Construction of mandibular ramus and condyle

Construction of the missing mandibular condyle and/or ramus/body presupposes that the glenoid fossa is present, or has been constructed or repositioned into approximately the correct place as compared to the normal side.

The assumption is made that the glenoid fossa is lined with soft tissue.

If this is not the case, the glenoid fossa must be relined with soft tissue before constructing the condyle. The best material to line the fossa with is fascia. Sometimes temporal fascia is available and can be turned over the construct as a pedicle flap. Sometimes it needs to be used as a free graft. In the absence of suitable local tissue (muscle should be avoided because it does have the potential to ossify) fascia lata can be harvested from the lateral aspect of the thigh.

Although many materials have been used for condylar construction in this situation, most surgeons' first choice remains a costochondral graft. Sometimes this needs to be supplemented by additional rib grafts.

Fibular osteocutaneous free flap can be used for reconstruction of the mandible with the aid of virtual preoperative planning.

Surgical approach is generally from a preauricular incision supplemented by a submandibular approach.

Occasionally these incisions may be joined as a parotid or face lift approach when the missing bone tissue from the mandible is so extensive that it is impossible to determine the bone plane for the ramus-condyle construction without first dissecting out the branches of the facial nerve.

The incisionis made in the anterior chest wall over the 6th or 7th rib in the infra-mammory fold. This can be challenging in young girls prior to breast development and an educated guess is required.

The important considerations are :

• Choice of sides: in general a costochondral graft for the left side is harvested from the right chest and vice versa because of the bone curvature required
• Incision of the periosteum over the rib to be harvested
• Retention of a rectangle of periosteum over the costochondral junction to reduce the risk of the bone becoming separated from the cartilage
• Raising of the periosteum with a periosteal elevator and a Doyen's rib raspatory. Great care should be taken when carrying this out beneath the cartilage as there is an increased risk of perforating the chest wall
• Ensuring the harvesting of a sufficient length of rib
• Division of the cartilage with a knife
• Avoiding damage to the underlying periosteum and the pleura
• Division of the rib laterally with rib sheers
• Accurate repair of the periosteum with sutures
• Sometimes it is necessary to harvest a second rib
• If the periosteum and/or the pleura are damaged it is sometimes possible to repair them with simple sutures provided that the lungs continue to expand normally. If they do not do so, the insertion a chest tube is necessary

The nature of the ramus-condyle construction will be determined by the amount of bone that is missing and by the availability of bone in the native distal stump of the mandible for fixation of the rib graft without damaging unerupted teeth.

Where the majority of the ramus is missing, or when all of the ramus and some of the body of the mandible are missing, it can be very difficult to determine the location of the facial nerve. In such cases a formal facial nerve dissection should be carried out.

In theory, an anatomical reconstruction would place the ramus-condyle construction deep to the nerve branches. In practice this does not allow sufficient lateral contour of the mandible for symmetry without risking damage to the facial nerve.

Consequently construction of these severe cases is generally carried out superficial to the facial nerve branches.

The cartilagenous cap of the rib graft is shaped with a knife to approximate the condyle morphology. The rib may need to be bent to produce the right shape and to adapt to the native mandible.

The chondral part of the rib is then positioned in the glenoid fossa under direct vision. Sometimes it is helpful to use a suture to hold it in position. It is important to ensure that it does not displace laterally.

Inferiorly it is fixed to the underlying mandible with at least two screws avoiding essential structures such as developing unerupted tooth germs and the inferior dental nerve.

Pear: One plate eyelet can be used as a washer to avoid splitting of the bone graft.

Sometimes there is a V-shaped gap between the mandible and the rib graft.. This gap should be filled with additional rib graft (shown in diagram) wedged into place or fixed with screw(s).

Patients who have larger bony defects, typically involving the ramus and body, may benefit from a vascularized bone containing flap transfer. The fibula is the transfer of choice due to its relatively large volume, reliable pedicle, and acceptable donor site.

Planning is carried out in virtual reality on a 3D-CT scan using appropriate software.

A virtual reconstruction of the mandible is performed using a virtual standard fibula template or a 3D-CT scan of the patient's fibula.

Either of the patient's fibulae can be used for a given defect. The choice of side is dependent on the vascular supply to the lower leg as determined by preoperative examinations and recipient vessels in the neck.

A cutting guide for the fibular harvesting, which also serves as a cutting guide for the wedge ostectomies needed to shape the harvested flap, is prepared using 3D printing.

A 3D-model of the virtually reconstructed mandible is prepared and a mandibular reconstruction plate is adapted to a near perfect fit. Alternatively the reconstruction plate is custom made by laser sintering, laser melting, or milling, without using standard bone plates.

The fibula free flap is harvested in a standard fashion using the pre-fabricated cutting guide.

The pre-fabricated cutting guide is then used to perform wedge ostectomies of the fibula. Use of Piezoelectric osteotomes facilitates the preservation of the vascular bundle and minimized damage to the periosteal blood supply.

The prebent mandibular reconstruction plate serves as a template for positioning the osteotomized fibula.

While care is taken to protect the vascular bundle, the osteotomized fibula is secured to the plate with monocortical locking screws.

The reconstruction plate is then secured to the native mandible with at least 3 bicortical locking screws.

The detailed procedure for the revascularization is outside the scope of this surgery reference.

However, in short the procedure consists of the following steps:

• Appropriate recipient vessels are selected in the neck and dissected so as to be available for anastomosis
• The recipient and the donor vessels adventitia are cleaned under a microscope
• Appropriate vessel geometry is assured and the vessels are placed into a microvascular clamp and anastomosis carried out using 9-0 nylon sutures
• Vascularization is restored after both arterial and venous anastomoses are completed

A postoperative 3D-CT scan is made to check the results of the reconstruction. The precision of the osteotomies facilitates bone healing.

Postoperative CT following removal of the reconstruction plate, showing ramal contour, and improvement of chin deviation and malocclusion.

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.