Patient specific osteosynthesis in bimaxillary orthognathic surgery

In orthognathic surgery, patients with a dysgnatic deformity are operated to
correct their functional and esthetical problems by realigning the upper or
lower jaw. In a selection of orthognathic patients, both the upper and lower
jaw are operated on (bimaxillary surgery). A much debated question in the field
of bimaxillary orthognathic surgery is the order of sequencing, either
maxilla-first or mandibula-first. Traditionally, the maxilla is first operated
on, followed by the mandible. Theoretically a mandible first approach could be
more precise due to a better condylair seating of the mandible then positioning
of the maxilla. However, reviewing literature on orthognathic sequencing, there
still seems to be limited consensus on which approach can provide the most
predictable result. Currently, the decision is dependent on surgeons experience
and preference.
Recently, we have shown accurate and promising results using patient specific
guides and osteosynthesis material to dictate the movement of the maxilla.
Seeing the limited consensus in literature on the best sequencing approach, the
question is raised whether patient specific osteosynthesis can increases the
accuracy and predictability of 3D planned orthognathic surgery bimaxillary
surgery. Indications for the use of conventional maxilla-first, conventional
mandible-first or a PSO approach are lacking. Current data on the accuracy of
mandible-first surgery and PSO are not directly comparable, as such an analysis
has not yet been reported.

The primary objective of this study is to answer if patient-specific
osteosynthesis increases the accuracy and predictability of 3D planned
orthognathic bimax surgery compared to conventional bimax surgery using the
mandible-first approach and mini-plate fixation. The secondary objective of
this study is to answer if patient-specific osteosynthesis influences the
one-year follow-up skeletal stability of the maxillary segment compared to
conventional ostoesynthesis using mini-plate fixation

In order to test the difference in accuracy of translation of 3D virtual
planning and predictability of outcome, this study requires a randomised
controlled prospective trial design. The control group will receive
conventional 3D virtually planned mandible-first translation guided by 3D
splints and fixed with conventional osteosynthesis and the intervention group
will receive 3D virtually planned translation guided patient specifically using
maxillary drill- and saw guides and patient specific osteosynthesis
materials.

The intervention in this study is an osteotomy of the upper and lower jaw
(bimaxillary osteotomy), performed using patient specific drill- and saw guides
and patient specific osteosynthesis of the maxilla in the intervention group.
The control group will receive a care as usual mandible-first osteotomy using
splints and conventional osteosynthesis.

The surgical procedure will not be subject to substantial changes for the
patient. The patient-specific osteosynthesis applies to the maxilla, so these
patients will be first operated on the maxilla followed by the mandible.
Conventional patients will be first operated on the mandible, followed by the
maxilla. Besides a change is sequencing, no differences in surgical procedure
are made. No larger incision will be made and no differences in the used
materials are planned besides the osteosynthesis (fixation) materials. The
patient specific fixation plates are fabricated out of CE-medical grade (V)
titanium by an ISO13485 and ISO 9001:2008 certified manufacturer (Createch
Medical, Mendaro Spain). The surgical guides are fabricated out of a plastic
(nylon), which is sterilisation proof, frequently used in surgeries. No
additional materials are used in the surgical procedure, despite the method
that is used (conventional or patient specific). As an escape procedure, in
case of the patient specific osteosynthesis, the regular 3D milled splint is
made for every patient as well. The regular titanium osteosynthesis can thereby
be applied at any time if the circumstances require this.