Digital planning and individual implants for secondary reconstruction of midfacial deformities: A pilot study

Objective To evaluate the feasibility and accuracy of implementing three-dimensional virtual surgical planning (VSP) and subsequent transfer by additive manufactured tools in the secondary reconstruction of residual post-traumatic deformities in the midface. Methods Patients after secondary reconstruction of post-traumatic midfacial deformities were included in this case series. The metrical deviation between the virtually planned and postoperative position of patient-specific implants (PSI) and bone segments was measured at corresponding reference points. Further information collected included demographic data, post-traumatic symptoms, and type of transfer tools. Results Eight consecutive patients were enrolled in the study. In five patients, VSP with subsequent manufacturing of combined predrilling/osteotomy guides and PSI was performed. In three patients, osteotomy guides, repositioning guides, and individually prebent plates were used following VSP. The median distances between the virtually planned and the postoperative position of the PSI were 2.01 mm (n = 18) compared to a median distance concerning the bone segments of 3.05 mm (n = 12). In patients where PSI were used, the median displacement of the bone segments was lower (n = 7, median 2.77 mm) than in the group with prebent plates (n = 5, 3.28 mm). Conclusion This study demonstrated the feasibility of VSP and transfer by additive manufactured tools for the secondary reconstruction of complex residual post-traumatic deformities in the midface. However, the median deviations observed in this case series were unexpectedly high. The use of navigational systems may further improve the level of accuracy

Vergleich der präoperativen Planung mit dem postoperativen Ergebnis bei computergestützt geplanten posttraumatischen Rekonstruktionen des Mittelgesichts

Das Ziel der Arbeit ist die postoperative Implantat- und Knochensegmentposition mit der präoperativ geplanten virtuellen Position bei sekundären Rekonstruktionen des Mittelgesichtsskeletts und primären Rekonstruktionen der Orbitawände ohne Verwendung von Navigationssystemen zu vergleichen. Die erste Studie wertet die Implementierung der VSP zur sekundären Korrektur von posttraumatischen Deformitäten im Bereich des lateralen und zentralen Mittelgesichts (des Jochbeines, Jochbogens und Oberkiefers) aus. Die zweite Studie untersucht die Implementierung der VSP zur primären Rekonstruktion der inferioren und medialen Orbitawände. Die Patientenkohorte in der ersten Studie besteht aus Patienten, die von 2013 bis 2019 in der Klinik für Mund-, Kiefer- und Gesichtschirurgie der LMU München wegen zuvor nicht adäquat versorgter Frakturen im zentralen und lateralen Mittelgesichtsbereich operativ behandelt wurden. Patienten mit isolierten Orbitawand- oder Le Fort I-Frakturen wurden von der Studie ausgeschlossen. In der zweiten Studie wurden Patienten retrospektiv eingeschlossen, die von 2015 bis 2019 in der Klinik für Mund-, Kiefer- und Gesichtschirurgie der LMU München aufgrund von isolierten Orbitawandfrakturen operiert wurden. 8 Patienten wurden in die erste Studie und 27 Patienten in die zweite Studie aufgenommen. Die mediane Abweichung zwischen geplanter und definitiver Position für die PSI und die Knochensegmente wurde erstens zwischen den gesamten Modelloberflächen mittels einem geeigneten Algorithmus der Software 3-Matic und zweitens an anatomisch korrespondierenden Referenzpunkten ausgemessen, analysiert und ausgewertet. In der ersten Studie betrugen die medianen Abstände zwischen der virtuell geplanten und der postoperativen Position der PSI 2,01 mm (n = 18) gegenüber einem medianen Abstand bezüglich der Knochensegmente von 3,05 mm (n = 12). Bei Patienten, bei denen PSI verwendet wurden, war die mediane Verschiebung der Knochensegmente geringer als in der Gruppe mit vorgebogenen Platten. Darüber hinaus konnte der Jochbeinbereich mit geringerer Abweichung als der Oberkieferbereich positioniert werden. Ferner zeigte sich die Zahnbogenregion im Vergleich zur kranialen Oberkieferregion eine höhere Positionierungsgenauigkeit. In der zweiten Studie zeigten die Medianwerte für die Referenzpunktabmessungen eine größere Abweichung bei den Implantaten zur Versorgung der medialen Orbitawand, nämlich 0,79 mm. Der Wert für die Gruppe der Orbitabodenimplantate lag bei 0,45 mm. Es konnte keine Korrelation zwischen der postoperativen Diplopie und der Passgenauigkeit der Implantatposition nachgewiesen werden. Die vorliegende Arbeit zeigt erstens die Machbarkeit der Übertragung der VSP durch CAD/CAM Werkzeuge für die sekundäre Rekonstruktion komplexer posttraumatischer Restdeformitäten im Mittelgesicht, jedoch mit relativ erhöhter Ungenauigkeit, und zweitens die Möglichkeit einer genauen Umsetzung der Planungsposition bei der Rekonstruktion der inferioren und/oder medialen Orbitawand. Die in der ersten Studie beobachteten höheren Abweichungen lassen sich durch Unterschiede in der Bewertungsmethode sowie durch die Komplexität der Deformitäten, Osteotomien und chirurgischen Verfahren erklären, so dass der Einsatz von Navigationssystemen die Genauigkeit der Repositionierung weiter verbessern könnte

A Computational/Experimental Platform for Investigating Three- Dimensional Puzzle Solving of Comminuted Articular Fractures

Reconstructing highly comminuted articular fractures poses a difficult surgical challenge, akin to solving a complicated three-dimensional (3D) puzzle. Pre-operative planning using CT is critically important, given the desirability of less invasive surgical approaches. The goal of this work is to advance 3D puzzle solving methods toward use as a pre-operative tool for reconstructing these complex fractures. Methodology for generating typical fragmentation/dispersal patterns was developed. Five identical replicas of human distal tibia anatomy, were machined from blocks of high-density polyetherurethane foam (bone fragmentation surrogate), and were fractured using an instrumented drop tower. Pre- and post-fracture geometries were obtained using laser scans and CT. A semi-automatic virtual reconstruction computer program aligned fragment native (nonfracture) surfaces to a pre-fracture template. The tibias were precisely reconstructed with alignment accuracies ranging from 0.03-0.4mm. This novel technology has potential to significantly enhance surgical techniques for reconstructing comminuted intra-articular fractures, as illustrated for a representative clinical case

Computer-assisted pre-operative automatic segmentation and registration tool for malunited radius osteotomy: A proof-of-concept study

Corrective osteotomy is a standard treatment for distal radius fractures in malunited radius cases. In order to increase the efficiency of the osteotomy pre-operative plan, in this study, a proof-of-concept framework of automatic computer-assisted segmentation and registration tool was developed for the purpose of malunited radius osteotomy pre-operative planning. The program consisted of the functions of segmentation, virtual cutting, automatic alignment and registration. One computed tomography (CT) scanning dataset of a patient's bilateral forearm was employed as an illustration example in this study. Three templates of 3D models including the healthy radius, and the pre- and post-correction injured radius were output as STL geometries for pre-operative plan purposes

Role of Mimics a Cad Software in 3D Reconstruction of CT Data in Oral and Maxillofacial Surgery

INTRODUCTION: Ever since radiations became a part of diagnosis after the discovery of X- rays by roentgen, it has undergone so many advances and the biggest leap of them all is the transition from 2D to 3D. 3D visualization and diagnosis has been made possible by computed tomography. With the arrival of 3D in radiography, the spectrum of use has widened in that it is not only being used for visualization, there is also use of the 3 dimensional images in diagnosing, treatment planning and surgical simulation which is now becoming a more popular method. Technological advances in computerized tomography (CT) have reduced time for data acquisition and thereby reduce the exposure time and the radiation risk for the patient. Now CT data can be exported in DICOM (Digital Imaging and Communication) format which is a format accepted universally by most of the softwares for reconstruction so that CT images may be economically and quickly generated using the CAD software. With Helical CT a single exposure is enough to obtain reconstructed images in all the 3 planes, Axial, Coronal and sagittal. 3D CT was judged superior to multiplanar two-dimensional CT. CT data can be exported into a CD in DICOM format. This data can be reconstructed into a 3D virtual object/model using various softwares. In our department Materialise Mimics is used for the reconstruction of CT data, visualizing, planning and surgical simulation. AIM AND OBJECTIVE: The purpose of the study is to evaluate the efficacy of Mimics a medical based CAD software in 3D reconstruction of CT data, visualization, surgical simulation and physical model fabrication which can be used in Oral and Maxillofacial Surgery. MATERIALS AND METHOD: This study was done in the department of Oral and MaxilloFacial Surgery, Ragas Dental College and Hospital, Uthandi, Chennai. Period of study was done during September 2008 to July 2010. CT was taken for selective patients. A CAD based medical software MIMICS (Materialise, Leuven, Belgium). is used for 3D reconstruction of the acquired CT data. CT protocol. CT Scan parameter for all the patients were as follows, Vertex to Manubrium, 130 kV and 81 mA/s, Slice increment 0.5mm, Width 512 pxl, Height 512 pxl, Pixel size .500 mm, Gantry tilt 0.00, Algorithm H70s. CONCLUSION: The data produced by the CT machines are a series of images. These images are printed on sheets and are viewed as conventional 2D images only and are not interactive. But through this software the CT data is now very interactive. A powerful processor, large virtual memory of the computer and dedicated graphics card is required. This software provides a better visualization of the anatomy and pathology, compared to conventional CT images. Accurate measurement between points and measuring of angles is possible with this software. Osteotomy, distraction and other surgical simulation can be done with this software. Splints templates and guides for intraoperative use can be fabricated. This software eliminates cumbersome procedures to the patient like facebow transfer and impression making. It is a good learning tool as it gives exact details of the anatomy. From this study we conclude that MIMICS a medical based CAD software is a very efficient tool in Visualization, Diagnosis, Treatment planning, Surgical Simulation and fabrication of Templates for intraoperative use in Oral and MaxilloFacial Surgery

Finite element model creation and stability considerations of complex biological articulation : the human wrist joint

The finite element method has been used with considerable success to simulate the behaviour of various joints such as the hip, knee and shoulder. It has had less impact on more complicated joints such as the wrist and the ankle. Previously published finite element studies on these multi bone joints have needed to introduce un-physiological boundary conditions in order to establish numerical convergence of the model simulation. That is necessary since the stabilising soft tissue mechanism of these joints is usually too elaborate in order to be fully included both anatomically and with regards to material properties. This paper looks at the methodology of creating a finite element model of such a joint focussing on the wrist and the effects additional constraining has on the solution of the model. The study shows that by investigating the effects each of the constraints, a better understanding on the nature of the stabilizing mechanisms of these joints can be achieved

Artificial intelligence in dentistry, orthodontics and orthognathic surgery: A literature review

Artificial intelligence is the ability of machines to work like humans. The concept initially began with the advent of mathematical models which gave calculated outputs based on inputs fed into the system. This was later modified with the introduction of various algorithms which can either give output based on overall data analysis or by selection of information within previous data. It is steadily becoming a favoured mode of treatment due to its efficiency and ability to manage complex conditions in all specialities. In dentistry, artificial intelligence has also popularised over the past few decades. They have been found useful for diagnosis in restorative dentistry, oral pathology and oral surgery. In orthodontics, they have been utilised for diagnosis, assessment of treatment needs, cephalometrics, treatment planning and orthognathic surgeries etc. The current literature review was planned to highlight the uses of artificial intelligence in dentistry, specifically in orthodontics and orthognathic surgery