Systematic review of effects of current transtibial prosthetic socket designs—Part 1: Qualitative outcomes

This review is an attempt to untangle the complexity of transtibial prosthetic socket fit, determine the most important characteristic for a successful fitting, and perhaps find some indication of whether a particular prosthetic socket type might be best for a given situation. Further, it is intended to provide directions for future research. We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and used medical subject headings and standard key words to search for articles in relevant databases. No restrictions were made on study design or type of outcome measure. From the obtained search results (n = 1,863), 35 articles were included. The relevant data were entered into a predefined data form that incorporated the Downs and Black risk of bias assessment checklist. Results for the qualitative outcomes (n = 19 articles) are synthesized. Total surface bearing sockets lead to greater activity levels and satisfaction in active persons with amputation, those with a traumatic cause of amputation, and younger persons with amputation than patellar tendon bearing sockets. Evidence on vacuum-assisted suction and hydrostatic sockets is inadequate, and further studies are much needed. To improve the scientific basis for prescription, comparison of and correlation between mechanical properties of interface material, socket designs, user characteristics, and outcome measures should be conducted and reported in future studies

Lower limb prosthetic interfaces: Clinical and technological advancement and potential future direction

The human–prosthesis interface is one of the most complicated challenges facing the field of prosthetics, despite substantive investments in research and development by researchers and clinicians around the world. The journal of the International Society for Prosthetics and Orthotics, Prosthetics and Orthotics International, has contributed substantively to the growing body of knowledge on this topic. In celebrating the 50th anniversary of the International Society for Prosthetics and Orthotics, this narrative review aims to explore how human–prosthesis interfaces have changed over the last five decades; how research has contributed to an understanding of interface mechanics; how clinical practice has been informed as a result; and what might be potential future directions. Studies reporting on comparison, design, manufacturing and evaluation of lower limb prosthetic sockets, and osseointegration were considered. This review demonstrates that, over the last 50 years, clinical research has improved our understanding of socket designs and their effects; however, high-quality research is still needed. In particular, there have been advances in the development of volume and thermal control mechanisms with a few designs having the potential for clinical application. Similarly, advances in sensing technology, soft tissue quantification techniques, computing technology, and additive manufacturing are moving towards enabling automated, data-driven manufacturing of sockets. In people who are unable to use a prosthetic socket, osseointegration provides a functional solution not available 50 years ago. Furthermore, osseointegration has the potential to facilitate neuromuscular integration. Despite these advances, further improvement in mechanical features of implants, and infection control and prevention are needed.N/

Design of a Single Layer Metamaterial for Pressure Offloading in Transtibial Amputees

While using a prosthesis, transtibial amputees can experience pain and discomfort brought on by significant changes in pressure across a finite area of skin, known as pressure gradients, at the interface between the residual limb and prosthetic socket. These pressure gradients can lead to dermatological issues, deep tissue damage, and prolonged joint and muscle pain. Current prosthetic interface solutions attempt to alleviate these pressure gradients by using highly compliant homogenous liners to distribute and therefore reduce pressures. This research investigates an approach to reduce peak pressure gradients around the limb through the design of a new inlay made from artificially structured materials, termed metamaterials, with tailored mechanical properties to act as an interface between the prosthetic socket and residual limb. The inlay is fabricated from a hyperelastic base material and has a triangular patterned unit cells which can be 3D printed with walls of various slopes. By adjusting the unit cell wall slopes and thicknesses, the metamaterial hyperelastic material properties can be customized. The hyperelastic material properties of this metamaterial are modeled using a third order representation, namely a Yeoh 3rd Order Hyperelastic Model. The 3rd Order Coefficients from this model can be adjusted and optimized, then these optimal hyperelastic material property parameters can be mapped back into the physical design space as changes in the unit cell wall thickness or slope to create an inlay that can meet the unique offloading needs of an amputee. The layout of this metamaterial within the inlay can also be adjusted and optimized to better adapt to the unique limb shape of an amputee. Furthermore, the material properties and layout of the metamaterial can be optimized simultaneously to design a customizable inlay solution that can even better meet the unique performance needs of an amputee. Multiple finite element analyses simulations evaluate the pressure gradient reduction capabilities of the metamaterial inlay. A series of inlays were designed through the optimization of metamaterial properties and layout and compared to a prosthetists’ prescription for the same patients. The metamaterial inlay shows, in all cases implemented, a greater reduction in peak pressure gradients than that of a common homogeneous silicone liner. The results show the potential feasibility of implementing this metamaterial as a customizable interface solution to meet the unique performance needs of individual transtibial amputees to better increase comfort and functionality

Generic, Geometric Finite Element Analysis of the Transtibial Residual Limb and Prosthetic Socket

Finite element analysis was used to investigate the stress distribution between the residual limb and prosthetic socket of persons with transtibial amputation (TTA). The purpose of this study was to develop a tool to provide a quantitative estimate of prosthetic interface pressures to improve our understanding of residual limb/prosthetic socket biomechanics and prosthetic fit. FE models of the residual limb and prosthetic socket were created. In contrast to previous FE models of the prosthetic socket/residual limb system, these models were not based on the geometry of a particular individual, but instead were based on a generic, geometric approximation of the residual limb. These models could then be scaled for the limbs of specific individuals. The material properties of the bulk soft tissues of the residual limb were based upon local in vivo indentor studies. Significant effort was devoted toward the validation of these generic, geometric FE models; prosthetic interface pressures estimated via the FE model were compared to experimentally determined interface pressures for several persons with TTA in a variety of socket designs and static load/alignment states. The FE normal stresses were of the same order of magnitude as the measured stresses (0-200 kPa); however, significant differences in the stress distribution were observed. Although the generic, geometric FE models do not appear to accurately predict the stress distribution for specific subjects, the models have practical applications in comparative stress distribution studies

Effect of multi-layer prosthetic foam liner on the stresses at the stump–prosthetic interface

The prosthetic liner plays a significant role in the redistribution of the pressure between the stump and the socket, as it adding a cushioning layer between the stump and the socket which relieves pain and makes the prosthesis more comfortable. This study employed nonlinear finite element analyses to investigate the peak pressure and shear stress at stump–prosthetic interface in the case of multi-layer prosthetic foam liner, this liner having an inner polymeric foam layer Surrounded by another type of polymeric foam layer, we used three different types of foams in different order to define this liner (flexible polyurethane foam, polyurethane-shape memory polymer foam, and natural rubber latex foam). That’s allows comparing 6 deferent configuration of multi-layer prosthetic foam liner.     &nbsp

Customization designs and biomechanical analysis of transtibial prosthetic leg

A prosthesis is a technical mechanism that is designed as a substitution of the function of a missing limb or body part. This device has been effectively used as an essential tool for amputees. Therefore, the main purpose of this study is to biomechanically evaluate and optimize the prosthetic's socket to produce a better construct for the improvement of performance. In this project, the methods started with a definition of the construction of the finite element model which is divided into four parts: amputee leg, sockets model. Modelling of the pylon, three-dimensional foot model. The focus was on the design of the socket then moving to the biomechanical study using a finite element method which involved several analyses of the effects of socket designs as well as its material properties, gait conditions. To do that, first and foremost, a three-dimensional prosthetics was designed. The sockets were developed with an estimated uniform thickness of 5 mm. The results of the finite element study showed that the perforated socket configuration had better stability in terms of displacement (0.19 mm) and von Mises stress (1.146 MPa), as compared to the conventional socket VMS (3.22347 MPa), and the displacement (0.19 mm) while open-sided socket von Mises stress (1.182 MPa), displacement (0.22 mm). Lastly, the von Mises stress and displacement analysis is applied on the prosthetic in three different gait conditions and the result of the socket was the VMS on the condition of toe-off (6.14 MPa) and the displacement during the toe-off phase, the results indicated that the model had a maximum displacement of (10.67 mm). In contrast, the lowest value was during the stance phase the von Mises stress (1.13 MPa), and the displacement was (0.21 mm). During heel strike VMS (5.52 MPa) and displacement (0.96 mm)

Clinical utility of pressure feedback to socket design and fabrication

Background: The clinical utility of measuring pressure at the prosthetic socket-residual limb interface is currently unknown. Objectives: This study aimed to identify whether measuring interface pressure during prosthetic design and fabrication results in closer agreement in pressure measurements between sockets made by different clinicians, and a reduction in pressure over areas of concern. It also investigated whether clinicians value knowing the interface pressure during the fabrication process. Study design: Mixed methods. Methods: Three prosthetists designed a complete prosthetic system for a transtibial residual limb surrogate. Standardised mechanical testing was performed on each prosthetic system to gain pressure measurements at four key anatomical locations. These measurements were provided to the clinicians, who subsequently modified their sockets as each saw fit. The pressure at each location was re-measured. Each prosthetist completed a survey that evaluated the usefulness of knowing interface pressures during the fabrication process. Results: Feedback and subsequent socket modifications saw a reduction in the pressure measurements at three of the four anatomical locations. Furthermore, the pressure measurements between prosthetists converged. All three prosthetists found value in the pressure measurement system and felt they would use it clinically. Conclusions: Results suggest that sensors measuring pressure at the socket-limb interface has clinical utility in the context of informing prosthetic socket design and fabrication. If the technology is used at the check socket stage, iterative designs with repeated measurements can result in increased consistency between clinicians for the same residual limb, and reductions in the magnitudes of pressures over specific anatomical landmarks. Clinical relevance This study provides new information on the value of pressure feedback to the prosthetic socket design process. It shows that with feedback, socket modifications can result in reduced limb pressures, and more consistent pressure distributions between prosthetists. It also justifies the use of pressure feedback in informing clinical decisions

Study and Characterization of Composite Materials: Biomedical Applications

In the scope of the Master’s Degree in Mechanical Engineering - Industrial Production, it was sought to study the impact of sustainable materials in biomedical applications, with special focus on composite materials. When gathering information to perform the state of the art of this work, regarding composite materials and some of their biomedical applications, it was found that there was not much evidence regarding the customized production of transfemoral prostheses using both sustainable materials and home-available low-cost manufacturing technologies. To contribute exploring the identified research gap, numerical models were developed to carry out simulations based on finite element analysis. In turn, these have made it possible to evaluate not only the effect of friction, but also the effect that the materials and their constitutive laws have on the stress field developed in the biomechanical system, which directly affects the comfort and health of patients. Additionally, the simulations also made it possible to analyze various materials to verify their suitability for the application in question. The results obtained made it possible to highlight sustainable materials with the potential to be used to produce sockets for transfemoral prostheses and, in turn, to demonstrate the possible suitability for customized production of these medical devices directly by patients in their homes, using low-cost additive technologies that can be easily available at home

Preliminary results on the effects of orthopedic implant stiffness fixed to the cut end of the femur on the stress at the stump-prosthetic interface

A lot of trans-femoral amputation patients experience skin breakdown due to the pressures and shear stresses in the stump-prosthesis interface. In this study, a finite element model was employed to investigate the stresses at the stump interface in the case of an orthopedic implant fixed to the cut end of the femur. By changing the stiffness of this implant, we aim to see how the stiffness of this implant affects the stresses in the interface between the amputated limb and the prosthesis. To find out the effects of implant stiffness, five values for the elastic modulus, ranging from 0.1 to 0.5 Mpa, with an interval of 0.1 Mpa were employed in the implant structure of the FE model. Obtained results show that the implant played important role in reducing the stresses at the stump-prosthesis interface where the contact pressure did not exceed 53 Kpa and 17.3 Kpa for shear stress in the stiffer case of an implant, while the contact pressure in the case of femur without implant exceeded 79Kpa and 42 Kpa for shear stress. We also noted that the intensity of the contact pressure and the shear stress is proportional to the stiffness of the implant, as the greater the implant stiffness, the higher the peak of these stresses

Exploring thermal discomfort amongst lower-limb prosthesis wearers

Amongst lower-limb prosthesis wearers, thermal discomfort is a common problem with an estimated prevalence of more than 50%. Overheating does not just create discomfort to the user, but it has been linked to excessive sweating, skin damage caused by a moist environment and friction. Due to impermeable prosthetic components and a warm moist environment, minor skin damage can result in skin infections that can lead to prosthesis cessation, increased social anxiety, isolation and depression. Despite the seriousness of thermal discomfort, few studies explore the issue, with research predominantly constrained to controlled laboratory scenarios, with only one out of laboratory study. In this thesis, studies investigate how thermal discomfort arises and what are the consequences of thermal discomfort for lower-limb prosthesis wearers. Research studies are designed around the principles of presenting lived experiences of the phenomenon and conducting research in the context of participants' real-life activities. A design exploration chapter investigates modifying liner materials and design to create a passive solution to thermal discomfort. However, this approach was found to be ineffective and unfeasible. Study 1 presents a qualitative study which investigates the user experience of a prosthesis, thermal discomfort and related consequences. Study 2 explores limb temperature of male amputees inside and outside the laboratory, with the latter also collecting perceived thermal comfort (PTC) data. Finally, Study 3 investigates thermal discomfort in the real-world and tracks limb temperature, ambient conditions, activities, and experience sampling of PTC. While there were no apparent relationships presented in sensor data, qualitative data revealed that in situations where prosthesis wearers perceived a lack of control, thermal discomfort seemed to be worse. When combined, the studies create two knowledge contributions. Firstly, the research provides a methodological contribution showing how to conduct mixed-methods research to obtain rich insights into complex prosthesis phenomena. Secondly, the research highlights the need to appreciate psychological and contextual factors when researching prosthesis wearer thermal comfort. The research contributions are also converted into an implication for prosthesis design. The concept of 'regaining control' to psychologically mitigate thermal discomfort could be incorporated into technologies by using 'on-demand' thermal discomfort relief, rather than 'always-on' solutions, as have been created in the past