1. Introduction

Figure 1. Anatomy of right foot bones (Superior view) [2].

Figure 1. Anatomy of right foot bones (Superior view) [2].

Figure 2. X-ray of left foot showing abnormal ossification around 3^rd MTP Joint [3].

Figure 2. X-ray of left foot showing abnormal ossification around 3^rd MTP Joint [3].

2. Related Works

3. Materials and Methods

Table 1. 3D design software comparison.

3.2. Comparative Study of Design Software

In this section we present a comparison analysis that involves a benchmarking of six of the most efficient 3D modeling and reconstruction software, each was evaluated according to several requirements, including accessibility, open-source compatibility, and general quality.

We chose the top four performers with the highest marks using a 10-point rating methodology for the evaluation procedure. It has led us to choose Table Edu 4.0, Materialise Mimics, SolidWorks and Meshmixer as the most efficient ones that meets our needs and expectations.

3.2.1. Blender

Blender is an open source, 3D modeling, animation and rendering software, widely used in the film, video game, animation and creative arts industry. It offers a full range of tools for modeling, texturing, lighting, animation and rendering virtual 3D objects and environments. One of the key features of Blender is its 3D modeling capabilities. It provides a versatile set of tools for creating 3D models using various techniques like polygonal modeling, sculpting, and procedural modeling. Artists and designers can shape and manipulate objects with precision and creativity [17].

3.2.2. Cinema 4D

Cinema 4D is a commercial modelling, animation and 3D rendering software developed by the German company Maxon Computer GmbH. It is generously used in the film, television and design industries to create 3D graphics, specific effects, animations and CG images. One of the notable features of Cinema 4D is its intuitive and user-friendly interface, making it accessible to both beginners and experienced 3D artists. [18].

3.2.3. Table EDU 4.0 (Anatomage)

Figure 3. Anatomage table.

Figure 3. Anatomage table.

Anatomage created the software platform Table Edu 4.0, which offers interactive tools for anatomy and medical education. It is intended for use in classrooms, labs, and other instructional environments. It’s a proprietary software for the realization, image dissection, virtual reality and manual segmentation that offers an immersive and fascinating approach to manipulate, dissect, manually segment, and explore anatomical structures by virtual reality with high quality 3D reconstruction [19].

3.2.4. 3D SLICER

3D Slicer is a free, open-source software for visualization, processing, segmentation, registration, and analysis of medical, biomedical, and other 3D images and meshes; and planning and navigating image-guided procedures. The primary purpose of 3D Slicer is to process and analyze medical imaging data, such as MRI, and CT scans to extract meaningful information for diagnosis, research, and treatment planning. It offers a comprehensive set of tools for image segmentation, allowing users to delineate anatomical structures and regions of interest within the medical images. This software's benefits include the ability to estimate distances and do 3D reconstructions from 2D pictures obtained using several medical energy modalities [19].

3.2.5. Materialise Mimics

Materialise Mimics is a 3D image processing, design and modeling software that allows users to import and process medical imaging data such as CT or MRI scans. Due to its capability to create high-quality 3D models of medical pictures, it is often used in the medical field. It is the best option for a variety of medical applications, including surgical planning, patient-specific implant design, and medical research, thanks to its sophisticated tools and algorithms and interaction with 3D printing software [20].

3.2.6. SolidWorks

SolidWorks is a CAD (Computer Aided Design) software used to create 3D models for design, engineering, and manufacturing purposes. Users of SolidWorks may convert 2D sketches into 3D models, which gives them the ability to edit designs in three dimensions for improved comprehension and communication among design team members. In the medical profession, it is used for the design and modeling of medical equipment including implants, prostheses, and surgical tools as well as for simulating human anatomy and analyzing the mechanics and structure of bones and tissue [21].

3.2.7. Meshmixer

Meshmixer is a software program developed by Autodesk, a leading software company specializing in 3D design, engineering, and entertainment software. He is often involved in the 3D printing process to adjust and repair 3D models, integrate different models, or provide supports for printing. The program offers a wide range of features, including adding texture, smoothing rough areas, and hollowing out models to save on printing material. In general, it is an effective, adaptable, and simple tool for 3D modeling and printing [22].

3.3. Comparative Study of Biomaterials (Benchmark)

The table below serves as a benchmark comparison between the top five most frequently applied materials in the field of implants. Each of the materials on the list has a special combination of advantages and weaknesses that make it suitable for a variety of implant devices and patient requirements. The table evaluates each material based on a number of factors, including its strength, durability, weight, cost, and comfort, by also considering the surgical outcomes and patient satisfaction associated with each material.

Table 2. Advantages and weaknesses of biomaterials.

Table 2. Advantages and weaknesses of biomaterials.

Biomaterials	Advantages	Weaknesses
Stainless steel	▪ Superior corrosion resistant ▪ Used for internal fixation	▪ Allergic reaction ▪ Weight ▪ Difficulty with imaging
Polyethylene	▪ Provides excellent soft tissue penetration and coverage	▪ Degradation ▪ Its rigid nature ▪ Damage to the surface
Cobalt alloys	▪ Good magnetic properties ▪ Corrosion resistant and biocompatible	▪ Toxicity ▪ Bone loss
Titanium and Titanium alloys	▪ Very high corrosion resistance ▪ Lightweight ▪ Biocompatible ▪ Non-magnetic ▪ Very low percentage of patients with allergic reactions	▪ High cost
Polymer	▪ Non-magnetic ▪ Long-term mechanical and chemical resistance	▪ Degradation ▪ Allergic reaction ▪ Poor mechanical strength

3.4. 3D Printers

3.4.1. Volumic Stream 30 Ultra

The Volumic Stream 30 Ultra is a high-performance desktop 3D printer for experts and advanced users. This printer has a maximum resolution of 50 microns, which enables it to create high-quality products. Additionally, it has a filament detecting system that recognizes breaks in the filament and has a restart printing functionality in case of a power interruption. It comes with Wi-Fi and USB connections, which makes it easier to transmit printing data [23].

Figure 4. Volumic Stream 30 Ultra 3D printer.

Figure 4. Volumic Stream 30 Ultra 3D printer.

3.4.2. Next Dent 5100

The Next Dent 5100 is a professional-grade 3D printer designed primarily for dental applications. It’s one of the first dental 3D printers employs biocompatible materials to create high-quality, patient-specific dental implants, prosthesis, and models. With a touchscreen interface and simple software, it is also simple to operate and makes print preparation and maintenance simple. The printer also has automated calibration and a selfdiagnosis mechanism to make sure it is always operating at its best. By applying a unique process called Laser Stereolithography (LSL), it can produce dental models with incredibly detailed features and precise measurements. This technology builds up the model from the bottom up by selectively curing the resin liquid with a laser layer by layer [24].

Figure 5. NextDent 5100 3D printer.

Figure 5. NextDent 5100 3D printer.

4. Experiments and Results

4.1. 3D Reconstruction of the Whole Foot

This comparative review presents an exploration of foot segmentation capabilities using three distinct software programs. Each software's unique capabilities and results are examined and highlighted through the lens of both 2D imaging and 3D reconstruction. Screenshots depicting the exact segmentation outputs achieved by each software program allow for a visual comparison, serving as a tangible testament to their respective efficacies and accuracies. This approach facilitates a comprehensive understanding of the strengths and nuances of each software, paving the way for an informed decision when choosing the best tool for specific needs in foot segmentation.

Table 3. 3D reconstructions of foot.

Table 3. 3D reconstructions of foot.

Software	2D imaging	3D reconstruction
3D Slicer
Materialise Mimics
Table EDU 4.0 (Anatomage)

Following this, we will embark on a detailed comparative analysis, scrutinizing the individual performance and capabilities of these tools, to ascertain their strengths and potential limitations.

Firstly, with regards to the 3D Slicer software, it demonstrates considerable capabilities in creating 3D reconstructions of the foot. While the overall results are laudable, it occasionally misses a few intricate details, indicating minor inconsistencies in precision. However, these small shortcomings do not significantly detract from its overall usefulness, affirming 3D Slicer's reputation as a reliable tool in the realm of medical imaging and 3D reconstruction.

Next, we consider Materialise Mimics. This software distinguishes itself with extraordinary precision and accuracy in creating 3D foot reconstructions. Its ability to accurately capture minute details of foot anatomy allows it to produce a top-notch 3D model. An outstanding feature that enhances Materialise Mimics' appeal is its capability to promptly export the restructured model into an STL file, ideally suited for 3D printing. This function increases operational efficiency, making it a highly effective tool.

Lastly, the Table Edu 4.0 version. This software delivers impressive results in terms of 3D foot reconstruction, perfectly replicating delicate anatomical details. However, it faces a significant limitation in its inability to export the reconstructed model into a 3D printable STL format. This limitation reduces the software's adaptability, restricting its application primarily to the Anatomage Table environment and limiting its usefulness in situations requiring physical models.

4.2. 3D Printing of the Bone

4.2.1. Using Volumic Stream 30 Ultra

The Volumic Stream 30 Ultra's 3D printing of a bone model. The printing process utilized a thermoplastic polymer called PLA filament and took a total of 1 hour and 11 minutes to complete. The printer features a heated print bed, which helps in maintaining the optimal temperature for the PLA filament to adhere properly.

Additionally, the printer is equipped with an extruder, a device responsible for feeding the PLA filament into the printer. The filament is melted and extruded through a nozzle onto the print bed, where it cools down and solidifies to form the initial layer of the bone model. This technique is repeated layer by layer until the entire bone model is finished.

Figure 6. 3D Printed bone using PLA.

Figure 6. 3D Printed bone using PLA.

4.2.2. Using Next Dent 5100

The printing process of this particular printer utilizes digital light processing (DLP) technology, where layers of resin liquid are solidified using UV light. To begin the process, a digital 3D volume of the bone is inputted into the printer's software. The bone model is then printed layer by layer, following the instructions from the digital 3D volume and using the DLP technique to cure the resin. Each layer is added on top of the previous one, gradually constructing the bone model. The entire printing process took approximately one hour to complete. Throughout this time, the printer continuously solidified the resin layers, bringing the bone model to its final form.

Figure 7. 3D printed bone using resin.

Figure 7. 3D printed bone using resin.

4.3. 3D Printing of the Hollowed Bones

4.3.1. Dimensions of the Removed Part of the Bones

The following set of images exemplify the quantified measurements of the bone volume extracted in preparation for the implantation in this specific case. These illustrations offer an extensive portrayal of the mandatory alterations made to the existing osseous structure, thereby facilitating an accurate fitting of the implant element. This specific volumetric assessment underscores the crucial nature of meticulous planning and precise execution in ensuring the success of implant surgeries. In this particular case, it further illuminates the amount of bone removal required to accommodate the implant optimally.

Figure 8. Dimensions of the phalangeal part.

Figure 8. Dimensions of the phalangeal part.

In this particular case, the images reveal precise measurements of the phalangeal bone section set for removal to accommodate the implant insertion. The head of the phalanx, which is the rounded topmost part of the bone, measures 16.37mm, signifying a substantial removal requirement to ensure a successful implant fit. Meanwhile, the upper part of the phalanx, often referred to as the base, measures 11.37mm.

Figure 9. Dimensions of the metatarsal part.

Figure 9. Dimensions of the metatarsal part.

On the other hand, the images provide specific measurements of the metatarsal bone portion designated for removal to make way for the implant. The head of the metatarsal bone, the distal rounded part, measures 17.09mm, indicating a significant volume for extraction to accommodate the implant device. The superior or upper section of the metatarsal, referred to as the base, is found to measure 12.68mm.

4.3.2. Flowchart of the 3D Printing of the Hollowed Bones

The following flowchart defines the steps taken to create a 3D reconstruction of the metatarsophalangeal hollowed bones to receive the implant. Firstly, the collection of 2D scan images of the patient's foot, which are usually stored in DICOM format. After being collected, these images are uploaded into the Materialise Mimics software. This specialized software is used for processing the DICOM images and plays a crucial role in the next step: the 3D segmentation of the whole foot. This software is able to offer a more thorough and accurate representation of the patient's anatomy by converting 2D images into a 3D structure. After the reconstruction, the metatarsophalangeal bones is then reconstructed and then exported as an STL file. The next phase involves threading, cleaning, and refining the model with another 3D modeling software called Meshmixer, by creating threads, removing unnecessary surfaces and refining the bones for more accurate definition, which improves the precision of the model, guaranteeing it is ready to receive the implant. The finishing step in this approach is the 3D printing of the bones with cavities, a Next Dent 3D printer is used in this instance.

Figure 10. Flowchart of the hollowed bones.

Figure 10. Flowchart of the hollowed bones.

4.4. Modeling the Implant

3D reconstruction is the process of creating a three-dimensional model or representation of an object or scene from two-dimensional data. Several sources, including images, medical imaging scans, laser scanning, and structured light scanning, can provide this data. Image capture, data preprocessing, feature recognition and matching, camera calibration, triangulation, and surface reconstruction are the typical stages in the 3D reconstruction process [25]. In order to identify the elements required to create the implant, after the segmentation of the whole foot we reconstructed the bones with the chosen software Materialise Mimics, then we created a 2D model sketch composed of 4 pieces using a CAD program which was SolidWorks, by following the lead of toes and fingers implants models that already existed. The same software is used to transfer the finished 2D drawing in 3D, after that we check if the dimensions and proportions are accurate and consistent with the specifications of the implant. Once the 3D model has been created, it must be edited and refined in preparation for 3D printing. We used Meshmixer to do so, which enables us to alter the 3D model while preserving the size and shape of the implant by deleting extraneous components or decreasing the mesh's density.

Figure 11. 2D sketch of the implant.

Figure 11. 2D sketch of the implant.

Figure 12. 3D model of the implant.

Figure 12. 3D model of the implant.

4.5. Components of the Implant and Its Functionalities

The following table illustrates the four separate components of the implant item, each accompanied by an image and a description of its individual functionalities. The accompanying descriptions clarify each component’s specific roles and how they contribute to the implant device’s overall functionality, while the accompanying pictures give each part a clear visual representation. This table representation provides a thorough knowledge of the construction and use of the implant, highlighting the significance and purpose of each part within the overall system.

Table 4. components of the implant.

Table 4. components of the implant.

Components	Pictures of the components	Functionalities
Metatarsal Component		Our Metatarsal Component is carefully engineered so it imitates the natural shape and functionality of the removed part of the metatarsal bone in the human foot. The complicated foot architecture serves as deliberate inspiration for the design of the metatarsal component, guaranteeing ideal weight distribution and pressure control as well as a smooth transition from the natural bone to the implant.
Phalangeal Component		The Phalangeal Component has been carefully designed to closely emulate the structural and functional aspects of the removed part of the human proximal phalanges. It’s complex structure is reflected in its design, ensuring ideal force distribution and effective motion. Maintaining the complicated mechanical interactions of this part, it enables asmooth transfer from the natural bone to the implant.
Insert		The Insert is carefully constructed and intended to resist the daily pressure of different movements while also facilitating a seamless connection with the other components of the implant system. It serves as a vital connection between the dynamic Metal Head and the static Phalangeal Component, guaranteeing a smooth range of motion. The design of the Insert originates in the sophisticated biomechanics of the human foot. Its purpose is not only to connect two crucial pieces of the implant structure but also to imitate the natural movement of the toes, providing users with a comfortable, natural-feeling range of motion.
Metal Head		Its purpose is to act as a body’s natural joint could, allowing for a variety of motion while reducing friction, which is essential for fluid and natural motion. Its smooth surface and spherical shape enable multidirectional mobility, giving the user the flexibility and freedom to go about their dailyactivities with comfort.

4.6. 3D Printing of the Implant

The creation of the implant joint involved a complex and intricate 3D printing process that consisted of four distinct parts. Specifically, two of these parts were specifically designed to replace the removed sections of both the metatarsal and phalangeal bones. The intention behind these components was to accurately replicate the missing bone segments and restore the structural integrity of the foot. The remaining two components served a crucial role in connecting the replaced bone parts and facilitating mobility between them. These linking components were carefully engineered to ensure smooth movement and enable the implant to function as closely as possible to the natural joint structure. The successful integration of these four components was vital to the overall functionality and effectiveness of the implant joint, as it aimed to restore not only the physical appearance but also the functional abilities of the foot.

Figure 13. Printed prototype inside the bone.

Figure 13. Printed prototype inside the bone.

4.7. Flowchart of the Implant Creation Steps

The second flowchart was produced to summarize the phases to develop an implant for the metatarsophalangeal joint using 3D modeling and printing. At first, models that have previously been made, like those of the metacarpophalangeal joints from the hand, served as sources of inspiration. The first essential step is to perform a 2D sketch modeling of the implant inspired by these models. For this purpose, the SolidWorks software was used due to its tools making it easy for this task. The sketch is then converted into a 3D model with the help of the same software. During this transition, the 3D volume of the previously segmented bones from the first flowchart serves as a basis. To achieve the maximum degree of accuracy and details in the implant model, the 3D model is next threaded, modified and further enhanced for better precision using the Meshmixer software once again.

After the 3D model has been validated, and for now, the 3D printer Next Dent 5100 was employed to print out the implant using resin. Yet, our future perspective is to boost the quality of our work by 3D printing this implant with the chosen biomaterial which is titanium.

Figure 14. Flowchart of the implant creation steps.

Figure 14. Flowchart of the implant creation steps.

5. Discussion

6. Conclusion

References

1. MacGregor, Robert, and Doug W. Byerly. "Anatomy, Bony Pelvis and Lower Limb, Foot Bones." (2020).
2. L.K. Chan, The anatomy of the human foot, in: A. Luximon (Ed.), Handb. Footwear Des. Manuf., second edi, Woodhead Publishing, 2021: pp. 3−28.
3. Batra AV, Sullivan JO (2018) A Rare Case of Benign Osteochondromatous Lesion beneath the 3rdMetatarsophalangeal Joint. J Orthop Res Physiother 4: 038. [CrossRef]
4. Kokubu, Yasuhiko, et al. "Postoperative clinical and functional outcomes in patients with tumor and tumor-like lesion of foot and ankle." Journal of Foot and Ankle Research 15.1 (2022): 75. 3. Scott Litin, M.D. “Mayo Clinic Family Health Book” 5th edition (2021). [CrossRef]
5. Ferguson, Jason L., and Sean P. Turner. "Bone cancer: diagnosis and treatment principles." American family physician98.4 (2018): 205-213.
6. Riggi, Nicolò, Mario L. Suvà, and Ivan Stamenkovic. "Ewing’s sarcoma." New England Journal of Medicine 384.2 (2021): 154-164.
7. Board, PDQ Pediatric Treatment Editorial. "Ewing Sarcoma Treatment (PDQ®)." PDQ Cancer Information Summaries [Internet]. National Cancer Institute (US), 2021.
8. Wang, Yitian, et al. "The functional outcomes and complications of different reconstruction methods for Giant cell tumor of the distal radius: comparison of Osteoarticular allograft and three-dimensional-printed prosthesis." BMC Musculoskeletal Disorders21.1 (2020): 1-15. [CrossRef]
9. Gan, Fengping, et al. "Treatment of giant cell tumor of bone around knee joint with three-dimensional printing personalized prosthesis." Zhongguo xiu fu Chong Jian wai ke za zhi= Zhongguo Xiufu Chongjian Waike Zazhi= Chinese Journal of Reparative and Reconstructive Surgery 34.6 (2020): 751-755. [CrossRef]
10. SCHRAMM, Martin, MAESTRO, Michel, et DECROOCQ, Lauryl. Implant métatarso phalangien sphérique en pyrocarbone HAPY®: note de technique. Revue de Chirurgie Orthopédique et Traumatologique, 2021, vol. 107, no 5, p. 583-586. [CrossRef]
11. EL GHALI, Btihal, EL MIDAOUI, Omar, EL GHALI, Mohamed Ayman, et al. Modeling and Implementation of a Lunate Implant Based on 3D Reconstruction of CT Scan Images. In : 2021 Fifth International Conference On Intelligent Computing in Data Sciences (ICDS). IEEE, 2021. p. 1-7.
12. Giant cell tumor CHANDHANAYINGYONG, Chandhanarat, SRIKONG, Korakod, PUNCREOBUTR, Chedtha, et al. Three-dimensional printed, proximal phalangeal prosthesis with metatarsophalangeal joint arthroplasty for the treatment of a giant cell tumor of the fifth toe: The first case report. International Journal of Surgery Case Reports, 2020, vol. 73, p. 84-89. [CrossRef]
13. Xu L, Qin H, Cheng Z, Jiang WB, Tan J, Luo X, Huang W. 3D-printed personalised prostheses for bone defect repair and reconstruction following resection of metacarpal giant cell tumours. Ann Transl Med. 2021 Sep;9(18):1421. [CrossRef]
14. ZARE, Mina, GHOMI, Erfan Rezvani, VENKATRAMAN, Prabhuraj D., et al. Silicone-based biomaterials for biomedical applications: antimicrobial strategies and 3D printing technologies. Journal of Applied Polymer Science, 2021, vol. 138, no 38, p. 50969. [CrossRef]
15. RAJAN, R. A., KERR, M., EVANS, H., et al. A prospective clinical and biomechanical analysis of feet following first metatarsophalangeal joint replacement. Gait & Posture, 2021, vol. 89, p. 211-216. [CrossRef]
16. CHENG, Jiangang, GAO, Yang, LONG, Zhuoyu, et al. Repair of distal fibular and lateral malleolus defects with individualized 3D-printed titanium alloy prosthesis: The first case report from China. International Journal of Surgery Case Reports, 2022, vol. 94, p. 107057. [CrossRef]
17. Sazzad, F., Goh, J.H., Ong, Z.X. et al. Three dimensional modeling of atrioventricular valves provides predictive guides for optimal choice of prosthesis. Sci Rep 12, 7432 (2022). [CrossRef]
18. DUMITRESCU, Gean-Carlos Nicholas, and Patricia Isabela BRAILEANU. "Custom Prosthetic Finger Device Using 3D Printable PA11 CF Powder." The Annals of “Dunarea de Jos” University of Galati. Fascicle IX, Metallurgy and Materials Science 46.1 (2023): 33-36.Cinema 4D official. [CrossRef]
19. FARAHAT, Zineb, HASNI, Mouad, MEGDICHE, Kawtar, et al.Comparative Study of DICOM Files Handling Software’s: Study Based on the Anatomage Table. In : Innovation in Information Systems and Technologies to Support Learning Research: Proceedings of EMENA-ISTL 2019 3. Springer International Publishing, (2020). p. 390-399.
20. ASIF, Muhammad Khan, NAMBIAR, Phrabhakaran, KHAN, Iqra Muhammad, et al. Enhancing the three-dimensional visualization of a foreign object using Mimics software. Radiology case reports, 2019, vol. 14, no 12, p. 1545-1549. [CrossRef]
21. Bratovanov, Nikolay. "Robot modeling, motion simulation and off-line programming based on SolidWorks API." 2019 Third IEEE International Conference on Robotic Computing (IRC). IEEE, 2019.
22. YUNGA, Alexis David Armijos, CORTE, Nicole Adriana Juela, OCAMPO, Fabiana Valentina Pesantez, et al. Comparative study of reliability in three software meshmixer, 3d slicer and nemocast of the intercanine and intermolar spaces of digital models. World Journal of Advanced Research and Reviews, 2023, vol. 17, no 1, p. 1040-1045. [CrossRef]
23. Paramasivam, V., G. Singh, and S. Santhanakrishnan. "3D printing of human anatomical models for preoperative surgical planning." Procedia Manufacturing 48 (2020): 684-690.Volumic stream 30 ultra official website. [CrossRef]
24. GIORDANO, Geoff. 3D Printing the Future of Healthcare: Additive manufacturing, or 3D printing, is fast-tracking developments in the medical device industry. Plastics Engineering, 2019, vol. 75, no 6, p. 14-17.
25. Phang, J.T.S., Lim, K.H. & Chiong, R.C.W. Un examen des techniques de reconstruction tridimensionnelle. Multimed Tools Appl 80, 17879–17891 (2021).