Ankle-foot orthoses (AFO) are prescribed to improve the patient’s quality of life. Supporting weak muscles or restraining spastic muscles leads to smoother and more stable locomotion. Commonly, AFO are made using thermoplastic vacuum forming, which requires a long time for production and has limited design options. Additive manufacturing (AM) can solve this problem, leading to a faster and cheaper solution. This review aimed to investigate what is the state-of-art using AM for AFO. Evaluating the used manufacturing processes, customization steps, mechanical properties, and biomechanical features in humans would provide significant insights for further research. The database searches combined AM and AFO with no year or publication type restrictions. Studies must have examined outcomes on human participants with the orthoses built by AM. Other types of orthotic devices or different manufacturing techniques were excluded. Nineteen studies met the inclusion criteria. As stated by having all studies conducted in the last nine years, this is a very recent domain. Different AM processes have been used, with the majority relying on Fused Deposition Modeling. Overall, the manuscripts’ quality is deficient, which is critical to promoting further studies with higher samples. Except for one paper, AM-printed AFO was comparable or superior to the thermoplastic vacuum forming AFO in mechanical tests, kinematics, kinetics, and participant feedback.

Intervertebral disc (IVD) degeneration disease (IDD) is considered the main cause for low back pain (LBP), which has a world socioeconomic burden of 70 billion euros a year. Tissue Engineering (TE) is an exponentially growing area due to its potential of finding patient-specific treatments in terms of immunological compatibility by using the patient’s own cells. Though, it is possible to increase TE patient-specificity by combining other technologies such as Reverse Engineering (RE) and Rapid Prototyping (RP). In this sense, it is possible to prepare a biodegradable scaffold that is both immunological and structurally compatible. This strategy has the potential to significantly increase implant integration and decrease immunological rejection, allowing the scaffold to be progressively replaced with newly synthesised tissue to ultimately regenerate the IVD into a fully functional anatomical motion segment. Herein is reported a preliminary proof-of-concept for that strategy using rabbit IVD’s cells as well as morphology and structure. In this sense, the annulus fibrosus (AF) structure was replicated by RE and RP into a polycaprolactone scaffold, and the cells were encapsulated in methacrylated gellan gum (GG-MA) hydrogel as a nucleus pulposus (NP) substitute. The AF scaffold’s cytotoxicity, mechanical behaviour, porosity and superficial morphology were also analysed. It was observed a significant level of biocompatibility from the AF replica and a similar porosity in relation with the native IVD. Cell adhesion, proliferation and viability were assessed until 21 days of culture in GG-MA. The metabolic activity was higher in the NP cells than in the fibroblast cell line, both cultured in GG-MA. In the future, this novel strategy is envisaged to treat IDD, and remove LBP, by fully regenerating the intervertebral disc.

The current strategies for the total or partial meniscus replacement with allograft transplantation or scaffold implantation need to be improved to overcome the limitations in the clinics. In addition to the required biological and biomechanical performance of the implants, the size and the shape of the implant are critical for the success of the treatment. The commercial implants are re-sized by cutting at the time of surgery according to the patientâ s need; however, not completely in a 3D manner. The meniscal implants should advance beyond the traditional biomaterial concept by being patient-specific not only in terms of size and shape but regarding the cells and biologics derived from the patient. Herein, we overview the recent reports related to manufacturing of patient-specific meniscal implants.

Lower back pain (LBP), which is strongly associated with intervertebral disc (IVD) degeneration, is one of the most frequently reported age- and work-related disorder in actual society, leading to a huge socio-economic impact worldwide. The current treatments have poor clinical outcomes and do not consider each patient needs. Thus, there is a growing interest in the potential of personalized cell-based tissue engineering (TE) approaches aimed to regenerate the damaged IVD and efficiently restore full disc function. In this work, a bioink composed by silk fibroin (SF) hydrogel combined with elastin was used to bioprint patient-specific substitutes mimicking IVD ultrastructure, in particular the outer region of the IVD (i.e. annulus fibrosus, AF). Following a reverse engineering approach, the proposed strategy makes use of a 3D model of AF obtained by semi-automatic morphological segmentation from magnetic resonance imaging dataset of human IVD. SF/elastin bioprinted scaffolds were characterized thoroughly in vitro, in terms of physico-chemical and biological performance. The bioprinted SF/elastin scaffolds were shown to possess structural and mechanical properties similar to the native AF and to support cell attachment and growth. Human adipose-derived stem cell cultured onto the SF/elastin bioprinted scaffolds were shown to adhere, proliferate and maintain metabolic activity and viability up to 21 days of culturing. The implantation of custom-made SF/elastin implants that best emulate a patient AF anatomy can potentially open up new personalized treatments for tackling IVD disorders by means of improving recovery time after surgery and helping to restore spine biofunctionality.

Organ shortage and transplantation needs have led to congestion in healthcare systems resulting in a huge socioeconomic impact. Tissue Engineering has been revolutionizing the engineering of functional tissues, making them great alternatives to achieve a better, faster and effective worldwide patient care. Fibrocartilage is an avascular and aneural tissue characterized by the reduced number of cells and can be found in different tissues, such as intervertebral disc (IVD) and meniscus. These tissues own poor regenerative properties where a massive number of individuals have been affected by their degeneration. The current available treatments have shown poor clinical outcomes and none of them can be consensually designated as the “gold” standard treatment. Tissue engineers have been trying to overcome all the current challenges by developing novel approaches where different biomaterials have been explored to achieve a suitable implant (Chap. I and II). However, the pursuit for the “perfect” biomimetic implant is still a big challenge. Therefore, the combination of high-resolution imaging techniques (magnetic resonance imaging and micro-computed tomography) with 3D printing can be a powerful tool to closely mimic the fibrocartilaginous native tissue. This approach can provide reproducibility of the produced scaffolds and allows the production of patient-specific implants, helping to improve patient recovery time and biofunctionality reestablishment (Chap. III). The concept of patientspecificity is explored in this thesis using natural-based materials, where silk fibroin (SF) plays the central role due to its high processing versatility and remarkable mechanical properties. In the first work, indirect printed patient-specific hierarchical scaffolds were produced combining SF with ionicdoped β-tricalcium phosphates (Chap. V). Furthermore, using a 3D printing extrusion-based technology, an innovative SF-based bioink was developed (Chap. VI). Using the previously developed horseradish peroxidase-mediated crosslinking system, 3D patient-specific memory-shape implants were produced (Chap. VII). As third work, a step forward in terms of mimicking the IVD native tissue was given, where the previously developed SF bioink was combined with elastin (Chap. VIII). Finally, an extrusion-based 3D printing hybrid system comprising a gellan gum/fibrinogen cell-laden bioink and a SF methacrylated bioink was developed to produce cell-laden patient-specific implants (Chap. IX). In summary, the proposed novel 3D printing approaches revealed to be promising alternatives for the production of patient-specific implants for fibrocartilage regeneration.

The complex meniscus tissue plays a critical role in the knee. The high susceptibility to injury has led to an intense pursuit for better tissue engineering regenerative strategies, where scafolds play a major role. In this study, indirect printed hierarchical multilayered scafolds composed by a silk fbroin (SF) upper layer and an 80/20 (w/w) ratio of SF/ionic-doped β-tricalcium phosphate (TCP) bottom layer were developed. Furthermore, a comparative analysis between two types of scafolds produced using diferent SF concentrations, i.e., 8% (w/v) (Hi8) and 16% (w/v) (Hi16) was performed. In terms of architecture and morphology, the produced scafolds presented homogeneous porosity in both layers and no diferences were observed when comparing both scafolds. A decrease in terms of mechanical performance of the scafolds was observed when SF concentration decreased from 16 to 8% (w/v). Hi16 revealed a static compressive modulus of 0.66±0.05 MPa and dynamical mechanical properties ranging from 2.17±0.25 to 3.19±0.38 MPa. By its turn, Hi8 presented a compressive modulus of 0.27±0.08 MPa and dynamical mechanical properties ranging from 1.03±0.08 MPa to 1.56±0.13 MPa. In vitro bioactivity studies showed formation of apatite crystals onto the surface of Hi8 and Hi16 bottom layers. Human meniscus cells (hMCs) and human primary osteoblasts were cultured separately onto the top layer (SF8 and SF16) and bottom layer (SF8/TCP and SF16/TCP) of the hierarchical scafolds Hi8 and Hi16, respectively. Both cell types showed good adhesion and proliferation as denoted by the live/dead staining, Alamar Blue assay and DNA quantifcation analysis. Subcutaneous implantation in mice revealed weak infammation and scafoldâ s integrity. The hierarchical indirect printed SF scafolds can be promising candidate for meniscus TE scafolding applications due their suitable mechanical properties, good biological performance and possibility of being applied in a patient-specifc approach.

Fibrocartilage is a very peculiar type of tissue that can be found in intervertebral disc and meniscus. It is characterized by its avascular nature and for the shear and compressive forces that can be subjected. The number of individuals affected by the degeneration of fibrocartilaginous tissues has been growing and the poor outcomes of the current treatments have led to an increased interest in new alternative approaches. Therefore, the combination of reverse engineering with 3D printing has been extensively explored in order to produce patient-specific implants capable of improving the current clinical outcomes. This review outlines the recent advances achieved in tissue engineering field, especially focusing on fibrocartilaginous tissue.

Dynamic phantoms of the heart are becoming a reality, with their use spread across both medical and research fields. Their purpose is to mimic the cardiac anatomy, as well as its motion. This work aims to create a dynamic, ultrasound-compatible, realistic and flexible phantom of the left and right ventricles, with application in the diagnosis, planning, treatment and training in the cardiovascular field for studies using echocardiography. Here, we focus on its design and production with polyvinyl alcohol cryogel (PVA-C), to be assembled with a pump and an electromechanical (E/M) system in a water tank. Based on a patient-specific anatomical model and produced using a 3D printing technique and molding, the PVA-C phantom mimics the ventricles' natural anatomy and material properties, while the pump and E/M systems mimic the natural movements and pressures. The PVA-C phantom was assessed by imaging and measuring it using a four-dimensional ultrasound machine. The PVA-C phantom demonstrated to be a versatile option to produce patient-specific biventricular models, preserving their shape after manufacturing and presenting good echogenic properties. Both chambers were clearly seen in the ultrasound images, together with the interventricular septum and the myocardial wall. Automated left ventricle measures revealed a decrease of its volume with regard to the designed model (98 ml to 74 ml). Overall, the preliminary results are satisfactory and encourage its use for the abovementioned purposes

This paper presents a qualitative and quantitative comparison between the finite element and the finite volume methods for the fluid-structure interaction simulation of blood flow through a real stenosed artery. The artery geometry corresponds to a severely stenosed (around 75% lumen reduction) portion of the brachiocephalic trunk, located immediately upstream of the bifurcation of this vessel into the right subclavian and right common carotid arteries. The patient-specific geometry was segmented from medical images of a computerized tomography scanner from an individual with the subclavian steal syndrome. Doppler ultrasound velocity measurements were used to determine and impose patient-specific boundary conditions. The numerical simulations were performed in commercial software, Ansys and COMSOL, with a comparative second order discretization for the pressure, velocity and displacement variables. The results of this research disclosed a reasonable overall agreement between the predicted hemodynamics for both approaches. The finite volume method software (Ansys) proved to be more efficient in computational time and memory requirements.