Surgical reconstruction of maxillary defects using a computer-assisted design/computer-assisted manufacturing-produced titanium mesh supporting a free flap

Efficiency and Applicability of Virtual Surgical Planning in Maxillofacial and Mandibular Bone Reconstruction: A Narrative Review

Background: Facial structures are critical to aesthetics and function. Deformities can cause significant problems. Advances in surgical techniques, including three-dimensional (3D) computer simulation and virtual surgical planning (VSP), have improved outcomes. VSP accurately predicts surgical outcomes, revolutionizing facial reconstruction. This article reviews VSP in facial bone reconstruction, highlighting its advantages and accuracy over traditional methods. Methods: A systematic search using Medline (PubMed), Web of Science, Scopus, and Google Scholar revealed 1645 articles that addressed the topic of this study. Results: The systematic search yielded 64 articles that were highly relevant to the study objective, underscoring the critical importance of virtual surgical planning (VSP) in enhancing surgical precision and patient satisfaction. VSP has become a key player in improving surgical interventions and reducing complications, reinforcing its role as the preferred method in modern reconstructive surgery and thus improving functional and aesthetic outcomes, significantly enhancing patient satisfaction, and ensuring accurate interpretation of treatment plans. When compared to traditional surgical planning (TSP), VSP offers increased accuracy, shorter operating times, and superior aesthetic outcomes. Conclusions: VSP has been shown to effectively manage the complex challenges of facial anatomy and has significantly enhanced the planning and execution of reconstructive surgeries. This has been achieved by leveraging advanced imaging and computer-aided design.

Delayed Maxillary Reconstruction with Free Osteocutaneous Fibula Flap Using CAD-CAM Technology

Background  Maxillary reconstruction poses unique challenges for the reconstructive surgeon because of the complex three-dimensional (3D) anatomy of the maxilla. Undertaking this endeavor on secondary reconstruction makes it more difficult due to problems in recreating the true defect. This study is an attempt to demonstrate the role of virtual surgical planning (VSP), 3D printing, and mock surgery in reconstructing such defects using free fibula flaps. Materials and Methods  This was a prospective study involving 10 patients of maxillary defects who underwent delayed reconstruction with a free fibula flap. The planning was done preoperatively using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. A mock surgery with 3D printed models was done before the surgery. After the surgery, the accuracy results were obtained by overlapping and measuring fixed point distances between preoperative virtual planning and postoperative computed tomography (CT) scan data. Results and Discussion  Nine patients underwent successful reconstruction and were satisfied with the outcome. One patient had flap loss. The mean shift along the horizontal, vertical, and 3D axes was less than 5 mm between the preoperative virtual planning and postoperative CT scan data, indicating accurate reconstruction. We also suggest strategies for soft-tissue and bony inset including inferolateral pedicle origin, anteriorly facing lateral fibular surface, and two bony struts for the alveolus. Conclusion  VSP and CAD-CAM technology in maxillary reconstructions help achieve an anatomically accurate neo-maxilla. The addition of mock surgery to the routine and the use of cutting guide avoid unpredictability and reduce the need for adaptation activities on the operating table. CAD-CAM technology despite its limitations is invaluable in maxillary reconstruction and is an important tool for a reconstructive plastic surgeon.

Multiple Buttresses Reconstruction of Maxilla with Fibular Flap Using Computer-aided Design/Computer-aided Manufacturing after Maxillectomy

Background

The maxilla comprises horizontal and vertical buttresses, each with specific functions, supporting various organs, such as the eyes, nose, and oral cavity. Notably, they combine to form a three-dimensional structure, which enables the buttresses to provide their inherent support strength. However, reconstructing the maxilla after maxillectomy by assembling new buttresses is challenging. We successfully reconstructed all the buttresses crucial for facial appearance and dental rehabilitation using a vascularized fibular flap.

Methods

Four patients underwent maxillary buttress reconstruction with a fibular flap after total or subtotal maxillectomy. We used computer-aided design/computer-aided manufacturing digital technology to osteotomize the fibula into multiple segments and assemble them to reconstruct the maxillary buttresses. Each buttress was assembled based on a preoperative simulation.

Results

All patients underwent immediate one-stage maxillary reconstruction. They had good maxillary buttress alignment and acquired good facial appearance, eye position, nasal airway, and prosthetically suitable maxillary alveolus ridge.

Conclusions

The combination of computer-aided design/computer-aided manufacturing digital technology and surgical techniques has enabled novel maxillary reconstruction, providing great hope to patients experiencing facial disfigurement and loss of function after maxillectomy.

Comparative analysis of GoPro and digital cameras in head and neck flap harvesting surgery video documentation: an innovative and efficient method for surgical education

BACKGROUND

An urgent need exists for innovative surgical video recording techniques in head and neck reconstructive surgeries, particularly in low- and middle-income countries where a surge in surgical procedures necessitates more skilled surgeons. This demand, significantly intensified by the COVID-19 pandemic, highlights the critical role of surgical videos in medical education. We aimed to identify a straightforward, high-quality approach to recording surgical videos at a low economic cost in the operating room, thereby contributing to enhanced patient care.

METHODS

The recording was comprised of six head and neck flap harvesting surgeries using GoPro or two types of digital cameras. Data were extracted from the recorded videos and their subsequent editing process. Some of the participants were subsequently interviewed.

RESULTS

Both cameras, set at 4 K resolution and 30 frames per second (fps), produced satisfactory results. The GoPro, worn on the surgeon's head, moves in sync with the surgeon, offering a unique first-person perspective of the operation without needing an additional assistant. Though cost-effective and efficient, it lacks a zoom feature essential for close-up views. In contrast, while requiring occasional repositioning, the digital camera captures finer anatomical details due to its superior image quality and zoom capabilities.

CONCLUSION

Merging these two systems could significantly advance the field of surgical video recording. This innovation holds promise for enhancing technical communication and bolstering video-based medical education, potentially addressing the global shortage of specialized surgeons.

Delayed Orbital Floor Reconstruction Using Mirroring Technique and Patient-Specific Implants: Proof of Concept

Enophthalmos is a severe complication of primary reconstruction following orbital floor fractures, oncological resections, or maxillo-facial syndromes. The goal of secondary orbital reconstruction is to regain a symmetrical globe position to restore function and aesthetics. In this article, we present a method of computer-assisted orbital floor reconstruction using a mirroring technique and a custom-made titanium or high-density polyethylene mesh printed using computer-aided manufacturing techniques. This reconstructive protocol involves four steps: mirroring of the healthy orbit computer tomography files at the contralateral affected site, virtual design of a customized implant, computer-assisted manufacturing (CAM) of the implant using Direct Metal Laser Sintering (DMLS) or Computer Numerical Control (CNC) methods, and surgical insertion of the device. Clinical outcomes were assessed using 3dMD photogrammetry and computed tomography measures in 13 treated patients and compared to a control group treated with stock implants. An improvement of 3.04 mm (range 0.3-6 mm) in globe protrusion was obtained for the patients treated with patient-specific implants (PSI), and no major complications have been registered. The technique described here appears to be a viable method for correcting complex orbital floor defects needing delayed reconstruction.

Stacked fibula flap for unilateral total maxillectomy reconstruction with orbital preservation

Unilateral total maxillectomy is indicated for locally advanced maxillary tumors that require complete removal of the midface bony structure and inferior orbital rim. Reconstruction of this defect is challenging due to aesthetic and functional concerns. A retrospective review of patients at two tertiary-care institutions undergoing unilateral total maxillectomy reconstruction with a stacked fibula flap from 2018 to 2022 was performed. Each patient's clinical course was reviewed, and attention was focused on the demonstration of surgical steps with photos. Twenty patients underwent stacked fibula flap reconstruction for unilateral total maxillectomy orbital preservation defects. Surgical extirpation was performed for malignancy (80%, 16/20) and for osteoradionecrosis or benign tumor in 20% (4/20). The complication rate was 30% (6/20). Most flaps survived (95%, 19/20). We present a modified, reproducible method of fibula flap reconstruction for unilateral total maxillectomy with orbital preservation that only requires two segments and maintains positive aesthetic and functional results.

Application of CAD-CAM Technologies for Maxillofacial Bone Regeneration: A Narrative Review of the Clinical Studies

The application of regenerative methods in treating maxillofacial defects can be categorized as functional bone regeneration in which scaffolds without protection are used and in-situ bone regeneration in which a protected healing space is created to induce bone formation. It has been shown that functional bone regeneration can reduce surgical time and obviate the necessity of autogenous bone grafting. However, studies mainly focused on applying this method to reconstruct minor bone effects, and more investigation concerning the large defects is required. In terms of in situ maxillofacial bone regeneration with the help of CAD-CAM technologies, the present data have suggested feasible mesh rigidity, perseverance of the underlying space, and apt augmentative results with CAD-CAM-based individualized Ti meshes. However, complications, including dehiscence and mesh exposure, coupled with consequent graft loss, infection and impeded regenerative rates have also been reported.

The state of virtual surgical planning in maxillary Reconstruction: A systematic review

Virtual surgical planning (VSP) and computer aided design utilization in head and neck reconstruction has become increasingly popular within the discipline. Advocates of the technology over traditional free hand surgery cite benefits including improved intraoperative efficiencies and postoperative outcomes that have been demonstrated during mandibular reconstruction. More recently, VSP for maxillary and mid facial reconstruction, generally considered more complex than their mandibular counterparts, have been applied with the hopes of similar benefits. However, our literature search revealed no large-scale randomized control trial substantiating these benefits. As such, the aim of this review was to synthesize the existing research on utilization of VSP in the context of maxillary reconstruction. Three databases were systematically searched for articles pertaining to maxillary reconstruction for oncologic, traumatic, or osteoradionecrosis indications. Four hundred and fourteen unique articles were reviewed by two independent reviewers ultimately revealing sixteen studies appropriate for qualitative synthesis including 142 patients. Results of our studies reveal the extreme heterogenicity of application of this technology under the label of virtual surgical planning. Outcome reporting methods were grossly inconsistent amongst all the articles resulting in inability to appropriately synthesize data quantitatively for a meta-analysis. Overall, there was no standard of reporting outcomes of maxillary reconstruction, and no randomized trials comparing virtual surgical planning versus freehand surgery and therefore there is insufficient data to objectively prove purported benefits. To facilitate future comparative studies, a minimal standard of reporting for maxillary VSP is presented and the need for a randomized control trial is highlighted.

Clinical Application of 3D-Printed Patient-Specific Polycaprolactone/Beta Tricalcium Phosphate Scaffold for Complex Zygomatico-Maxillary Defects

(1) Background: In the present study, we evaluated the efficacy of a 3D-printed, patient-specific polycaprolactone/beta tricalcium phosphate (PCL/β-TCP) scaffold in the treatment of complex zygomatico-maxillary defects. (2) Methods: We evaluated eight patients who underwent immediate or delayed maxillary reconstruction with patient-specific PCL implants between December 2019 and June 2021. The efficacy of these techniques was assessed using the volume and density analysis of computed tomography data obtained before surgery and six months after surgery. (3) Results: Patients underwent maxillary reconstruction with the 3D-printed PCL/β-TCP scaffold based on various reconstructive techniques, including bone graft, fasciocutaneous free flaps, and fat graft. In the volume analysis, satisfactory volume conformity was achieved between the preoperative simulation and actual implant volume with a mean volume conformity of 79.71%, ranging from 70.89% to 86.31%. The ratio of de novo bone formation to total implant volume (bone volume fraction) was satisfactory with a mean bone fraction volume of 23.34%, ranging from 7.81% to 66.21%. Mean tissue density in the region of interest was 188.84 HU, ranging from 151.48 HU to 291.74 HU. (4) Conclusions: The combined use of the PCL/β-TCP scaffold with virtual surgical simulation and 3D printing techniques may replace traditional non-absorbable implants in the future owing to its accuracy and biocompatible properties.

Navigation-assisted maxillofacial reconstruction: accuracy and predictability

The aim of this study was to evaluate the accuracy of navigation-assisted maxillofacial reconstruction and to identify the predictors of the clinical outcomes. A total of 112 patients who underwent navigation-assisted maxillofacial reconstruction with free flaps between 2014 and 2019, performed by a single surgical team, were assessed. Accuracy was evaluated by superimposing the postoperative computed tomography data with the preoperative virtual surgical plan. Predictors of the clinical outcomes affecting the accuracy were identified and analysed. The mean deviation and root mean square (RMS) estimate of the orbital, maxillary, and mandibular reconstructions were 0.88 ± 3.25 mm and 3.38 ± 0.73 mm, 0.77 ± 3.44 mm and 3.69 ± 0.82 mm, and 1.07 ± 4.16 mm and 4.67 ± 3.95 mm, respectively (P < 0.05). There was no significant difference in orbital volume or projection between the preoperative, postoperative, and healthy orbits (P = 0.093 and P = 0.225, respectively). Multivariate linear regression analysis confirmed significant associations between the accuracy of navigation-assisted mandibular reconstruction and preservation of the condyle, type of reconstruction, type of osteosynthesis plate, and number of bony segments. Navigation-assisted midface reconstruction yielded a higher level of accuracy in the final surgical outcome when compared to mandibular reconstruction. Computer-assisted techniques and intraoperative navigation can be an alternative or adjunct to current surgical techniques to improve the final surgical outcome, especially in more complex maxillofacial reconstructions.

Determination of ultra-trace levels of titanium in human serum using inductively coupled plasma tandem mass spectrometry based on O2/H2 reaction gas

This study proposes a new strategy to determine ultra-trace Ti in human serum using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). The human serum samples were diluted with 1% (v/v) HNO₃, followed by the determination of ultra-trace Ti using ICP-MS/MS. In the MS/MS mode, a small amount of H₂ was mixed with O₂ (the reaction gas) in a collision reaction cell (CRC) to form an O₂/H₂ reaction mixture, and then, the conversion of Ti⁺ to TiO⁺ was determined by the O₂ mass shift method. High concentrations of Ca, S, and P in human serum were ionized in plasma, and the formed Ca⁺, SO⁺, and PO ⁺ reacted with O₂ in CRC to form CaO⁺, SO₂⁺, and PO₂⁺ to interfere with the determination of TiO⁺. We employed the mass shift reaction of H₂ and oxide ions to eliminate this interference. This method was evaluated using the human serum sample spike recovery experiment and comparative analysis by sector field (SF)-ICP-MS. The results showed that using reaction gas mixture O₂/H₂ reduced the background equivalent concentration (BEC) of Ti and improved sensitivity. The values determined by this method were consistent with the SF-ICP-MS values, which confirmed its accuracy and reliability. The limit of detection (LOD) of Ti was 0.78-7.20 ng L^-1, the recovery was 96.0%-104%, and the relative standard deviation (RSD) was 2.0%-4.2%. This method has solved the problem that the determination of ultra-trace Ti in human serum cannot be accurately determined using O₂ reaction mode. It realizes the interference-free and highly sensitive determination of the ultra-trace Ti in samples with high levels of Ca, S, and P and provides a new technique for high-throughput and accurate determination of ultra-trace Ti in human serum.

Long-term Effect of Individualized Titanium Mesh in Orbital Floor Reconstruction After Maxillectomy

OBJECTIVE

The aim of this study was to determine the clinical outcomes and long-term stability of individualized titanium mesh combined with free flap for orbital floor reconstruction after maxillectomy and to identify the risk factors for titanium mesh exposure.

MATERIAL AND METHODS

The data of 66 patients who underwent maxillectomy and orbital floor defect reconstruction by individualized titanium mesh in Peking University School and Hospital of Stomatology between 2011 and 2019 were retrospectively reviewed. Postoperative ophthalmic function and success of aesthetic restoration were assessed. Titanium mesh exposure was recorded and the risk factors were identified.

RESULTS

Mean follow-up was for 24.8 months (range, 6-92 months). Ophthalmic function was successfully restored in 63/66 patients. Aesthetic restoration was not considered satisfactory by 10 patients. Titanium mesh exposure occurred in six patients (exposure rate, 9.1%). Preoperative radiotherapy was identified as an independent risk factor for mesh exposure (OR = 28.8, P = 0.006). Previous surgery, postoperative radiotherapy, pathological type of the primary lesion, the type of tissue flap applied, and the use of intraoperative navigation were not significant risk factors. Six patients with titanium mesh exposure underwent second surgery, but mesh exposure recurred in two patients due to insufficient soft tissue coverage.

CONCLUSION

Individualized titanium mesh with free flap can effectively restore maxilla-orbital defects. Preoperative radiotherapy is an independent predictor of postoperative titanium mesh exposure. Adequate soft tissue coverage of the mesh may reduce the risk of mesh exposure.

LEVEL OF EVIDENCE

Level 4 (case-control study) Laryngoscope, 2021.

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.

Facial Reconstruction: A Systematic Review of Current Image Acquisition and Processing Techniques

Introduction: Plastic and reconstructive surgery is based on a culmination of technological advances, diverse techniques, creative adaptations and strategic planning. 3D imaging is a modality that encompasses several of these criteria while encouraging the others. Imaging techniques used in facial imaging come in many different modalities and sub-modalities which is imperative for such a complex area of the body; there is a clear clinical need for hyper-specialized practice. However, with this complexity comes variability and thus there will always be an element of bias in the choices made for imaging techniques. Aims and Objectives: The aim of this review is to systematically analyse the imaging techniques used in facial reconstruction and produce a comprehensive summary and comparison of imaging techniques currently available, including both traditional and novel methods. Methods: The systematic search was performed on EMBASE, PubMed, Scopus, Web of Science and Cochrane reviews using keywords such as "image technique/acquisition/processing," "3-Dimensional," "Facial," and "Reconstruction." The PRISMA guidelines were used to carry out the systematic review. Studies were then subsequently collected and collated; followed by a screening and exclusion process with a final full-text review for further clarification in regard to the selection criteria. A risk of bias assessment was also carried out on each study systematically using the respective tool in relation to the study in question. Results: From the initial 6,147 studies, 75 were deemed to fulfill all selection criteria and selected for meta-analysis. The majority of papers involved the use of computer tomography, though the use of magnetic resonance and handheld scanners using sonography have become more common in the field. The studies ranged in patient population, clinical indication. Seminal papers were highlighted within the group of papers for further analysis. Conclusions: There are clearly many factors that affect the choice of image acquisition techniques and their potential at being ideal for a given role. Ultimately the surgical team's choice will guide much of the decision, but it is crucial to be aware of not just the diagnostic ability of such modalities, but their treatment possibilities as well.

Clinical and volumetric outcomes after vertical ridge augmentation using computer-aided-design/computer-aided manufacturing (CAD/CAM) customized titanium meshes: a pilot study

Background

One of the most recent innovations in bone augmentation surgery is represented by computer-aided-design/computer-aided-manufacturing (CAD/CAM) customized titanium meshes, which can be used to restore vertical bone defects before implant-prosthetic rehabilitations. The aim of this study was to evaluate the effectiveness/reliability of this technique in a consecutive series of cases.

Methods

Ten patients in need of bone augmentation before implant therapy were treated using CAD/CAM customized titanium meshes. A digital workflow was adopted to design virtual meshes on 3D bone models. Then, Direct Metal Laser Sintering (DMLS) technology was used to produce the titanium meshes, and vertical ridge augmentation was performed according to an established surgical protocol. Surgical complications, healing complications, vertical bone gain (VBG), planned bone volume (PBV), lacking bone volume (LBV), regenerated bone volume (RBV), average regeneration rate (RR) and implant success rate were evaluated.

Results

All augmented sites were successfully restored with definitive implant-supported fixed partial dentures. Measurements showed an average VBG of 4.5 ± 1.8 mm at surgical re-entry. Surgical and healing complications occurred in 30% and 10% of cases, respectively. Mean values of PBV, LBV, and RBV were 984, 92, and 892 mm³, respectively. The average RR achieved was 89%. All 26 implants were successfully in function after 1 year of follow-up.

Conclusions

The results of this study suggest that the bone augmentation by means of DMLS custom-made titanium meshes can be considered a reliable and effective technique in restoring vertical bone defects.

The application of 3D-printed titanium mesh in maxillary tumor patients undergoing total maxillectomy

OBJECTIVE

To evaluate the clinical outcomes of reconstruction of maxillary class III defect using 3D-printed titanium mesh.

METHODS

Twelve patients with maxillary class III defect from April 2015 to December 2016 were retrospectively studied. A 3D individualized maxillary stereo model based on mirror images of the unaffected maxilla was obtained to fabricate an anatomically adapted titanium mesh using computer-assisted design and manufacture. The individual titanium mesh was inserted into the maxillary class III defect after total maxillectomy. The incidence of postoperative complications was evaluated. The postoperative orbital volume and protrusion degree of eye were measured.

RESULTS

All patients were satisfied with their postoperative facial symmetry, without developing diplopia or endophthalmos. The postoperative orbital volumes were 26.41 ± 0.52 mL on the affected side and 26.55 ± 0.45 mL on the unaffected side. The postoperative protrusion degrees of affected and unaffected eyes were 16.21 ± 0.48 and 16.82 ± 0.79 mm, respectively. Titanium mesh exposure was observed in 2 patients and mild limitation of mouth opening was observed in 4 patients who underwent postoperative radiotherapy.

CONCLUSION

Reconstruction of maxillary class III defect with 3D-printed titanium mesh can achieve successful clinical outcomes, which recovered orbital volume and protrusion degree of eye. Twelve patients with maxillary class III defect were satisfied with their postoperative facial symmetry, without developing diplopia or endophthalmos. We investigated that reconstruction of maxillary class III defect with 3D-printed titanium mesh can achieve successful clinical outcomes.

[Rational choice of revascularized autograft in midface reconstruction]

The article presents an analysis of the results of the use of revascularized autografts in the plastic elimination of combined defects in the middle zone of the face. Difficulties and negative moments of each of them were revealed and recommendations were given on the rationality of their clinical application with the development of the algorithm of surgical tactics.

Single-Unit 3D-Printed Titanium Reconstruction Plate for Maxillary Reconstruction: The Evolution of Surgical Reconstruction for Maxillary Defects-A Case Report and Review of Current Techniques

The complex 3-dimensional anatomy of the facial skeleton creates a unique challenge for surgical reconstruction. Even more difficult is the precise reconstruction of the maxilla owing to its lack of solid bony support after large resections. Virtual surgical planning (VSP) technology has many applications in head and neck surgery, such as preoperative planning, fabrication of cutting guides and stereolithographic models, and fabrication of custom implants. We present the case of a patient who had undergone surgical resection of a mucoepidermoid carcinoma of the maxilla and immediate reconstruction with a vascularized free fibula flap using VSP. Using a custom 3-dimensional, titanium printed plate, which corresponded precisely with the surgical defect, the maxilla and midface were reconstructed to ideal dimensions with no unplanned surgical manipulation and a shorter overall operating time. We have described the technique and reviewed the pertinent reported data.

Low-cost, self-made CAD/CAM-guiding system for mandibular reconstruction

Facial symmetry, as well as function, remains the big challenge for surgeons who attempt mandibular reconstruction. Nowadays several studies recommend the use of computer aided surgery (CAS) and CAD/CAM technology to guide mandibular segmental osteotomies and reconstruction using free fibula flap. Although these systems have radically changed the way of doing mandibular reconstructive surgery, they are expensive and require extended periods of time for prototypation. This may be an important limitation in case of malignant neoplasms which require short-term treatment. The aim of our study is to investigate the reliability and efficiency of a protocol to obtain cutting guides produced in a "homemade" way. This study includes four consecutive patients who underwent a segmental mandibulectomy and fibula osteo-cutaneous free flap reconstruction for oral squamous cell carcinoma between January and September 2016. The CAD/CAM system algorithm proposed was based on the use of free open source software for digital planning and 3D layer plastic deposition printer. A cost of about 3 Euro for each case was estimated. An average mean distance between 3D preoperative and postoperative mesh points of 1.631 mm and a standard deviation of 5.496 mm has been demonstrated by 3D volume overlay analysis. Overlapping results with much shorter prototyping time was required with the in-house procedure described as compared to the available commercial system. In conclusion, we expect that this technique will reduce operative time and cost however further study and large series are needed to confirm our results and better define the applicability in everyday surgical practice.

Development of a novel anatomical thin titanium mesh plate with reduction guidance and fixation function for Asian zygomatic-orbitomaxillary complex fracture

For this study we developed an anatomical thin titanium mesh (ATTM) plate for Asian zygomaticomaxillary complex (ZMC) fracture repair with reduction guidance and fixation function. The ATTM plate profile was designed as an L-shape to fix at the anterior maxilla and lateral buttress of the ZMC. Computer-aided stamping analysis was performed on four screw-hole patterns in the ATTM plate - a control without screw-holes, square screw-holes, double screw-holes, and large-diameter, double screw-holes - using upper/lower dies of averaged ZMC reconstruction models. A regular ATTM plate of 0.6 mm thickness was manufactured and pre-bent using a patient-matched stamping process to verify its feasibility on three ZMC fracture models with one, two, and three fracture segments. The stamping analysis found that the double screw-holes design resulted in the most favorable performance among all the designs because of maximum von Mises stress (408 MPa) under the ultimate tensile strength. Positioning practice showed that the stamped, pre-bent ATTM plate can be used as a reduction guide to provide precise ZMC segment fixation in a completely passive fashion while limiting redundant rotation/micromovement between the separate bones in all directions. This study concluded that the ATTM plate with double screw-hole pattern design, using a patient-matched, pre-bent technique, can fit the ATTM plate/ZMC interface well, decrease mobility of unstable fracture segments, and provide good original facial contour recovery, while improving reduction efficiency.

Navigation-guided resection of maxillary tumours: The accuracy of computer-assisted surgery in terms of control of resection margins - A feasibility study

INTRODUCTION

Surgical treatment of maxillary tumours is often highly complex. The three-dimensional anatomy of the mid-face renders both correct intraoperative orientation and adequate oncological safety difficult to obtain. Recently, computer-assisted techniques and intraoperative navigation have been applied to oncological surgery treating head and neck cancer. However, only a few studies have explored whether preoperative virtual resection planning and intraoperative control of resection margins allow assessment of the surgical margins of the tumour. In our present feasibility study, we developed a protocol for preoperative mapping of tumour margins using computed tomography and/or magnetic resonance imaging, virtual planning of the surgical resection, and intraoperative navigation during actual resection of advanced maxillary tumours.

MATERIALS AND METHODS

Twenty patients were included in this feasibility study. We prospectively selected ten patients requiring surgery to treat malignant maxillary tumours. A control group of ten patients was retrospectively selected. The simulation protocol featured the following steps: 1. "Contouring" of the tumour: identification of the tumour and the borders thereof on the axial, sagittal, and coronal planes; 2. Definition of the resection margins by positioning "landmarks" at least 1 cm from the tumour edges on the axial, sagittal, and coronal planes; 3. Simulation of osteotomy lines passing through the landmarks, and evaluation of the bony defects to be reconstructed. Tumour margins were controlled by using a pointer to identify mobilised regions and then checking the overlap between the planned resection (shown on the LCD screen of the navigation system) and the real anatomical situation.

RESULTS

A total of 127 margins were pathologically assessed in the test group, and 85 were assessed in the control group. Overall, 9% of surgical margins were positive in the test group, and 16% were positive in the control group (p = 0.0047). A significant difference was apparent in terms of deep margin evaluation: in test patients, 87% of margins were clear; this figure was 75% for the control group (p = 0.0038). No significant difference in either mucosal or bone margin clearance was evident. The preoperative planning errors were <5 mm for 91% of all planned resection margins.

CONCLUSION

The navigation-guided resection protocol seems to improve tumour-free margin status in patients with advanced maxillary tumours. Further confirmatory trial, enrolling a larger cohort of patients, is needed to strengthen these preliminary results and advantages of this procedure.