Search

Navigation-assisted surgery is the gold standard for complex reconstructive procedures of the midface and facial skeleton, and artificial and anatomical landmarks are often used for reference. The correct identification of these landmarks before surgery is crucial for the accuracy of the navigation system. This study aimed to investigate the human errors in reference point placement. This retrospective study investigated 228 reference-point positions in 51 cases where navigation was utilized. The discrepancies between the actual reference point-position and manually planned preoperative reference points were quantified using Brainlab iPlanCMF 3.0.6. The referencing methods used in these cases included dental registration splints, osteosynthesis materials, anatomical landmarks, and combinations of these methods. The average discrepancy in the actual and manually planned reference points was 0.29 ± 0.41 mm. The use of anatomical landmarks demonstrated a significantly lower deviation (p < 0.05), although the differences between the errors in reference-point placement using dental registration splints, osteosynthesis materials, or combinations of these methods were not statistically significant. The frequency of misplacement of reference points was significantly higher than expected. These errors might have been caused by human bias during manual placement of the points or intraoperative difficulties caused by extensive metal artifacts. Thus, we postulate that the surgical personnel involved in planning navigation-assisted surgery should undergo intensive training. The development of new referencing methods that are less susceptible to these causes of error might help overcome human bias., Competing Interests: Declaration of Competing Interest The authors declare that there is no conflict of interest regarding this original article., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Often, midfacial defects are not only relevant regarding functional aspects but also esthetics of such congenital or acquired deformities impair significantly the patients' quality of life. Reconstructions of the midface do not only include replacing lost or non-developed tissue but moreover to achieve predictable results with regard to esthetics as well as function for the individual patient. Digital planning modalities including different surface and volume data in combination with modern additive manufacturing techniques for biomodel and implant production and intraoperative support by using real and virtual 3D volume data for navigation and intraoperative imaging, but also securing the outcome based on postoperative analysis have been implemented in modern midface reconstruction and represent new standards for medical care. The objective of this paper is to describe modern options of patient-specific midfacial reconstruction with integration of computer-assisted planning and production techniques., Competing Interests: Prof. Gellrich und Dr. Rahlf haben Vortragstätigkeiten für Gebrüder Martin GmbH mit Honorarvergütung., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).)

Posttraumatic reconstruction of the neurocranium and viscerocranium is an essential part of modern oral and maxillofacial surgery, in addition to oncological surgery, surgery of congenital craniofacial deformities and dental surgery. Due to the complex anatomy of the facial skull and significant esthetic and functional demands on its reconstruction, reconstructive trauma surgery in this area places the highest demands on the surgeon. This is all the more true if definitive craniomaxillofacial surgical treatment can sometimes only be performed with considerable delays for the benefit of other life-threatening injuries. In order to take these prerequisites into account, achievements of modern biomedical technology, such as intraoperative real-time navigation, computer-assisted planning and computer-assisted manufacturing (CAD/CAM) of patient-specific biomodels and implants, came up early for use in oral and maxillofacial surgery. In combination with intraoperative three-dimensional imaging, these methods result in a treatment pathway tailored to the individual patient, which is directly checked for quality at every step and thus ensures the best possible result for the patient. The use of these technologies extends far beyond the original indications in the area of orbital reconstruction and restoration of bony defects with simple geometry, such as skull defects. Nowadays, even the most complex pan-facial fractures can be restored esthetically and functionally by means of digitalized preliminary planning and individualized skull, orbital and zygomatic implants as well as total temporomandibular joint prostheses., (© 2021. Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Competing Interests: Disclosure The authors have nothing to disclose.

Intraorbital space-occupying lesions always pose a challenge, both in terms of definite surgical removal as well as preoperative sampling for histopathological examination. Despite the use of modern high-resolution imaging techniques, the dignity of orbital lesions can often not be determined with sufficient certainty preoperatively. As the amount and complexity of treatment possibilities continue to increase, detailed diagnostics in advance of treatment choice are essential. Histological classification of orbital lesions can still be considered the gold standard for reliable diagnoses, leading to appropriate treatment. Over recent years minimally invasive surgical approaches have gained more importance in the treatment and diagnosis of cranio-maxillo-facial tumor and trauma. The aim of our study was to adapt and establish a precise procedure for orbital biopsies. 23 patients suffering from space-occupying lesions of unknown dignity were included. Trajectory-guided procedures were pre-planned for all cases. In most cases minimally invasive procedures were suitable for taking biopsies of the orbit. For only two patients a conventional, non-minimally invasive, lateral orbitotomy had to be performed. Further evaluation of the presented procedure demonstrates clearly that trajectory-guided biopsies of the orbit can be performed correctly and effectively, regardless of the suspected lesion's size., (Copyright © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

The benefit of computer-assisted planning in orthognathic surgery has been extensively documented over the last decade. This study aims to evaluate the accuracy of a virtual orthognathic surgical plan by a novel three dimensional (3D) analysis method. Ten patients who required orthognathic surgery were included in this study. A virtual surgical plan was achieved by the combination of a 3D skull model acquired from computed tomography (CT) and surface scanning of the upper and lower dental arch respectively and final occlusal position. Osteotomies and movement of maxilla and mandible were simulated by Dolphin Imaging 11.8 Premium ® (Dolphin Imaging and Management Solutions, Chatsworth, CA). The surgical plan was transferred to surgical splints fabricated by means of Computer Aided Design/Computer Aided Manufacturing (CAD/CAM). Differences of three dimensional measurements between the virtual surgical plan and postoperative results were evaluated. The results from all parameters showed that the virtual surgical plans were successfully transferred by the assistance of CAD/CAM fabricated surgical splint. Wilcoxon's signed rank test showed that no statistically significant deviation between surgical plan and post-operational result could be detected. However, deviation of angle U1 axis-HP and distance of A-CP could not fulfill the clinical success criteria. Virtual surgical planning and CAD/CAM fabricated surgical splint are proven to facilitate treatment planning and offer an accurate surgical result in orthognathic surgery., (Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

In this study, selective laser melted patient specific functional implants (PSFI) were utilised in combination with a fibula free flap, for mandible reconstruction. The shape and length of the PSFI, the shaping of fibula graft, its angulation and the length of the screws, were virtually planned before the surgery. Information, such as resection margin and screw lengths, were coded on the implant. 22 patients were reconstructed with PSFI and fibula transplantation. Data collected related to the size of the defect, pre- and postoperative intercondylar distance, ischemia time, time consumed to shape the fibula graft and complications. All patients were reconstructed as planned. Depending on the extension of the defect, the fibula grafts were shaped into different shapes, within 41.6 ± 4.9 min. The mean difference of pre- and post-operational condyle distances was 1.2 ± 1.4 mm. Postoperative complications such as wound healing disturbance and plate exposure occurred in 8 patients. All PSFIs remained within reconstruction sites during the follow up period. 8 out of the 22 patients had full dental rehabilitation with implants. Based on our results, the use of PSFIs in the reconstruction of mandibular segmental defects may contribute to a better clinical outcome. Further work will be required in order to evaluate their mechanical properties in detail., (Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Purpose: Computer-assisted surgery is used for decision making, treatment, and quality control throughout the reconstruction process of unilateral midface defects. The current approaches exploit the symmetry of the face by mirroring the intact side on the defect side using various segmentation methods. All commercially available implementations, however, are somewhat time consuming and dependent on the level of expertise of the user. We present a method for automatic reconstruction of unilateral midface defects using registration., Material and Methods: To reconstruct a skull by registration, the defect volume has to be virtually deleted from the skull. This modified data set is then mirrored and registered onto the original, defect-free skull. The fusion of these two skulls is the virtual reconstructed skull bridging the defect. Reconstruction by registration was performed for 24 different skulls without motion or dental restoration artifacts. Subsequently, simulation was performed with four accurately defined, various-sized, defects of the orbito-zygomatic complex. The results of the automated virtual reconstructions were compared with those obtained for the same defects as determined using conventional atlas-based planning software (iPlan). To simulate various clinical situations, four groups each containing six skulls were evaluated: the complete skull, midface and neurocranium, midface and lower jaw, and midface alone. The differences were compared using the similarity coefficients of Sørensen-Dice and Jaccard. Statistical analyses were performed using the t-test and Mann-Whitney U test., Results: The reconstruction results were similar for all the groups. The Sørensen-Dice coefficients of similarity for all reconstructed skulls were 0.869 and 0.874 for the registration and atlas-based reconstructions, respectively. The corresponding Jaccard coefficients were 0.774 and 0.781, respectively. Atlas-based reconstruction showed significantly better results in group 3 (midface and lower jaw) alone., Conclusion: Virtual automated reconstruction by registration had equivalent accuracy to conventional atlas-based reconstruction across a spectrum of defects, from simple orbital to complex orbito-zygomatic defects. However, for those involving the midface and lower jaw, atlas-based reconstruction showed significantly better results. Although the new approach is somewhat hardware demanding, it is user independent, dispensing with the need for time-consuming adjustments to the results of planning. The first clinical application of registration reconstruction revealed performance equivalent to that of the conventional approach., (Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Objectives: Clinical success of oral implants is related to primary stability and osseointegration. These parameters are associated with delicate surgical techniques. We herein studied whether template-guided drilling has a significant influence on drillholes diameter and accuracy in an in vitro model., Materials and Methods: Fresh cadaveric porcine mandibles were used for drilling experiments of four experimental groups. Each group consisted of three operators, comparing guide templates for drilling with free-handed procedure. Operators without surgical knowledge were grouped together, contrasting highly experienced oral surgeons in other groups. A total of 180 drilling actions were performed, and diameters were recorded at multiple depth levels, with a precision measuring instrument., Results: Template-guided drilling procedure improved accuracy on a very significant level in comparison with free-handed drilling operation (p ≤ 0.001). Inaccuracy of free-handed drilling became more significant in relation to measurement depth. High homogenic uniformity of template-guided drillholes was significantly stronger than unguided drilling operations by highly experienced oral surgeons (p ≤ 0.001)., Conclusion: Template-guided drilling procedure leads to significantly enhanced accuracy. Significant results compared to free-handed drilling actions were achieved, irrespective of the clinical experience level of the operator., Clinical Relevance: Template-guided drilling procedures lead to a more predictable clinical diameter. It shows that any set of instruments has to be carefully chosen to match the specific implant system. The current in vitro study is implicating an improvement of implant bed preparation but needs to be confirmed in clinical studies.

Purpose: Advances in technology have allowed increasing degrees of accuracy in the treatment of orbital deformities. The purpose of this study was to compare the accuracy of pre-bent titanium mesh (PBTM) and selective laser-melted patient-specific implants (PSIs) in unilateral orbital reconstruction after traumatic injury. The authors hypothesized that selective laser-melted PSIs would more accurately reconstruct the orbit., Materials and Methods: A retrospective review of 34 cases of primary reconstruction of unilateral orbital fractures treated using selective laser-melted PSIs (group 1, n = 17) or PBTM (group 2, n = 17) was performed. The primary outcome measurements were orbital volume excess and the anterior, medial, and posterior intraorbital angles. The Mann-Whitney U test was used to assess the difference in orbital volume and angular deviation between the 2 groups. The level of statistical significance was set at .05. All P values were 2-sided., Results: The comparison of mean values for the 2 groups showed significant differences for the anterior angle (PBTM: mean, 11.3; standard deviation [SD], 1.8; PSI: mean, 4.1; SD, 0.7; P = .001), but not the medial (PBTM: mean, 11.6; SD, 2.0; PSI: mean, 8.2; SD, 1.9; P = .170) and posterior (PBTM: mean, 10.8, SD, 2.8; PSI: mean, 8.2, SD, 1.4; P = .760) angles between the unaffected and reconstructed orbits. The postoperative difference in volume between the unaffected and reconstructed orbits differed significantly between the 2 study groups (PBTM: mean, 0.6; SD, 0.1; PSI: mean, 0.4; SD, 0.1; P = .029)., Conclusion: The results of this study suggest that complex orbital fractures can be reconstructed with an even higher degree of accuracy with selective laser-melted PSIs than with PBTM., (Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Introduction: In the treatment of cancer in the head and neck region, computer-assisted surgery can be used to estimate location and extent by segmentation of the tumor. This article presents a new tool (Smartbrush), which allows for faster automated segmentation of the tumor., Methods: This new method was compared with other well-known techniques of segmentation. Thirty-eight patients with keratocystic odontogenic tumors were included in this study. The tumors were segmented using manual segmentation, threshold-based segmentation and segmentation using Smartbrush. All three methods were compared concerning usability, time expenditure and accuracy., Results: The results suggest that segmentation using Smartbrush is significantly faster with comparable accuracy., Conclusions: After a period of adjustment to the program, one can comfortably get reliable results that, compared with other methods, are not as dependent on the user's experience. Smartbrush segmentation is a reliable and fast method of segmentation in tumor surgery., (Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Background: As a prerequisite in navigation-assisted surgery, a three-dimensional image data set with registration marker is necessary. Often patients are presented, not being aware of facing a computer-assisted surgical intervention (CAS), with an already performed computed tomography (CT) data set without marker. The aim of this study was to evaluate the accuracy of a new method which allows performing CAS by enhancing the initial markerless data set with a marked subvolume gained by cone beam (CBCT) scan., Methods: Therefore four registration markers are inserted and afterwards the patient is strongly limited to the field of interest scanned by CBCT scan (marked data set). Superimposed with the initial data set, a data set with reference markers and with full information is obtained. Registration procedure was performed with group A (25 patients, superimposed marked CBCT scan) and group B (25 patients, initially marked CT scan) using BrainLab® navigation by two observers and overall system accuracy was measured using the registration landmarks and additional intraoperative landmarks (tooth cusps)., Results: Adequate image quality assumed, no significant difference between group A and B was detected. Enhancing an initially performed data set with registration marker by using a marked subvolume could improve the workflow for navigation-assisted surgery due to the availability of cone beam scan technology, provide excellent resolution with reduced metal artifacts nearby dental restorations, and reduce radiation dose for the patient., Conclusion: Regarding the advantages of the new method which allows performing CAS by enhancing the initial markerless data set with a marked subvolume gained by cone beam (CBCT) scan, this technique will play a major part in navigation-assisted surgery and will address widespread general methodological solutions that are of great interest in multidisciplinary treatment., (Copyright © 2013 John Wiley & Sons, Ltd.)

Background: The aim of orbital wall reconstruction is to reestablish anatomically exact orbital volumes to avoid long-term complications. Navigation could facilitate complex reconstructions., Methods: Quality of the orbital reconstruction (n=94) was measured based on (A) volume changes and (B) on 3D shape deviations compared to the unaffected side. Volume analysis included segmentation of the orbital cavity in the pre- and post-operative 3D data set (VoXim®, IVS Solutions, Germany), and shape analysis was performed by vector-based 3D tools (Comparison®, 3Dshape, Germany)., Results: Orbital volume of the unaffected side ranged from 26.6 ml±2.8 ml in male and 25.2 ml±2.6 ml in female (CT). Significant orbital enlargement was found in orbital fractures with involvement of the posterior third of the orbital floor and in comminuted fracture pattern. Reconstructed orbital volume ranged from 26.9±2.7 ml in male and 24.26±2.5 ml in female (CBCT). 3D Analysis of the color mapping showed minor deviations compared to the mirrored unaffected side., Conclusion: Measurements demonstrate that even in comminuted orbital fractures true-to-original reconstruction is feasible.

Ablative surgery of the orbit is often associated with dramatic changes in facial geometry. Surgical intervention is often necessary to correct the functional and esthetic appearance in those patients who are anophthalmic, having an intact eyelid appearance and an orbital prosthesis. The outcome of the surgical correction depends on the shape of the orbital implants and their adequate placement. In the case of comparatively small rearrangements, the effect of implants on soft tissues can be estimated by surgeons on the basis of their experience. However, large deformities in complex cases (including large deformation of soft tissue or asymmetry) can be hardly predicted on the basis of simple empirical considerations. The purpose of the present technical note was to describe a new procedure of inverse design of customized orbital titanium meshes. To demonstrate this procedure, an anophthalmic patient with superior sulcus deformity and enophthalmos was enrolled. The volume and structure of the extraocular muscles, soft tissue, and bony structure of the orbital walls were examined using high-resolution multislice computed tomography. Next, a geometric model of the patient's anatomy was generated from the tomography data. Afterward, the orbital prosthesis was virtually relocated to a new position. Then, the desired correction of the particular soft tissue regions was performed using virtual sculpturing tools. Next, the deformation of the soft tissues and initial prosthesis boundaries were computed from the predefined displacements of the relocated tissue regions with the help of the Finite Element Method. The differential volume between the initial and designated position of the orbital prosthesis yielded the preferred implant shape required to effect the desired correction of soft tissue. During surgery, the preplanned position of the customized titanium meshes was guided using a navigation system. Although the inverse design of custom-tailored titanium meshes for precision treatment of severe enophthalmos in anophthalmic patients appears to be a promising approach, it has rarely been applied in the past because of the technological complexity and additional time required. With the present study, we have launched a series of clinical evaluations of this novel method. To date, scientific evidence and trials showing a predictable simulation using an inverse finite element approach in the correction of severe enophthalmos in anophthalmic patients with computer-assisted fabricated individual titanium meshes for reconstruction of orbital walls have been rare., (Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to evaluate the error magnitude in the clinical application of face-bow devices. Technical and methodologic inaccuracies, as well as deviations from reference planes, were determined., Materials and Methods: The presented method is part of a 3-dimensional virtual planning procedure for orthognathic surgery and included 15 patients with dentoskeletal deformities. Cone beam computed tomography datasets obtained from patients with a referenced face-bow plane and a centric registration splint were matched with cone beam computed tomography datasets of the registered plaster model of the maxilla mounted in an articulator. To assess potential sources of methodologic errors, angulations were measured between the virtual face-bow plane and the horizontal cross bar of the virtual articulator. To evaluate the reproducibility of the anatomic reference plane, angulations between the Frankfort plane and the horizontal cross bar of the articulator were measured. Statistical significance was set at P < .05 and tested by univariate analysis of variance., Results: Technical and methodologic errors showed a mean deviation of 3.5°, with a median of 3.6° and SD of 2.7°. The values did not reach statistical significance (P = .1). However, there was a significant error (P < .05) in determining the position of the anatomic reference plane by face-bow transfer. The mean deviation was 7.7° (values ranged between 1.2° and 18.9°), with a median of 6.7° and SD of 5.3°., Conclusions: In this study the traditional use of face-bow devices showed inaccuracies in model mounting as well as in assignment of anatomic reference planes. Three-dimensional virtual computer-assisted planning seems to be more accurate than conventional methods., (Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: Since 1911, when Dollinger first described surgical orbital decompression, many different techniques and approaches have been described, including 1-, 2-, and 3-wall decompressions with orbital fat removal. The indications for surgical treatment have been widened and include additional to optic neuropathy severe proptosis causing exposure keratopathy and disfigurement. Popular techniques for surgical decompression are the transantral or transpalpebral approach to the medial wall and orbital floor. Sometimes theses approaches are combined with lateral canthotomy incisions for access to the lateral wall ("3-wall decompression"). This report shows a compilation of different techniques using computer-assisted surgery for a 3-wall decompression with the introduction of the "temporal cage" in patients suffering from Graves' disease and the combination with zygomatic bone osteotomy., Patients and Methods: Twelve patients suffering from Graves' disease presented for surgical treatment in our clinic. For surgical planning, a computed tomographic scan with navigation markers was carried out. The navigation was planned with voxel-based navigation software (VoXim or BrainLab)., Results: Of the patients, 1 had unilateral and 11 had bilateral decompressions. Of the 11 patients with bilateral procedures, 1 patient underwent simultaneous and 10 underwent sequential procedures. The 3-wall decompression in all cases was performed by transconjunctival approach. Temporary double vision could be observed in all cases. There was a significant reduction in proptosis., Conclusion: It was concluded that this approach and the computer-assisted surgery would be the operation of first choice when there is an indication for orbital decompression., (Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Over the past years, computer-assisted surgery has gained more importance in craniomaxillofacial surgery, especially in primary and secondary treatment of head and neck malignancies. The basis for oncologic treatment of the head and neck region requires detailed planning using computed tomography, cone-beam computed tomography, or magnetic resonance imaging in combination with computer-assisted, infrared-based navigation system. These techniques allow a preplanned image-guided path to the tumor region for taking biopsies, resection, or reconstruction. The aim of this work was to show the advances and technical benefits for tumor surgery in a daily clinical routine from the view of the craniomaxillofacial surgeon. The target of our working group was to develop and clinically evaluate a novel three-dimensional planning and navigation software solution for treatment of craniofacial tumors. This work was carried out on 5 categories for oncologic surgical procedures in which computer-assisted surgery was applied from 2005 to 2011: preplanned trajectorial-guided tumor biopsy, intraoperative image-controlled tumor resection, tumor mapping, reconstruction after tumor surgery (true to original), and oral rehabilitation (backward planning). Successful preoperative planning, import of image data suitable for navigation, and intraoperative precise infrared-based navigation were obtained for all 5 categories without any complications. Image-guided navigation technique for head and neck oncologic surgery provides a precise, safe surgical method with real-time excellent anatomic orientation. Regarding the advantages of computer-assisted surgery, this technique will play a major part in craniofacial reconstructive surgery and will address widespread general methodologic solutions that are of great interest in multidisciplinary oncologic treatment.

Introduction: This case report describes a suicidal gunshot wound to the head using a handgun (9 x 19 mm). During mandibular penetration, the solid hollow point projectile (Aktion4) was deformed but did not fragment. The mandible, mid-face, orbit, and nasal complex were severely damaged. Here, the authors present, for the first time, a new approach for bilateral mid-facial fractures., Materials and Methods: For virtual reconstruction, a naso-orbito-ethmoidal complex of an unaffected skull (same age, sex, and ethnic group) was merged into the computed tomography (CT) data set. Based on this data set, a navigation assisted operation was performed., Conclusion: The favorable outcome leads us to recommend the technique of merging comparable CT data for reconstructive planning of bilateral mid-facial fractures.

Surgical procedures in the head and neck region require a detailed knowledge of this region's complex anatomy. Anatomic changes due to tumor growth present special challenges for the surgeon. In addition to the clinical examination, which is still of fundamental importance, imaging procedures such as computer-aided surgical navigation technology are currently being used in the preoperative, intraoperative, and postoperative assessments of anatomic changes. For purposes of analysis, we have analyzed the application of navigation technology into 2 categories: 1) minimally invasive procedure and biopsy; and 2) resection of extensive tumors and reconstruction after tumor surgery. Navigation can make tumor surgery more reliable by specifying correct safety margins, protecting vital structures, and facilitating the reconstruction process.

Objective: Computer-aided surgery (CAS) has proved to be useful in reconstructive craniomaxillofacial surgery. Preoperative creation of virtual models by segmentation of the computerized tomography (CT) dataset and mirroring of the unaffected side allows for precise planning of complex reconstructive procedures. The aim of this study was to evaluate the accuracy of the preoperative planning and the postoperative result regarding the skeletal reconstruction., Study Design: In a first step, the symmetry of unaffected human skulls and faces were evaluated by 20 midface CT data of skulls and 20 surface-scan data of healthy individuals. By mirroring and adjusting the original and mirrored datasets using a 3-dimensional modeling software, an automatic measurement procedure could evaluate the mean and the maximal modulus of the distances between both datasets. In a second step, 18 consecutive cases were selected which had been treated with CAS support. Group 1 consisted of orbital floor and/or medial wall fractures (n = 12), group 2 consisted of zygomatic bone fractures (n = 4), and group 3 included 2 patients who were treated by secondary orbital reconstruction including reosteotomy of the zygomatic bone (n = 2). To verify the surgical result, the preoperative CT dataset including the virtual planning and the postoperative CT dataset were compared by using image fusion. Additionally, postoperative surface scans and the clinical symptoms of the patients were evaluated., Results: No differences between the skull and face symmetry were found. Mean values for distances considering the skull symmetry were 0.83 mm for male and 0.71 mm for female and for the face symmetry 0.65 mm for male and 0.76 mm for female. Comparing the preoperative planning with the postoperative outcome, a mean accuracy of 1.49-4.12 mm with maximum modulus of 2.49-6.00 mm was achieved. Orbital true-to-original reconstructions and the secondary reconstructions were more precise than the reposition of the zygomatic bones. The postoperative acquired surface scans resulted in mean distances from 0.89 to 1.784 mm. Despite these deviations, all patients demonstrated satisfying clinical outcome., Conclusion: The natural asymmetry in humans influences the accuracy of preoperative planning procedure, when the mirroring tool is used. The accuracy transforming the preoperative planning to the surgical reconstruction using CAS depends on location, surgical approach, and matter of reconstruction.

We used a navigation system for computer-assisted preoperative planning based on cone beam tomography with virtual reconstruction to obtain symmetry of the orbit and intraoperative control of virtual contours. In operations for reconstruction of the orbital floor this technique offers a reliable intraoperative control in an area of limited exposure and visibility. There was no significant difference in visualisation of anatomical structures between the cone beam tomographic digital imaging and communication (DICOM) data and computed tomographic data. Cone beam tomography seems to be suitable for computer-assisted planning in the management of orbital trauma with reduced costs and less radiation.

Ablative tumor surgery and orbital and midface reconstruction, as much as orthognathic surgery, requires detailed planning using computed tomography (CT) or magnetic resonance imaging (MRI). These techniques also allow simulation of complex surgeries preoperatively. Proper reconstruction depends on reliable information to choose the correct type of grafts and to predict the outcome. This study evaluates the benefit and indications of computer-assisted surgery in the treatment of 107 patients who underwent craniomaxillofacial surgery. Based on a CT or MRI data set, an optical navigation system was used for preoperative planning, intraoperative navigation, and postoperative control. Surgery could be preoperatively planned and intraoperatively navigated. Preoperatively, it required that soft and hard tissues were measured using the mirrored data set of the unaffected side; the size and location of the graft were chosen virtually. Intraoperatively contours of transplanted tissues were navigated to the preoperatively simulated reconstructive result. Computer-assisted treatment was successfully completed in all 107 cases. Preoperatively outlined safety margins could be exactly controlled during tumor resection. Reconstruction was designed and performed precisely as virtually planned. Image-guided treatment improves preoperative planning by visualizing the individual anatomy, outlining the intended reconstructive outcome, and by objectifying the effect of adjuvant therapy. Intraoperative navigation makes tumor and reconstructive surgery more reliable by showing the safety margins, saving vital structures, and leading the reconstruction to preoperatively planned objectives.

Purpose: Computer-assisted surgery (CAS) has not been a routine part of craniomaxillofacial surgery to date. This report investigates the use of CAS to promote the safe removal of ankylosed temporomandibular joint bone in the skull base., Patients and Methods: Out of a total pool of experience with 102 navigation-guided CAS procedures between January 1998 and December 2000, we report on 2 cases of navigation-aided resection of severe ankylosis of the mandibular condyle with a predetermined safety margin of the resection toward the middle cranial fossa, and identification of the foramen ovale., Result: The use of CAS with navigation resulted in the promotion of safe surgical excision of the ankylosed skull base tissue., Conclusions: We regard navigation-aided resection of an ankylosis fo the mandibular condyle as a valuable additional technique in this potentially complicated procedure., (Copyright 2002 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 60:1275-1283, 2002)

Until now, computer-assisted surgery has not been practiced as part of the surgical routine of posttraumatic orbital reconstruction. The purpose of this study was to investigate the use of a navigation system for computer-assisted preoperative planning with virtual reconstruction to obtain symmetry of the orbits and intraoperative control of virtual contours in comparison with the clinically achieved surgical results. A further objective of the computer-assisted orbital analysis was to use an ideal measurement for the two-dimensional and three-dimensional changes following orbital reconstruction and to check the equality of the postoperative values for the affected orbits in comparison with those of the unaffected sides. Patients with unilateral posttraumatic orbital defects (n = 18) underwent computer-assisted surgery and preoperative planning using a spiral computed tomography database. Surgical procedures were preplanned with virtual correction by mirroring an individually defined three-dimensional segment from the unaffected side onto the deformed side, creating an ideal unilateral reconstruction. These computer-models were intraoperatively used as virtual templates to navigate the preplanned contours and the globe projection using the Stryker-Leibinger navigation system. Individual noninvasive registration with an overall inaccuracy of approximately 1 mm was achieved by using a maxillary occlusal splint with four markers. The mirroring of the unaffected side allowed an ideal virtual reconstruction. A mean decrease in enlarged orbital volume of 4.0 (SD +/- 1.9) cm was achieved, as was a mean increase in the sagittal globe projection of 5.88 (SD +/- 2.98) mm. With a paired Student test, the decrease between the preoperative and postoperative differences of the affected and unaffected sides was proved significant for orbital volume, globe projection, and computed tomography-based Hertel scale changes (p < 0.01). In 15 of 18 cases, simultaneous malar bone advancement resulted primarily in an additional increase in orbital volume before intraorbital augmentation with calvarial split-bone grafts could be performed. Intraorbital bony augmentation included one (n = 1), two (n = 7), three (n = 8), and all four (n = 2) orbital walls. Computer-assisted preoperative planning enables the surgeon to predict reconstructive surgical steps before the operation. Highly vulnerable structures such as the optic nerve can be detected and avoided intraoperatively, and virtually preplanned bone graft positions and/or orbital frame contours can be checked. Computer-assisted preoperative planning and surgery thus advance the difficult surgical field of orbital reconstruction, particularly through a greater exploitation of radiologic information without additional radiation to the patient.

Smaller implants and less invasive techniques for osteotomies using an endoscope assisted approach may facilitate the surgical procedures in cranio-maxillofacial distraction osteogenesis. Although sophisticated distraction devices are routinely used, there are still certain problems which need to be addressed. The preoperative planning, even of complex cases can be facilitated by using modern imaging techniques such as computer assisted surgery (CAS). The placement of the devices and the outline of complex osteotomies can be controlled intra-operatively. CAS allows for postoperative monitoring and for the long term follow up. The vector of distraction can be monitored and, depending on the device, a change of the vector of distraction may be possible during the activation period.

The reconstruction of the anterio-posterior inclination of the medial aspect of the orbital floor, despite a wide 360° exposure, including coronal and conjunctival incisions, is a challenging task in severe injuries of the orbit with massive comminution and complete displacement of the medial orbital wall and orbital floor.Out of a total of 20 patients with orbital fractures, five underwent a surgical intervention of repositioning the medial aspect of the orbital floor and especially the transition area between the orbital floor and medial orbital wall, using navigation-aided procedures. Using the mirroring tool of the Stryker–Leibinger STN-system, post-operative CTs indicated an average difference of the globe position of -4.9% between the operated side and the unaffected side, depending on the position of the medial aspect of the orbital floor. Navigation-aided procedures proved to be an essential precondition for achieving precise and predictable results in orbital reconstruction.In such cases, unlike those with an intact medial orbital wall remnant as a surgical target, bone grafts for reconstruction of the orbital floor cannot be implanted as onlay grafts. [Copyright &y& Elsevier]