Application of 3D Printing in Management of Complex Fractures

Transcription

1 Application of 3D Printing in Management of Complex Fractures Poster No.: C-1304 Congress: ECR 2015 Type: Educational Exhibit Authors: T. Kelil 1, A. Imanzadeh 1, T. Pietila 2, G. Bonci 1, Y. Epelboym 1, F. J. Keywords: DOI: Rybicki, MD, PhD. 1 ; 1 Boston, MA/US, 2 Plymouth/US Experimental, Musculoskeletal bone, Computer Applications-3D, Trauma /ecr2015/C-1304 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 12

2 Learning objectives 1. Describe 3D printing for surgical planning and management of complex pelvic fractures. 2. Discuss the steps involved in generating a useful STL file for 3D printing from DICOM CT images. Background Management of complex fractures such as those involving the pelvis poses a unique challenge to orthopedic surgeons, owing to the inherent complex 3-dimensional anatomy of the pelvis and surrounding vital structures (1-2). Better understanding of fracture patterns and orientation is indispensible for precise preoperative surgical planning and as a result improved surgical outcomes (3). Additionally, in keeping with patient-centric therapies, there is an unmet need for surgeons to use tools and methods tailored to the individual patient. 3D printed models address these needs by providing superior understanding of complex fractures and allowing patient specific surgical management. Findings and procedure details Complex 3-dimensional geometry of the pelvis and the required intricate intraoperative manipulations make pelvic reconstruction surgeries challenging and technically demanding (3). Adequate display of the relationship between involved structures and spatial comprehension of fracture orientation is paramount for successful reconstruction. Traditional assessment of pelvic fractures involves radiographs (Figure 1) and computed tomography (CT) (Figure 2,3). Both provide a 2-dimensional (2D) representation of the 3D anatomy. Volume rendering (Figure 4) can be viewed from any projection, but images are viewed on a 2-dimensional computer monitor screen (4). 3D printing provides tangible models that enable better comprehension of the complexity of fractures and the 3D geometry of the pelvis. Pelvic reconstruction is technically demanding; each patient has unique anatomy and fracture patterns vary depending on the mechanism of injury. Complete visualization of fracture alignment and better understanding of the complexity of the fracture minimizes unexpected intraoperative findings and allows the surgeon to take necessary precautions Page 2 of 12

3 in advance. Preoperative simulation includes determining optimal hardware positioning such as measuring screw length and location, plus designing the route of screw entry. This lowers intraoperative and sedation time (5). Selecting the entry site and approach can also reduce the size of the incision. Customized, 3D printed curved plates are preferred in comparison to the standard practice of bending hardware intraoperatively. 3D printed models thus provide surgeons an opportunity to tangibly evaluate fracture configuration, simulate the surgical procedures, and when necessary prepare customized hardware (6-9). Preoperative - Evaluation of fracture pattern and complexity - Planning and simulation of the surgical procedure including selection of surgical point of entry - Selection of precise screw length and trajectory - Assist in pre-bending of reconstruction plates - Selection of correct size of implant and angle of placement - Creation of custom hardware or implant matched to patient anatomy - Aid in obtaining informed consent as 3D models enhance patient understanding of the procedure Intraoperative - Serve as an aid of communication between surgical team members - Reduce intraoperative time as a result of preoperative simulation and the use of pre-bent plates and appropriate screw lengths - Reduce sedation time, as procedures are shorter - Minimize incision size and intraoperative bleeding as precise approach and manipulation are planned preoperatively Post operative - Models can be used as a library of various fracture types for medical Page 3 of 12

4 students and residents - Serve as educational tool for surgeons and trainees to practice reduction and implant placement on real cases since senior surgeons or fellows perform most of the complicated cases Steps involved in 3D printing The term "3D printing" refers to fabrication of a tangible object from a digital file by a 3D printer. Digital Imaging and Communications in Medicine (DICOM) image files cannot be used directly for 3D printing as 3D printers recognize Standard Tessellation Language (STL) format files that define surfaces as a collection of triangles (called facets) (Figure 5). Further post processing steps are required to convert DICOM files to STL format and make them readable by 3D printers. Images should be reconstructed from isotropic voxels with slice thickness less than or equal to 1.25 mm. The conversion of DICOM to STL format requires the radiologist to separate structures of interest into individual objects. Specific software packages enable segmentation of DICOM images using semiautomated and manual segmentation algorithms, allowing the user to demarcate desired parts. The segmented data are then exported in a file format that can be recognized by 3D printers. In most cases, the STL output is not optimized for printing and further refinement is required. Computer Aided Design (CAD) software is used to perform further post processing steps in order to make the model more homogeneous. The following general steps are needed to generate a printable STL file from CT DICOM images 1) Segmentation This step involves identifying specific voxels in a region of interest such as the cortical bone from the remaining DICOM data. This can be accomplished by isolating voxels with attenuation within a specified Hounsfield Unit (HU) range. Selecting voxels within the specified HU range that are physically connected to a seed point of interest creates an intermediate model. 2) Editing the intermediate model This step simplifies the model and limits the amount of printing material needed by excluding unneeded portions of the intermediate model. For example, the normal distal femurs can be removed from the intermediate model of the pelvis by breaking voxel-tovoxel connections. Page 4 of 12

5 3) Exporting the intermediate model to CAD software CAD based post-processing steps further refine the model by eliminating rough areas, gaps and surface imperfections. 4) 3D printing the STL file The file can then be imported into a software package that supports 3D printing of STL files. The orientation can then be adjusted, and the material selected. The appropriate hardware technology and printed materials should be tailored to the clinical needs. In general, there are various technologies available to create 3D models including stereolithography, selective laser sentring, laminated object manufacturing, fused deposition modeling, Solid Ground Curing and Ink Jet printing techniques (6). Factors to consider in choosing which technology to use include availability, cost, speed, biocompatibility, and most importantly anticipated usage of the product (e.g., a model for surgical planning versus a custom made implant). Images for this section: Page 5 of 12

6 Fig. 1: Radiograph demonstrates bilateral pubic rami (arrows) and right sacral fractures (arrow head) Page 6 of 12

7 Fig. 2: Reformatted coronal CT image of the pelvis demonstrates a comminuted right sacral fracture (arrow). Page 7 of 12

8 Fig. 3: Reformatted coronal CT image of the pelvis demonstrates bilateral pubic rami fractures (arrowheads) Page 8 of 12

9 Fig. 4: Volume rendered 3D image of the pelvis demonstrates bilateral pubic rami (arrows) and right sacral fractures (arrowheads). Page 9 of 12

10 Fig. 5: STL file generated from CT DICOM images demonstrates right sacral (arrows) and bilateral pubic rami fractures (arrowheads). This file format is readable by 3D printers and can be used to generate the corresponding 3D model. Page 10 of 12

11 Conclusion 3D printing provides superior understanding of the complexity and alignment of pelvic fractures and facilitates intraoperative navigation when compared to other methods to portray CT images. The use of 3D printed models in surgical planning and preoperative simulation allows efficient procedures that are tailored to each patient, leading to improved surgical outcomes. These models can also be used to create customized hardware and implants. Additionally, models can be used for educational purposes such as a library of various fracture types and means of practicing surgical procedures. Personal information Tatiana Kelil, MD. Department of Radiology, Brigham and Women's Hospital, Harvard Medical School. Tkeli@partners.org References 1. Khurana B, Sheehan S, Sodickson A, et al. Pelvic Ring Fractures: What the Orthopedic Surgeon Wants to Know. Radiographics. 2014: 34(5): Kinik H, Armangil M. Extensile triradiate approach in the management of combined acetabular fractures. Arch Orthop Trauma Surg. 2004; 124: Lykomitros VA, Papavasiliou KA, Alzeer ZM, et al. Management of Traumatic Sacral Fractures: a retrospective case series study. Injury. 2010;41(3) Niiikura T, Sugimoto M, Lee SY et al. Tactile surgical navigation system for complex acetabular fracture surgery. Orthopedics 2014:37(4): Honiball JR. The applications of 3D printing in reconstructive surgery. Industrial Engineering at the University of Stellenbosch, South Africa, sequence=1. 6. Bagaria A, Rasalkar D, Bagaria S et al. Medical Applications of Rapid Prototyping - A new Horizon, Advanced applications of Rapid Prototyping Technology in Modern Engineering, Dr.M.Hoque(Ed.), InTech, DOI: /2005 Page 11 of 12

12 7. Bagaria V, Deshpande S, Ras- alkar DD, Kuthe A, Paunipagar BK. Use of rapid prototyping and three-dimensional reconstruction modeling in the management of complex fractures. Eur J Radiol. 2011; 80: Deshmukh TR, Kuthe AM, Vaibhav B. Preplanning and simulation of surgery using rapid modeling. J Med Eng Technol. 2010; 34: Hurson C, Tansey A, O'Donnchadha B, et al. Rapid prototyping in the assessment, classification and preoperative planning of acetabular fractures. Injury. 2007; 38: Page 12 of 12