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

The AERO prosthetic liner: socket pressure distribution, comfort and material composition

PURPOSE

This study aimed to evaluate the pressure distribution and comfort of transtibial prosthesis wearers using an affordable ethyl-vinyl acetate (EVA) roll-on (AERO) liner.

METHOD

Fifteen unilateral transtibial prosthesis users wore patella tendon bearing (PTB) sockets with a polyethylene foam (PE-lite) liner were enrolled this study. AERO liners were provided to all participants. Six force sensors were applied to the residual limb to evaluate pressure distribution during treadmill walking, and the socket comfort score (SCS) was used to evaluate comfortability. Fourier transform infrared (FT-IR) spectroscopy was performed on the EVA and PE-lite liners.

RESULTS

Eleven participants used prefabricated AERO liners and four participants used custom-made AERO liners. The pressure distribution was analysed by the coefficient of variation (CV): PE-lite was 75.7 ± 6.0 and AERO liner 83.3 ± 4.1. Residual limb pressure was significantly decreased when using the AERO liner (p = .0007), with a large effect size (r = 0.87). Mean SCS was 7.5 ± 1.3 and 8.9 ± 1.1 for PE-lite and AERO liner respectively.

CONCLUSION

Better pressure distribution and comfort were observed when the participants used the AERO liner. AERO had a greater proportion of calcium carbonate (CaCO3). These findings suggest that the AERO liner is a better off-the-shelf option for persons using traditional prosthetic sockets and liners.

Insights into the spectrum of transtibial prosthetic socket design from expert clinicians and their digital records

Background

Transtibial prosthetic sockets are often grouped into patella tendon bearing (PTB) or total surface bearing (TSB) designs, but many variations in rectifications are used to apply these principles to an individual's personalised socket. Prosthetists currently have little objective evidence to assist them as they make design choices.

Aims

To compare rectifications made by experienced prosthetists across a range of patient demographics and limb shapes to improve understanding of socket design strategies.

Methodology

163 residual limb surface scans and corresponding CAD/CAM sockets were analysed for 134 randomly selected individuals in a UK prosthetics service. This included 142 PTB and 21 TSB designs. The limb and socket scans were compared to determine the location and size of rectifications. Rectifications were compiled for PTB and TSB designs, and associations between different rectification sizes were assessed using a variety of methods including linear regression, kernel density estimation (KDE) and a Naïve Bayes (NB) classification.

Results

Differences in design features were apparent between PTB and TSB sockets, notably for paratibial carves, gross volume reduction and distal end elongation. However, socket designs varied across a spectrum, with most showing a hybrid of the PTB and TSB principles. Pairwise correlations were observed between the size of some rectifications (e.g., paratibial carves; fibular head build and gross volume reduction). Conversely, the patellar tendon carve depth was not associated significantly with any other rectification, indicating its relative design insensitivity. The Naïve Bayes classifier produced design patterns consistent with expert clinician practice. For example, subtle local rectifications were associated with a large volume reduction (i.e., a TSB-like design), whereas more substantial local rectifications (i.e., a PTB-like design) were associated with a low volume reduction.

Clinical implications

This study demonstrates how we might learn from design records to support education and enhance evidence-based socket design. The method could be used to predict design features for newly presenting patients, based on categorisations of their limb shape and other demographics, implemented alongside expert clinical judgement as smart CAD/CAM design templates.

A pneumatic reconfigurable socket for transtibial amputees

Many transtibial amputees rate the fit between their residual limb and prosthetic socket as the most critical factor in satisfaction with using their prosthesis. This study aims to address the issue of prosthetic socket fit by reconfiguring the socket shape at the interface of the residual limb and socket. The proposed reconfigurable socket shifts pressure from sensitive areas and compensates for residual limb volume fluctuations, the most important factors in determining a good socket fit. Computed tomography scan images are employed to create the phantom limb of an amputee and to manufacture the reconfigurable socket. The performance of the reconfigurable socket was evaluated both experimentally and numerically using finite element modelling. The study showed that the reconfigurable socket can reduce interface pressure at targeted areas by up to 61%.

Toward the Development of User-Centered Neurointegrated Lower Limb Prostheses

The last few years witnessed radical improvements in lower-limb prostheses. Researchers have presented innovative solutions to overcome the limits of the first generation of prostheses, refining specific aspects which could be implemented in future prostheses designs. Each aspect of lower-limb prostheses has been upgraded, but despite these advances, a number of deficiencies remain and the most capable limb prostheses fall far short of the capabilities of the healthy limb. This article describes the current state of prosthesis technology; identifies a number of deficiencies across the spectrum of lower limb prosthetic components with respect to users' needs; and discusses research opportunities in design and control that would substantially improve functionality concerning each deficiency. In doing so, the authors present a roadmap of patients related issues that should be addressed in order to fulfill the vision of a next-generation, neurally-integrated, highly-functional lower limb prosthesis.

Evaluating Feasibility and Durability of the Aero Prosthetic Liner in Transtibial Prosthetic Users

BACKGROUND

The choice of prosthetic socket interface material significantly affects user comfort and satisfaction. The Affordable Ethylene-Vinyl Acetate Roll-On (AERO) liner was created with the aim of improving functionality and streamlining the wearing process for users.

OBJECTIVE

The purpose of this study was to comprehensively assess user satisfaction, comfort, and durability of the AERO liner and compare it with the common soft Pe-Lite liner.

METHODOLOGY

Fourteen individuals with transtibial amputation participated in this three-month randomized crossover trial study. The Prosthesis Evaluation Questionnaire (PEQ), Expanded Socket Comfort Score (ESCS), and liner thickness measurements were used to comprehensively compare the AERO and Pe-Lite liner.

FINDINGS

The AERO liner demonstrated notable improvements in prosthetic comfort and functionality over Pe-Lite liner. After three months use, there was a significant reduction in reported frustration with the AERO liner (p=0.023, r=0.604) in the PEQ subscale. Specific aspects, such as walking with the prosthesis (p=0.030, r=0.601) and odor perception (p=0.024, d=0.579), favored the use of the AERO liner. The expanded socket comfort score (ESCS) revealed significant superiority for the AERO liner "at best" (p=0.04) and "on average" (p=0.02) after one and three months, respectively. Liner thickness analysis showed significant reductions at the mid-patellar tendon location for the AERO liner at one (0.57±0.48) and three months (0.90±0.69, p=0.01) and in the posterior region after three months (0.63±0.64, p=0.05).

CONCLUSION

Our study highlights the potential advantages of the AERO liner in enhancing comfort and satisfaction. Yet, durability and thinning of the liner when compared to Pe-Lite may be a concern which may eventually affect socket fit. These findings contribute to ongoing efforts to optimize prosthetic interventions and improve the quality of life of individuals with lower limb prosthesis in resource-limited environments.

Development and validation of the Self-Management Assessment for the Residuum and prosThesis system designed for persons with limb loss (SMART)

OBJECTIVE

To develop a system of reliable and valid knowledge assessments of self-management in persons with lower limb loss, along with the accompanying targeted educational interventions (TEIs), known as the Self-Management Assessment for the Residuum and prosThesis (SMART) system.

DESIGN

This 2-phase study used mixed methodology. Phase 1 was development, face validation, and content validation of the 60-item knowledge assessment measure (SMART 60) and the TEI. Phase 2 assessed internal consistency reliability using Kuder-Richardson Formula 20 and the creation of the SMART system, consisting of modules developed from the SMART 60. Validity of the measures using known groups' comparison was analyzed by comparing clinicians (prosthetists and physical therapists) with persons with lower limb loss. Participants were recruited from the Amputee Coalition National Conference in 2018 and 2019.

RESULTS

A total of 140 participants completed this study. Four modules from the SMART 60 were created and designed to integrate as a system. Face validity survey average scores found that 9/10 participants either agreed or strongly agreed that the SMART system has high readability, perceived usefulness, and value for both new and experienced prosthetic users. Measure length ranged from 10 to 45 items with a reliability ranging from Kuder-Richardson Formula 20 = 0.70-0.82. The SMART system demonstrated known-groups validity ( p < 0.05).

CONCLUSION

The SMART system is an integrated series of self-management knowledge assessments with reasonable to good internal consistency reliability and known-groups validity. The TEIs provide directed solutions to identified knowledge gaps on the assessments.

The Impact of Limited Prosthetic Socket Documentation: A Researcher Perspective

The majority of limb prostheses are socket mounted. For these devices, the socket is essential for adequate prosthetic suspension, comfort, and control. The socket is unique among prosthetic components as it is not usually mass-produced and must instead be custom-made for individual residual limbs by a prosthetist. The knowledge of what constitutes "good" socket fit is gained by expert prosthetists and technicians over years of experience, and rarely documented. The reliance on tacit knowledge makes it difficult to standardize the criteria for a well-fitting socket, leading to difficulties understanding the impact of socket fit. Despite its importance, the workflow for socket fitting is often overlooked in literature. Due to the customized nature of sockets, if information is provided in literature, generally only the type of socket and suspension mechanism is noted, with information regarding the fitting and manufacturing processes omitted. In this article, the concerns, issues and consequences arising from lack of upper and lower limb socket documentation are discussed from a researcher perspective, supported by healthcare professionals and socket fabrication specialists. Key changes are proposed to the way socket manufacturing and evaluation are documented to assist future research.

A Visual Feedback Tool for Quantitative Pressure Monitoring in Lower-Limb Prosthetic Sockets

Obtaining a good socket fit is an iterative process dependent on the skill and experience of the prosthetist creating it and requires individualisation based on the size and shape. There is no standard measurement system used to aid prosthetic socket creation despite the severe impacts on physical health and quality of life if one is ill fitting. Pressure sensors embedded in a prosthetic socket were used to collect data at the socket–residuum interface. To choose an interpolation method, the sensor array was simplified to a 2D grid with a border for extrapolation and tested using previously collected walking test pressure data. Four multivariable interpolation methods were evaluated to create a colour map of the pressure data. Radial basis function interpolation was chosen, as it produced a clear image with a graduated interpolation between data points, and was used to create a colour map across the surface of a 3D prosthetic socket model. For the model to be accessible to clinical audiences, a desktop application was created using PyQt to view the model. The application allowed for connection to the sensors via Bluetooth, with the pressure data updating on the 3D model in real time. Clinician feedback on the application showed the potential for a clinical product; however, further development informed by feedback from rehabilitation clinicians and prosthesis users is required.

Characterising Residual Limb Morphology and Prosthetic Socket Design Based on Expert Clinician Practice

Functional, comfortable prosthetic limbs depend on personalised sockets, currently designed using an iterative, expert-led process, which can be expensive and inconvenient. Computer-aided design and manufacturing (CAD/CAM) offers enhanced repeatability, but far more use could be made from clinicians’ extensive digital design records. Knowledge-based socket design using smart templates could collate successful design features and tailor them to a new patient. Based on 67 residual limb scans and corresponding sockets, this paper develops a method of objectively analysing personalised design approaches by expert prosthetists, using machine learning: principal component analysis (PCA) to extract key categories in anatomic and surgical variation, and k-means clustering to identify local ‘rectification’ design features. Rectification patterns representing Total Surface Bearing and Patella Tendon Bearing design philosophies are identified automatically by PCA, which reveals trends in socket design choice for different limb shapes that match clinical guidelines. Expert design practice is quantified by measuring the size of local rectifications identified by k-means clustering. Implementing smart templates based on these trends requires clinical assessment by prosthetists and does not substitute training. This study provides methods for population-based socket design analysis, and example data, which will support developments in CAD/CAM clinical practice and accuracy of biomechanics research.

Effects of Prosthetic Socket Design on Residual Femur Motion Using Dynamic Stereo X-Ray - A Preliminary Analysis

Individuals with transfemoral amputation experience relative motion between their residual limb and prosthetic socket, which can cause inefficient dynamic load transmission and secondary comorbidities that limit mobility. Accurately measuring the relative position and orientation of the residual limb relative to the prosthetic socket during dynamic activities can provide great insight into the complex mechanics of the socket/limb interface. Five participants with transfemoral amputation were recruited for this study. All participants had a well-fitting, ischial containment socket and were also fit with a compression/release stabilization socket. Participants underwent an 8-wk, randomized crossover trial to compare differences between socket types. Dynamic stereo x-ray was used to quantify three-dimensional residual bone kinematics relative to the prosthetic socket during treadmill walking at self-selected speed. Comfort, satisfaction, and utility were also assessed. There were no significant differences in relative femur kinematics between socket types in the three rotational degrees of freedom, as well as anterior-posterior and medial-lateral translation (p > 0.05). The ischial containment socket demonstrated significantly less proximal-distal translation (pistoning) of the femur compared to the compression/release stabilization socket during the gait cycle (p < 0.05), suggesting that the compression/release stabilization socket provided less control of the residual femur during distal translation. No significant differences in comfort and utility were found between socket types (p > 0.05). The quantitative, dynamic analytical tools used in the study were sensitive to distinguish differences in three-dimensional residual femur motion between two socket types, which can serve as a platform for future comparative effectiveness studies of socket technology.

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.

Influence of the scale reduction in designing sockets for trans-tibial amputees

The development of artificial prosthetic lower limbs aims to improve patient's mobility while avoiding secondary problems resulting from the use of the prostheses themselves. The residual limb is a pressure-sensitive area where skin injuries and pain are more likely to develop. Requirements for adequate prosthetic limbs have now become urgent to improve amputee's quality of life. This study aims to understand how socket design parameters related to geometry can influence pressure distribution in the residual limb. A finite element model was developed to simulate the mechanical loading applied on the residual limb of a below-knee amputee while walking. A sensitivity analysis to socket initial geometry, scaling the socket downward in the horizontal plane, was performed. Recordings include stress levels on the skin and in the residual limb deep soft tissues. Peak stress was reduced by up to 51% with a limited reduction of the socket size. More important scale reduction of the residual limb would lead to possible negative effects, such as stress concentrations in sensitive areas. This result confirms the interest of the prosthetist to develop a well-fitting socket, possibly a little smaller than the residual limb itself, in order to avoid residual limb mobility in the socket that could cause friction and stress concentrations. Non-homogeneous geometrical reductions of the socket should be further investigated.

Sustainable Development: A Below-Knee Prostheses Liner for Resource Limited Environments

This research sought to develop a fabricable prosthetic liner that could be fabricable, intuitive, and a cost-effective means of providing advanced prosthetics in developing settings. An affordable ethyl-vinyl-acetate roll-on (AERO) liner for permitting a total surface bearing suction socket design was created and provided to a single participant for in vivo outcome measurements. The liner was fabricated from locally produced low-density ethyl-vinyl-acetate (EVA) foam. A liner fabrication process was developed and described, and one participant was provided 3 mm and 6 mm AERO liner variants for outcome evaluations. Six-minute walk test, residual limb temperature, and socket comfort score (SCS) while in AERO liner were collected. Thirty-day step counts of AERO liner with prosthesis and thermoplastic elastomer (TPE) liner with prosthesis were collected. The results of in vivo evaluations indicate increased speed, slightly higher residuum temperature, and increased comfort of the 6 mm AERO liner. Pedometer tallied step counts for the AERO liner and TPE liner prostheses were similar. The 6 mm AERO liner provided the best comfort and function of the two thicknesses in liners, and step count data indicated that the volume of patient activity was similar to when wearing the TPE liner prosthesis. Roll-on fabricable low-cost liners offer an affordable means of providing total surface bearing suction prostheses for resource limited environments (RLE). A prosthetist or technician can use the existing skills and lab to create liners.

Effect of temperature-control liner materials on long-term outcomes of lower limb prosthesis use: a randomized controlled trial protocol

Background

In people living with limb loss, addressing the resulting functional deficit with prostheses increases the risk for secondary conditions such as pressure sores, impaired blood perfusion, and injuries from accidental falls. Any of those occurrences can render the prosthesis temporarily useless, making it challenging for users to engage in many activities of daily life, including work, exercise, and social participation. Many of the described issues originate at the interface between residual limb and prosthetic socket, where the objectives of sufficient weight distribution and suspension are conflicting with the necessity to facilitate heat exchange and limit contact pressure and friction.

Recently, prosthesis liners that contain phase-change material have become commercially available, holding the promise that the micro climate at the interface between the residual limb skin and the prosthetic socket can be regulated to reduce the users’ tendency to sweat. Preliminary studies on these liners indicate that the socket temperatures inside the socket stayed lower and rose slower than in conventional liners. However, the clinical relevance of those findings remains unclear.

The purpose of this study is to investigate whether longer (6+ months) periods of use of phase-change material based temperature-control liners have clinically meaningful effects.

Methods

The protocol is a double-blind longitudinal cross-over research design. A sample of trans-tibial prosthesis users are wearing their regular gel or silicone liners for six months and phase-change material liners for another six months in a randomized sequence. Their prostheses is equipped with activity monitors to detect days when they could not wear their prosthesis. In six-week intervals, individuals’ activity, physical performance, and overall prosthesis assessment is recorded using standardized methods.

Discussion

Expected results will inform prescription and reimbursement practice of phase-change material-based prosthesis liners and will help improve and economize prosthetic fitting for people with limb loss. The design and duration of the protocol, including randomization, blinding, and within-subject comparison, will generate scientific evidence of a comparably high level. Inclusion of a comparably large sample and different climates, e.g. across all four seasons, will make findings applicable to a large number of prosthesis users.

Trial registration

Clinicaltrials.gov, NCT03428815. Registered on 12 February 2018.

Predictive prosthetic socket design: part 2-generating person-specific candidate designs using multi-objective genetic algorithms

In post-amputation rehabilitation, a common goal is to return to ambulation using a prosthetic limb, suspended by a customised socket. Prosthetic socket design aims to optimise load transfer between the residual limb and mechanical limb, by customisation to the user. This is a time-consuming process, and with the increase in people requiring these prosthetics, it is vital that these personalised devices can be produced rapidly while maintaining excellent fit, to maximise function and comfort. Prosthetic sockets are designed by capturing the residual limb’s shape and applying a series of geometrical modifications, called rectifications. Expert knowledge is required to achieve a comfortable fit in this iterative process. A variety of rectifications can be made, grouped into established strategies [e.g. in transtibial sockets: patellar tendon bearing (PTB) and total surface bearing (TSB)], creating a complex design space. To date, adoption of advanced engineering solutions to support fitting has been limited. One method is numerical optimisation, which allows the designer a number of likely candidate solutions to start the design process. Numerical optimisation is commonly used in many industries but not prevalent in the design of prosthetic sockets. This paper therefore presents candidate shape optimisation methods which might benefit the prosthetist and the limb user, by blending the state of the art from prosthetic mechanical design, surrogate modelling and evolutionary computation. The result of the analysis is a series of prosthetic socket designs that preferentially load and unload the pressure tolerant and intolerant regions of the residual limb. This spectrum is bounded by the general forms of the PTB and TSB designs, with a series of variations in between that represent a compromise between these accepted approaches. This results in a difference in pressure of up to 31 kPa over the fibula head and 14 kPa over the residuum tip. The presented methods would allow a trained prosthetist to rapidly assess these likely candidates and then to make final detailed modifications and fine-tuning. Importantly, insights gained about the design should be seen as a compliment, not a replacement, for the prosthetist’s skill and experience. We propose instead that this method might reduce the time spent on the early stages of socket design and allow prosthetists to focus on the most skilled and creative tasks of fine-tuning the design, in face-to-face consultation with their client.

Influences and trends of various shape-capture methods on outcomes in trans-tibial prosthetics: A systematic review

INTRODUCTION

In trans-tibial prosthetics, shape-capture methods are employed to create a representation of the residuum. Shape-capture methods can be grouped into the categories of 'hands-on', 'hands-off' and computer-aided design.

OBJECTIVE

This review examines the influences and trends of shape-capture methods on the outcomes of quality, comfort of user and clinical efficiency, in the population of trans-tibial prosthesis users.

STUDY DESIGN

Systematic Review.

METHOD

Databases and relevant journals were searched. Participants included trans-tibial prosthetics users/limb models. Interventions included shape-capture methods. Outcomes included quality, comfort of user and clinical efficiency.

RESULTS

Overall, 22 papers were evaluated; 8 papers evaluated hands-on and hands-off methods, 2 evaluated computer-aided design and 12 evaluated measurement systems used with shape capture. No papers relating to clinical efficiency were found.

CONCLUSION

Overall evidence was weak in suggesting that effects on outcomes were due to the sole influences of shape capture. However, studies suggest that hands-on methods are dependent on a prosthetist's skill. Hands-off methods, although repeatable, might still require experience to attain a good fit. Computer-aided design studies were mostly done on theoretical models. Shape-capture measurements require more consistent 'gold standards'. The relation between socket fit and comfort is still unclear. Overall, more research is required in each area.

CLINICAL RELEVANCE

A good fitting prosthetic socket is crucial for efficient and comfortable use of a prosthesis. To attain the best chances of a good fit, it is important that the characteristics of the residuum are captured as accurately as possible during the initial "shape capture" stage. This paper attempts to categorize and evaluate the existing shape capture methods on their influence and trends on various outcomes - Quality of shape capture, comfort of user and clinical efficiency.

Real time monitoring of transtibial elevated vacuum prostheses: A case series on socket air pressure

Prosthetic elevated vacuum is a suspension method used to reduce daily volume changes of the residual limb. Evaluation of the effectiveness of these systems is limited due to a lack of correlation to actual socket air pressure, particularly during unconstrained movements. This may explain some of the variability in functional outcomes reported in the literature. Our objective was to develop a light-weight portable socket measurement system to quantify internal socket air pressure, temperature, and acceleration; and to present preliminary results from implementation with three transtibial prosthesis users with mechanical elevated vacuum pumps. Participants completed five functional tasks with and without the vacuum pumps actively connected, including the 2-Minute Walk test, 5-Times Sit-to-Stand test, 4-Square Step test, L-Test, and Figure-8 test. Results demonstrated different gait profiles and pressure ranges for each user. Two of the participants demonstrated substantially lower air pressure (higher vacuum) over time while the pump was active compared to inactive. The minimum air pressure measured for all participants was -34.6 ± 7.7 kPa. One participant did not show substantial changes in pressure over time for either pump condition. Functional task performance was not significantly different between pump conditions. Correlation with accelerometer readings indicated peak positive pressures occurred just following initial contact of the foot in early stance, and the most negative pressures (highest vacuum) were observed throughout swing. This study has demonstrated the use of a portable data logging tool that may serve the clinical and research communities to quantify the operation of elevated vacuum systems, and better understand the variability of mechanical pump operation and overall system performance.

Systematic Review of Studies Examining Transtibial Prosthetic Socket Pressures with Changes in Device Alignment

Suitable lower-limb prosthetic sockets must provide an adequate distribution of the pressures created from standing and ambulation. A systematic search for articles reporting socket pressure changes in response to device alignment perturbation was carried out, identifying 11 studies. These were then evaluated using the American Academy of Orthotists and Prosthetists guidelines for a state-of-the-science review. Each study used a design where participants acted as their own controls. Results were available for 52 individuals and five forms of alignment perturbation. Four studies were rated as having moderate internal and external validity, the remainder were considered to have low validity. Significant limitations in study design, reporting quality and in representation of results and the suitability of calculations of statistical significance were evident across articles. Despite the high inhomogeneity of study designs, moderate evidence supports repeatable changes in pressure distribution for specific induced changes in component alignment. However, there also appears to be a significant individual component to alignment responses. Future studies should aim to include greater detail in the presentation of results to better support later meta-analyses.

Techniques for Interface Stress Measurements within Prosthetic Sockets of Transtibial Amputees: A Review of the Past 50 Years of Research

The distribution of interface stresses between the residual limb and prosthetic socket of a transtibial amputee has been considered as a direct indicator of the socket quality fit and comfort. Therefore, researchers have been very interested in quantifying these interface stresses in order to evaluate the extent of any potential damage caused by the socket to the residual limb tissues. During the past 50 years a variety of measurement techniques have been employed in an effort to identify sites of excessive stresses which may lead to skin breakdown, compare stress distributions in various socket designs, and evaluate interface cushioning and suspension systems, among others. The outcomes of such measurement techniques have contributed to improving the design and fitting of transtibial sockets. This article aims to review the operating principles, advantages, and disadvantages of conventional and emerging techniques used for interface stress measurements inside transtibial sockets. It also reviews and discusses the evolution of different socket concepts and interface stress investigations conducted in the past five decades, providing valuable insights into the latest trends in socket designs and the crucial considerations for effective stress measurement tools that lead to a functional prosthetic socket.