Analysis of simulated mandibular reconstruction using a segmental mirroring technique
Introduction
A primary goal of oromandibular reconstruction is to preserve function through re-establishing mandibular continuity and maintaining symmetric contour (Cohen et al., 2009). Deforming pathologic processes of the mandible pose unique challenges to reconstructive surgeons as achieving optimal contour is necessary for restoring normal occlusion, which is influenced by the degree of deformation. Intraoperative adaptation of a reconstruction plate over a distorted segment of bone will result in an inadequate fit between the plate and bone graft potentially leading to malocclusion, temporomandibular joint dysfunction and an increased risk for plate extrusions (Abou-elfetouh et al., 2011, Li et al., 2011, Lee et al., 2007). However, this is also dependent on the extent and location of defect following resection (Brown et al., 2016).
A recently developed technique involves digitally removing a tumor of the mandible using a CT generated three-dimensional (3D) computer model, filling the defect with a “mirrored”, or inverted, image of the unaffected contralateral segment of the mandible and printing a 3D stereolithographic model to bend a reconstruction plate. While this technique has been reported in various case studies to be successful in reconstruction of the mandible secondary to deforming tumors (e.g. ameloblastoma, etc), trauma and osteoradionecrosis, no study has examined the accuracy of this method using quantitative parameters based on the classification of defect (Cohen et al., 2009, Lee et al., 2007, Hannen, 2006, Khalifa et al., 2016, Singare et al., 2004).
Numerous systems have been proposed for classifying mandibular defects resulting from segmental mandibulectomy. More recently, Brown et al. (2016) developed a classification system based on the most commonly encountered defects following oncologic resection (Brown et al., 2016). This system categorizes defects into four classes with subclasses for inclusion of the mandibular condyle (Table 1). The location and extent of resection often dictates the type of osteocutaneous/osseous free flap reconstruction. Other factors in determining type of flap include age, comorbidities, occupational/recreational activities and decisions regarding dental rehabilitation. The fibular, scapular and iliac crest free flaps are among the most commonly selected (Brown et al., 2016).
The objective of the study was to determine the degree of conformance between simulated mandibular defects, based on the Brown et al. (2016) classification system, and the corresponding inverted segments of the contralateral mandible using high resolution CT generated 3D computer models.
Section snippets
Study design and sample selection
The study population was comprised of patients randomly selected from an institutional melanoma database between January 1, 2005 and September 30, 2015 (Princess Margaret Cancer Centre, Department of Otolaryngology, University Health Network). To be included in the study, patients must have completed high resolution CT imaging of the head/neck with minimal metal artifacts from dentures and fillings. Patients were excluded from the study if there was evidence of bony disease involving the
Results
This retrospective cross-sectional study included a total of 10 patients (6 males, 4 females; mean age 55 ± 18; age range 31–85) that met criteria for inclusion and exclusion.
Discussion
Given that segmental mirroring has been reported as a successful technique within case reports in the literature, our hypothesis was that a high degree of conformance would be observed, but that variability would exist dependent on defect class of the mandible to be simulated for reconstruction (Cohen et al., 2009, Lee et al., 2007, Hannen, 2006, Khalifa et al., 2016, Singare et al., 2004). This was borne out by the data which demonstrated that mirrored segments from each of the four classes
Conclusion
While an overall high degree of conformance can be achieved when modeling the mandible using a segmental mirroring technique, variations exist that are dependent on the classification of defect. These variations should be taken into consideration when pre-planning for surgery. Inclusion of the condyle within a model will result in reduced conformance when using the mirroring technique. While modeling of class III reconstructions using the mirroring technique demonstrated the highest degree of
Acknowledgments
This work is funded by the Guided Therapeutics (GTx) Program, University Health Network, Strobele Family GTx Research Fund, Kevin and Sandra Sullivan Chair in Surgical Oncology, Hatch Engineering Fellowship Fund, and Princess Margaret Hospital Foundation.
References (12)
- et al.
A new classification for mandibular defects after oncological resection
Lancet Oncol
(2016) - et al.
Mandibular reconstruction using stereolithographic 3-dimensional printing modeling technology
Oral Surg Oral Med Oral Pathol Oral Radiol Endod
(2009) - et al.
Stereolithographic modeling technology applied to tumor resection
J Oral Maxillofac Surg
(2005) Recreating the original contour in tumor deformed mandibles for plate adapting
Int J Oral Maxillofac Surg
(2006)- et al.
Segmental mirroring: does it eliminate the need for intraoperative readjustment of the virtually pre-bent reconstruction plates and is it economically valuable?
J Oral Maxillofac Surg
(2016) - et al.
Mandibular defect reconstruction with the help of mirror imaging coupled with laser stereolithographic modeling technique
J Formos Med Assoc
(2007)
Cited by (21)
Patient-centred outcomes and dental implant placement in computer-aided free flap mandibular reconstruction: a systematic review and meta-analysis
2022, British Journal of Oral and Maxillofacial SurgeryCitation Excerpt :Use of computerised surgical planning (CSP) and computer-aided design and manufacturing (CAD/CAM) is on the rise in plastic and reconstructive surgery, with free flap mandibular reconstruction recognised as one of the most common applications of these technologies.1 CSP allows surgeons to optimise the surgical plan by mirroring the contralateral portion of the mandible,2 integrating angiographic data of the donor site,3,4 and facilitating coordination with teams performing mandibular resection and dental restoration.5,6 Subsequently, CAD/CAM increases fidelity to the virtual plan through 3D-printed surgical cutting guides,3,6–10 templates for pre-bending reconstruction plates,6,11,12 and prefabricated patient-specific reconstruction plates.13
Tomographic similarity scan with a computed modified absolute mandibular midsagittal plane for precise and objective localization of mandibular asymmetry
2021, Computers in Biology and MedicineCitation Excerpt :Traditionally, asymmetry evaluation was performed on an anteroposterior 2D projection parallel to the coronal plane [5]; however, it is prone to errors due to overlapping structures, magnification, and variation in head posture during capture [6]. Three-dimensional (3D) evaluation with cone-beam computed tomography (CBCT) has gained popularity, but the analytical means are primarily the same [7]. Irrespective of the imaging method, these analyses include identifying landmarks forming median reference planes to measure asymmetry.
Objective evaluation of orbito-zygomatic reconstruction with scapular tip free flaps to restore facial projection and orbital volume
2021, Oral OncologyCitation Excerpt :The preclinical study included 20 measurements from a random sample of CT scans from 10 subjects with unaltered zygomatic and scapular anatomy. Using a technique developed in the Guided Therapeutics (GTx) Laboratory at the University Health Network, a conformance analysis [6,8] was performed for both cohorts. Briefly, the whole method consists of importing computer tomographic images into a computer workstation, where bone and soft tissues are differentiated by density threshold combined with manual contouring.
Comparing Contour Restoration of Mandibular Body Defects With Fibula, Iliac Crest, and Scapular Tip Flaps: A Conformance Virtual Study
2021, Journal of Oral and Maxillofacial SurgeryCitation Excerpt :Overall conformance between each bony flap and the matched bony-angle segment of the mandible was measured as the mean root-mean-square (RMS) conformance distance (mm) (Fig 1D). RMS conformance distance is a measure of morphologic similarity as described in prior studies,12 and its value is inversely proportional to the morphologic similarity between structures. In addition, contour conformance was calculated, and was defined as the conformance between the lateral surface of each flap already positioned and the lateral aspect of the mandible (comparison of the lateral aspects only) (Fig 1E).
Scapular tip-thoracodorsal artery perforator free flap for total/subtotal glossectomy defects: Case series and conformance study
2020, Oral OncologyCitation Excerpt :The scapular tip was superimposed to the FOM volume manually, using the contoured mandible as visual guide to obtain the best alignment. Overall conformance between the scapular tip and FOM volume was measured as the mean root-mean-square (RMS) conformance distance (mm), which is a parameter providing a metric for morphologic similarity, as described in prior studies [28–30]. Moreover, conformance between the surface of the anterior border of the scapular tip and corresponding lingual aspect of the mandible (hereby defined “border conformance”) was measured with the same method (Fig. 2).
Computer-aided designed 3D-printed polymeric scaffolds for personalized reconstruction of maxillary and mandibular defects: a proof-of-concept study
2024, European Archives of Oto-Rhino-Laryngology
- 1
The first two authors (Joel C Davies and Harley HL Chan) equally contributed to the production of this manuscript.