Maxillomandibular fixation (MMF) - Bone supported devices
1. Principles
The use of skeletally-based intermaxillary fixation (IMF) with screws and plates (eg, matrix wave plate) for maxillomandibular immobilization is considered an alternate technique.
Indications and contraindications
Indications:
- Emergency cases
- Patients with infectious diseases
- As an alternative, if arch bars cannot be applied
- Selected patients with simple fracture patterns or undergoing orthognathic and reconstructive surgery
Contraindications:
- Severely comminuted and displaced fractures
- Unstable, segmented fractures
- Children, if tooth buds are still in place
- Fracture patients with multiple mobile teeth
Check the position of the tooth roots, infraorbital nerve, and inferior alveolar nerve before starting.
The position of the screws should be symmetrical in opposing jaws and should not interfere with the operative approach or internal fixation devices.
Long-term immobilization using IMF screws is not recommended because it can result in damage to the surrounding mucosa.
Teaching video
AO Teaching video on maxillomandibulary fixation (MMF)
2. Screw design
IMF screws are made of stainless steel. They are self-drilling and self-tapping.
The screw head is raised and contains two holes set at 90° to each other for wire placement.
3. Screw placement
Correct screw locations
Various IMF screw placement patterns exist and are dictated by the fracture location and the patient's dentition.
The insertion point is limited by the position of the following:
- Inferior alveolar nerve
- Infraorbital nerve
- Tooth roots
For correct placement, IMF screws must be located in the alveolus avoiding the tooth roots.
Screw insertion
Introduce two self-drilling and self-tapping screws directly through the mucosa on one side. Take care that the screw head does not compress the gingiva when fully seated.
Insert two more IMF screws on the opposite side in the same manner.
4. Maxillomandibular fixation (MMF)
Maxillomandibular fixation is performed with 0.4 mm wires.
The wire ligature is wrapped around the screw head grooves.
Before tightening the wires, the correct occlusion must be established.
X-pattern
For more stability, wiring in an “X” pattern can be added.
- Tightening the wires may create a posterior open bite. Additional IMF screws or Ernst ligatures placed on the posterior dentition may prevent or correct this condition.
- Over-tightening the wires can lead to a lateral rotation of the fragment.
- There may be a lack of stability due to the long span of the wires.
5. Alternative: screws and plate
From a 2.0 mandible plate, cut pieces of 2-hole length for the maxilla and 3-hole length for the mandible.
Bend these pieces away from the bone and fix them monocortically with 6 mm long 2 mm screws.
After establishing the occlusion, establish mandibulomaxillary fixation with 0.4 mm wires.
There may be a lack of stability because of the long span of the wires.
Edentulous fragments can be secured using inter-arch miniplates, which are applied transmucosally.
6. Alternative: MMF plating systems
These systems use locking screws to minimize pressure on the gingiva.
The matrix wave plate is a bone-anchored intermaxillary fixation system that provides flexibility in the placement of the screws.
A more rigid variant, which is more like an arch bar screwed into the bone, may offer additional stabilization in cases with alveolar comminution.
These plates may behave like an external fixator for the alveolar segment.
