Various implant systems are available for the treatment of midfacial fractures based on the midface system 1.0, 1.3, 1.5, and 2.0. The numbers refer to the outer screw thread diameter in mm.
These plates are often referred to as “miniplates”.
Plating of the periorbital region is best done with screw thread diameters of between 1.0, 1.3, or 1.5 mm. Low profile plates are recommended so the patient is not disturbed by implant prominence. However, if increased stability is needed, stronger implants must be selected.
Plating of buttresses such as the zygomaticomaxillary buttress (where high masticatory forces are transmitted) requires thicker plates than infraorbital rim fractures.
For each of the four screw dimensions, a range of various shaped plates of varied thickness exist.
|Choice of screws|
The quality and thickness of the bone determine the choice of screw type. The pitch of the thread is important for anchorage. Most screws used in the midface are self-tapping.
There are two kinds of screws used in the midface:
Self-tapping (see illustration, top screw)
Self-drilling (see illustration, bottom screw)
Self-drilling screws offer the advantage of no predrilling prior to placing the screw. However, self-drilling screws require a significant amount of force to be applied to the bone in order to engage the screw thread into the bone. This can potentially displace bone fragments.
Number of screws
Usually, plates should be fixed with at least two screws in each fracture fragment.
Another plate and screw system which streamlines screw sizes and plates for the midface is available. In the Matrix Midface system, only one screw type with a diameter of 1.55 mm can be used with plates of varying thicknesses, depending on the specific fixation requirements of each fracture.
The illustration shows the four thicknesses of plates available in the Matrix Midface system. Note that the same screw fits all four plates.
Depending on the size and location of the defect of the orbital walls and orbital floor, reconstruction can be achieved by using implants of various materials and plate/mesh shapes.
The illustration shows a fan-shaped titanium plate (A), a similar plate with porous polyethylene coating (B), a titanium orbital reconstruction plate (C), and preformed anatomic orbital plates (D).
Alternatively, porous polyethylene implants or bone grafts can be used.
In non-load-bearing defect zones of the midface (typically maxillary sinus walls) bridging and camouflaging of the defect area with 3-D mesh might be appropriate.
|Types of screw drivers|
Bone thickness varies significantly in the midface. In the thin bones of the NOE area screw insertion with self-retaining screw drivers may be problematic due to the force required to decouple the screw driver from the screw head after screw insertion.
Therefore screw drivers with holding sleeves may be preferable. The choice of screw driver is according to surgeon preference.