Alignment of the Double-Barrel Fibula Free Flap for Better Cosmesis and Bone Height for Osseointegrated Dental Implants:

Modeling Methods in Craniofacial Virtual Surgical Planning

Despite the widespread use of virtual surgical planning (VSP), few papers describe the modeling methods used to generate the digital simulations that underpin VSP. This paper aims to review the modeling methods that are currently available for use in VSP and the implications of their use in clinical practice. A literature review was undertaken of the two broad categories of modeling techniques; contour-based planning-namely mirroring from the contralateral side, templating from a normative database, and extrapolation from surrounding landmarks-and occlusal-based planning (OBP). The indications for each modeling method were discussed, including mandibular/maxillary reconstruction, pediatric craniofacial surgery, and orthognathic, as well as the limitations to the accuracy of modeling types. Unilateral defects of the upper/midface, wherein contour accuracy is paramount, are best reconstructed using mirroring methods, whereas bilateral defects-or cases with asymmetry due to craniofacial dysmorphology-are most suited to normative-data-based methods. Cases involving resection of the alveolar margin, in which functional occlusion is the primary outcome are best managed with OBP. Similarly, orthognathic surgery typically uses OBP, although complex cases involving asymmetry, such as clefts, may benefit from a combination of OBP and normative data methods. The choice of modeling methods is, therefore, largely driven by the defect type and the goals of reconstruction.

Biomechanical Analysis of Various Reconstructive Methods for the Mandibular Body and Ramus Defect Using a Free Vascularized Fibula Flap

Several different methods exist for reconstructing the mandibular body and ramus defect with the use of a free vascularized fibula flap, but none have adequately addressed the long-term mechanical stability and osseointegration. The aim of this study is to compare the biomechanics of different surgical methods and to investigate the best approach for reconstructing the mandibular body and ramus defect. Five finite element models based on different reconstructive methods were simulated. Stress, strain, and displacement of connective bone sections were calculated for five models and compared. The models were printed using a 3D printer, and stiffness was measured using an electromechanical universal testing machine. The postoperative follow-up cone beam computed tomography (CBCT) was taken at different time points to analyze bone mineral density of connective bone sections. The results showed that the “double up” (DU) model was the most efficient for reconstructing a mandibular body and ramus defect by comparing the mechanical distribution of three sections under vertical and inclined loading conditions of 100 N. The stiffness detection showed that stiffness in the DU and “double down” (DD) models was higher compared with the “single up” (SU), “single down” (SD), and “distraction osteogenesis” (DO) models. We used the DU model for the surgery, and postoperative follow-up CBCT showed that bone mineral density of each fibular connective section increased gradually with time, plateauing at 12 weeks. We conclude that a free vascularized fibula flap of the DU type was the best approach for the reconstruction of the mandibular body and ramus defect. Preoperative finite element analysis and stiffness testing were shown to be very useful for maxillofacial reconstruction.

[Evolution of the mandibular defects reconstruction with free fibula flapx]

One of the most important steps in achieving aesthetical and functional result in mandible reconstruction with fibula free flap is positioning of the bony part relative to the basis of the native mandible. Positioning fibular bony part continuing inferior mandible border may produce a high discrepancy between the residual mandible and fibula bone that results in difficulty in denture rehabilitation. Positioning fibular bony part continuing alveolar mandible border creates asymmetric jowls and changed shape of jawline in border-line zone. The double-barrel technique solves this problem, but needs a meticulous preoperative planning and precision free fibula flap modelling.

Mandibular Reconstruction Based on the Concept of Double Arc Reconstruction

The natural mandible has 2 arcs, the marginal arc and the occlusal arc. The marginal arc is situated along the lower margin of the mandible and affects the contour of the lower third of the face. The occlusal arc is situated along the dental arc and affects the stability of prosthodontics. The gap between these 2 arcs widens in the molar area. Our developed concept of "double arc reconstruction" involves making these 2 arcs for the reconstructed mandible. For the double-barrel fibula reconstruction, 2 bone segments are used to make both arcs. For reconstructions using the iliac crest, the double arc is made by inclination of the top of the bone graft toward the lingual side. Ten patients underwent double arc reconstruction: 2 underwent reconstruction with the double-barrel fibula, and 8 underwent reconstruction with the iliac crest. Four patients had a removable denture prosthesis, 1 had an osseointegrated dental implant, and 5 did not require further prosthodontic treatment. The shape of the reconstructed mandible after double arc reconstruction resembles the native mandible, and masticatory function is good with the use of a dental implant or removable denture prosthesis, or even without prosthodontics.