Functionality and Comfort Design of Lower-Limb Prosthetics

This systematic literature review concentrates on the design elements of prosthetic limbs intended for individuals with lower-limb amputations. The review's coverage encompasses peer-reviewed journal articles, conference proceedings, and pertinent materials from the gray literature. The review encompasses research conducted in various disciplines, such as biomechanics, engineering, rehabilitation, and clinical practice. The inclusion criteria for this review involve studies that address the design of prosthetic limbs, including but not limited to socket design, alignment techniques, material selection, control systems, and user-centered design approaches. Studies evaluating functional outcomes, user satisfaction, and quality of life measures related to prosthetic limb design are also included. This review excludes studies that focus solely on surgical techniques, rehabilitation protocols, or clinical outcomes unrelated to prosthetic limb design. Additionally, studies that do not provide sufficient information on the design aspects or lack empirical data are excluded from the review.

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The objective of conducting a systematic literature review on the design of amputated lower limbs is to provide a comprehensive and evidence-based analysis of the existing knowledge in this field. The review aims to identify and evaluate relevant research studies, articles, and publications that address various aspects of prosthetic limb design for individuals with lower-limb amputations. The review aims to identify and analyze the key design factors that influence the development of prosthetic limbs for amputated lower limbs. This includes examining aspects such as biomechanical considerations, material selection, alignment techniques, socket design, interface technology, and customization options. The present work seeks to assess the impact of different design approaches on functional outcomes for individuals with lower-limb amputations. This includes analyzing gait analysis, energy expenditure, mobility, stability, balance, and performance in various activities of daily living. This involves examining factors such as comfort, fit, aesthetics, cosmesis, psychosocial integration, and overall user experience. The review aims to identify design features that contribute to higher user satisfaction and improved psychosocial well-being. The review seeks to explore and discuss emerging technologies and innovations in prosthetic limb design for amputated lower limbs. This includes examining the potential applications of robotics, sensor technology, artificial intelligence (AI), and wearable devices in enhancing the functionality and usability of prosthetic limbs.

The significance of ideal design is magnified by ongoing technological progress. Prosthetic limb design stands to gain from breakthroughs like microprocessors, sensors, and robotics, allowing for intelligent prosthetic systems that dynamically adjust to users' motions, enhancing control, stability, and responsiveness. Technological advancements also facilitate the integration of wearable devices and smart interfaces, allowing users to monitor their activity levels, adjust settings, and receive real-time feedback. These features enhance the functionality and usability of prosthetic limbs, promoting a seamless interaction between the user and the device (How to Remove Surgical Staples [+ Free Cheat Sheet]).

Comfort is a vital aspect of prosthetic limb design. A well-designed prosthesis considers factors such as socket fit, cushioning, and interface pressure management to minimize discomfort and skin-related issues. Proper weight distribution and alignment of the prosthetic limb alleviate excessive pressure on the residual limb, reducing the risk of pain, skin breakdown, and long-term complications. Customization is another critical component of optimal design. Each individual's residual limb is unique in terms of size, shape, and sensitivity. A customized prosthetic limb ensures a precise fit and accommodates the specific needs and functional requirements of the user. Customization also extends to aesthetic considerations, allowing individuals to personalize their prosthetic limbs, contributing to their self-esteem and body image. Prosthetic limb design significantly impacts an individual's psychological and social well-being. Aesthetics and cosmesis play a vital role in promoting body image, self-confidence, and social acceptance. Advancements in design techniques, materials, and coverings allow for the creation of realistic-looking prosthetic limbs that closely resemble natural limbs, reducing the stigma associated with limb loss. User-centered design approaches empower individuals by involving them in the design process, considering their preferences and addressing their psychosocial needs. This collaboration fosters a sense of ownership and promotes a positive user experience, enhancing user satisfaction and overall well-being. By providing functional and aesthetically pleasing prosthetic limbs, individuals can feel more confident, actively engage in social interactions, and regain a sense of normalcy in their lives.

The pivotal role of optimal design in crafting prosthetic limbs cannot be overstated, directly influencing functionality, comfort, and the well-being of those with limb loss. Prosthetic limb design surpasses aesthetics, encompassing a holistic grasp of biomechanics, user requirements, and technological progress. This work highlights the importance of optimal design for prosthetic limbs and its significant impact on enhancing mobility, promoting independence, and improving the overall well-being of individuals. One of the primary goals of prosthetic limb design is to restore and enhance mobility for individuals with limb loss. Optimal design takes into account the biomechanical principles of human locomotion, ensuring that the prosthesis closely mimics the natural movement of the missing limb. By providing appropriate joint dynamics, alignment, and weight distribution, prosthetic limbs enable users to engage in various activities, such as walking, running, and climbing stairs. An optimal design ensures a seamless integration between the residual limb and the prosthetic component, allowing for efficient energy transfer and reducing the effort required during locomotion. This results in improved walking efficiency, reduced fatigue, and enhanced overall functionality, enabling individuals to regain their independence and actively participate in daily activities. Chen et al. (2022) studied a robust gait phase estimation method using thigh angle models to avoid measurement errors. A Kalman filter-based smoother is designed to further enhance the estimation. The proposed method is evaluated through offline analysis and validated in real-time experiments.

Toe or partial foot amputation type of amputation involves the removal of one or more toes or a portion of the forefoot. It is commonly performed for conditions such as gangrene, infections, or deformities that affect a localized area of the foot. Transmetatarsal amputation involves the removal of the forefoot up to the metatarsal bones. It is performed when there is a need to remove a larger portion of the foot while preserving the ankle joint and the ability to bear weight on the residual limb. Lisfranc or Chopart amputation involves the removal of the midfoot, including the metatarsal bones, tarsal bones, and their corresponding articulations. This type of amputation is typically performed in cases of severe trauma or deformities affecting the midfoot. Syme amputation is a surgical procedure that involves the removal of the foot and ankle joint while preserving the heel pad. This procedure aims to provide a weight-bearing surface for better prosthetic fitting and improved functional outcomes. Transtibial amputation refers to the removal of the lower leg, including the tibia and fibula bones, while preserving the knee joint. It is one of the most common types of lower-limb amputations and is performed for various reasons, including trauma, vascular diseases, or complications of diabetes. Knee disarticulation involves the removal of the lower-limb at the knee joint level, preserving the femur bone. This type of amputation is typically performed when preserving the knee joint is beneficial for maintaining stability, allowing for better prosthetic fitting and functional outcomes. Transfemoral amputation, also known as above-knee amputation, involves the removal of the entire lower limb, including the femur bone. This is a more complex procedure that requires the use of a prosthetic knee joint for functional mobility. Hip disarticulation is the most extensive form of lower-limb amputation, involving the removal of the entire lower limb along with the hip joint. This procedure is performed in rare cases where there is extensive disease or trauma involving the hip joint.

Lower-limb amputation involves the removal of a part or the entire lower extremity, including bones, muscles, and soft tissues. The extent of the amputation can vary depending on the underlying conditions, the extent of tissue damage, and the goals of the procedure. Amputations can be categorized into different levels based on the location of the amputation relative to anatomical landmarks. Following are the classification of lower-limb amputation:

In addition to the biomechanical considerations, the design of amputated lower limbs has a significant psychosocial impact on individuals. Prosthetic limb design can greatly influence an individual's psychological well-being, self-esteem, and social integration. The appearance and aesthetics of prosthetic limbs play a crucial role in user acceptance and confidence. Designing prostheses that closely resemble the natural limb can help amputees regain a sense of normalcy and promote positive body image. Additionally, advances in prosthetic limb aesthetics, such as the use of realistic skin-like coverings and customizable designs, contribute to the overall acceptance and integration of prostheses into the individual's self-identity. User-centered design approaches are vital in ensuring user satisfaction and quality of life outcomes. Engaging amputees in the design process, considering their unique needs, preferences, and functional requirements, allows for personalized and tailored prosthetic limb solutions. User involvement empowers individuals, fosters a sense of ownership, and promotes a more positive experience with the prosthetic limb. Psychosocial integration is another significant aspect influenced by prosthetic limb design. A well-designed prosthetic limb can enable individuals to participate in social activities, enhance their self-confidence, and reduce stigmatization. Providing individuals with functional and aesthetically pleasing prostheses contributes to their overall well-being, allowing them to engage in various activities and roles within their communities.

The study selection process for the systematic literature review on the design of amputated lower limbs was as follows. The titles and abstracts of the identified studies were screened to determine their relevance to the research question and inclusion criteria. Studies that clearly did not meet the inclusion criteria or were irrelevant to the topic were excluded at this stage. The remaining studies from the initial screening underwent a full-text assessment. The full-text articles were carefully reviewed to determine if they met all the inclusion criteria and provided relevant information on the design aspects of prosthetic limbs for amputated lower limbs. Studies that did not meet the inclusion criteria or lacked the required information were excluded. The included studies underwent data extraction, where relevant information such as study characteristics (author, year of publication), study design, sample size, methodology, key findings, and outcomes were extracted and organized in a standardized format. This process ensured that important information from each study was captured for analysis. The quality and risk of bias of the included studies were assessed using appropriate tools or checklists. This assessment helped evaluate the strength and reliability of the evidence provided by each study and considered potential sources of bias that may have affected the validity of the findings. The extracted data were synthesized and analyzed to identify common themes, patterns, and trends in the design of prosthetic limbs for amputated lower limbs. This synthesis may have included a narrative synthesis or, if appropriate, a meta-analysis of the quantitative data.

Identify the key design factors and considerations involved in the development of prosthetic limbs for individuals with lower-limb amputations, including biomechanical considerations, material selection, alignment techniques, socket design, interface technology, and customization options. Evaluate the impact of different design approaches on functional outcomes, including gait analysis, energy expenditure, mobility, stability, balance, and performance in various activities of daily living for individuals with lower-limb amputations. Assess user satisfaction and quality of life outcomes associated with different prosthetic limb designs, including factors such as comfort, fit, aesthetics, cosmesis, psychosocial integration, and overall user experience. Explore emerging technologies and innovations in prosthetic limb design for amputated lower limbs, including robotics, sensor technology, AI, and wearable devices, and their potential applications in enhancing functionality and usability. Identify gaps in the existing literature and provide recommendations for future research and development in the design of prosthetic limbs for individuals with lower-limb amputations. By addressing these research objectives, this study aims to provide valuable insights into the design factors and considerations that contribute to optimal prosthetic limb designs. The findings can inform clinical practice and prosthetic limb development, and ultimately improve the functional outcomes, user satisfaction, and quality of life for individuals with lower-limb amputations.

BIOMECHANICAL CONSIDERATIONS IN DESIGN

The design of prosthetic limbs for individuals with lower-limb amputations is a complex process that requires a comprehensive understanding of biomechanical principles. Biomechanics plays a crucial role in determining the functionality, comfort, and overall performance of these devices. Present review provides an overview of the biomechanical factors that influence the design of amputated lower-limb prosthetics, including socket design, alignment, joint mechanics, and gait analysis. The socket is a critical component of the prosthetic limb that interfaces with the residual limb. Its design significantly affects the fit, stability, and weight-bearing distribution. The socket must be customized to the shape of an individual's residual limb to ensure a precise fit, maximize contact area, and distribute forces evenly. It should also provide adequate support and promote efficient energy transfer during walking and other activities. Proper socket design reduces pressure points, enhances comfort, and minimizes the risk of skin breakdown and discomfort. Alignment refers to the correct positioning of the prosthetic limb in relation to the user's anatomy. Proper alignment is crucial to achieve optimal biomechanical function and gait symmetry. Alignment factors include the angular positioning of the knee, ankle, and foot, as well as the sagittal, coronal, and transverse planes. Precise alignment helps maintain proper joint mechanics, reduces stress on the residual limb, and improves stability and balance during walking and other movements.

Prosthetic limbs must replicate the natural joint mechanics of the lower limb to ensure smooth and efficient movement. The mechanical behavior of prosthetic joints, such as the knee and ankle, should closely mimic the natural range of motion, joint axes, and kinematics. This allows users to perform activities such as walking, running, and climbing stairs with minimal deviations from normal biomechanics. Proper joint mechanics facilitate a more natural gait pattern, reduces energy expenditure, and enhances overall functionality and user satisfaction. Gait analysis is a valuable tool for evaluating the biomechanical performance of prosthetic limbs. It involves the measurement and assessment of various parameters during walking, such as step length, stride length, cadence, ground reaction forces, and joint angles. By analyzing gait patterns, clinicians and researchers can identify biomechanical deviations and assess the effectiveness of prosthetic limb designs. Gait analysis helps optimize alignment, socket fit, and component selection, leading to improved walking efficiency, reduced fatigue, and enhanced functional outcomes.

Optimal weight distribution is crucial for comfortable and efficient use of prosthetic limbs. Uneven weight distribution can lead to discomfort, pressure points, and skin irritation. Prosthetic limb designs should distribute weight evenly across the residual limb and the prosthetic components to minimize excessive loading and prevent overuse injuries. A balanced weight distribution also helps users maintain stability, balance, and control during activities, contributing to enhanced mobility and overall functionality. To ensure the prolonged durability of prosthetic limbs, specific recommendations and best practices can be implemented. Regular maintenance routines, including thorough cleaning and lubrication of components, can prevent premature wear and damage. Proper usage techniques and weight management are essential to avoid excessive strain on the prosthetic. Consideration of these biomechanical factors is essential in the design of amputated lower-limb prosthetics. An integrated approach that combines socket design, alignment, joint mechanics, and gait analysis results in optimal prosthetic limb functionality and improved user outcomes. By understanding the biomechanical principles and their impact on design, prosthetists and engineers can create personalized and efficient prosthetic limb solutions that maximize mobility, comfort, and overall quality of life for individuals with lower-limb amputations. Table 1 summarizes some recent studies carried out in prosthetic design.

Table 1:

No.AuthorsObjectiveMethodologyOutcome1 Wang et al. (2023) Design an adjustable frame-type prosthetic socket with constant force to adapt to stump volume fluctuations.Design a constant force device based on shape memory alloy for maintaining constant stump–socket interface stress.An adjustable prosthetic socket that allows users to adjust the socket volume, maintains constant interface stress, and adapts to stump volume fluctuations.2 Fidelis and Arowolo (2023) Design and implement a mechanical, body-powered, transfemoral prosthetic device for affordable functional ambulation.Utilize anthropometric measurements to design an ergonomic prosthetic device using AutoCAD rendering and engineering methods like casting and welding.Successful fabrication of a transfemoral prosthetic limb consisting of a polypropylene socket, galvanized iron knee joint, and perlite foot, restoring ambulatory function for the amputee.3 Van Der Stelt et al. (2023) Develop a workflow for producing low-cost 3D-printed transtibial prosthetic sockets in LMICs.Use CAD and CAM to scan and 3D-print prosthetic sockets, with locally sourced foot and imported prosthetic parts.Cost-effective production of transtibial prosthetic sockets, with a 3D-printed socket costing $20 and total material cost of the prosthesis amounting to approximately $100. Potential to sell a 3D-printed prosthesis for $170, benefiting individuals in LMICs.4 Tang et al. (2023) Optimize socket design to reduce local load on residual limb.Divide residual limb into load-bearing regions and apply modifications to socket design based on carrying capacity.Reduced contact interface pressures in specific regions, increased walking distance, and improved pressure distribution.5 Dickinson et al. (2022) Assess the repeatability of plaster casting and 3D scanning for prosthetic socket design.Conduct a comparative reliability assessment in participants with transtibial amputation.Deviation analysis shows high repeatability for plaster casting and varying reliability for different 3D scanners.6 Vásquez and Pérez (2022) Design a low-cost alignment device for lower transfemoral prostheses.Implement conceptual design methodology, model the device in SolidWorks, and analyze its mechanical resistance using finite element analysis in ANSYS.Carbon film material shows promising results for a 3D printed alignment device prototype, with potential for mass production and implementation in prosthetic centers worldwide.7 Sturma et al. (2022) Develop a structured rehabilitation protocol after TMR surgery.Conduct a Delphi study involving European clinicians and researchers in upper limb prosthetic rehabilitation, utilizing a web-based survey to gather expert consensus on rehabilitation steps and their importance.A 16-step rehabilitation protocol for TMR patients was established, emphasizing the need for multiprofessional teamwork and patient selection and education.8 Ratnakar and Ramu (2021) Utilize CT scan-based technology and finite element analysis to develop and evaluate 3D models of prosthetic sockets for lower-limb amputations.Develop 3D models from CT images using image-processing software, modify them in CAD, and convert them to the STL format. Analyze the models in ANSYS under static and dynamic conditions to evaluate stress distribution. Prepare a 3D model with a 3D printer based on simulation results.Enhanced evolution and prefabrication of prosthetic sockets, providing a development method for healthcare providers. Positive patient satisfaction with transtibial prosthetics made using 3D printers.9 Gubbala and Inala (2021) Design and develop a prosthetic socket for lower-limb amputation using 3D printing technology.Utilize CT-based 3D models and perform finite element-based simulation and analysis. Extract models from CT images using image-processing software, modify them in