Research results

Up to thirteen case studies have been developed within the IREBID project:

- Tracheal stents: two new tracheal stents were designed in order to reduce the complications associated with stenting as a palliative treatment of tracheal stenosis. The first one is a customized wavy D-shape design. It was designed following a design methodology validated by doctors. Several prototypes were fabricated using a FDM technology and medical grade silicone. An efficient and adequate manufacturing process is under development. Moreover, a model of the stent inside the trachea was generated and simulations about its behavior performed. On the other hand, a fully customized tracheal model was designed using CT data from a patient. A first prototype was obtained using regular silicone. A more accurate manufacturing system is being studied. Some experiments with tracheal sheep were carried out.

- Scapholunate implants: two proposals of scapholunate implants were studied as a new strategy to treat scapholunate ligament impartment. One design was proposed using magnets. However, several drawbacks were found and this proposal was leaved behind. The second proposal was found using a design methodology. Several designs were proposed and selected by wrist experts. One evolved design was modeled and its behavior simulated inside a human wrist. Moreover, some prototypes were obtained. At this moment, some changes in the design are proposed and a manufacturing strategy evaluated.

- Skull: two skull models were developed in order to study the cranial behavior to generate innovative cranial implants or protective equipment. A simplified skull model was proposed by experts on anatomy. The model was designed and manufactured using additive technologies. Moreover, several simulations were performed in order to validate it under fracture patterns. On the other hand, a complete skull model was developed as a virtual platform using BioCAD protocol, surface modeling software and finite element method (FEM) analysis software.

- Hip: To solve some problems associated with hip implants, a porous new prosthesis with mechanical properties similar to the femur bone was designed. Numerical simulations were used to assess the behavior of the porous prosthesis. In vitro and in vivo experiments were done to analyze cell growth. A first prototype was obtained. On the other hand, a new device to measure intra-acetabular pressures was designed and manufactured. The device is being used by trauma experts.

- Pelvic floor: Several studies have shown that pelvic floor injuries during a vaginal delivery can be considered a significant factor in the development of urinary incontinence, fecal incontinence, and pelvic organ prolapse. The objective of this case study was to contribute in the clarification of the mechanisms behind pelvic floor disorders. Several images were modeled using BioCAD and InVesalius software. A FEM analysis was performed and the behavior of the pelvic floor was simulated. Therefore, a constitutive model able to describe the mechanical behavior was generated. On the other hand, a TENS device was designed with the assistance of gynecologists to stimulate pelvic floor muscles and study their behavior in infants. More studies are needed to manufacture the device and validate it.

- Exoskeleton: Severe neuromotor disabilities limit daily activities and independence of patients. To improve such situation, the aim of this case study was to develop an exoskeleton device to help patients to move on their own. The new design developed has seven degrees of freedom giving structural support and aiding the movement. The device was created to act as a locomotive structure to avoid muscular atrophy. A biomechanical study was done, as well as, an extensive market analysis. A first prototype was manufacture. Further studies need to be done to develop the electronics and improve the design.

- Bioreactor: Tissue engineering involves the implantation of scaffolds seed with cells. A strategy to obtain these structures is the cultivation of the scaffolds with the cells in bioreactors. However, the quality of such devices needs to be improved. For this reason, a new bioreactor was designed. This bioreactor was composed of several chambers to cultivate different tissues under different stimulus. Moreover, it comprehended several stimulations, rotations, and oscillatory movements in order to obtain an efficient perfusion. At this point, the first prototype of this bioreactor needs to be manufactured.

- Biodegradable screws: Several implants are being used during surgery in orthopedics. Permanent implants have some complications associated. In this context, biodegradable implantable screws were designed and manufactured. Nowadays, the degradability rate, geometry, and mechanical properties are being studied.

- Laparoscopic surgery simulator: The goal of this case study was to create a low-cost, open source, and flexible laparoscopic surgery simulator to allow medical students and surgery residents to get practical experience in surgical procedures. The project was named SIMYOS (from SIMulation for surgerY with Open Source approach). Three major areas were included in the project: mechatronic design, virtual environment (including geometrical modeling, physical modeling, and implementation methods to simulate reality) and medical knowledge. A design and prototype of the simulator were obtained and different applications were developed. Finally, the device was tested and its system behavior evaluated. A platform about the results obtained in this case study was created and it is available online (http://simyos.mty.itesm.mx)

- Biopsy micro-forceps: To shorter procedure times, to collect more samples with better quality, and to reduce the costs associated a new biopsy micro-forceps was designed and fabricated. For the design, several interviews with doctors and a thorough state of the art and market analysis were performed. The design had external and internal components. A prototype of the device was produced. In addition, for the capsule (micro-forceps component) different dispositions were obtained and tested with chicken breast and liver. Future work is needed to study the possibility of using PMMA or biodegradable materials, to improve the final design, and to obtain a functional prototype.

- Maxillofacial: A methodology to obtain customized mandible prostheses was developed taking into account tension, deformations, ergonomics, and biocompatibility requirements. The cooperation between doctors and engineers was essential to obtain suitable products able to satisfy patients’ needs. Mandible and palate prostheses designs were proposed and prototypes produced. Moreover, FEM simulations were used to validate the designs.

- Micro-needles: Research is being developed to obtain micro-needles for drug delivery. In this case study, several designs and prototypes were produce to obtain micro-needles patches able to reach the dermis without provoking pain. The design and fabrication strategy were deeply studied and evaluated using micro-milling technology. Future work is needed to produce the holes inside the needles and reservoir for drug storage.

- Spinal space cages: Commercial spinal space implants present some problems such as low bone growth, migration, spine stabilization, and soft tissue formation. Therefore, a new spinal space cage design was proposed. The new design was generated considering some requirements: biocompatibility, biodurability, bone fusion, spinal column stabilization, stable placement, easy insertion, customization, radiopacity, and low cost. A design methodology, involving QFD and TRIZ, was used to obtain the designs. Thus, several solutions were proposed and evaluated by FEM analysis.

In addition, research and training on several manufacturing technologies to produce medical devices, such as additive technologies, micro-machining technologies, biofabrication, laser technologies, and rapid prototyping technologies among others was carried out in order to obtain more accurate and efficient products. The study of these manufacturing technologies, as well as other computer technologies, was used as training activities for researchers.

Figure 1 Designs and models of some medicals devices developed within the IREBID project: (a) tracheal stent design and simulation; (b) scapholunate ligament model (with bones), implant design, and simulation of the implant within the bones; (c) simplified skull model, complete skull parts, and complete skull model assembled; (d) FEM model of the pelvic floor during pregnancy; (e) design of the bioreactor; (f) design of the mandibular implant assembled with the bone; and (g) design of the surgery simulator

Figure 2 Prototypes and models of some medicals devices developed within the IREBID project: (a) tracheal stents models fabricated using conventional silicone, medical grade silicone, and PLA; (b) first prototype of a scapholunate ligament implant; (c) simplified skull model fabricated using FDM; (d) Hip prosthesis fabricated with AM technology; (e) pelvic floor model to study its behavior; (f) exoskeleton first prototype; (g) mandibular implant made of Titanium assembled with a bone model made of polymer; and (h) first prototype of a surgery simulator and a liver model used