A novel workflow to fabricate a patient-specific 3D printed accommodative foot orthosis with personalized latticed metamaterial

Static and dynamic optimisation of fluid-filled responsive orthotic insoles

This study was focused on developing an optimisation-based methodology to create customised solid-liquid composite (SLC) orthotic insoles. The goal was to reduce peak plantar pressures through gait through a dynamic numerical optimisation. A gait simulation was developed through a series of numerical models with increasing complexity. These models were validated against experimental analyses. The insole was designed based on numerical optimisation techniques that regionally tailored the insole with the aim to reduce temporal peak pressures. A prototype of the optimised insole was created using additive manufacturing and tested experimentally. The numerical gait simulation showed good correlation with experimental results. The largest differences are attributed to the bone geometry adopted from a previous study from a subject of different age, gender and size demographics. The optimisation process showed significant reductions in peak plantar pressures in the static peak pressures by approximately 8% and in the summation of dynamic peak pressures by 50%. Experimental validation confirmed the numerical predictions, highlighting the effectiveness of the optimised insole. The findings suggest that the optimised insoles can improve plantar pressure distributions and reduce peak pressures, making them a viable alternative to traditional orthotic insoles. Future research should focus on more accurate geometry for the numerical models and clinical trials.

The mechanical response of polymeric gyroid structures in an optimised orthotic insole

This study aims to explore the mechanical behaviour of polymeric gyroid structures under compression within the context of orthotic insoles, focussing on custom optimisation for lower peak plantar pressures. This research evaluates the compressive response of gyroid structures using a combination of experimental testing and numerical modelling. Stereolithography was used to manufacture gyroid samples for experimental tests, and explicit finite element analysis was used to model the gyroid's response numerically. Hyperfoam, first-order polynomial, and second-order polynomial hyperelastic constitutive models were considered to homogenise the mechanical response of the structure. The homogenised properties of the structure were then implemented in an optimisation algorithm to obtain the optimal gyroid structure for a given subject by minimising the standard distribution of plantar pressures. Findings indicate that the compressive response polymeric gyroid structures can be represented with a homogeneous material. The hyperfoam model was chosen due to its accuracy and interpolation quality. The optimisation process successfully identified configurations that maximise the mechanical advantages of gyroid lattices, demonstrating significant improvements in plantar pressure distributions. The optimised insole showed a 30% reduction in the standard deviation of the plantar pressure and a 10% reduction in the peak stress. The optimisation method reduced peak pressures by 12.2 kPa compared to a traditional medium-density Poron orthotic insole, and 94.3 kPa compared barefoot conditions. The mechanical response of gyroid structures has successfully been modelled, analysed and homogenised. The study concludes that custom gyroid-based orthotic insoles offer a promising solution for personalised foot care.

Assessing 3D printable density-graded lattice structures to minimize risk of tissue damage from compression-release stabilized sockets

BACKGROUND

Pressure, shear stress, and friction can contribute to soft tissue damage experienced by a residual limb. Current compression/release stabilized (CRS) socket designs may pose a risk to soft tissue from abrupt compression differences within the socket.Objectives:Density-graded lattice structures are investigated for their potential to mitigate risk of tissue damage by assessing their ability to produce more gradual transitions between high-compression and low-compression areas.Study Design:A full factorial experimental design was used to reveal the effects of changes among three variables: lattice geometry, density alteration, and displacement magnitude. A total of 144 experimental conditions were examined.

METHODS

Lattice samples representing areas of compression and release based on a novel cushioned transhumeral level CRS style socket design were 3D printed. Compression testing was performed on 2 types of lattice structures which incorporated 1 of 8 design elements to alter density and axial stiffness. The effect on stiffness of the sample as a function of lattice type and density alteration was recorded under 3 loading conditions.

RESULTS

The offset diamond lattice type with blend radius density alterations produced the only samples meeting criteria set for compression areas of the socket. No samples satisfied criteria for release areas. Transitional density lattices that gradually tapered between the best performing compression and release values were successfully produced.

CONCLUSIONS

Transitional density lattices offer promise for mitigation of soft tissue damage through minimization of compression differentials throughout the socket. Wider implications for this research include use in sockets for other levels of amputation and in orthotics. Future work will focus on lattice optimization to improve release behavior within a modified CRS socket.

Bioinspired Design of 3D-Printed Cellular Metamaterial Prosthetic Liners for Enhanced Comfort and Stability

Traditional prosthetic liners are often limited in customization due to constraints in manufacturing processes and materials. Typically made from non-compressible elastomers, these liners can cause discomfort through uneven contact pressures and inadequate adaptation to the complex shape of the residual limb. This study explores the development of bioinspired cellular metamaterial prosthetic liners, designed using additive manufacturing techniques to improve comfort by reducing contact pressure and redistributing deformation at the limb-prosthesis interface. The gyroid unit cell was selected due to its favorable isotropic properties, ease of manufacturing, and ability to distribute loads efficiently. Following the initial unit cell identification analysis, the results from the uniaxial compression test on the metamaterial cellular samples were used to develop a multilinear material model, approximating the response of the metamaterial structure. Finite Element Analysis (FEA) using a previously developed generic limb-liner-socket model was employed to simulate and compare the biomechanical behavior of these novel liners against conventional silicone liners, focusing on key parameters such as peak contact pressure and liner deformation during donning, heel strike, and the push-off phase of the gait cycle. The results showed that while silicone liners provide good overall contact pressure reduction, cellular liners offer superior customization and performance optimization. The soft cellular liner significantly reduced peak contact pressure during donning compared to silicone liners but exhibited higher deformation, making it more suitable for sedentary individuals. In contrast, medium and hard cellular liners outperformed silicone liners for active individuals by reducing both contact pressure and deformation during dynamic gait phases, thereby enhancing stability. Specifically, a medium-density liner (10% infill) balanced contact pressure reduction with low deformation, offering a balance of comfort and stability. The hard cellular liner, ideal for high-impact activities, provided superior shape retention and support with lower liner deformation and comparable contact pressures to silicone liners. The results show that customizable stiffness in cellular metamaterial liners enables personalized design to address individual needs, whether focusing on comfort, stability, or both. These findings suggest that 3D-printed metamaterial liners could be a promising alternative to traditional prosthetic materials, warranting further research and clinical validation.

Advancements in diabetic foot insoles: a comprehensive review of design, manufacturing, and performance evaluation

The escalating prevalence of diabetes has accentuated the significance of addressing the associated diabetic foot problem as a major public health concern. Effectively offloading plantar pressure stands out as a crucial factor in preventing diabetic foot complications. This review comprehensively examines the design, manufacturing, and evaluation strategies employed in the development of diabetic foot insoles. Furthermore, it offers innovative insights and guidance for enhancing their performance and facilitating clinical applications. Insoles designed with total contact customization, utilizing softer and highly absorbent materials, as well as incorporating elliptical porous structures or triply periodic minimal surface structures, prove to be more adept at preventing diabetic foot complications. Fused Deposition Modeling is commonly employed for manufacturing; however, due to limitations in printing complex structures, Selective Laser Sintering is recommended for intricate insole designs. Preceding clinical implementation, in silico and in vitro testing methodologies play a crucial role in thoroughly evaluating the pressure-offloading efficacy of these insoles. Future research directions include advancing inverse design through machine learning, exploring topology optimization for lightweight solutions, integrating flexible sensor configurations, and innovating new skin-like materials tailored for diabetic foot insoles. These endeavors aim to further propel the development and effectiveness of diabetic foot management strategies. Future research avenues should explore inverse design methodologies based on machine learning, topology optimization for lightweight structures, the integration of flexible sensors, and the development of novel skin-like materials specifically tailored for diabetic foot insoles. Advancements in these areas hold promise for further enhancing the effectiveness and applicability of diabetic foot prevention measures.

Effects of Plantar Fascia Release and the Use of Foot Orthoses Affect Biomechanics of the Medial Longitudinal Arch of the Foot: A Cadaveric Study

OBJECTIVE

The aim of the study is to evaluate the effect of minimally invasive ultrasound-guided fascial release and a foot orthoses with first metatarsal head cutout on the biomechanics of the medial longitudinal arch of the foot in cadaveric specimens.

DESIGN

A cross-sectional study was designed (20 body donors). Anthropometric measurements of the foot, foot posture index, and the windlass test and force were measured in different conditions: unloaded, loaded position, with foot orthoses, after a 25% plantar fascia release and after a 50% release.

RESULTS

For the anthropometric measurements of the foot, differences were found in foot length ( P = 0.009), arch height ( P < 0.001), and midfoot width ( P = 0.019) when comparing the unloaded versus foot orthoses condition. When foot orthoses were compared with 25% plantar fascial release, differences were found in foot length ( P = 0.014) and arch height ( P < 0.001). In the comparison with 50% plantar fascial release, differences were found in the arch height ( P < 0.001). A significant interaction between foot orthoses condition and grades was found in the arch height during the windlass test ( P = 0.021).

CONCLUSIONS

The results indicate that the presence of foot orthoses leads to a significant increase in arch height compared with other conditions. Furthermore, when plantar fascia release is performed, the arch does not exhibit any signs of collapse.

3D printing and bioprinting in the battle against diabetes and its chronic complications

Diabetes is a metabolic disorder characterized by high blood sugar. Uncontrolled blood glucose affects the circulatory system in an organism by intervening blood circulation. The high blood glucose can lead to macrovascular (large blood vessels) and microvascular (small blood vessels) complications. Due to this, the vital organs (notably brain, eyes, feet, heart, kidneys, lungs and nerves) get worsen in diabetic patients if not treated at the earliest. Therefore, acquiring treatment at an appropriate time is very important for managing diabetes and other complications that are caused due to diabetes. The root cause for the occurrence of various health complications in diabetic patients is the uncontrolled blood glucose levels. This review presents a consolidated account of the applications of various types of three-dimensional (3D) printing and bioprinting technologies in treating diabetes as well as the complications caused due to impaired blood glucose levels. Herein, the development of biosensors (for the diagnosis), oral drug formulations, transdermal drug carriers, orthotic insoles and scaffolds (for the treatment) are discussed. Next to this, the fabrication of 3D bioprinted organs and cell-seeded hydrogels (pancreas engineering for producing insulin and bone engineering for managing bone defects) are explained. As the final application, 3D bioprinting of diabetic disease models for high-throughput screening of ant-diabetic drugs are discussed. Lastly, the challenges and future perspective associated with the use of 3D printing and bioprinting technologies against diabetes and its related chronic complications have been put forward.

Exploring the mechanical properties of 3D-printed multilayer lattice structures for use in accommodative insoles

Full-contact insoles fabricated from multilayer foams are the standard of care (SoC) for offloading and redistributing high plantar pressures in individuals with diabetes at risk of plantar ulceration and subsequent lower limb amputation. These devices have regional variations in total thickness and layer thickness to create conformity with a patient's foot. Recent work has demonstrated that metamaterials can be tuned to match the mechanical properties of SoC insole foams. However, for devices fabricated using a multilayer lattice structure, having regional variations in total thickness and layer thickness may result in regional differences in mechanical properties that have yet to be investigated. Three lattices, two dual-layer and one uniform-layer lattice structure, designed to model the mechanical properties of SoC insoles, were 3D-printed at three structure/puck thicknesses representing typical regions seen in accommodative insoles. The pucks underwent cyclic compression testing, and the stiffness profiles were assessed. Three pucks at three structure/puck thicknesses fabricated from SoC foams were also tested. Initial evaluations suggested that for the latticed pucks, structure thickness and density inversely impacted puck stiffness. Behaving most like the SoC pucks, a dual-layer lattice that increased in density as structure thickness increased demonstrated consistent stiffness profiles across puck thicknesses. Identifying a lattice with constant mechanical properties at various structure thicknesses may be important to produce a conforming insole that emulates the standard of care from which patient-specific/regional lattice modulations can be made.

3D Printing of Individual Running Insoles - A Case Study

Purpose

The study's starting point is to find a low-cost and best-fit solution for comfortable movement for a recreational runner with knee pain using an orthopedic device. It is a case study. The research aims to apply digitization, CAD/CAM tools, and 3D printing to create an individual 3D running insole. The objective is to incorporate flexible shape optimization would provide comfort reductions in foot plantar pressures in one subject with knee pain while running. The test hypothesis was if it is possible to make it from one material. For this purpose, we created a new digital workflow based on the Decision Tree method and analyzed pain and comfort scores during user testing of prototypes.

Patient and Methods

The input data were obtained during a professional examination by a specialist doctor in the orthopedic outpatient clinic in the motion laboratory (DIERS 4D Motion Lab, Germany) with the output of data on the proband's complex movement stereotype. Surface and volumetric data were obtained in the biomedical laboratory with the 3D scanner. We modified the digital 3D foot models in 3D mesh software, developed the design in SW Gensole (Gyrobot, UK), and finally incorporated the internal structure and the surface layer of the insole data of the knowledge from the medical examination, comfort analyses, and scientific studies findings.

Results

Four complete 3D-printed prototypes (n=4) with differences in density and correction elements were designed. All of them were fabricated on a 3D printer (Prusa i3 MK3S, Czech Republic) with flexible TPU material suitable for skin contact. The Participant tested each of them five times in the field during a workout and final insoles three months on the routine training.

Conclusion

A novel workflow was created for designing, producing, and testing full 3D-printed insoles. The product is fit for immediate use.

Evaluation of novel plantar pressure-based 3-dimensional printed accommodative insoles - A feasibility study

BACKGROUND

Custom insoles are commonly prescribed to patients with diabetes to redistribute plantar pressure and decrease the risk of ulceration. Advances in 3D printing have enabled the creation of 3D-printed personalized metamaterials whose properties are derived not only from the base material but also the lattice microstructures within the metamaterial. Insoles manufactured using personalized metamaterials have both patient-specific geometry and stiffnesses. However, the safety and biomechanical effect of the novel insoles have not yet been tested clinically.

METHODS

Individuals without ulcer, neuropathy, or deformity were recruited for this study. In-shoe walking plantar pressure at baseline visit was taken and sensels with pressure over 200 kPa was used to define offloading region(s). Three pairs of custom insoles (two 3D printed insoles with personalized metamaterials (Hybrid and Full) designed based on foot shape and plantar pressure mapping and one standard-of-care diabetic insole as a comparator). In-shoe plantar pressure measurements during walking were recorded in a standardized research shoe and the three insoles and compared across all four conditions.

FINDINGS

Twelve individuals were included in the final analysis. No adverse events occurred during testing. Maximum peak plantar pressure and the pressure time integral were reduced in the offloading regions in the Hybrid and Full but not in the standard-of-care compared to the research shoe.

INTERPRETATION

This feasibility study confirms our ability to manufacture the 3D printed personalized metamaterials insoles and demonstrates their ability to reduce plantar pressure. We have demonstrated the ability to modify the 3D printed design to offload certain parts of the foot using plantar pressure data and a patient-specific metamaterials in the 3D printed insole design. The advance in 3D printed technology has shown its potential to improve current care.