- Email: [email protected]
Virtual planning for craniomaxillofacial surgery – 7 Years of experience
Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Virtual planning for craniomaxillofacial surgery e 7 Years of experience Nicolai Adolphs a, *, Ernst-Johannes Haberl b, Weichen Liu c, Erwin Keeve c, Horst Menneking a, Bodo Hoffmeister a a Dept. of Oral and Maxillofacial Surgery, Clinical Navigation, Surgical Robotics, University Hospital Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany b Pediatric Neurosurgery, University Hospital Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany c Clinical Navigation, Surgical Robotics, University Hospital Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 8 May 2013 Accepted 8 October 2013
Contemporary computer-assisted surgery systems more and more allow for virtual simulation of even complex surgical procedures with increasingly realistic predictions. Preoperative workflows are established and different commercially software solutions are available. Potential and feasibility of virtual craniomaxillofacial surgery as an additional planning tool was assessed retrospectively by comparing predictions and surgical results. Since 2006 virtual simulation has been performed in selected patient cases affected by complex craniomaxillofacial disorders (n ¼ 8) in addition to standard surgical planning based on patient specific 3d-models. Virtual planning could be performed for all levels of the craniomaxillofacial framework within a reasonable preoperative workflow. Simulation of even complex skeletal displacements corresponded well with the real surgical result and soft tissue simulation proved to be helpful. In combination with classic 3d-models showing the underlying skeletal pathology virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional work and expenses may be justified by increased possibilities of visualisation, information, instruction and documentation in selected craniomaxillofacial procedures. Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Virtual surgical planning Craniomaxillofacial surgery
1. Introduction For craniomaxillofacial planning, individual 3-dimensional surgical models based on patient specific datasets have been used routinely in order to visualise skeletal pathology since their introduction to the field 25 years ago. The gold standard for the fabrication of individual 3D-models is DICOM (Digital Imaging and Communication in Medicine) datasets that are routinely acquired during preoperative imaging by conventional high resolution multi slice computed tomography (MSCT) (Brix and Lambrecht, 1987; Lambrecht and Brix, 1989). Although technologies in image acquisition, data processing and CAD/CAM-environments have evolved
* Corresponding author. Klinik für Mund-, Kiefer- und Gesichtschirurgie, Zentrum für rekonstruktive und plastisch-ästhetische Gesichtschirurgie, Klinische Navigation und Robotik, Charité Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, Mittelallee 2, D-13353 Berlin, Germany. Tel.: þ49 30450555022; fax: þ49 30450555901. E-mail addresses: [email protected], [email protected] (N. Adolphs).
rapidly, model production remains cost and time consuming and model surgery would result in destruction of the model, respectively changing the initial situation. Because of this virtual surgical planning has been advocated in order to overcome the known drawbacks of the classic surgical models (Girod et al., 2001). Computer-assisted planning and simulation of craniofacial surgery has been in the focus of clinicians from the very beginning. In 1993 Altobelli described the basic workflow, possibilities and limitations of computer-assisted three-dimensional planning for craniofacial surgery in his fundamental paper (Altobelli et al., 1993). At that time comparable possibilities were mainly related to scientific institutions or laboratories due to sophisticated requirements. In the meantime numerous technical developments have contributed to overcome the initial obstacles and computer-assisted surgery is well established today. Workflows have been simplified significantly with respect to more user friendly applications. In 1995 Girod et al. integrated surface datasets from 3d laser scanners in order to improve outcome predictions and in 2001 the same authors reported on the clinical application of the underlying workflow for craniofacial surgery (Girod et al., 1995, 2001). Currently
1010-5182/$ e see front matter Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcms.2013.10.008
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
2
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
surgical plan was performed without intraoperative navigation, however surgical cutting guides were partially used. Retrospective assessment of virtual planning was performed by comparison of virtual surgery (skeletal movements and soft tissue prediction) to the real surgical procedure and corresponding outcome according to preoperative planning records and intra- and postoperative photo documentation. A semi-quantitative scale was applied in order to evaluate the power of the simulations and their benefit within a surgical environment.
different solutions for virtual craniomaxillofacial planning have gained marketability and are basically appropriate for routine clinical use (Bell, 2011). In orthognathic and reconstructive surgery computer-aided surgical simulation has shown their clinical feasibility (Gateno et al., 2007; Swennen et al., 2009; Aboul-Hosn Centenero and Hernandez-Alfaro, 2012; Hsu et al., 2013). Despite this there is still a lack of surgical outcome reports for craniofacial applications (Markiewicz and Bell, 2011). 2. Materials and methods
3. Results Since 2006 virtual planning has been used in the department of craniomaxillofacial surgery, Campus Virchow Klinikum, Charité Berlin using software solutions (SimplantCMF/SurgicaseCMF/ProplanCMF) of the company Materialise (Leuven, Belgium) for selected patient cases with a focus on craniofacial disorders in addition to individual patient specific 3d-models. Preoperative workflow was according to a standardised protocol and consisted in imaging by conventional high resolution multi slice computed tomography respectively cone beam ct (CBCT) scanning (ILUMAÒ, IMTEC Europe, Oberursel, Germany). Corresponding DICOM datasets were used for both model production and virtual planning. Individual 3d-models were fabricated by an industrial service provider (Alphaform, Munich, Germany) who specialise in rapid prototyping by the selective laser sintering technique (SLS) in order to visualise the underlying skeletal pathology. Assessment and evaluation of the skeletal craniofacial pathology was performed according to the 3d-model and the skeletal correction respectively, with the “surgical plan” subsequently derived by the craniofacial team. A surgical drawing indicating the planned osteotomy lines for the required skeletal movements was created and sent to the CMFsoftware engineers of Materialise. As controlling of the planning software needs training and should be used routinely for fast processing the authors selected the company’s “software service” on a “case by case” modus using online conference options. A web meeting was arranged accordingly between the craniofacial team and Materialise after DICOM data and surgical drawings had been transferred by a web-based file transfer protocol (ftp). Virtual osteotomies for skeletal movements were prepared by the engineers according to the surgical drawings in advance and only minor modifications were necessary during the web meeting. Skeletal displacements and the resulting soft tissue effects were subsequently simulated together by the engineer (controlling the software) and the surgeon (assessing the skeletal movements) during online collaboration. Virtual planning of skeletal corrections included all levels of the craniofacial framework. Transfer of the
Virtual planning has been applied in eight selected patient cases affected by different craniomaxillofacial disorders as shown in Table 1. Corrections of all levels of the craniofacial framework according to Tessier’s concept were simulated preoperatively by using the workflow described above. According to our experiences in all patients, simulation of even complex craniomaxillofacial procedures proved to be useful and virtual planning clearly supported real surgery which resulted in positive assessments for all simulated patients. The overall rating for virtual planning of complex craniomaxillofacial procedures as demonstrated in this series was positive (Table 1). The benefit of virtual surgery varied by case. In general, virtual simulations of the procedures were in good accordance with the real surgical result. Skeletal displacements could be simulated according to the conventional “surgical plan” and resulting soft tissue simulations displayed at least satisfactory (þ) predictions applicable for clinical use. From the surgical point of view the main advantage of the virtual simulation was the option to “play around” and test the effects of different skeletal variations with respect to soft tissue changes. Once the osteotomies are defined the software allows for quickly calculating different distances or angulations of skeletal displacements. Their predictive effects can be observed immediately and necessary corrections can be performed. In this way an individual treatment plan can be adapted and optimised easily during online collaboration. A nice additional feature with respect to patient information and educational purposes are video animations that dynamically demonstrate the resulting soft tissue effects which proved to be helpful especially for the planning of distraction osteogenesis. Vector and length of distraction could be varied virtually, the different results were illustrated by animations and the optimal strategy was selected accordingly (Fig. 1). In all distraction cases virtual planning proved to be very useful as there was a clear concept of the ideal vector prior to real surgery (Figs. 1 and 3).
Table 1 Series of eight patients who underwent virtual planning additional to conventional 3d-model based planning for skeletal craniomaxillofacial corrections (n ¼ 8; 2006e2013). Patient/ Year/Age
Prediction of Prediction of Comments skeletal changes soft tissues changes
Overall rating
1/2006/13 Craniofacial Dysostosis/ AntleyeBixler syndrome 2/2009/19 Postradiogenic hemifacial growth deficit (Fig. 1aeg) 3/2009/28 Posttraumatic dish face deformity
þ
þ
Complex multi-plane movement
þ
þþ
þþ
Multi-step corrections required
þþ
þþ
þþ
4/2010/12
þþ
þþ
Single-step correction of facial þþ width and height Vector planning, airway assessment þþ
þþþ
þþþ
þþ
þ
þþþ þþþ
þþ þ
5/2011/12 6/2010/25
7/2011/11 8/2012/4
Diagnosis/underlying skeletal pathology
Simulated surgical procedure
Fronto-Facial-Advancement by internal distraction devices Unilateral mandibular ramus distraction Bilateral zygomatic reduction/ two-jaw surgery Treacher-Collins syndrome Bilateral mandibular ramus distraction Midfacial Hypoplasia due to BCLP Le Fort I advancement by internal maxillary distraction Craniofrontonasal dysplasia Cranioplasty, Box osteotomies, transpalatal maxillary distraction, two jaw surgery Frontonasal dysplasia (Fig. 2aej) Box osteotomies Craniofacial dysostosis/Apert Fronto-Facial-Advancement by syndrome (Fig. 3aef) internal distraction devices
CBCT-imaging vector planning þþþ Visualisation of tooth buds Multiple planes, multi-step surgery, þþ additional soft tissue corrections Precise transfer by cutting guide Complex multi-plane movement, vector planning
þþþ þþþ
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
3
epithelial malignancy of the left oral commissure at 4 years of age (Fig. 1a, b). Within a staged reconstructive surgical concept mandibular distraction for lengthening of the ascending ramus (30 mm) was scheduled as a first step in order to reconstruct the lower facial frame. Preoperative virtual simulation showed that an additional paramedian osteotomy bridged by a rotating miniplate was necessary in order to allow for adequate positioning of the left mandibular angle after 30 mm of distraction (Fig. 1c). Soft tissue simulation suggested that there would be a persisting lack of volume in the left midface which would require additional surgery (Fig. 1d). Superimposition of virtual planning (yellow) and effective result (red) showed a reasonable accordance because distraction was performed in two steps as appropriate available devices allowed only for 20 mm length of distraction. Fig. 1g demonstrates the clinical situation after mandibular distraction being in good accordance with the preoperative soft tissue simulation of the virtual planning (Fig. 1d). According to this patient, virtual planning was helpful in order to understand and communicate the need for multi-step surgery for adequate correction of the deformity present prior to surgery. Additional surgery consisted in soft tissue expansion of the cheek, reconstruction of the oral commissure and transpalatal. Rhinoplasty is still pending. If limited procedures addressing mainly one facial plane were simulated the soft tissue predictions were precise (þþþ) as well demonstrated for the transverse facial plane in patient 7 of the series (correction of hypertelorism by orbital box osteotomies, Fig. 2aej). In patients receiving staged surgery with stepwise correction of multiple planes of the craniofacial framework (e.g. orbital box osteotomies (transverse plane) followed by maxillary expansion (horizontal plane) followed by mandibulomaxillary reorientation/ two jaw surgery (vertical and sagittal plane)) simulation of the whole treatment was performed in advance as well, however virtual surgery was less predictive compared to limited movements addressing only “one” facial plane. With respect to the transfer of the planning “real” surgery in all patients was performed without navigation as it has not been implemented in the software in this series. Surgical cutting guides proved to be helpful as shown in patient 7. An individual cutting guide was designed and produced according to the preoperative virtual planning. By this guide the surgical plan could be transferred exactly to the operative site and significantly supported craniofacial correction (Fig. 2e, f). 3.2. Patient 7 of the series, Fig. 2aej
Fig. 1. aeg: Patient 2 of the series: 19-year-old male patient affected by postradiogenic unilateral facial growth deficit e clinical (a) and skeletal (b) situation before surgery e virtual simulation of ramus distraction (c) and resulting soft tissue changes (d) e superimposition of planned (yellow) and effective (red) skeletal changes after surgery (e, f) e clinical situation after ramus distraction (g) corresponding to soft tissue simulation (d).
3.1. Patient 2 of the series, Fig. 1aee 19-Year-old male patient affected by severe postradiogenic unilateral growth deficiency after combined treatment of an
11-Year-old boy affected by frontonasal dysplasia resulting in obvious hypertelorism and widow’s peak (Fig. 2a, b). Skeletal surgical correction was scheduled due to psychosocial reasons before puberty as there was no relevant functional impairment. The surgical plan consisted of orbital box osteotomies with resection of medial bony excess in order to reduce the intraorbital distance. Soft tissue simulation proved to be very helpful in this particular case in order to assess the amount of bony removal that would be required for an obvious effect. Consequently the increased interorbital distance was reduced from 36 mm to a more physiological value of 23 mm (Fig. 2c, d). Based on the virtual planning a cutting guide was designed and fabricated which was used during craniofacial correction for the removal of medial bony excess in order to allow for medialisation of both orbital boxes (Fig. 2e, f). Skeletal correction was clearly supported by this device and operation time probably reduced (Fig. 2g). Superimposition of preoperative planning (Fig. 2c) and postoperative scans (Fig. 2g, h) clearly demonstrates that ideal transfer of the planning could be realised by this approach. 18 months after skeletal correction and 12 months after secondary soft tissue correction and bilateral medial canthopexy
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
4
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
Fig. 2. aek: Patient 7 of the series: 11-year-old boy affected by frontonasal dysplasia e hypertelorism and widows peak e preoperative clinical (a) and skeletal (b) situation e virtual planning of skeletal correction using a patient specific cutting guide (c, d) e intraoperative situation after “guided” bony removal (e, f) e postoperative skeletal situation (g) and superimposition of planning and effective surgical result (h) e corresponding soft tissue simulations (i, j) e clinical situation 18 months postoperatively after additional soft tissue correction (k).
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
5
Fig. 3. aef: Patient 8 of the series: 4-year-old girl affected by Apert-syndrome e preoperative clinical (a) and skeletal (b) situation e simulation of skeletal situation after single stage craniofacial correction (frontofacial advancement by internal distraction, devices removed) (c) e planning report demonstrating skeletal movements and corresponding soft tissue changes (d) e cephalogram during active distraction (e) e clinical situation 6 weeks postop. (f).
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
6
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
there is a certain discrepancy between soft tissue simulations and reality, but the principal effect of the skeletal correction could be assessed before surgery with a reasonable display not taking in account ongoing growth and secondary soft tissue management (Fig. 2hej). Even without a surgical cutting guide, virtual surgery contributed to improve the surgical approach in all patients by improved possibilities of visualisation. Sensitive structures like tooth buds could be visualised before Le Fort-I-osteotomy for maxillary advancement in order to determine the level of the Le Fort-Iosteotomy (patient 5). In this patient preoperative imaging was performed by cone beam CT which facilitated preoperative workflow. Corresponding DICOM files were used for both virtual planning of internal Le Fort-I distraction as well as for model production in order to select appropriate internal distraction devices. If appropriate pre- and postoperative imaging was performed superimposition of data was possible in order to evaluate real surgical effects as shown in patient 2 (Fig. 1e, f) and patient 7 (Fig. 2b, g, h). Although the superimposition would require additional postoperative image processing it might contribute to further quality control in craniomaxillofacial procedures as it is possible to quantify effective skeletal movements. This feature has not been implemented in this series. In even more complex craniofacial skeletal movements possible pitfalls could be detected preoperatively by virtual planning. This is exemplarily shown in a patient who underwent asymmetric craniofacial distraction (Fig 3aef). 3.3. Case 3, Fig. 3aef 4-Year-old girl from Libya affected by Apert-syndrome with functional impairment of upper airways due to restriction of frontobasal and midfacial growth (Fig. 3a, b). Virtual simulation was performed for single stage correction of anterior skull base and midfacial retrusion by combining frontoorbital remodelling and LeFort-III midfacial distraction. Le Fort-III-midfacial advancement was targeted anterior and slightly downwards with regard to the anterior skull base, frontoorbital bandeau and frontal bone were left floating above (Fig. 3c) (Adolphs et al., 2012). Virtual planning demonstrated that asymmetric advancement of the midface should was needed in order to achieve symmetric situations at the infraorbital rims (Fig. 3d). Surgery was performed according to that planning in three segments including frontal bone, frontoorbital bandeau and Le Fort-III complex. Internal distraction devices were selected preoperatively according to the best fit to the 3d-model of the patient in order to provide optimal stability during active distraction and consolidation period. During the clinical procedure the devices were mounted without technical difficulties with regard to the desired vector. Real distraction was performed according to the virtual planning with an increased activation of the left device. A lateral cephalogram taken during active distraction showed a very good correspondence to the virtual skeletal planning with a basally increased osteotomy gap indicating that the skeletal displacement took place according to the preoperative planning (Fig. 3c, e). A lateral view ten days after the ending of active distraction showed an obvious increase in midfacial projection, corresponding to the preoperative soft tissue simulation with respect to the underlying skeletal displacements. Variations at the nasal tip region which do not correspond to the midfacial advancement can be noticed. 4. Discussion The value of individual 3d-models for the planning of craniomaxillofacial corrections has been emphasised since their introduction (Bill et al., 1995; Sailer et al., 1998). Altobelli and Lo
described the options of computer-assisted planning and virtual craniomaxillofacial surgery twenty years ago (Altobelli et al., 1993; Lo et al., 1994), however wide application was limited due to sophisticated technical requirements. In 2001 Girod specified a new method for simulation and prediction of craniofacial surgery suggesting that this technique might be superior to established model surgery (Girod et al., 2001). In 2003 Gateno described his experiences in virtual planning of midfacial distraction osteogenesis and emphasised the potential of this technology. At that time planning protocols were in a rudimentary phase (Gateno et al., 2003). Westermark in 2005 described his experiences using 3d-planning for corrective maxillofacial surgery in 15 patients. Especially in complex cases, surgical decisions were supported by preoperative simulations. The value for teaching aspects, patient information and documentation as well as quality assurance was emphasised (Westermark et al., 2005). Initial obstacles of virtual planning software have been resolved and different software solutions have gained marketability in the meantime (Bell, 2011). There seems to be an agreement between different users of virtual surgical planning technology that there is a clear benefit to it. These systems support correct evaluation of craniofacial deformity consequently improving accurate diagnosis, optimising treatment planning and transfer of the planning to the patient (Markiewicz and Bell, 2011; Zhao et al., 2012). Operation time can be reduced and these systems may even be cost effective when compared to traditional planning solutions (Xia et al., 2006). Our experiences confirm these different aspects. In 2006 we performed our first virtual planning for a complex craniofacial correction in a syndromal disorder using the first software version of Materialise (SimplantCMF) and found it very helpful in order to assess the different surgical options. Real surgery was performed in accordance to the virtual surgical plan. The postoperative result was very similar to the preoperative prediction although minor changes have been made (Adolphs et al., 2011). After that initial experience virtual surgery was applied to comparable complex cases and proved to be useful in addition to conventional 3d-models (Adolphs and Haberl, 2012). With respect to the soft tissues, it was clear from the very beginning that only approximate results could be expected as it was conceded by the company that simulations involving the nasal tip region might be erroneous and therefore should be interpreted with caution. Corresponding advice is mentioned on the planning reports. Soft tissue simulations showed satisfactory predictions and proved helpful in order to give an impression of the effects of underlying skeletal movements. With an increasing amount of change of the craniofacial framework soft tissue simulation was less predictive in our series which might also be related to staged surgical approaches. Virtual surgery was always performed completely in one onlinesetting in advance. Stepwise simulations after each correction might provide better results, but they would require additional imaging and time for planning. Recent reports about the accuracy of prediction planning using comparable software solutions conclude that prediction is clinically satisfactory but can be associated with obvious errors. This is in good accordance with our results (Aboul-Hosn Centenero and Hernandez-Alfaro, 2012; Shafi et al., 2013). The integrated workflow for the contemporary application of virtual surgical planning technology is specified in a recent review of Zhao and co-workers (Zhao et al., 2012). The authors concede that the management of the dataflow and communication can be demanding and recommend a time frame of 4 weeks for preoperative management which seems reproducible as analogue pathways have been used in our practice. A reasonable approach is to assume that time for preoperative planning does not exceed time for real surgery.
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
Further improvement of the preoperative workflow can be expected when an all-in-one-planning-solution is selected which includes virtual planning, model fabrication and production of specific cutting guides based on the same datasets, which is already offered by the company with respect to an integrated workflow. Modern workflows favour the use of DICOM datasets that can be acquired by cone beam CT’s thus reducing irradiation exposure for the patient (Aboul-Hosn Centenero and Hernandez-Alfaro, 2012). According to our own experiences cone beam derived DICOM datasets can be used for integrated surgical planning including virtual surgery and 3d-model fabrication which are suitable within a surgical environment. Additional options, such as surgical cutting guides, justify additional time and effort for virtual planning in selected cases. Rohner has pointed out the value of patient specific guides in complex maxillofacial reconstruction (Rohner et al., 2013). The combination with intraoperative navigation might further increase surgical precision and is certainly an additional option. Superimposition of preoperative planning and the postoperative skeletal result in order to quantify effective skeletal displacements is likely to improve quality control in craniomaxillofacial procedures, but as the perioperative workflow is still complex and additional costs are at least not completely reimbursed by insurance companies, routine use of virtual surgery is likely to be limited for selected cases. 5. Conclusion Virtual craniomaxillofacial planning has become a helpful additional planning tool in order to choose the optimal surgical approach within individualised treatment concepts. In combination with classic 3d-models virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional time and costs can be justified by the increased use of visualisation, information, instruction and documentation in selected patient cases and therefore virtual planning seems to be a contemporary and appropriate supplement to established planning tools. Conflict of interest statement All authors disclose any financial interest and personal relationship to organisations and companies that are mentioned in the article. Acknowledgements We wish to express our thanks to PD Dr. Ernst Johannes Haberl, Head of the Section “Pediatric Neurosurgery” for his close collaboration in our craniofacial patients. Special thanks to the software engineers Luis Muyldermans, Marten Zandbergen, Joris Bellinckx, Annelies Genbrugge (Materialise, Leuven, Belgium) who were involved in the planning sessions. We wish to express our thanks to both the Anaesthetic team as well as the Paediatric ICU team for the perioperative management of the paediatric patients. Many thanks also to Dr. Nadine Thieme, Klinik für Strahlenheilkunde, Charité, Berlin (Chairman: Prof. Dr. Hamm) for providing CT-scans and 3d-
7
reconstructions. Special thanks to Franz Hafner for his organisational skills in arranging photo documentation for this article. References Aboul-Hosn Centenero S, Hernandez-Alfaro F: 3D planning in orthognathic surgery: CAD/CAM surgical splints and prediction of the soft and hard tissues results e our experience in 16 cases. J Craniomaxillofac Surg 40: 162e168, 2012 Adolphs N, Haberl EJ: Kraniofaziale Chirurgie: state of the art 2012. Der MKGChirurg 5: 266e278. http://dx.doi.org/10.1007/s12285-012-0308-9, 2012 Adolphs N, Klein M, Haberl EJ, Menneking H, Hoffmeister B: Frontofacial advancement by internal distraction devices. A technical modification for the management of craniofacial dysostosis in early childhood. Int J Oral Maxillofac Surg 41: 777e782, 2012 Adolphs N, Klein M, Haberl EJ, Graul-Neumann L, Menneking H, Hoffmeister B: Antley-Bixler-Syndrome e staged management of craniofacial malformations from birth to adolescence e a case report. J Craniomaxillofac Surg 39: 487e495, 2011 Oct Altobelli DE, Kikinis R, Mulliken JB, Cline H, Lorensen W, Jolesz F: Computer-assisted three-dimensional planning in craniofacial surgery. Plast Reconstr Surg 92: 576e585, 1993 discussion 586e577 Bell RB: Computer planning and intraoperative navigation in orthognathic surgery. J Oral Maxillofac Surg 69: 592e605, 2011 Bill JS, Reuther JF, Dittmann W, Kubler N, Meier JL, Pistner H, et al: Stereolithography in oral and maxillofacial operation planning. Int J Oral Maxillofac Surg 24: 98e103, 1995 Brix F, Lambrecht JT: Preparation of individual skull models based on computed tomographic information. Fortschr Kiefer Gesichtschir 32: 74e77, 1987 Gateno J, Teichgraeber JF, Xia JJ: Three-dimensional surgical planning for maxillary and midface distraction osteogenesis. J Craniofac Surg 14: 833e839, 2003 Gateno J, Xia JJ, Teichgraeber JF, Christensen AM, Lemoine JJ, Liebschner MA, et al: Clinical feasibility of computer-aided surgical simulation (CASS) in the treatment of complex cranio-maxillofacial deformities. J Oral Maxillofac Surg 65: 728e734, 2007 Girod S, Keeve E, Girod B: Advances in interactive craniofacial surgery planning by 3D simulation and visualization. Int J Oral Maxillofac Surg 24: 120e125, 1995 Girod S, Teschner M, Schrell U, Kevekordes B, Girod B: Computer-aided 3-D simulation and prediction of craniofacial surgery: a new approach. J Craniomaxillofac Surg 29: 156e158, 2001 Hsu SS, Gateno J, Bell RB, Hirsch DL, Markiewicz MR, Teichgraeber JF, et al: Accuracy of a computer-aided surgical simulation protocol for orthognathic surgery: a prospective multicenter study. J Oral Maxillofac Surg 71: 128e142, 2013 Lambrecht JT, Brix F: Planning orthognathic surgery with three-dimensional models. Int J Adult Orthodon Orthognath Surg 4: 141e144, 1989 Lo LJ, Marsh JL, Vannier MW, Patel VV: Craniofacial computer-assisted surgical planning and simulation. Clin Plast Surg 21: 501e516, 1994 Markiewicz MR, Bell RB: Modern concepts in computer-assisted craniomaxillofacial reconstruction. Curr Opin Otolaryngol Head Neck Surg 19: 295e301, 2011 Rohner D, Guijarro-Martinez R, Bucher P, Hammer B: Importance of patient-specific intraoperative guides in complex maxillofacial reconstruction. J Craniomaxillofac Surg 41: 382e390, 2013 Jul Sailer HF, Haers PE, Zollikofer CP, Warnke T, Carls FR, Stucki P: The value of stereolithographic models for preoperative diagnosis of craniofacial deformities and planning of surgical corrections. Int J Oral Maxillofac Surg 27: 327e333, 1998 Shafi MI, Ayoub A, Ju X, Khambay B: The accuracy of three-dimensional prediction planning for the surgical correction of facial deformities using Maxilim. Int J Oral Maxillofac Surg 42: 801e806, 2013 Jul Swennen GR, Mollemans W, Schutyser F: Three-dimensional treatment planning of orthognathic surgery in the era of virtual imaging. J Oral Maxillofac Surg 67: 2080e2092, 2009 Westermark A, Zachow S, Eppley BL: Three-dimensional osteotomy planning in maxillofacial surgery including soft tissue prediction. J Craniofac Surg 16: 100e 104, 2005 Xia JJ, Phillips CV, Gateno J, Teichgraeber JF, Christensen AM, Gliddon MJ, et al: Costeffectiveness analysis for computer-aided surgical simulation in complex cranio-maxillofacial surgery. J Oral Maxillofac Surg 64: 1780e1784, 2006 Zhao L, Patel PK, Cohen M: Application of virtual surgical planning with computer assisted design and manufacturing technology to cranio-maxillofacial surgery. Arch Plast Surg 39: 309e316, 2012
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
Contents lists available at ScienceDirect
Journal of Cranio-Maxillo-Facial Surgery journal homepage: www.jcmfs.com
Virtual planning for craniomaxillofacial surgery e 7 Years of experience Nicolai Adolphs a, *, Ernst-Johannes Haberl b, Weichen Liu c, Erwin Keeve c, Horst Menneking a, Bodo Hoffmeister a a Dept. of Oral and Maxillofacial Surgery, Clinical Navigation, Surgical Robotics, University Hospital Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany b Pediatric Neurosurgery, University Hospital Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany c Clinical Navigation, Surgical Robotics, University Hospital Charité, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 8 May 2013 Accepted 8 October 2013
Contemporary computer-assisted surgery systems more and more allow for virtual simulation of even complex surgical procedures with increasingly realistic predictions. Preoperative workflows are established and different commercially software solutions are available. Potential and feasibility of virtual craniomaxillofacial surgery as an additional planning tool was assessed retrospectively by comparing predictions and surgical results. Since 2006 virtual simulation has been performed in selected patient cases affected by complex craniomaxillofacial disorders (n ¼ 8) in addition to standard surgical planning based on patient specific 3d-models. Virtual planning could be performed for all levels of the craniomaxillofacial framework within a reasonable preoperative workflow. Simulation of even complex skeletal displacements corresponded well with the real surgical result and soft tissue simulation proved to be helpful. In combination with classic 3d-models showing the underlying skeletal pathology virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional work and expenses may be justified by increased possibilities of visualisation, information, instruction and documentation in selected craniomaxillofacial procedures. Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Virtual surgical planning Craniomaxillofacial surgery
1. Introduction For craniomaxillofacial planning, individual 3-dimensional surgical models based on patient specific datasets have been used routinely in order to visualise skeletal pathology since their introduction to the field 25 years ago. The gold standard for the fabrication of individual 3D-models is DICOM (Digital Imaging and Communication in Medicine) datasets that are routinely acquired during preoperative imaging by conventional high resolution multi slice computed tomography (MSCT) (Brix and Lambrecht, 1987; Lambrecht and Brix, 1989). Although technologies in image acquisition, data processing and CAD/CAM-environments have evolved
* Corresponding author. Klinik für Mund-, Kiefer- und Gesichtschirurgie, Zentrum für rekonstruktive und plastisch-ästhetische Gesichtschirurgie, Klinische Navigation und Robotik, Charité Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, Mittelallee 2, D-13353 Berlin, Germany. Tel.: þ49 30450555022; fax: þ49 30450555901. E-mail addresses: [email protected], [email protected] (N. Adolphs).
rapidly, model production remains cost and time consuming and model surgery would result in destruction of the model, respectively changing the initial situation. Because of this virtual surgical planning has been advocated in order to overcome the known drawbacks of the classic surgical models (Girod et al., 2001). Computer-assisted planning and simulation of craniofacial surgery has been in the focus of clinicians from the very beginning. In 1993 Altobelli described the basic workflow, possibilities and limitations of computer-assisted three-dimensional planning for craniofacial surgery in his fundamental paper (Altobelli et al., 1993). At that time comparable possibilities were mainly related to scientific institutions or laboratories due to sophisticated requirements. In the meantime numerous technical developments have contributed to overcome the initial obstacles and computer-assisted surgery is well established today. Workflows have been simplified significantly with respect to more user friendly applications. In 1995 Girod et al. integrated surface datasets from 3d laser scanners in order to improve outcome predictions and in 2001 the same authors reported on the clinical application of the underlying workflow for craniofacial surgery (Girod et al., 1995, 2001). Currently
1010-5182/$ e see front matter Ó 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcms.2013.10.008
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
2
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
surgical plan was performed without intraoperative navigation, however surgical cutting guides were partially used. Retrospective assessment of virtual planning was performed by comparison of virtual surgery (skeletal movements and soft tissue prediction) to the real surgical procedure and corresponding outcome according to preoperative planning records and intra- and postoperative photo documentation. A semi-quantitative scale was applied in order to evaluate the power of the simulations and their benefit within a surgical environment.
different solutions for virtual craniomaxillofacial planning have gained marketability and are basically appropriate for routine clinical use (Bell, 2011). In orthognathic and reconstructive surgery computer-aided surgical simulation has shown their clinical feasibility (Gateno et al., 2007; Swennen et al., 2009; Aboul-Hosn Centenero and Hernandez-Alfaro, 2012; Hsu et al., 2013). Despite this there is still a lack of surgical outcome reports for craniofacial applications (Markiewicz and Bell, 2011). 2. Materials and methods
3. Results Since 2006 virtual planning has been used in the department of craniomaxillofacial surgery, Campus Virchow Klinikum, Charité Berlin using software solutions (SimplantCMF/SurgicaseCMF/ProplanCMF) of the company Materialise (Leuven, Belgium) for selected patient cases with a focus on craniofacial disorders in addition to individual patient specific 3d-models. Preoperative workflow was according to a standardised protocol and consisted in imaging by conventional high resolution multi slice computed tomography respectively cone beam ct (CBCT) scanning (ILUMAÒ, IMTEC Europe, Oberursel, Germany). Corresponding DICOM datasets were used for both model production and virtual planning. Individual 3d-models were fabricated by an industrial service provider (Alphaform, Munich, Germany) who specialise in rapid prototyping by the selective laser sintering technique (SLS) in order to visualise the underlying skeletal pathology. Assessment and evaluation of the skeletal craniofacial pathology was performed according to the 3d-model and the skeletal correction respectively, with the “surgical plan” subsequently derived by the craniofacial team. A surgical drawing indicating the planned osteotomy lines for the required skeletal movements was created and sent to the CMFsoftware engineers of Materialise. As controlling of the planning software needs training and should be used routinely for fast processing the authors selected the company’s “software service” on a “case by case” modus using online conference options. A web meeting was arranged accordingly between the craniofacial team and Materialise after DICOM data and surgical drawings had been transferred by a web-based file transfer protocol (ftp). Virtual osteotomies for skeletal movements were prepared by the engineers according to the surgical drawings in advance and only minor modifications were necessary during the web meeting. Skeletal displacements and the resulting soft tissue effects were subsequently simulated together by the engineer (controlling the software) and the surgeon (assessing the skeletal movements) during online collaboration. Virtual planning of skeletal corrections included all levels of the craniofacial framework. Transfer of the
Virtual planning has been applied in eight selected patient cases affected by different craniomaxillofacial disorders as shown in Table 1. Corrections of all levels of the craniofacial framework according to Tessier’s concept were simulated preoperatively by using the workflow described above. According to our experiences in all patients, simulation of even complex craniomaxillofacial procedures proved to be useful and virtual planning clearly supported real surgery which resulted in positive assessments for all simulated patients. The overall rating for virtual planning of complex craniomaxillofacial procedures as demonstrated in this series was positive (Table 1). The benefit of virtual surgery varied by case. In general, virtual simulations of the procedures were in good accordance with the real surgical result. Skeletal displacements could be simulated according to the conventional “surgical plan” and resulting soft tissue simulations displayed at least satisfactory (þ) predictions applicable for clinical use. From the surgical point of view the main advantage of the virtual simulation was the option to “play around” and test the effects of different skeletal variations with respect to soft tissue changes. Once the osteotomies are defined the software allows for quickly calculating different distances or angulations of skeletal displacements. Their predictive effects can be observed immediately and necessary corrections can be performed. In this way an individual treatment plan can be adapted and optimised easily during online collaboration. A nice additional feature with respect to patient information and educational purposes are video animations that dynamically demonstrate the resulting soft tissue effects which proved to be helpful especially for the planning of distraction osteogenesis. Vector and length of distraction could be varied virtually, the different results were illustrated by animations and the optimal strategy was selected accordingly (Fig. 1). In all distraction cases virtual planning proved to be very useful as there was a clear concept of the ideal vector prior to real surgery (Figs. 1 and 3).
Table 1 Series of eight patients who underwent virtual planning additional to conventional 3d-model based planning for skeletal craniomaxillofacial corrections (n ¼ 8; 2006e2013). Patient/ Year/Age
Prediction of Prediction of Comments skeletal changes soft tissues changes
Overall rating
1/2006/13 Craniofacial Dysostosis/ AntleyeBixler syndrome 2/2009/19 Postradiogenic hemifacial growth deficit (Fig. 1aeg) 3/2009/28 Posttraumatic dish face deformity
þ
þ
Complex multi-plane movement
þ
þþ
þþ
Multi-step corrections required
þþ
þþ
þþ
4/2010/12
þþ
þþ
Single-step correction of facial þþ width and height Vector planning, airway assessment þþ
þþþ
þþþ
þþ
þ
þþþ þþþ
þþ þ
5/2011/12 6/2010/25
7/2011/11 8/2012/4
Diagnosis/underlying skeletal pathology
Simulated surgical procedure
Fronto-Facial-Advancement by internal distraction devices Unilateral mandibular ramus distraction Bilateral zygomatic reduction/ two-jaw surgery Treacher-Collins syndrome Bilateral mandibular ramus distraction Midfacial Hypoplasia due to BCLP Le Fort I advancement by internal maxillary distraction Craniofrontonasal dysplasia Cranioplasty, Box osteotomies, transpalatal maxillary distraction, two jaw surgery Frontonasal dysplasia (Fig. 2aej) Box osteotomies Craniofacial dysostosis/Apert Fronto-Facial-Advancement by syndrome (Fig. 3aef) internal distraction devices
CBCT-imaging vector planning þþþ Visualisation of tooth buds Multiple planes, multi-step surgery, þþ additional soft tissue corrections Precise transfer by cutting guide Complex multi-plane movement, vector planning
þþþ þþþ
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
3
epithelial malignancy of the left oral commissure at 4 years of age (Fig. 1a, b). Within a staged reconstructive surgical concept mandibular distraction for lengthening of the ascending ramus (30 mm) was scheduled as a first step in order to reconstruct the lower facial frame. Preoperative virtual simulation showed that an additional paramedian osteotomy bridged by a rotating miniplate was necessary in order to allow for adequate positioning of the left mandibular angle after 30 mm of distraction (Fig. 1c). Soft tissue simulation suggested that there would be a persisting lack of volume in the left midface which would require additional surgery (Fig. 1d). Superimposition of virtual planning (yellow) and effective result (red) showed a reasonable accordance because distraction was performed in two steps as appropriate available devices allowed only for 20 mm length of distraction. Fig. 1g demonstrates the clinical situation after mandibular distraction being in good accordance with the preoperative soft tissue simulation of the virtual planning (Fig. 1d). According to this patient, virtual planning was helpful in order to understand and communicate the need for multi-step surgery for adequate correction of the deformity present prior to surgery. Additional surgery consisted in soft tissue expansion of the cheek, reconstruction of the oral commissure and transpalatal. Rhinoplasty is still pending. If limited procedures addressing mainly one facial plane were simulated the soft tissue predictions were precise (þþþ) as well demonstrated for the transverse facial plane in patient 7 of the series (correction of hypertelorism by orbital box osteotomies, Fig. 2aej). In patients receiving staged surgery with stepwise correction of multiple planes of the craniofacial framework (e.g. orbital box osteotomies (transverse plane) followed by maxillary expansion (horizontal plane) followed by mandibulomaxillary reorientation/ two jaw surgery (vertical and sagittal plane)) simulation of the whole treatment was performed in advance as well, however virtual surgery was less predictive compared to limited movements addressing only “one” facial plane. With respect to the transfer of the planning “real” surgery in all patients was performed without navigation as it has not been implemented in the software in this series. Surgical cutting guides proved to be helpful as shown in patient 7. An individual cutting guide was designed and produced according to the preoperative virtual planning. By this guide the surgical plan could be transferred exactly to the operative site and significantly supported craniofacial correction (Fig. 2e, f). 3.2. Patient 7 of the series, Fig. 2aej
Fig. 1. aeg: Patient 2 of the series: 19-year-old male patient affected by postradiogenic unilateral facial growth deficit e clinical (a) and skeletal (b) situation before surgery e virtual simulation of ramus distraction (c) and resulting soft tissue changes (d) e superimposition of planned (yellow) and effective (red) skeletal changes after surgery (e, f) e clinical situation after ramus distraction (g) corresponding to soft tissue simulation (d).
3.1. Patient 2 of the series, Fig. 1aee 19-Year-old male patient affected by severe postradiogenic unilateral growth deficiency after combined treatment of an
11-Year-old boy affected by frontonasal dysplasia resulting in obvious hypertelorism and widow’s peak (Fig. 2a, b). Skeletal surgical correction was scheduled due to psychosocial reasons before puberty as there was no relevant functional impairment. The surgical plan consisted of orbital box osteotomies with resection of medial bony excess in order to reduce the intraorbital distance. Soft tissue simulation proved to be very helpful in this particular case in order to assess the amount of bony removal that would be required for an obvious effect. Consequently the increased interorbital distance was reduced from 36 mm to a more physiological value of 23 mm (Fig. 2c, d). Based on the virtual planning a cutting guide was designed and fabricated which was used during craniofacial correction for the removal of medial bony excess in order to allow for medialisation of both orbital boxes (Fig. 2e, f). Skeletal correction was clearly supported by this device and operation time probably reduced (Fig. 2g). Superimposition of preoperative planning (Fig. 2c) and postoperative scans (Fig. 2g, h) clearly demonstrates that ideal transfer of the planning could be realised by this approach. 18 months after skeletal correction and 12 months after secondary soft tissue correction and bilateral medial canthopexy
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
4
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
Fig. 2. aek: Patient 7 of the series: 11-year-old boy affected by frontonasal dysplasia e hypertelorism and widows peak e preoperative clinical (a) and skeletal (b) situation e virtual planning of skeletal correction using a patient specific cutting guide (c, d) e intraoperative situation after “guided” bony removal (e, f) e postoperative skeletal situation (g) and superimposition of planning and effective surgical result (h) e corresponding soft tissue simulations (i, j) e clinical situation 18 months postoperatively after additional soft tissue correction (k).
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
5
Fig. 3. aef: Patient 8 of the series: 4-year-old girl affected by Apert-syndrome e preoperative clinical (a) and skeletal (b) situation e simulation of skeletal situation after single stage craniofacial correction (frontofacial advancement by internal distraction, devices removed) (c) e planning report demonstrating skeletal movements and corresponding soft tissue changes (d) e cephalogram during active distraction (e) e clinical situation 6 weeks postop. (f).
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
6
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
there is a certain discrepancy between soft tissue simulations and reality, but the principal effect of the skeletal correction could be assessed before surgery with a reasonable display not taking in account ongoing growth and secondary soft tissue management (Fig. 2hej). Even without a surgical cutting guide, virtual surgery contributed to improve the surgical approach in all patients by improved possibilities of visualisation. Sensitive structures like tooth buds could be visualised before Le Fort-I-osteotomy for maxillary advancement in order to determine the level of the Le Fort-Iosteotomy (patient 5). In this patient preoperative imaging was performed by cone beam CT which facilitated preoperative workflow. Corresponding DICOM files were used for both virtual planning of internal Le Fort-I distraction as well as for model production in order to select appropriate internal distraction devices. If appropriate pre- and postoperative imaging was performed superimposition of data was possible in order to evaluate real surgical effects as shown in patient 2 (Fig. 1e, f) and patient 7 (Fig. 2b, g, h). Although the superimposition would require additional postoperative image processing it might contribute to further quality control in craniomaxillofacial procedures as it is possible to quantify effective skeletal movements. This feature has not been implemented in this series. In even more complex craniofacial skeletal movements possible pitfalls could be detected preoperatively by virtual planning. This is exemplarily shown in a patient who underwent asymmetric craniofacial distraction (Fig 3aef). 3.3. Case 3, Fig. 3aef 4-Year-old girl from Libya affected by Apert-syndrome with functional impairment of upper airways due to restriction of frontobasal and midfacial growth (Fig. 3a, b). Virtual simulation was performed for single stage correction of anterior skull base and midfacial retrusion by combining frontoorbital remodelling and LeFort-III midfacial distraction. Le Fort-III-midfacial advancement was targeted anterior and slightly downwards with regard to the anterior skull base, frontoorbital bandeau and frontal bone were left floating above (Fig. 3c) (Adolphs et al., 2012). Virtual planning demonstrated that asymmetric advancement of the midface should was needed in order to achieve symmetric situations at the infraorbital rims (Fig. 3d). Surgery was performed according to that planning in three segments including frontal bone, frontoorbital bandeau and Le Fort-III complex. Internal distraction devices were selected preoperatively according to the best fit to the 3d-model of the patient in order to provide optimal stability during active distraction and consolidation period. During the clinical procedure the devices were mounted without technical difficulties with regard to the desired vector. Real distraction was performed according to the virtual planning with an increased activation of the left device. A lateral cephalogram taken during active distraction showed a very good correspondence to the virtual skeletal planning with a basally increased osteotomy gap indicating that the skeletal displacement took place according to the preoperative planning (Fig. 3c, e). A lateral view ten days after the ending of active distraction showed an obvious increase in midfacial projection, corresponding to the preoperative soft tissue simulation with respect to the underlying skeletal displacements. Variations at the nasal tip region which do not correspond to the midfacial advancement can be noticed. 4. Discussion The value of individual 3d-models for the planning of craniomaxillofacial corrections has been emphasised since their introduction (Bill et al., 1995; Sailer et al., 1998). Altobelli and Lo
described the options of computer-assisted planning and virtual craniomaxillofacial surgery twenty years ago (Altobelli et al., 1993; Lo et al., 1994), however wide application was limited due to sophisticated technical requirements. In 2001 Girod specified a new method for simulation and prediction of craniofacial surgery suggesting that this technique might be superior to established model surgery (Girod et al., 2001). In 2003 Gateno described his experiences in virtual planning of midfacial distraction osteogenesis and emphasised the potential of this technology. At that time planning protocols were in a rudimentary phase (Gateno et al., 2003). Westermark in 2005 described his experiences using 3d-planning for corrective maxillofacial surgery in 15 patients. Especially in complex cases, surgical decisions were supported by preoperative simulations. The value for teaching aspects, patient information and documentation as well as quality assurance was emphasised (Westermark et al., 2005). Initial obstacles of virtual planning software have been resolved and different software solutions have gained marketability in the meantime (Bell, 2011). There seems to be an agreement between different users of virtual surgical planning technology that there is a clear benefit to it. These systems support correct evaluation of craniofacial deformity consequently improving accurate diagnosis, optimising treatment planning and transfer of the planning to the patient (Markiewicz and Bell, 2011; Zhao et al., 2012). Operation time can be reduced and these systems may even be cost effective when compared to traditional planning solutions (Xia et al., 2006). Our experiences confirm these different aspects. In 2006 we performed our first virtual planning for a complex craniofacial correction in a syndromal disorder using the first software version of Materialise (SimplantCMF) and found it very helpful in order to assess the different surgical options. Real surgery was performed in accordance to the virtual surgical plan. The postoperative result was very similar to the preoperative prediction although minor changes have been made (Adolphs et al., 2011). After that initial experience virtual surgery was applied to comparable complex cases and proved to be useful in addition to conventional 3d-models (Adolphs and Haberl, 2012). With respect to the soft tissues, it was clear from the very beginning that only approximate results could be expected as it was conceded by the company that simulations involving the nasal tip region might be erroneous and therefore should be interpreted with caution. Corresponding advice is mentioned on the planning reports. Soft tissue simulations showed satisfactory predictions and proved helpful in order to give an impression of the effects of underlying skeletal movements. With an increasing amount of change of the craniofacial framework soft tissue simulation was less predictive in our series which might also be related to staged surgical approaches. Virtual surgery was always performed completely in one onlinesetting in advance. Stepwise simulations after each correction might provide better results, but they would require additional imaging and time for planning. Recent reports about the accuracy of prediction planning using comparable software solutions conclude that prediction is clinically satisfactory but can be associated with obvious errors. This is in good accordance with our results (Aboul-Hosn Centenero and Hernandez-Alfaro, 2012; Shafi et al., 2013). The integrated workflow for the contemporary application of virtual surgical planning technology is specified in a recent review of Zhao and co-workers (Zhao et al., 2012). The authors concede that the management of the dataflow and communication can be demanding and recommend a time frame of 4 weeks for preoperative management which seems reproducible as analogue pathways have been used in our practice. A reasonable approach is to assume that time for preoperative planning does not exceed time for real surgery.
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008
N. Adolphs et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2013) 1e7
Further improvement of the preoperative workflow can be expected when an all-in-one-planning-solution is selected which includes virtual planning, model fabrication and production of specific cutting guides based on the same datasets, which is already offered by the company with respect to an integrated workflow. Modern workflows favour the use of DICOM datasets that can be acquired by cone beam CT’s thus reducing irradiation exposure for the patient (Aboul-Hosn Centenero and Hernandez-Alfaro, 2012). According to our own experiences cone beam derived DICOM datasets can be used for integrated surgical planning including virtual surgery and 3d-model fabrication which are suitable within a surgical environment. Additional options, such as surgical cutting guides, justify additional time and effort for virtual planning in selected cases. Rohner has pointed out the value of patient specific guides in complex maxillofacial reconstruction (Rohner et al., 2013). The combination with intraoperative navigation might further increase surgical precision and is certainly an additional option. Superimposition of preoperative planning and the postoperative skeletal result in order to quantify effective skeletal displacements is likely to improve quality control in craniomaxillofacial procedures, but as the perioperative workflow is still complex and additional costs are at least not completely reimbursed by insurance companies, routine use of virtual surgery is likely to be limited for selected cases. 5. Conclusion Virtual craniomaxillofacial planning has become a helpful additional planning tool in order to choose the optimal surgical approach within individualised treatment concepts. In combination with classic 3d-models virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional time and costs can be justified by the increased use of visualisation, information, instruction and documentation in selected patient cases and therefore virtual planning seems to be a contemporary and appropriate supplement to established planning tools. Conflict of interest statement All authors disclose any financial interest and personal relationship to organisations and companies that are mentioned in the article. Acknowledgements We wish to express our thanks to PD Dr. Ernst Johannes Haberl, Head of the Section “Pediatric Neurosurgery” for his close collaboration in our craniofacial patients. Special thanks to the software engineers Luis Muyldermans, Marten Zandbergen, Joris Bellinckx, Annelies Genbrugge (Materialise, Leuven, Belgium) who were involved in the planning sessions. We wish to express our thanks to both the Anaesthetic team as well as the Paediatric ICU team for the perioperative management of the paediatric patients. Many thanks also to Dr. Nadine Thieme, Klinik für Strahlenheilkunde, Charité, Berlin (Chairman: Prof. Dr. Hamm) for providing CT-scans and 3d-
7
reconstructions. Special thanks to Franz Hafner for his organisational skills in arranging photo documentation for this article. References Aboul-Hosn Centenero S, Hernandez-Alfaro F: 3D planning in orthognathic surgery: CAD/CAM surgical splints and prediction of the soft and hard tissues results e our experience in 16 cases. J Craniomaxillofac Surg 40: 162e168, 2012 Adolphs N, Haberl EJ: Kraniofaziale Chirurgie: state of the art 2012. Der MKGChirurg 5: 266e278. http://dx.doi.org/10.1007/s12285-012-0308-9, 2012 Adolphs N, Klein M, Haberl EJ, Menneking H, Hoffmeister B: Frontofacial advancement by internal distraction devices. A technical modification for the management of craniofacial dysostosis in early childhood. Int J Oral Maxillofac Surg 41: 777e782, 2012 Adolphs N, Klein M, Haberl EJ, Graul-Neumann L, Menneking H, Hoffmeister B: Antley-Bixler-Syndrome e staged management of craniofacial malformations from birth to adolescence e a case report. J Craniomaxillofac Surg 39: 487e495, 2011 Oct Altobelli DE, Kikinis R, Mulliken JB, Cline H, Lorensen W, Jolesz F: Computer-assisted three-dimensional planning in craniofacial surgery. Plast Reconstr Surg 92: 576e585, 1993 discussion 586e577 Bell RB: Computer planning and intraoperative navigation in orthognathic surgery. J Oral Maxillofac Surg 69: 592e605, 2011 Bill JS, Reuther JF, Dittmann W, Kubler N, Meier JL, Pistner H, et al: Stereolithography in oral and maxillofacial operation planning. Int J Oral Maxillofac Surg 24: 98e103, 1995 Brix F, Lambrecht JT: Preparation of individual skull models based on computed tomographic information. Fortschr Kiefer Gesichtschir 32: 74e77, 1987 Gateno J, Teichgraeber JF, Xia JJ: Three-dimensional surgical planning for maxillary and midface distraction osteogenesis. J Craniofac Surg 14: 833e839, 2003 Gateno J, Xia JJ, Teichgraeber JF, Christensen AM, Lemoine JJ, Liebschner MA, et al: Clinical feasibility of computer-aided surgical simulation (CASS) in the treatment of complex cranio-maxillofacial deformities. J Oral Maxillofac Surg 65: 728e734, 2007 Girod S, Keeve E, Girod B: Advances in interactive craniofacial surgery planning by 3D simulation and visualization. Int J Oral Maxillofac Surg 24: 120e125, 1995 Girod S, Teschner M, Schrell U, Kevekordes B, Girod B: Computer-aided 3-D simulation and prediction of craniofacial surgery: a new approach. J Craniomaxillofac Surg 29: 156e158, 2001 Hsu SS, Gateno J, Bell RB, Hirsch DL, Markiewicz MR, Teichgraeber JF, et al: Accuracy of a computer-aided surgical simulation protocol for orthognathic surgery: a prospective multicenter study. J Oral Maxillofac Surg 71: 128e142, 2013 Lambrecht JT, Brix F: Planning orthognathic surgery with three-dimensional models. Int J Adult Orthodon Orthognath Surg 4: 141e144, 1989 Lo LJ, Marsh JL, Vannier MW, Patel VV: Craniofacial computer-assisted surgical planning and simulation. Clin Plast Surg 21: 501e516, 1994 Markiewicz MR, Bell RB: Modern concepts in computer-assisted craniomaxillofacial reconstruction. Curr Opin Otolaryngol Head Neck Surg 19: 295e301, 2011 Rohner D, Guijarro-Martinez R, Bucher P, Hammer B: Importance of patient-specific intraoperative guides in complex maxillofacial reconstruction. J Craniomaxillofac Surg 41: 382e390, 2013 Jul Sailer HF, Haers PE, Zollikofer CP, Warnke T, Carls FR, Stucki P: The value of stereolithographic models for preoperative diagnosis of craniofacial deformities and planning of surgical corrections. Int J Oral Maxillofac Surg 27: 327e333, 1998 Shafi MI, Ayoub A, Ju X, Khambay B: The accuracy of three-dimensional prediction planning for the surgical correction of facial deformities using Maxilim. Int J Oral Maxillofac Surg 42: 801e806, 2013 Jul Swennen GR, Mollemans W, Schutyser F: Three-dimensional treatment planning of orthognathic surgery in the era of virtual imaging. J Oral Maxillofac Surg 67: 2080e2092, 2009 Westermark A, Zachow S, Eppley BL: Three-dimensional osteotomy planning in maxillofacial surgery including soft tissue prediction. J Craniofac Surg 16: 100e 104, 2005 Xia JJ, Phillips CV, Gateno J, Teichgraeber JF, Christensen AM, Gliddon MJ, et al: Costeffectiveness analysis for computer-aided surgical simulation in complex cranio-maxillofacial surgery. J Oral Maxillofac Surg 64: 1780e1784, 2006 Zhao L, Patel PK, Cohen M: Application of virtual surgical planning with computer assisted design and manufacturing technology to cranio-maxillofacial surgery. Arch Plast Surg 39: 309e316, 2012
Please cite this article in press as: Adolphs N, et al., Virtual planning for craniomaxillofacial surgery e 7 Years of experience, Journal of CranioMaxillo-Facial Surgery (2013), http://dx.doi.org/10.1016/j.jcms.2013.10.008