3D preoperative modelling and 3D printing of mandible : a novel technique for optimal mandible reconstruction Poster No.:

C-1473

Congress:

ECR 2013

Type:

Educational Exhibit

Authors:

S. AUBRY, J. Pauchot, J. Lachat, L. Tavernier, C. Peyron, B. Kastler; Besancon/FR

Keywords:

Cancer, Surgery, Computer Applications-Virtual imaging, Computer Applications-3D, Image manipulation / Reconstruction, CT-Quantitative, CT, Head and neck, Ear / Nose / Throat, Computer applications

DOI:

10.1594/ecr2013/C-1473

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Learning objectives To describe step by step our novel technique for 3D preoperative modelling and 3D printing of mandible, which represents a new technique aiming at improving pre-operative mapping and outcomes of mandible surgery. We will describe the steps to model and 3D print a full size resin model of the mandible of patients treated by surgical resection of neoplasia and reconstruction with free flap. Special attention will be given to the role of the radiologist in image processing made from preoperative MDCT and cooperation with the surgical team and engineers in order to minimize production time and cost of the resin model.

Fig. 1: Mandible reconstruction with fibula free flap, planned by 3D preoperative printing of mandible. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR Images for this section:

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Fig. 1: Mandible reconstruction with fibula free flap, planned by 3D preoperative printing of mandible.

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Background The goal for surgery in mandible is to optimize methods of reconstruct mandible defects individually and immediately. Mandibular reconstruction with fibula free flap is the actual reference method [1 on page ]. To accomplish this, the surgeon is faced with technical difficulties: - It requires microsurgery. - Because of the 3D configuration of the mandible, the surgeon must accurately calculate angulations of multiple osteotomies and perform an osteosynthesis whose goal is to restore the initial morphology and function of the mandible. These technical difficulties must be mastered in order to avoid: - an increase in operative time, which could be deleterious generally for the patient (anaesthesia) and locally (viability of free flap), - consequences for masticatory function, - and aesthetic consequences. Virtual surgical planning allows to effectively quantify the bone stock required preoperatively and facilitates intraoperative modelling of the fibular flap. Therefore, a more precise reconstruction is obtained resulting in improved functional and aesthetic outcomes. The recent developments in 3D printing techniques offer the possibility to plan surgery directly using resin models in order to design osteotomies and titanium plate preoperatively.

Imaging findings OR Procedure details

Patients were studied preoperatively with contrast-enhanced 64slices MDCT scan of craniofacial region for a presurgical evaluation of reconstructive surgery of the mandible. As pre-operative cervical MDCT scan covered mandible, it was used to avoid redundant CT-scan. •

Our population

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From April to September 2012, 2 consecutive patients aged 46 y.o and 62 y.o. were enrolled in our protocol of pre-surgical 3D printing of the mandible. •

MDCT scanning protocol

- Sensation 64 MDCT, Siemens or Brilliance 64 MDCT, Philips - 18G IV cannula placed in a distal arm vein - Simple lateral scout - Scan volume from sphenoid sinus to clavicles - Biphasic injection 50 ml @ 3 ml/s iodinated contrast medium (300 mgI/mL) + delayed 70s 90 ml injection @ 3 ml/s iodinated contrast medium (300 mgI/mL) + 50 ml @ 3ml/ s saline chase - Pitch factor : 0,454 ; 120 kV ; Dose angular modulation

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Fig. 2: Axial CT-slice. Bone windowing. Osteolytic lesion of the left horizontal branch of the mandible. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR • MDCT reformat / VR segmentation protocol Because of close proximity of temporal and mandible bones in the region of temporomandibular articulation, automatic bone removal tools could not be used. As a TM

consequence, mandible segmentation was manual using Osirix SARL, Geneva, Switzerland) and a combination of :

(V 3.9.1 64bit, Pixmeo

- reduction box and cutting with scissors tool, - region of interest around mandible.

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As a result, every bone voxel except mandible was set to negative density (HU).

Fig. 3: Axial CT-slice of mandible after segmentation step. Case N°1. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR 3D volume rendering images with bone CLUT only showed mandible.

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Fig. 4: 3D volume rendering image of segmented mandible. Case N°1. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR •

3D modelling

After manual segmentation of mandible, Osirix with default values:

TM

3D surface rendering tool was loaded

- decimate resolution : 0.5 - smoothing iterations : 20

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- first surface - value of the pixel : 300 (can be increased in case of noisy result) Then 3Dfiles were saved using a file format known as Standard Tessellation Language (.stl).

Fig. 5: 3D surface rendering image of mandible, saved as a .stl 3D-file. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR •

3D printing

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3D printing has been done by AIP-PRIMECA Franche-Comté (ENSMM, Besançon, France) : It is a service shared by the University of Franche-Comté, the national engineering institute in mechanics and microtechnologies (ENSMM), and the Technology University of Belfort-Montbéliard. This institution brings together expertise and resources for education, research and industry in the areas of integrated design in mechanics and production engineering. .stl data were imported and loaded in Geomagic Studio software (Version 12, Geomagic Inc., Morrisville, USA). The volume was cleaned by the tool "mesh doctor".

Fig. 6: 3D surface rendering image, « cleaned » before 3D printing.

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References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR Inside the 3Dprinter, a dualtipped extrusion head deposits liquefied model (Acrylonitrile Butadiene Styrene - ABS) and support material following precise paths. Parts are built layerbylayer from the bottom, then soluble support material dissolves away in a water based solution. Dimension Elite printer (Stratasys Inc., Eden Prairie, USA): - Maximum size of the model: 200 * 200 * 275 mm - Resolution: 600 dpi - Printing Time: 10 hours - Duration of withdrawal of support: 2h - Approximate cost for printing one mandible: 70 Euros based on the volume of the object to print, out the acquisition cost of the printer. In the first case, a segment of the patient's fibula was also modelled using the same technique to calculate preoperatively the fibular osteotomies

Fig. 7: 3D resin model of mandible and fibula with preoperative planning of osteotomies

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References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR •

Pre-surgical planning

3D reproduction of the patient's mandible is used to: - Configure the osteosynthesis plate - Prepare osteotomies

Fig. 8: 3D resin model of mandible and preoperative shaping of titanium plate. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR

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The resin supports a heat of 70 ° C: the mandible resin model resin was sterilized by ethylene oxide. This sterilization process required 5 days of degassing. The titanium plate was sterilized with steam at 134 ° C.

Fig. 9: 3D resin model of mandible and titanium plate sterilization. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR •

Surgical time

Firstly, two reconstruction plates were placed parallel to the mandible basilar edge not affected by the resection. These temporary plates allowed recovering the reduction criteria of remaining mandible. The preformed reconstruction plate was then applied temporarily and screw holes were formed. At the same time, the fibula free flap was taken from the same side of anastomosis. It included flexor hallucis longus muscle to restore the volume of the floor of the mouth. The flap was lifted in one time and left pedicled. After lower limb revascularization, fibular osteotomies were performed under withers according to the schedule.

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End-to-end microsurgical anastomoses were performed under the microscope, on the facial vessels (case 1) or superior thyroid vessels (case 2). Anticoagulation prophylaxis was initiated postoperatively.

Fig. 10: Intraoperative photographs. Fibula free flap was taken (left) then fibular osteotomies were performed to fit perfectly the preformed mandibular plate (right). References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR •

Outcome

The postoperative course was uneventful in both cases at the face. Radiotherapy was introduced in the second postoperative month. Scarring at the donor site of the flap was delayed two months due to the exposure of the peroneal tendons. No patient had discomfort in daily life in relation to the removal of fibula. Patients underwent rehabilitation dentistry. Excellent functional and aesthetic result, were confirmed on CT scan

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Fig. 11: Post-operative MDCT control in case N°1. 3D Volume rendering of mandible. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR

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Fig. 12: Comparison between pre-operative and post-operative MDCT. 3D Volume rendering of mandible. Case N°2. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR

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Fig. 13: Second patient before and after surgery. References: Radiology, CHRU Besancon, Hopital Jean Minjoz - Besancon/FR Images for this section:

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Fig. 2: Axial CT-slice. Bone windowing. Osteolytic lesion of the left horizontal branch of the mandible.

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Fig. 3: Axial CT-slice of mandible after segmentation step. Case N°1.

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Fig. 4: 3D volume rendering image of segmented mandible. Case N°1.

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Fig. 5: 3D surface rendering image of mandible, saved as a .stl 3D-file.

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Fig. 6: 3D surface rendering image, « cleaned » before 3D printing.

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Fig. 12: Comparison between pre-operative and post-operative MDCT. 3D Volume rendering of mandible. Case N°2.

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Fig. 11: Post-operative MDCT control in case N°1. 3D Volume rendering of mandible.

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Fig. 10: Intraoperative photographs. Fibula free flap was taken (left) then fibular osteotomies were performed to fit perfectly the preformed mandibular plate (right).

Fig. 9: 3D resin model of mandible and titanium plate sterilization.

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Fig. 8: 3D resin model of mandible and preoperative shaping of titanium plate.

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Fig. 7: 3D resin model of mandible and fibula with preoperative planning of osteotomies

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Fig. 13: Second patient before and after surgery.

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Conclusion Reconstruction of the mandible by fibula free flap remains a delicate surgery for several reasons: - Three-dimensional configuration of the mandible, - Existence at each of its ends of an articulation with three degree of freedom, - Conducting microsurgical anastomosis in patients with comorbidities often unfavorable (active smoking, radiotherapy). Computed aided design and computed aided manufacturing to plan the intervention: - reduces operative time and blood loss [2 on page reduces ischemia time,

] , and as a consequence,

- allows to restore the anatomy of mandible with millimetric accuracy in 70% of cases [3 on page ; 4 on page ], and as a consequence preserves the function of temporomandibular joint and improves aesthetics outcome. Various techniques have been proposed for the reconstruction plan. The simplest is 3D printing of the model from which a long osteosynthesis plate bridging the two remaining fragments of mandible is shaped. It has been used by many authors [4-10 on page ]. Some criticize the use of a single plate because of biomechanics disadvantages and bulk [11 on page ]. However, this simple solution has several advantages : - It may allow achieving the mandible reduction criteria when it may be set up before resection, - It facilitates the conformation of the fibula, especially when fibular osteotomies are not planned, - It helps to soften the mandibular shape - It saves time : Time to shape the plate is 0.42h (0.25-0.68) [8 on page

].

3D printing processes that have been previously reported in this indication are stereolithography [12 on page ] and plaster of Paris [6 on page ; 13 on page ]. Stereolithography is the first rapid prototyping process developed. It gave its name to the .STL file. It realizes polymerization of a photosensitive epoxy resin. Calcium sulphate, better known as "plaster of Paris" can also be used in the same process but is non-biocompatible and cannot be used in contact with the patient. The material we

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used, ABS, is considered to be one of the easiest material to work with when you start 3D printing. It is fast: printing a mandible takes about 10 minutes. It is also cheap: approximately 70 Euros for one mandible. The printer Elite costs approximately 25,000 Euros but 3D-printers become more and more accessible with first price around 5000 €. Wang described an original alternative [14 on page ]: he uses a 3D model in paper of the mandible, calculated by computer. When there is a significant deformation of the mandible, 3D printing of the mandible may not be exploited. Some authors modelize the reconstruction of the mandible by fibula before printing [15 on page ]. It is also possible to determine the levels and angulation of fibular and mandibular osteotomies using CAD to achieve cutting guides. As a conclusion, the volumetric MDCT acquisitions and open-source post processing software, has allowed an accurate assessment of the mandible and fibula morphology. 3D resin models obtained from 3D virtual models were used to design the mandibular and fibular osteotomies, and to design titanium plate preoperatively. The implementation of this new technique required the establishment of a multidisciplinary team involving the radiologist, the surgeons, the engineer and the sterilization service. This allowed to effectively quantify the bone stock required preoperatively, to facilitate intraoperative modelling of the fibula, to shorten surgery, and to obtain perfect anatomically reconstruction resulting in improved functional and aesthetic outcomes. It is faster, easier and cheaper than other techniques described before.

References 1 Hidalgo DA (1989) Fibula free flap: a new method of mandible reconstruction. Plast Reconstr Surg, 84(1):71-79. 2 Cunningham LL, Jr., Madsen MJ, Peterson G (2005) Stereolithographic modeling technology applied to tumor resection. J Oral Maxillofac Surg, 63(6):873-878. 3 Liu XJ, Gui L, Mao C, Peng X, Yu GY (2009) Applying computer techniques in maxillofacial reconstruction using a fibula flap: a messenger and an evaluation method. J Craniofac Surg, 20(2):372-377. 4 Yeung RW, Samman N, Cheung LK, Zhang C, Chow RL (2007) Stereomodelassisted fibula flap harvest and mandibular reconstruction. J Oral Maxillofac Surg, 65(6):1128-1134. 5 Bell RB, Weimer KA, Dierks EJ, Buehler M, Lubek JE (2011) Computer planning and intraoperative navigation for palatomaxillary and mandibular reconstruction with fibular free flaps. J Oral Maxillofac Surg, 69(3):724-732.

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6 Katsuragi Y, Kayano S, Akazawa S, et al. (2011) Mandible reconstruction using the calcium-sulphate three-dimensional model and rubber stick: a new method, 'mould technique', for more accurate, efficient and simplified fabrication. J Plast Reconstr Aesthet Surg, 64(5):614-622. 7 Leiggener C, Messo E, Thor A, Zeilhofer HF, Hirsch JM (2009) A selective laser sintering guide for transferring a virtual plan to real time surgery in composite mandibular reconstruction with free fibula osseous flaps. Int J Oral Maxillofac Surg, 38(2):187-192. 8 Lethaus B, Poort L, Bockmann R, Smeets R, Tolba R, Kessler P (2012) Additive manufacturing for microvascular reconstruction of the mandible in 20 patients. J Craniomaxillofac Surg, 40(1):43-46. 9 Rohner D, Guijarro-Martinez R, Bucher P, Hammer B (2012) Importance of patientspecific intraoperative guides in complex maxillofacial reconstruction. J Craniomaxillofac Surg. doi: S1010-5182(12)00239-9 [pii] 10.1016/j.jcms.2012.10.021 10 Vakharia KT, Natoli NB, Johnson TS (2012) Stereolithography-aided reconstruction of the mandible. Plast Reconstr Surg, 129(1):194e-195e. 11 Boyd TG, Huber KM, Verbist DE, Bumpous JM, Wilhelmi BJ (2012) CASE REPORT Removal of Exposed Titanium Reconstruction Plate After Mandibular Reconstruction With a Free Fibula Osteocutaneous Flap With Large Surgical Pin Cutters: A Case Report and Literature Review. Eplasty, 12:e42. 12 Cohen A, Laviv A, Berman P, Nashef R, Abu-Tair J (2009) Mandibular reconstruction using stereolithographic 3-dimensional printing modeling technology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 108(5):661-666. 13 Yamanaka Y, Yajima H, Kirita T, et al. (2010) Mandibular reconstruction with vascularised fibular osteocutaneous flaps using prefabricated stereolithographic mandibular model. J Plast Reconstr Aesthet Surg, 63(10):1751-1753. 14 Wang TH, Tseng CS, Hsieh CY, et al. (2009) Using computer-aided design paper model for mandibular reconstruction: a preliminary report. J Oral Maxillofac Surg, 67(11):2534-2540. 15 Zheng GS, Su YX, Liao GQ, et al. (2011) Mandible reconstruction assisted by preoperative virtual surgical simulation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. doi: S1079-2104(11)00344-1 [pii] 10.1016/j.tripleo.2011.05.016

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Personal Information Corresponding Author : Name : Dr Sébastien Aubry Adress : Department of radiology Musculoskeletal Imaging CHRU Besançon Boulevard Fleming 25030 Besançon Cedex FRANCE Tel : (+33) 381 668 245 Fax : (+33) 381 668 969 Email : [email protected]

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