Prosthetic Liner Guide: Types, Benefits & More

29 Apr.,2024

 

Prosthetic Liner Guide: Types, Benefits & More

Often not given the proper attention they deserve, prosthetic liners are crucial for added comfort and greater efficiency. These devices can dramatically improve an amputee's quality of life, so choosing suitable prosthesis liner material is vital for maximum protection and healthy recovery.

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PrimeCare produces custom prosthetics in Albuquerque and Las Cruces. We've helped many patients with various needs choose suitable prosthetic liners. This brief guide covers the different types of liners and their benefits, as well as prosthetic liner care and technological innovations.

What Is a Prosthetic Liner and Why Is It Important?

A prosthetic leg liner is a unique lightweight sheath, like a second skin, made from silicone or other synthetic materials that fit snugly and comfortably around an amputee's residual limb.

Wearing amputee liners offer better fitting, increased comfort, and protection against moisture and skin issues. They keep prosthetics in place and reduce the risk of sores and itching.

If you require a prosthesis either above or below the knee, wearing a prosthetic liner is imperative. Essentially, amputee liners provide comfort and protection to the residual limb throughout the day.

Types of Prosthetic Liners

When looking at prosthetic leg liners, the two main factors to consider are pliability and durability.

Below are the most commonly used types:

— Durable Silicone Liner

Medical-grade silicon liners for prosthetics are non-irritating and comfortable on the skin. They do not cause a reaction with substances such as sweat and have excellent shock-absorbing properties to lessen shearing forces that harm the limb and scar tissue.

Regarding its softness and robustness, silicone liners are a mid-range choice that holds some of the elasticity of TPE liners but has more durability than urethane liners. Additionally, they are hypoallergenic and capable of withstanding prolonged usage and daily stretching.

— Urethane Liners

Stiff, inflexible urethane liners offer high durability and aid even pressure distribution. Urethane liners are particularly well-suited for users with a high degree of activity who use prosthetic limbs with active vacuum sockets. These liners have a higher tensile stiffness, which provides improved suspension for active users.

— Thermoplastic Elastomer (TPE)

TPE liners are the perfect choice for those with atypical residual limb shapes, as the liner's soft and pliable material molds to an individual's limb shape over time, allowing for ultimate comfort and convenience. Moreover, the ability of TPE to absorb shear forces makes it a popular material for prosthetic liner design. This property enables prosthetists to pre-stretch the liner before fitting, making it a comfortable option for amputees, particularly those with sensitive skin or skin grafts, allowing them to walk without straining their limbs.

— Mineral Oil Gel

Those with a bony residual limb or hypersensitive areas can benefit greatly from mineral oil gel liners. They are soft and forgiving and protect against rubbing within the prosthetic socket. Additionally, mineral oil gel liners contain vitamins that help keep the skin healthy and moist, reducing the risk of skin breakdown. The only drawback is less durability compared to other types of liners.

— Polyurethane

Urethane liners have exemplary "flow properties," which gives them the capacity to shift their gel away from areas where the pressure is higher, allowing for an even distribution of pressure and a more comfortable fit. These characteristics make them a good choice for sensitive, bony, or scarred residual limbs and active individuals who need a liner to withstand high levels of wear and tear.

— Copolymer

The copolymer is best for amputees with sensitive skin or low activity levels due to its soft, cushiony, and highly elastic properties. This thermoplastic elastomer also contains skin-friendly white oil, which provides extra protection to residual limbs with dry skin. When it comes to suspension, copolymer performs best when used with pin or suction suspension.

— Prosthetic Sleeves

Prosthetic sleeves are elastic garments worn over prosthetic limbs to provide a comfortable and secure fit. They also help to reduce skin irritation caused by friction during wearing and movement. Made from soft, stretchy materials such as spandex or lycra, which allow the limb to flex easily, they also contain fabric liners that reduce sweat and keep the prosthesis from slipping. Prosthetic sleeves may also be fabricated with pockets for storing small items and providing additional support to the limb.

To clarify and reiterate: A prosthetic sleeve (shrinker sleeve/stockinette) makes it easier to wear a prosthetic liner. It distributes pressure and reduces volume, friction, and rotation. Prosthetic liner cushions and shapes the residual limb provides an even interface between limb & socket, and reduces friction/provides feedback.

Prosthetic Liner Shapes & Thicknesses

Prosthetic leg liners vary in shape and thickness, with cylindrical and conical shapes offering more uniform protection. Cylindrical liners range in thickness from 5 mm to 10 mm, while conical liners usually vary between 3 mm to 7 mm.

Custom liners are also available to accommodate those with typical limb shapes. These liners are thicker in areas such as the bottom front or side, which protects prominent bones. They also have thinner areas that allow for a greater range of motion, such as behind the knee, to accommodate knee flexion.

What's the Typical Lifespan of Amputee Liners?

No matter the user's physical features, daily activities, and hygienic habits, a breathable prosthetic liner will eventually degrade, leading to skin irritation and discomfort. It's common for very active amputees to replace their liners twice a year.

Signs that it is time to buy a new prosthetic liner include discoloration, hardening, and a separation between the outer and inner layers of fabric. If unsure, you should consult your prosthetist to determine if a liner replacement is needed.

How Often Should I Wear My Liner Prosthesis?

If you are breaking in a new liner, your prosthetist will provide specific instructions for you to follow. If you experience any skin irritation after putting the liner on, please stop using it and contact your prosthetist immediately.

Below is a general guideline for breaking in a new liner:

  • Day one: Wear your liner for one hour in the morning and one hour in the afternoon.
  • Day two: Wear your liner for two hours in the morning and two hours in the evening.
  • Day three: Wear your liner for three hours in the morning and another three hours in the evening.
  • Day four: Follow the same step above, but extend the duration to four hours.
  • Day five: Wear your liner the whole day.

If at any point during the process, your skin becomes irritated, then proceed to the next step once you've spoken to your prosthetist, primarily if blistering or prolonged redness occurs.

Please note: it is normal to experience some redness as your residual limb adjusts to the liner. However, this should subside within 15 minutes of removing the liner.

Prosthetic Liner Care

Follow these tips to prolong the life of your prosthetic liner and learn how to clean a prosthetic leg liner:

  • Wash the liner inside out with mild, non-allergenic, fragrance-free soap and warm water. Gently blot dry with a towel, turn right-side out, and leave on the drying stand overnight.
  • If the liner is fabric covered, take care not to soak the fabric, as this can weaken its structural integrity.
  • Check the liner for signs of damage, both inside and out; schedule an appointment with your prosthetist if there's significant wear and tear.
  • Always ensure the liner is clean, dry, and has no debris stuck inside before rolling it on your leg.
  • When putting it on, ensure it is inverted and covers the end of the limb; air pockets can lead to unintended suction resulting in water blisters.

How Much Does a Prosthetic Liner Cost in Albuquerque?

A prosthetic liner price can range from $350 to $625 depending on several factors, such as the liner's type and complexity, the materials used, the manufacturing process, additional features, and the product brand.

Advancing Prosthetic Liner Technologies

Pin-locking prosthetic liners have revolutionized prosthetics by streamlining the process of securely attaching a prosthesis to the residual limb.

A prosthetic locking liner uses small removable pins to quickly and securely "lock" into the prosthesis. The pins fit into the socket in various patterns to accommodate individual activities and specific needs.

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This customization reduces shear and friction between the limb and the prosthetic socket, yielding a better grip, higher comfort level, and improved control over prosthesis movement.

Not only that but a pin-locking prosthesis and liner enhances the suspension of prosthetic limbs due to their secure and stable fit and even distribution of pressure across the residual limb.

Furthermore, new and innovative prosthetic socket designs are being created to cater to individual anatomy and offer more creative materials such as 3D printed and carbon fiber-based sockets. Through customization, these designs achieve better comfort and fit for the individual based on their anatomy.

Also, these materials are lighter yet more robust, allowing wearers to be more agile and move quickly.

Which Prosthetic Liner Is Right for Me?

When selecting the best amputee liner for you, there isn't a "one-size-fits-all" approach.

At PrimeCare, we start by reviewing your level of comfort and mobility regardless of whether you already have a prosthetic or are a new amputee.

Then we consider your limb's residual shape, suspension technology, and other factors like skin compatibility, comfort, durability, and security.

In other words, your prosthetic liner must accommodate a wide range of daily volume fluctuations, be durable, and maintain a close fit to minimize movement within the socket - this is paramount for maintaining healthy and active lifestyles.

Empowering Lives with Prosthetic Leg Liners

It's essential to talk to your prosthetist when selecting a prosthetic liner. They will discuss the various types in detail, as well as which is ideal for your individual needs and preferences, including comfortability, durability, and cost-effectiveness. As time passes, your body's needs will change, and switching to your prosthetic liner is expected.

At PrimeCare, we always aim to provide liners made from the highest-quality materials that improve mobility and quality of life. We offer a range of direct sockets and above and below-the-knee prosthetic liners from an industry-leading manufacturer, Össur.

Don't hesitate to contact us for more information.

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.

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 ( Siddiqui et al., 2023b ; Deathe and Miller, 2005 ).

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 ( Ma et al., 2019 ; Pei et al., 2021 ). 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 ( Cohen and Hoberman, 1983 ; Dunn, 1996 ; Gallagher and MacLachlan, 2001 ; Behel et al., 2002 ).

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 ( Jönsson et al., 2011 ). 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 ( Taylor et al., 1996 ). 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 the 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 ( Wong et al., 2016 ). Figure 1 shows the major classification of lower-limb amputation. 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 ( Jackson et al., 2001 ). 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 ( Datta et al., 1992 ; Pezzin et al., 2004 ; Johannes et al., 2019 ; Safari, 2020 ; Yu et al., 2021 ).

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 ( Horgan and MacLachlan, 2004; Deathe and Miller, 2005; Kahle et al., 2008; Highsmith et al., 2010; Siddikali and Sreekanth, 2020; Pinhey et al., 2022). 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 ( Köhler et al., 2021). 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 ( Schmalz et al., 2002; Zhang et al., 2019, 2020).

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 facilitates a more natural gait pattern, reduces energy expenditure, and enhances overall functionality and user satisfaction ( Schmalz et al., 2002; Orendurff et al., 2006; Bae et al., 2009). Gait analysis is a valuable tool for evaluating the biomechanical performance of prosthetic limbs ( Ferrari et al., 2008; Peters et al., 2010; El Habachi et al., 2015; Leardini et al., 2017). 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 ( Stagni et al., 2005, 2009; Koh et al., 2009; Li et al., 2012; Gasparutto et al., 2015).

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 ( Simon et al., 2016). 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 ( Duprey et al., 2017). 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 CAD software, and convert them to STL format. Conduct static and dynamic analyses of the prosthetic stump and socket using ANSYS. Prepare a 3D model with a 3D printer based on simulation results.Estimation of pressure distribution, evaluation of below-knee prosthesis function under static and dynamic conditions. Advancement in prosthetic socket evolution and prefabrication using finite element approach. Contribution to an overall prefabrication evaluation system for healthcare providers. Positive patient satisfaction with transtibial prosthetics made using 3D printers and simulation process.10 Cabibihan et al. (2021) Evaluate the functionality, durability, and cost of popular designs of body-powered, 3D printed prosthetic hands for long-term usage.Selected representative sample of 3D printed prosthetic hands and assessed their suitability for grasping postures, durability, and cost. Tested the prosthetic hand’s ability to perform 3 out of 33 grasping postures. Evaluated the material and cables used in the hand for their ability to withstand a 22 N normal grasping force. Analyzed the cost model to determine the production cost of a 3D printed hand.The selected 3D printed prosthetic hand design demonstrated the ability to perform functional grasping postures for everyday objects. The material and cables used were able to withstand the required grasping force. The cost model indicated that a 3D printed hand could be produced at a low cost, as low as $19. These findings provide a baseline for the development of functional and affordable prosthetic hands, benefiting children with congenital missing limbs and war-wounded individuals.11 Siddiqui et al. (2023a) Investigate the effect of different materials on the functionality of prosthetic running blades.Conduct finite element modeling and numerical simulations to study the static behavior of a prosthetic running blade under various load conditions. Evaluate the performance based on total deformation, equivalent stress, and strain energy. Compare the use of titanium alloy (grade 5), carbon fiber, stainless steel (AISI 316), and aluminum alloy (2024 T4) as materials for running blades.Titanium alloy exhibits high durability and tensile strength but is costly for manufacturing running blades. Aluminum alloy (2024 T4) blades experience more deformation compared to titanium and carbon fiber blades. Carbon fiber offers excellent mechanical properties and has outstanding tensile properties, making it suitable for creating running blades.
Socket design

Socket design is a critical aspect of prosthetic limb development, as it serves as the interface between the residual limb and the prosthesis ( Gerschutz et al., 2012; Gariboldi et al., 2022). The socket plays a crucial role in distributing forces, providing stability, and ensuring user comfort. This text provides an overview of the key principles and considerations involved in socket design for individuals with lower-limb amputations. One of the primary objectives of socket design is to achieve an individualized fit for each user. Residual limbs come in various shapes, sizes, and contours, requiring custom-made sockets to ensure proper contact and load distribution. Individualized fit minimizes pressure points, reduces shear forces, and enhances overall comfort. To achieve this, prosthetists employ techniques such as plaster casting, 3D scanning, and digital modeling to capture the unique anatomy of the residual limb ( Rai et al., 2022). Efficient load distribution is crucial for optimal functionality and comfort. The socket must evenly distribute forces across the residual limb to prevent localized pressure and potential skin breakdown. Various strategies are employed to achieve proper load distribution, such as the use of pressure-relief areas, padding, and flexible materials. Pressure mapping technologies and computer simulations help evaluate the load distribution characteristics of different socket designs ( Lenhart et al., 2015; Siddikali and Sreekanth, 2020). Socket design must provide adequate stability and suspension to ensure secure attachment of the prosthetic limb to the residual limb. Stability refers to the control of rotational and translational movements, while suspension involves maintaining the prosthesis in position during various activities. Various suspension methods, including suction, vacuum-assisted, and strap-based systems, are utilized to achieve secure and comfortable suspension. The socket design should accommodate the necessary suspension mechanism while ensuring stability and minimizing unwanted movements ( Quinlan et al., 2020a, 2020b).

The choice of materials and construction techniques significantly impact the performance of the socket. Materials should be lightweight, durable, and compatible with the user’s skin. Commonly used materials include thermoplastics, carbon composites, and silicone liners. Advanced manufacturing methods, such as 3D printing, allow for complex socket designs and customization. Proper fabrication techniques, including lamination, molding, and thermoforming, ensure the desired shape, strength, and durability of the socket ( Gerschutz et al., 2011, 2012). User comfort is a critical consideration in socket design. Discomfort or pain can significantly affect the user’s adherence and satisfaction with the prosthetic limb. Socket design should consider factors such as cushioning, pressure distribution, breathability, and temperature control ( Gariboldi et al., 2023). Innovative technologies, including gel liners, adjustable interfaces, and modular components, help enhance comfort by reducing pressure points and improving socket fit and adjustability. Proper alignment of the socket is essential for optimal biomechanical function and gait symmetry ( Marinopoulos et al., 2022). The alignment ensures that the prosthesis replicates the natural anatomical position and joint axes of the lower limb. Precise alignment contributes to improved stability, reduced energy expenditure, and more efficient gait patterns. Alignment adjustments may be necessary during the fitting process to fine-tune the socket’s orientation and optimize user performance. Socket design should allow for adjustability and adaptability to accommodate changes in the residual limb, such as volume fluctuations, muscle atrophy, or bony prominences. Adjustable components, modular systems, and interchangeable interfaces enable prosthetists to make necessary modifications without requiring a complete socket replacement ( Dickinson et al., 2023). This adaptability extends the lifespan of the socket and ensures an optimal fit and function over time. The interface between the residual limb and the socket, along with the suspension system, significantly influences socket performance ( Quinlan et al., 2020a). Soft interfaces, such as silicone liners, help improve comfort, cushioning, and moisture management. Suspension systems, including suction, vacuum, or strap-based systems, provide secured attachment and control of the prosthetic limb.

Patient-centric design considerations

In recent years, there has been a paradigm shift toward patient-centric design in the field of prosthetics. Recognizing the importance of meeting the unique needs and preferences of individual users, prosthetic design has evolved to prioritize the patient’s comfort, functionality, and overall satisfaction. Here we explore the key considerations in patient-centric design, including customization, user involvement, comfort, functionality, aesthetics, and psychosocial factors. One of the fundamental aspects of patient-centric design is customization. Every individual has unique anatomical characteristics, functional requirements, and personal preferences. Customization allows prosthetists to tailor the design, fit, and functionality of prosthetic limbs to meet the specific needs of each patient. This includes considerations such as residual limb shape, size, and volume, as well as the alignment, components, and interface materials used in the prosthesis. Customization ensures a better fit, improved comfort, and enhanced overall functionality for the individual user ( Beekman and Axtell, 1987; Reinbolt et al., 2005; Akarsu et al., 2013). Involving the patient in the design process is crucial for achieving patient-centric outcomes. By actively engaging individuals with amputations in decision-making, prosthetists can gain valuable insights into their unique needs, goals, and expectations. Patient involvement allows for open communication, shared decision-making, and a collaborative approach to design. Prosthetists can gain a better understanding of the user’s lifestyle, preferences, and activities, enabling them to create prosthetic solutions that align with the user’s specific requirements and optimize their functional outcomes.

Comfort is a paramount consideration in patient-centric design. Prosthetic limbs should be comfortable to wear for extended periods, minimizing discomfort, pressure points, and skin irritation. Factors such as socket design, padding, suspension systems, and interface materials play a crucial role in enhancing comfort. Customized socket design ensures a proper fit and weight distribution, reducing pressure on the residual limb. The use of cushioning materials, such as silicone liners or gel interfaces, improves comfort and reduces friction. Attention to detail in design and fabrication helps minimize discomfort and maximize overall satisfaction for the user. Patient-centric design places a strong emphasis on improving the functionality of prosthetic limbs. The aim is to enable users to perform a wide range of activities, including walking, running, climbing stairs, and engaging in sports or recreational activities. Prosthetic components, such as knees, feet, and power systems, are chosen based on the user’s functional requirements and activity level. The alignment, joint mechanics, and range of motion should closely mimic the natural limb to facilitate more natural movement and gait patterns ( Adouni et al., 2012). By focusing on functionality, patient-centric design empowers individuals to regain their independence and participate fully in daily activities. The visual appearance of prosthetic limbs is an essential consideration in patient-centric design ( Hall and Dornan, 1990). Aesthetics can have a significant impact on an individual’s self-esteem, body image, and social acceptance. Prosthetists work closely with patients to create prosthetic limbs that match their skin tone, incorporate realistic features, and align with their personal preferences. Advances in cosmetic covers, realistic silicone skin, and patterned socket designs allow for greater customization and aesthetic appeal. By considering the aesthetics, patient-centric design seeks to address not only the physical but also the psychological well-being of individuals with amputations. Patient-centric design acknowledges the psychosocial impact of prosthetic limbs on individuals’ lives. It recognizes the importance of addressing psychological, emotional, and social aspects alongside physical considerations. Prosthetic limbs should enhance self-confidence, body image, and quality of life for the user. Factors such as ease of use, reliability, and social acceptance are crucial. Peer support, counseling, and psychological interventions are also integrated into patient-centricity.

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