retract upwards the lip and mucoperiosteal flap, exposing the antero-lateral maxilla.
The surgical guide is then inserted on the exposed anterior maxilla. The screw holes in the guide (which are for the distractor screws) are drilled and the osteotomy cut marked. The guide is then removed.
The osteotomy is completed as outlined.
Posteriorly a fine gently curved osteotome is used with the curvature pointing downwards to complete the cut up to the pterygomaxillary junction.
Pitfall: The direction of the cut posteriorly is important as it must not travel upwards. That could result in a posterior osteotomy fracture line that may either result in excessive bleeding or travel upwards into the orbit.
Lateral wall and nasal crest
The lateral walls of the nose and the nasal crest of the maxilla in the midline are then divided with nasal osteotomes while protecting the nasal mucosa.
Special "guarded" osteotomes are used for this purpose to protect the nasal mucosa.
A curved pterygoid chisel is placed with the curvature pointing medially and inferiorly between the tuberosity and the pterygoid plates.
A mallet is used to drive the osteotome medially to complete the pterygomaxillary dysjunction. The position of the tip of the osteotome can be checked with a palpating finger.
Pitfall: An upward and posteriorly oriented osteotome will not reliably separate the maxilla from the pterygoid plates. It is also associated with increased risk of bleeding from the pterygoid plexus and internal maxillary artery.
5. Downfracture and mobilization of the maxilla
The lower part of the maxilla is mobilized initially by digitally pushing it downwards. The term downfracture was coined to describe this downward movement and the fracture of the posterior wall of the maxilla which has not been cut with either saws or chisels.
By contrast to a conventional Le Fort I advancement only limited mobilization of the maxilla is carried out. This should only be performed after inserting a custom made cast steel palatal protection plate to avoid damaging the palate or accidently fracturing the maxilla.
Special care has to be taken not to break the anterior wall of the maxilla to ensure precise placement of the distractor.
It may be necessary also to trim the lateral wall of the nose and the nasal septum with bone rongeurs in order to ensure that the "travel" of the distractor is not disturbed.
Insertion of distractors
The pre-bent distractors are fixed with screws into the pre-drilled holes. It should be noted that a perforation is required in the posterior mucoperiosteal flap for the port of the distractor. The distractors are activated to verify the movement and then wound back to their original position.
Clinical situation demonstrating the position of the distractor ports.
After a latency period of 4-5 days distraction commences at the rate of approximately 1 mm/day. The patient or a relative performs the daily activations. Periodic (usually weekly) review is carried out until the desired maxillary position is reached. Overdoing the advancement by 1-2 mm at this stage is recommended to compensate for settling and minor relapse. Adjustments of the occlusion with the distractors in position have not proven possible.
Removal of the distractors
The distractors can be removed after a minimum of 8 weeks of consolidation.
A second surgical procedure under general anaesthesia is required to remove the distractors. The presence of scar tissue and new bone formation makes such removal challenging. Cutting the device into pieces may facilitate removal.
After the removal of the distractors, light orthodontic class 3 elastics can now be used to fine-tune the dental occlusion and to help maintain the maxillary advancement.
7. Aftercare following distraction osteogenesis
Apply ice packs (may be effective in a short term to minimize edema).
The sterile dressing placed over the skin incisions is maintained for a minimum of 48 hours. Thereafter routine wound care should be instituted around the activation rod.
Antibiotic prophylaxis is continued for 1-5 days depending on the nature, complexity, and duration of the surgical procedure.
Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. A small soft toothbrush with toothpaste should be used. Antiseptic rinses can be used in the early postoperative period. 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.
Early post-operative x-rays are obtained to verify correct device placement. Additional postoperative imaging is performed as needed.
Remove sutures from skin after approximately 5 days if nonresorbable sutures have been used.
Regular follow up examinations to monitor healing and the postoperative occlusion are required.
Avoid sun exposure and tanning to skin incisions for several months.