Osteotomy and internal fixation

The treatment of an established malunion in the mandible consists of:

• Dental casts and splints (optional)
• Removal of hardware (If present)
• Osteotomies of the consolidated fracture
• MMF
• Internal fixation following a proper reduction (If plates are not available, MMF may be applied in selected cases.)
• Grafting if needed
• Removal of MMF

In case of severe malocclusion and a consolidated fracture, osteotomies may be planned with the help of model surgery on models mounted on an articulator.

After the desired occlusion is obtained, an occlusal splint (blue) is made to transfer the occlusion obtained in the model surgery to the patient.

Alternatively a stereolithographic model made from 3D-CT scans can be used to plan the osteotomies as well as the production of the splint and pre-bending of plate.

If the patient was previously treated operatively, ideally the same approach is used as in the initial surgery.

When the original approach does not provide ideal exposure of the fracture site, the following approaches can be used.

For symphyseal and parasymphyseal fractures the trans oral approach usually offers sufficient access.

However, if this is not the case, a transcutaneous approach such as the submental approach may be selected.

For most body and angle fractures a transoral approach usually offers sufficient access.

However, if this is not the case, the submandibular approach may be selected.

For the ramus and the lower part of the condylar neck, the retromandibular approach or...

...the submandibular approach may be selected.

It is important that all of the previously installed fixation material is removed.

In malunion, bone growth over the plate and screw heads may have occurred. The bone can be removed using a burr while taking care not to damage the slots in the screw head.

If the screw is integrated in the bone, it may break during removal. There is no need for additional osteotomies to recover the broken screw shaft.

The plate is then removed.

Osteotomy of the consolidated fracture site is necessary to correctly reposition the bone according to the surgical splint and/or occlusion.

The osteotomy is performed. While a burr will produce a larger defect which may need later bone grafting, a saw or a piezo device will produce a more accurate osteotomy line. The use of an osteotome alone to perform the osteotomy may result in fragmentation of the bone.

To avoid damage of the teeth, the interdental osteotomy can be completed with a thin osteotome.

Passive mobilization of the fragments must be obtained.

Bone fragments are repositioned and the occlusion is re-established. Any bony interferences must be removed. The patient is placed in MMF with or without the use of a prefabricated occlusal splint.

For step-by-step description of how to establish MMF, follow this link.

The selection of bone plate(s) is performed according to the fixation demands. For further details on selection and implementation, please refer to the trauma section.

New hardware should be applied avoiding the use of previous screw holes.

If inadequate bone contact exists after fixation, the gap is grafted with autogenous cancellous bone.

The cancellous bone is compressed into the gap and applied around the osteotomy site.

MMF is released and the occlusion is verified.

If arch bars or MMF screws are used intraoperatively, they are usually removed at the conclusion of surgery if proper fracture reduction and fixation have been achieved. Arch bars may be maintained postoperatively if functional therapy is required or if required as part of the fixation.

Postoperative x-rays are taken within the first days after surgery. In an uneventful course, follow-up x-rays are taken after 4–6 weeks.

The patient is examined approximately 1 week postoperatively and periodically thereafter to assess the stability of the occlusion and to check for infection of the surgical site. During each visit, the surgeon must evaluate the patient's ability to perform adequate oral hygiene and wound care, and provide additional instructions if necessary.

The treatment of infected nonunions normally involves longer than the typical hospital stay, allowing daily examinations and intravenous antibiotics until the signs and symptoms of infection resolve.

Adequate dental care is required in most patients having undergone mandibular surgery.

If a malocclusion persists, the surgeon must ascertain its etiology (with appropriate imaging technique). If the malocclusion is secondary to surgical edema or muscle splinting, training elastics may be beneficial. The lightest elastics as possible are used for guidance, because active motion of the mandible is desirable. Patients should be shown how to place and remove the elastics using a hand mirror.

If the malocclusion is secondary to a bony problem due to malreduction or hardware failure or displacement, elastic training will be of no benefit. The patient must return to the operating room for revision surgery. A slight malocclusion can be corrected by by orthodontics or dental adjustments with the help of a dentist.

Follow-up appointments are at the discretion of the surgeon, and depend on the stability of the occlusion on the first visit. If a malocclusion is noted and treatable with training elastics, weekly appointments are recommended.

Postoperatively, patients will have to follow three basic instructions:

1. Diet
Depending upon the stability of the internal fixation, the diet can vary between liquid and semi-liquid to “as tolerated”, at the discretion of the surgeon. Any elastics are removed during eating.

2. Oral hygiene
Patients having only extraoral approaches are not compromised in their routine oral hygiene measures and should continue with their daily schedule. Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. The presence of the arch-bars and any elastics makes this a more difficult procedure than normal. A soft toothbrush (dipping in warm water makes it softer) should be used to clean the surfaces of the teeth and arch-bars. Any elastics are removed for oral hygiene procedures. Chlorhexidine oral rinses should be prescribed and used at least three times each day to help sanitize the mouth. For larger debris, a 1:1 mixture of hydrogen peroxide/chlorhexidine can be used. The bubbling action of the hydrogen peroxide helps remove debris. A Waterpik® or similar device is a very useful tool to help remove debris from the wires. If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions as this may lead to wound dehiscence. The assistance of a dental hygienist may be helpful.

3. Physiotherapy
Physiotherapy can be prescribed at the first visit and opening and excursive exercises begun as soon as possible. Goals should be set, and, typically, 40 mm of maximum interincisal jaw opening should be attained by 4 weeks postoperatively. If the patient cannot fully open his mouth, additional passive physical therapy may be required such as Therabite or tongue-blade training, as well as assistance from a physiotherapist if required.