Accuracy of computer-assisted surgery in mandibular reconstruction: A postoperative evaluation guideline

Three-dimensional assessment of upper airway changes associated with mandibular positional deviations following fibula free flap reconstruction

OBJECTIVES

Fibula free flaps (FFF) are the standard approach to mandibular reconstruction after partial resection, with the goal of restoring aesthetics and masticatory function. The graft position affects both and must be carefully selected. Correlations between sagittal positioning and upper airway anatomy are known from orthognathic surgery. This study aims to evaluate changes in mandibular position and upper airway anatomy after reconstructive surgery with FFF and corresponding correlations.

MATERIALS AND METHODS

Mandibular position after reconstruction was evaluated using three-dimensional datasets of pre- and postoperative computed tomography scans of patients treated between 2020 and 2022. Three-dimensional measurements were performed on both condyles and the symphyseal region. Changes in upper airway volume and minimum cross-sectional area (minCSA) were analysed. Intra-rater reliability was assessed. Correlations between changes in upper airway anatomy and sagittal mandibular position were tested.

RESULTS

The analysis included 35 patients. Intra-rater reliability was good to excellent. Condylar deviations and rotations were mostly rated as small. Changes in symphyseal position were considerably greater. Median airway volume decreased in the oropharynx and hypopharynx. Posterior deviation of the symphysis was associated with a decreasing minCSA in the hypopharynx and vice versa.

CONCLUSIONS

The overall accuracy of mandibular reconstructions with FFF is high, but there is room for optimization. The focus of research should be extended from masticatory to respiratory rehabilitation.

CLINICAL RELEVANCE

Effects on respiratory function should be considered prior to graft positioning. The clinical relevance of upper airway changes within the complex rehabilitation of reconstructive surgery patients needs to be further investigated.

Cutting guides in mandibular tumor ablation: Are we as accurate as we think?

Purpose

Tumor margin status is critical in local tumor recurrence and is a significant prognostic factor in head and neck cancer survival. With the introduction of computer-assisted surgical planning, one of the main challenges is the accurate positioning of the surgical cutting guide but there is limited evidence of the accuracy of the 3D cutting guides in mimicking virtually planned osteotomy. This study evaluates the accuracy of osteotomy lines produced by 3D-printed cutting guides and assesses the overall accuracy of mandibular reconstruction.

Material and Methods

The pre and postoperative 3D models were aligned using an automated surface registration feature based on the iterative closest point algorithm. The differences in osteotomy line deviation, linear and angle measurements, and 3D volume quantification of the pre and post models were measured.

Results

We included 14 patients (8 men and 6 women with ages ranging from 13 to 75 years) with a segmental mandibular resection who met all of the inclusion criteria. The smallest defect size was 4.4 cm, the largest defect was 12.2 cm, and the average was 7.30 cm +/- 2.80 cm. The average deviation between virtually planned osteotomy and actual surgical osteotomy was 1.52 +/-1.02 mm. No covariates were associated with increased inaccuracy of the 3D-printed cutting guides.

Conclusion

The finding of this study suggests that virtual surgical planning is an unambiguous paradigm shift in the predictability of the surgical plan and achievement of the reconstruction goals. The 3D-printed cutting guides are a very accurate and reliable tool in translating virtual ablation plans to an actual surgical resection margin.

Deep Circumflex Iliac Artery Flap Reconstruction in Brown Class I Defect of the Mandible Using a Three-Component Surgical Template System

BACKGROUND

Computer-assisted surgery is widely used in mandibular reconstruction, but the process is not well described for cases using the deep circumflex iliac artery flap (DCIA) as the donor site. This study aimed to present a DCIA-based three-component surgical template system (3-STS) in patients with a mandibular Brown class I defect.

METHODS

This retrospective cohort study compared clinical outcomes of mandibular reconstruction with DCIA flap using 3-STS or conventional surgical templates. The primary outcome of the study was the accuracy of reconstruction, and the secondary outcomes included surgical time and bone flap ischemia time. Surgery-related parameters and functional outcomes were also recorded and compared.

RESULTS

Forty-four patients (23 in the 3-STS group and 21 in the control group) between 2015 and 2021 were included. Compared with the control group, the 3-STS group had higher accuracy of reconstruction, indicated by lower deviation in absolute distance (1.45 ± 0.76 mm versus 2.02 ± 0.89 mm; P = 0.034), and less deviation in coronal and sagittal angles (0.86 ± 0.53 degree versus 1.27 ± 0.59 degrees, P = 0.039; and 2.52 ± 1.00 degrees versus 3.25 ± 1.25 versus, P = 0.047) between preoperative and postoperative computed tomographic imaging. Surgical time and bone flap ischemia time were significantly reduced in the 3-STS group compared with the control group (median time, 385 minutes versus 445 minutes and 32 minutes versus 53 minutes, respectively; P < 0.001). In addition, masseter attachment was preserved in the 3-STS group but not in the control group. No differences were found in adverse events or other clinical variables.

CONCLUSION

The 3-STS can improve accuracy, simplify intraoperative procedures to increase surgical efficiency, and preserve functionality in mandibular reconstruction for Brown class I defects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Tenants of Mandibular Reconstruction in Segmental Defects

The premises of mandibular reconstruction are the restoration of occlusion and mandibular contour for the purpose of preserving the facial identity, oral airway, and effective speech and mastication. Establishing functional occlusion is the primary tenant in all mandibular reconstruction. In cases of segmental defects, particularly in dentate regions of the mandible, there has been a paradigm shift over the past two decades in how surgeons are approaching the restoration of load-bearing mandibular continuity with capacity for dental implantation. Here we discuss considerations for deciding the most effective method of reconstruction in segmental defects.

Cutting-edge patient-specific surgical plates for computer-assisted mandibular reconstruction: The art of matching structures and holes in precise surgery

Objectives

Cutting-edge patient-specific surgical plates (PSSPs) are supposed to improve the efficiency, precision, and functional outcomes of mandibular reconstruction. This study characterized the premium role of PSSPs in precise surgery and explored their working principles in computer-assisted mandibular reconstruction (CAMR).

Methods

The PSSPs-enhanced surgical precision was investigated through the model surgery and representative cases. Spatial deviations of reconstruction were characterized by comparing the reconstructed mandible with the virtually designed mandible. Working principles of PSSPs were distinguished by a review of evolving surgical techniques in CAMR.

Results

In the model surgery, spatial deviations between the virtually planned mandible and the reconstructed mandible were 1.03 ± 0.43 mm in absolute distance deviation, 1.70 ± 1.26 mm in intercondylar length, and 1.86 ± 0.91 mm in intergonial length in the study group of PSSPs, significantly smaller than in the control group of conventional prebent surgical plates. Meanwhile, in the study group, distance deviations were 0.51 ± 0.19 mm in bone-plate distance and 0.56 ± 0.28 mm in drilled screw holes, indicating the art of matching structures and holes. The PSSPs-enhanced CAMR was further demonstrated in three representative cases of mandibular reconstruction. Finally, four primary techniques of CAMR were summarized based on a review of 8,672 articles. The premium role of PSSPs was distinguished by the benefits of matching structures and holes.

Conclusions

The PSSPs-enhanced surgical precision was verified through the model surgery and demonstrated in human surgery. Compared to other surgical techniques of CAMR, PSSPs contributed to the precise surgery by the art of matching structures and holes.

Accuracy of virtual surgical planning in mandibular reconstruction: application of a standard and reliable postoperative evaluation methodology

OBJECTIVE

The purpose of this study was to determine the accuracy of virtual surgical planning for mandibular reconstruction, along with the implementation of a postoperative evaluation methodology.

MATERIALS AND METHODS

The study is a prospective case series for computer-assisted mandibular reconstruction surgery. Analysis of the degree of agreement between virtual measurements and postoperative actual outcomes was performed. The reliability of the proposed evaluation methodology was assessed and analyzed using the Inter-Class Coefficient (ICC) test. Statistical significance was set at the 5% level.

RESULTS

Nine consecutive patients were selected. The analysis of all angular and linear parameters reported a highly statistically significant degree of agreement between the preoperative and postoperative measurements (P < 0.001). Furthermore, an extreme degree of reliability was reported when the evaluation methodology was scrutinized (ICC = 0.9).

CONCLUSION

The excellent degree of agreement between the virtual plan and the actual outcome reported in this study validated the surgical accuracy of virtually assisted mandibular reconstruction. This study pointed out the reliability and reproducibility of the standardized evaluation protocol in an attempt to obtain a tolerable value for the acceptable postoperative results regarding the accuracy of computer-assisted surgery.

Virtual planning and 3D-printed guides for mandibular reconstruction: Factors impacting accuracy

Objectives

Examine accuracy and factors impacting accuracy for mandibular reconstruction with virtual surgical planning, 3D printed osteotomy guides and preoperatively bent mandibular reconstruction plate (VSP/3Dprinted-guide/plate).

Method

Retrospective review of osseous-free-flap mandibular reconstructions with VSP/3Dprinted-guide/plate between January 2015 and July 2020 at a single academic medical center.Patient demographics, disease, and treatment variables were extracted. Accuracy was assessed by 3D-model-overlay with cephalometric and donor-bone segment length measurements. Multivariate analyses were performed to determine factors impacting cephalometric accuracy.

Results

60 cases met criteria: 41 (68%) cancer, 14 (23%) osteoradionecrosis (ORN), 5 (8%) secondary mandibular reconstruction. Thirteen cases (22%) were Brown class III or IV. Thirty-nine cases (65%) had ≥2 flap bone segments. Average donor-bone length was 82 mm (SD: 28). 3D-model-overlay accuracy demonstrated minimal deviation between planned and actual reconstruction: intercondylar distance = 2.10 mm (SD: 2.2); intergonial distance = 2.23 mm (SD: 1.9); anterior-posterior distance (APD) = 1.76 mm (SD: 1.5); gonial angle (GA) = 3.11 degrees (SD: 2.4). Mean change in donor-bone segment length inferiorly was 2.67 mm (SD: 2.6) and superiorly 3.27 mm (SD: 3.2). Higher number of donor-bone segments was associated with decreased accuracy in GA (p = .023) and longer donor-bone length was associated with decreased accuracy in APD (p = .031).

Conclusion

To our knowledge this is the largest series assessing surgical accuracy of VSP/3Dprinted-guide/plate for osseous-free-flap mandibular reconstruction. We demonstrate highly accurate results, with increased number of donor-bone segments and donor-bone length associated with decreased accuracy. Our findings further support VSP/3Dprinted-guide/plate as a reliable and accurate tool for mandibular reconstruction.

Level of Evidence

Level 4.

Three-dimensional evaluation of condylar position after mandibular reconstruction with a fibula free flap—comparison of different surgical techniques

Three-dimensional positional changes of the temporomandibular joint after mandible reconstruction using microvascular fibula flaps were investigated in 58 patients. The results of preoperative virtually planned surgery, intraoperative resection- and cutting-guided surgery, and non-guided surgery were compared. Pre- and postoperative computed tomography data of each patient were processed and superimposed digitally. The condyle deviations and rotations along the axes and planes of the skull, as well as Euclidean distances, were determined. Reliability analyses, descriptive statistics, and non-parametric tests were performed with the alpha level set at P = 0.05. Reliability proved to be excellent for all variables. The median Euclidean distance was 2.07 mm for the left condyle and 2.11 mm for the right condyle. Deviations of ≥ 10 mm occurred in nine (16%) cases. The maximum deviation occurred in the horizontal plane and the least deviation in the sagittal plane. Median rotation was ≤ 1.4° around all axes. The condylar displacements did not differ significantly between the different surgical techniques investigated. The three-dimensional measurement method applied is highly reliable for evaluating the three-dimensional condylar position after mandibular reconstruction.

The Amsterdam UMC protocol for computer-assisted mandibular and maxillary reconstruction; A cadaveric study

OBJECTIVES

In this cadaveric study, the accuracy of CAS guided mandibular and maxillary reconstruction including immediate dental implant placement in different Brown defect classes is assessed.

MATERIALS AND METHODS

The virtual planning and surgical procedure was conducted according to a newly proposed Amsterdam UMC reconstruction protocol. Postoperative evaluation was performed according to a previously proposed evaluation guideline.

RESULTS

Fourteen mandibular and 6 maxillary reconstructions were performed. Average mandibular angle deviations were 1.52°±1.32, 1.85°±1.58, 1.37°±1.09, 1.78°±1.37, 2.43°±1.52 and 2.83°±2.37, respectively for the left and right axial angles, left and right coronal angles and left and right sagittal angles. A total of 62 dental implants were placed in neomandibles with an average dXYZ values of 3.68 ± 2.21 mm and 16 in neomaxillas with an average dXYZ values of 3.24 ± 1.7 mm.

CONCLUSION

Promising levels of accuracy were achieved for all mandibular angles. Dental implant positions approached the preoperative preferred positions well, within the margin to manufacture prosthetic devices.

A Comprehensive Approach for Measuring Spatial Deviations of Computer-Assisted Mandibular Reconstruction

BACKGROUND

Computer-assisted surgery has become the mainstream in mandibular reconstruction, but the lack of a standard measuring approach for spatial deviations of mandible hinders postoperative verification and the comparison of different subjects. This study aims to set up a comprehensive approach for measuring spatial deviations of computer-assisted mandibular reconstruction.

METHODS

A systematic review was conducted to extract all measurements for computer-assisted mandibular reconstruction. Thereafter, eligible measurements were included in the authors' comprehensive approach, which categorized the measurements according to different anatomical structures and landmarks.

RESULTS

A total of 80 studies were included in the authors' systematic review, and 31 measurements were extracted. The authors established a comprehensive panel of anatomical landmarks to facilitate measurement, including parts, points, lines, planes, and angles. These measurements encompassed spatial deviations of the overall mandible, condyle, gonial angle, bone grafts, midline, surgical plate, osteotomy, and miscellaneous indicators. A calculation spreadsheet was developed to collect landmarks and compute deviations automatically with built-in formulas. Finally, a simplified panel of measurements was recommended for spatial deviations of mandibular reconstruction.

CONCLUSIONS

A comprehensive approach for measuring spatial deviations of computer-assisted mandibular reconstruction was established. Future studies will confirm this approach as an effective and scientific system for postoperative verification of computer-assisted mandibular reconstruction.

Reconstruction of the mandibular symphysis: pilot study compares three different flaps

BACKGROUND

Restoration of mandibular continuity, functionality and attempting to return patients to their premorbid state is the ultimate goal of reconstruction. Some studies compare different flaps but the reconstructed portions vary and there is little consensus on the best option for a particular defect.

METHODS

This pilot study compares three different reconstructive options with free flap. We will analyze the accuracy of the reconstruction, the post-operative complications related to the reconstruction, the morbidity of the donor site. This pilot study compares three different reconstructive options with free flap in the reconstruction of the mandibular symphysis: iliac crest, scapula and fibula.

RESULTS

In our sample the morbidity of the donor site was overlapping, as for all three choices free from complications. In post resection edentulous patients, the fibula seems to guarantee better positioning, while in patients with residual occlusion the iliac crest (figure n.4 and n.5) seems to allow a more congruous repositioning. The fibula seems to have a superiority over the other flaps in terms of accuracy in all types of patient.

CONCLUSIONS

Contrary to the most recent work on the accuracy of CAD / CAM, we have analyzed the error in the reconstruction of a specific segment and in the repositioning of the residual mandibular component without the use of guided computer programming.

Accuracy of Computer-Assisted Surgery in Maxillary Reconstruction: A Systematic Review

Computer-assisted surgery (CAS) in maxillary reconstruction has proven its value regarding more predictable postoperative results. However, the accuracy evaluation methods differ between studies, and no meta-analysis has been performed yet. A systematic review was performed in the PubMed, Embase, and Cochrane Library databases, using a Patient, Intervention, Comparison and Outcome (PICO) method: (P) patients in need of maxillary reconstruction using free osteocutaneous tissue transfer, (I) reconstructed according to a virtual plan in CAS software, (C) compared to the actual postoperative result, and (O) postoperatively measured by a quantitative accuracy assessment) search strategy, and was reported according to the PRISMA statement. We reviewed all of the studies that quantitatively assessed the accuracy of maxillary reconstructions using CAS. Twelve studies matched the inclusion criteria, reporting 67 maxillary reconstructions. All of the included studies compared postoperative 3D models to preoperative 3D models (revised to the virtual plan). The postoperative accuracy measurements mainly focused on the position of the fibular bony segments. Only approximate comparisons of postoperative accuracy between studies were feasible because of small differences in the postoperative measurement methods; the accuracy of the bony segment positioning ranged between 0.44 mm and 7.8 mm, and between 2.90° and 6.96°. A postoperative evaluation guideline to create uniformity in evaluation methods needs to be considered so as to allow for valid comparisons of postoperative results and to facilitate meta-analyses in the future. With the proper validation of the postoperative results, future research might explore more definitive evidence regarding the management and superiority of CAS in maxillary and midface reconstruction.

A Novel Treatment Concept for Advanced Stage Mandibular Osteoradionecrosis Combining Isodose Curve Visualization and Nerve Preservation: A Prospective Pilot Study

Background

Osteoradionecrosis (ORN) of the mandible is a severe complication of radiation therapy in head and neck cancer patients. Treatment of advanced stage mandibular osteoradionecrosis may consist of segmental resection and osseous reconstruction, often sacrificing the inferior alveolar nerve (IAN). New computer-assisted surgery (CAS) techniques can be used for guided IAN preservation and 3D radiotherapy isodose curve visualization for patient specific mandibular resection margins. This study introduces a novel treatment concept combining these CAS techniques for treatment of advanced stage ORN.

Methods

Our advanced stage ORN treatment concept includes consecutively: 1) determination of the mandibular resection margins using a 3D 50 Gy isodose curve visualization, 2) segmental mandibular resection with preservation of the IAN with a two-step cutting guide, and 3) 3D planned mandibular reconstruction using a hand-bent patient specific reconstruction plate. Postoperative accuracy of the mandibular reconstruction was evaluated using a guideline. Objective and subjective IAN sensory function was tested for a period of 12 months postoperatively.

Results

Five patients with advanced stage ORN were treated with our ORN treatment concept using the fibula free flap. A total of seven IANs were salvaged in two men and three women. No complications occurred and all reconstructions healed properly. Neither non-union nor recurrence of ORN was observed. Sensory function of all IANs recovered after resection up to 100 percent, including the patients with a pathologic fracture due to ORN. The accuracy evaluation showed angle deviations limited to 3.78 degrees. Two deviations of 6.42° and 7.47° were found. After an average of 11,6 months all patients received dental implants to complete oral rehabilitation.

Conclusions

Our novel ORN treatment concept shows promising results for implementation of 3D radiotherapy isodose curve visualization and IAN preservation. Sensory function of all IANs recovered after segmental mandibular resection.

Three-dimensional virtual surgical planning in the oncologic treatment of the mandible

OBJECTIVES

In case of surgical removal of oral squamous cell carcinomas, a resection of mandibular bone is frequently part of the treatment. Nowadays, such resections frequently include the application of 3D virtual surgical planning (VSP) and guided surgery techniques. In this paper, current methods for 3D VSP leads for optimisation of the workflow, and patient-specific application of guides and implants are reviewed.

RECENT FINDINGS

Current methods for 3D VSP enable multi-modality fusion of images. This fusion of images is not restricted to a specific software package or workflow. New strategies for 3D VSP in Oral and Maxillofacial Surgery include finite element analysis, deep learning and advanced augmented reality techniques. These strategies aim to improve the treatment in terms of accuracy, predictability and safety.

CONCLUSIONS

Application of the discussed novel technologies and strategies will improve the accuracy and safety of mandibular resection and reconstruction planning. Accurate, easy-to-use, safe and efficient three-dimensional VSP can be applied for every patient with malignancies needing resection of the mandible.

Sequential application of novel guiding plate system for accurate transoral mandibular reconstruction

OBJECTIVES

The aim of this article is to introduce and share our experience in the sequential use of a novel guiding plate system for accurate mandibular reconstruction via transoral approach and evaluate its clinical effects.

METHODS

Ten patients were operated with transoral mandibulectomy and simultaneous mandibular reconstruction using a novel guiding plate system. Postoperatively, aesthetic assessment and quantitative evaluation were analyzed by measuring the parameters like discrepancy in osteotomy lines, mandibular similarity and symmetry. The independent samples t-test was used and P < 0.05 was considered as significant.

RESULTS

All patients underwent planned transoral surgical procedure successfully. The postoperative aesthetic assessment was rated as excellent. The discrepancy between virtual and actual osteotomy lines, at anterior and posterior regions was 0.80 ± 0.08 and 0.98 ± 0.37 mm, respectively. The postoperative evaluation revealed that mandibular similarity was 0.85 ± 0.03, coronal mandibular angle (CMA) 0.66 ± 0.40, axial mandibular angle (AMA) 1.97 ± 1.25, and sagittal mandibular angle (SMA) 1.97 ± 1.05. There was statistically significant difference in the mean values of osteotomy line discrepancy, mandibular similarity and symmetry, among novel guiding plate and traditional plate groups.

CONCLUSIONS

The novel guiding plate system is a viable and easy-to-use technology for improving the surgical outcomes in patients requiring transoral mandibulectomy and simultaneous mandibular reconstruction by overcoming the problem of limited access due to the presence of lips and cheeks. This can highly improve the precision in osteotomy, fixation of the prebent titanium reconstruction plate, spatial relation transfer, and achieving better symmetry and similarity of mandibular contour.

Three-Dimensionally Printed Patient-Specific Surgical Plates Increase Accuracy of Oncologic Head and Neck Reconstruction Versus Conventional Surgical Plates: A Comparative Study

Background

Surgeons are pursuing accurate head and neck reconstruction to enhance aesthetic and functional outcomes after oncologic resection. This study aimed to investigate whether accuracy of head and neck reconstruction is improved with the use of three-dimensionally (3D)-printed patient-specific surgical plates compared with conventional plates.

Methods

In this comparative study, patients were prospectively recruited into the study group (3DJP16) with 3D-printed patient-specific surgical plates. The patients in control group with conventional surgical plates were from a historic cohort in the same unit. The primary end point of the study was the accuracy of head and neck reconstruction. The secondary end points were accuracy of osteotomy, intraoperative blood loss, total operative time, and length of hospital stay.

Results

The study recruited of 33 patients, including 17 in the study group and 16 in the control group. The patients’ baseline characteristics were similar between the two groups. The absolute distance deviation of the maxilla or mandible was 1.5 ± 0.5 mm in the study group and 2.1 ± 0.7 mm in the control group [mean difference, − 0.7 mm; 95% confidence interval (CI) − 1.1 to − 0.3; p = 0.003], showing superior accuracy of reconstruction for the patients with 3D-printed patient-specific surgical plates. Improved accuracy of reconstruction also was detected in terms of bilateral mandibular angles and bone grafts. Concerning the secondary end points, the accuracy of the osteotomy was similar in the two groups. No difference was found regarding intraoperative blood loss, total operative time, or length of hospital stay.

Conclusions

This is the first study to prove that compared with conventional plates, 3D-printed patient-specific surgical plates improve the accuracy of oncologic head and neck reconstruction.

Electronic supplementary material

The online version of this article (10.1245/s10434-020-08732-y) contains supplementary material, which is available to authorized users.

Combination of CAD/CAM and Augmented Reality in Free Fibula Bone Harvest

Supplemental Digital Content is available in the text.

The CAD/CAM technology for mandibular reconstruction has improved the results in terms of outcomes in restoring mandibular complex defects. Augmented reality (AR) represents an evolution of the navigation-assisted surgery. This technology merges the images of the virtual planning with the anatomy of the patient, representing in this way an enhanced scene for the surgeon’s eye. AR can also display in a single scene additional information for the surgeon. Despite of classical navigation, this scenario can be obtained with marker-less registration method, without using reference points or fiducial markers. This technologic evolution together with the large use in our experience of CAD/CAM protocol for mandibular reconstruction we developed this feasibility study to evaluate the possibility of using a marker-less image registration system. Moreover, we tried to evaluate the overlaying of the virtual planning and its reproducibility using AR. We performed a case series of 3 consecutive patients who underwent mandibular reconstruction using AR-assisted fibular free flap harvesting applying our digital workflow. Once launched, the mobile app installed on our tablet, the registration is performed according to a shape recognition system of the leg of the patient, rendering in real time a superimposition of the anatomy of the bony, vascular, and skin of the patient and also the surgical planning of the reconstruction. AR-assisted fibular free flap harvesting was performed. We believe that AR can be a prospective improving technology for mandibular complex reconstruction.