Three-Dimensional Computer-Assisted Surgical Planning and Manufacturing in Complex Maxillary Reconstruction

Key points

  • Maxillary reconstruction is a complex part of head and neck surgery.

  • Considering the defects using the Brown classification and using the concept of midfacial buttresses helps guide surgeons to choosing the appropriate bony reconstruction.

  • A variety of techniques using 3-dimensional computer-assisted planning can be used ranging from printing biomodels, to 3-dimensional printing models, cutting guides, plates, and fixation guides.

Maxillary reconstruction is a challenging area of head and neck reconstructive surgery. Since the advent of microvascular reconstruction, the surgeon has a large armamentarium of options to consider after ablative surgery to the maxilla and midface. With the development of computer-assisted surgical planning, the reconstructive surgeon can now accurately design and plan bony reconstruction of the midface to within millimeter accuracy, and this has changed the way we approach this area. The maxillectomy defect can produce a complex defect often involving a variety of structures, including the tooth bearing alveolus, the palate, paranasal sinuses, nasal cavity, and orbital cavity. Several bones are often involved, including the maxilla, the palatine bone, the ethmoid bone, the zygomatic bone, and less frequently the nasal bones. Loss of these anatomic structures leads to complex functional and aesthetic consequences and, when considering reconstruction in these patients, the surgeon should determine their goals for each individual patient, because these will help to choose the ideal reconstructive option. These goals can include closure of an oronasal communication, achieving midfacial soft tissue support and symmetry, avoiding velopharyngeal insufficiency, maintaining eye position, dental rehabilitation, and bony support for a facial prosthesis.

In this article, we present an overview of the use of 3-D computer-assisted surgical planning to achieve accurate reconstructions of the complex maxillary defect. We briefly discuss the Brown classification system and use it to guide the reader through the various reconstructive options for the complex maxillary defect.

Three-dimensional computer-assisted surgical planning and manufacturing

Significant progress into the development of 3-dimensional (3D) printing and computer-aided design and manufacture has led to a rapid growth in virtual surgical planning options. The main choices for any hospital or department are whether to purchase a 3D printer and the planning software and design everything in house or to outsource to a company with a proprietary workflow. The extent of virtual planning for every case can range from printing of a stereolithographic model alone that allows a 3D analysis of the case and potential for prebending plates, to completely custom planning with 3D printing of models, guides, and plates. In our unit, as an additional workflow of our maxillofacial prosthetics laboratory, 3D printers have been purchased, and Materialize™ software used for surgical planning. The advantages of an in-house system includes rapid prototyping and planning to be performed, allows the surgeons to easily communicate with the technicians and biomedical engineers to make small modifications when necessary, less expensive for the institution, and requires less time for planning and manufacturing ( Table 1 ). In our unit, the planning is all completed virtually, 3D biomodels and cutting guides are printed, and the plates are prebent on the biomodels and sterilized. Prebending reconstruction plates allows for a more cost-effective option than printing in hospital grade titanium. Several cases will be shown to highlight how 3D-assisted surgical planning has revolutionized our practice and improved surgical outcomes in maxillary reconstruction.

Table 1
Planning process in Maxillofacial Laboratory at Queen Elizabeth Hospital, Birmingham for the average oncology case, for virtual planning, design of cutting guides, and reconstruction plate bending in the laboratory. The average time required for each stage and additional steps for proprietary planning are included
Stage Action Average time required Additional steps for proprietary planning
3D planning (PC workup
  • Download of scans

  • Segmentation and clean up of scans

  • Osteotomy and resection planning and planning of graft

  • Guide design

  • Model preparation for print export and save

  • Production of theater images for print out and patient notes

5 h
  • Sending of scans to proprietary server

  • Virtual conference for planning of resection and guide

  • Design plans sent for approval to operative team

  • Approval of plans and commencement of production

  • Can take addition of several days

3D printing and postprocessing of model
  • Reference model print time

  • Printer clean after printing

  • Printed model postprocess and clean up

  • Guide print time

  • Printed guide postprocessing and clean up

14 h
Laboratory process of plate
  • Plate bending and production of location tags – laser welding

  • Predrilling of holes in model and guides – marking plate on the model

  • Plate preparation – sandblasting, ultrasonic treatment with citric acid to anodize

  • Packaging for sterilization

2 h
  • 3D printing of reconstruction plates is often possible for additional cost

  • Delivery time needed from base of proprietary company to institution

Sterilization 6 h
  • Delivery of sterile cutting guides, models and plates

  • Institutional sterilization may also be required

Completion 27 h Variable delivery between 2 and 4 wk

The last column includes additional steps needed if proprietary company used for 3D computer-assisted planning and manufacture.

Classification of midface defects

Several classifications exist for midfacial defects; however, the Brown classification will be used in this article. The Brown classification was described in 2010, provides a framework for considering potential reconstructive options for maxillary and midface defects, and will be used in this report ( Fig. 1 ). The classification consists of 6 vertical and 4 horizontal maxillectomy defect patterns. The vertical classification involves (1) maxillectomy not causing an oronasal fistula, (2) not involving the orbit, (3) involving the orbital floor and potentially the orbital adnexae but the eye remains in situ, (4) with orbital enucleation or exenteration, (5) orbitomaxillary defect (ie, without involving the alveolus), and (6) nasomaxillary defect. The horizontal classification involves (a) a palatal defect only, not involving the dental alveolus, (b) less than or one-half unilateral, (c) less than or equal to one-half bilateral transverse anterior, and (d) greater than one-half maxillectomy. In addition to using this classification, it is also valuable to consider the bony buttresses of the midface. The key bony buttresses to consider in midface reconstruction as per Yamamoto and colleagues are the horizontal–zygomaticomaxillary (infraorbital) and vertical nasomaxillary buttress, and the oblique pterygomaxillary (zygomatic buttress) ( Fig. 2 ). Having an understanding of these buttresses helps the reconstructive surgeon to choose the ideal reconstructive option.

Fig. 1
Brown’s horizontal and vertical classification of maxillary and midface defects.
(Reprinted with permission from Elsevier. From Brown JS, Shaw RJ. Reconstruction of the maxilla and midface: Introducing a new classification. Lancet Oncol. 2010;11(10):1002.)

Fig. 2
Skull model demonstrating the principle of midfacial buttresses for reconstruction. NMB, nasomaxillary buttress; PMB, pterygomaxillary buttress; ZMB, zygomaticomaxillary buttress.

The Birmingham approach to midfacial defect reconstruction

In this section, we discuss our approach to complex maxillary and midfacial reconstruction and demonstrate various cases where this approach was used ( Fig. 3 ).

Fig. 3
Flow diagram reflecting the Birmingham approach to maxillary reconstruction based on the Brown classification. Note each defect type is color coded to include the additional steps for each reconstructive option for that particular defect.

Class I defects

In class I and some class II defects (IIa and low-level and posterior IIb), the goal of reconstruction is closure of an oroantral or oronasal fistula and dental rehabilitation. When the patient is dentate, very good results are achieved with either prosthetic obturation or soft tissue reconstruction alone or in combination with zygomatic implants. When the class IIb defect is posterior to the canine or first premolar, there is no advantage to bony reconstruction in these cases.

Class II defects

In anterior or large class IIb, II2, or IId defects, there is significant loss of cheek and upper lip support, which requires an underlying bony framework to preserve facial form and symmetry. In these cases, our preference is the fibula free flap. The fibula is ideal in these cases because it can provide a substantial length of bone, has a long pedicle, has a reliable soft tissue skin paddle, and provides a good bony framework for dental implants. In hemimaxillectomy (class IIb/IIc) defects, the fibula can either be used to recreate the shape of the alveolar arch ( Figs. 4 and 5 ) or it can be reliably used to recreate the pterygomaxillary buttress. In class II defects, the reconstruction can often be done with a single straight strut of fibula ( Fig. 6 ), but it may need to incorporate multiple osteotomies if the anterior maxilla is too prognathic in relationship to the zygoma or if the defect crosses the midline. The fibula used in this way can often provide adequate soft tissue support for the cheek and upper lip and it provides a framework for implant rehabilitation for at least the anterior teeth. Even in a class IId defect, the fibula provides adequate bone length for complete maxillary low-level reconstruction.

Aug 5, 2020 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Three-Dimensional Computer-Assisted Surgical Planning and Manufacturing in Complex Maxillary Reconstruction

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