Transtibial Prosthetic Socket Research Articles

Design of a custom metamaterial insert for improved pressure distribution within transtibial prosthetic sockets.

Uneven pressure distribution within a transtibial prosthetic socket can lead to discomfort, skin degradation, and suspended prosthesis use. Current custom interfaces to improve pressure distribution are often costly, time-intensive to fabricate, or cannot be incorporated into standard socket fabrication methods. In this technical note, we describe the design and preliminary clinical evaluation of a novel transtibial prosthetic socket insert with modifiable mechanical properties, which can be incorporated into the current clinical cycle of care. The custom insert (termed "inlay") relies on a triangular unit cell, which can be modified based on the desired stiffness profile. Inserts are 3D printed in a soft polymer material and inset into shape-matched voids in a socket creating regions of custom offloading. Preliminary clinical efficacy of the inserts was assessed in a pilot long-term cross-over evaluation. After Institutional Review Board approval, 3 pilot participants wore a shape-matched replica of their habitual socket modified for insert use and a shape-matched socket without. Sockets were worn for 4-week each, and inner socket pressures were measured with thin film pressure sensors at the end of the wear period. Peak pressures within the distal tibial region of interest were decreased for 2 of 3 participants during midstance of level-ground walking when wearing the socket with inlays. The technical methods and results presented provide a new method to address high pressure regions within a transtibial prosthetic socket. The 3D-printed inlays can be rapidly produced allowing for easy modification and replacement without require new socket fabrication.

Evaluating the Effectiveness of Transtibial Prosthetic Socket Shape Design Using Artificial Intelligence: A Clinical Comparison With Traditional Plaster Cast Socket Designs

ObjectiveTo investigate the feasibility of creating an artificial intelligence (AI) algorithm to enhance prosthetic socket shapes for transtibial prostheses, aiming for a less operator-dependent, standardized approach. DesignThe study comprised 2 phases: first, developing an AI algorithm in a cross-sectional study to predict prosthetic socket shapes. Second, testing the AI-predicted digitally measured and standardized designed (DMSD) prosthetic socket against a manually measured and designed (MMD) prosthetic socket in a 2-week within-subject cross-sectional study. SettingThe study was done at the rehabilitation department of the Radboud University Medical Center in Nijmegen, the Netherlands. ParticipantsThe AI algorithm was developed using retrospective data from 116 patients from a Dutch orthopedic company, OIM Orthopedie, and tested on 10 randomly selected participants from Papenburg Orthopedie. InterventionsUtilization of an AI algorithm to enhance the shape of a transtibial prosthetic socket. Main Outcome MeasuresThe algorithm was optimized to minimize the error in the test set. Participants’ socket comfort score and fitting ratings from an independent physiotherapist and prosthetist were collected. ResultsPredicted prosthetic shapes deviated by 2.51 mm from the actual designs. In total, 8 of 10 DMSD and all 10 MMD-prosthetic sockets were satisfactory for home testing. Participants rated DMSD-prosthetic sockets at 7.1 ± 2.2 (n=8) and MMD-prosthetic sockets at 6.6 ± 1.2 (n=10) on average. ConclusionsThe study demonstrates promising results for using an AI algorithm in prosthetic socket design, but long-term effectiveness and refinement for improved comfort and fit in more deviant cases are necessary.

Optimization, Sodium Hydroxide and Plantain Fibres: Mechanical Properties of Unsaturated Polyester Composites for Transtibial Prosthetic Socket

Low mechanical behaviors of natural fibres in the reinforcement of polymer composites have remain an issue of concern. This study is aimed at investigating the effect of NaOH treatment on the mechanical properties of plantain fiber for the transtibial prosthetic sockets made of polyester resin. Plantain fiber was extracted from the plantain bast using water retting techniques. The fibres were modified using alkaline treatment method of 5 – 25% for variable time of 30 to 150 minutes. It was optimized using 3-level Factorial design (3-LCD) of response surface methodology based on tensile properties of treated fibres. The polyester composites of plantain and glass fibers were prepared using hand-layup techniques. Instron Universal testing machine-3369 model was used to determine the tensile and impact properties of fibers and polyester composites. Rockwell hardness tester-RBHT/S-39 model was used to determine the hardness property. The optimum process conditions of 5 % NaOH for 119 minutes improved plantain fiber tensile strength, modulus, strain, energy, and extension by improved by 102.03, 208.07, 9.70, 210.52 and 205.73 %, respectively. The ultimate tensile strength and modulus was obtained at 10 and 12.5% fiber loading. The hardness and impact strength of NaOH modified unsaturated polyester composites was marginally more than 3.51 and 10.69% of glass fiber reinforced unsaturated composites, respectively, at 12.5% fiber loading. FTIR analysis revealed the improvement in mechanical properties. Thus, NaOH modified plantain fiber unsaturated polyester composites serves as a better alternative for making transtibial prosthetic socket.

Implementation of Additive Manufacturing Workflows into the Prosthetic & Orthotic Industry: Case Study

The prosthetic and orthotic industry is evolving to include innovative technologies as solutions to material and labour usage, promoting more sustainable and cleanly practises for both staff and patients. 3D printing, scanning and software have revolutionised the workflows of clinicians, technicians and administrative staff. To determine the reliability and repeatability of additive manufacturing (AM) workflows in a P&O company, observation and interview analyses were undertaken within an established prosthetic and orthotic company. The collection of data from these opportunities offered valuable insight into workflow sessions, employee feedback and predetermined themes regarding both traditional and AM processes for the production of Transtibial prosthetic sockets. Findings revealed the reduction in workflow sessions, technician resource and storage requirements when working through AM processes, although there is a lack of opportunity and resource for clinicians and technicians to learn how to use these digitalised processes. Although both traditional and 3D printed sockets receive similar feedback from patients regarding comfort and fit, discrepancies in socket weight were noted. A further understanding on the culture and adoption barriers of AM processes should be investigated for clinicians, technicians and administrative staff across a larger sample size.

Application of ultrasound to monitor in vivo residual bone movement within transtibial prosthetic sockets

Transtibial prosthetic users do often struggle to achieve an optimal prosthetic fit, leading to residual limb pain and stump-socket instability. Prosthetists face challenges in objectively assessing the impact of prosthetic adjustments on residual limb loading. Understanding the mechanical behaviour of the pseudo-joint formed by the residual bone and prosthesis may facilitate prosthetic adjustments and achieving optimal fit. This study aimed to assess the feasibility of using B-mode ultrasound to monitor in vivo residual bone movement within a transtibial prosthetic socket during different stepping tasks. Five transtibial prosthesis users participated, and ultrasound images were captured using a Samsung HM70A system during five dynamic conditions. Bone movement relative to the socket was quantified by tracking the bone contour using Adobe After-Effect. During the study a methodological adjustment was made to improve data quality, and the first two participants were excluded from analysis. The remaining three participants exhibited consistent range of motion, with a signal to noise ratio ranging from 1.12 to 2.59. Medial–lateral and anterior–posterior absolute range of motion varied between 0.03 to 0.88 cm and 0.14 to 0.87 cm, respectively. This study demonstrated that it is feasible to use B-mode ultrasound to monitor in vivo residual bone movement inside an intact prosthetic socket during stepping tasks.

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

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

Soft robotics-inspired sensing system for detecting downward movement and pistoning in prosthetic sockets: A proof-of-concept study.

Vertical displacement of the residual limb within transtibial prosthetic socket, often known as "pistoning" or downward movement, may lead to skin breakdowns and ulcers. Downward movement is particularly difficult to self-manage for diabetic individuals living with amputation because of diminished sensation in the residual limb from peripheral neuropathy. Therefore, a customizable sensor at the distal end that can alert the users when high-risk downward movement and pistoning occurs is urgently needed. Presented herein for the first time is a lightweight, inexpensive sensing system inspired by soft robotics that can detect the occurrence and severity of downward movement at the distal end. The sensing system consists of a multilayered torus-shaped balloon, allowing easy integration with pin-lock socket systems. The design allows sensing of vertical displacement without imparting high reaction forces back onto the distal end. A benchtop compression tester was used to characterize system performance. Systematic and parametric benchtop tests were conducted to examine the sensor's physical characteristics. Long-term (24-h) stability of the sensor was also recorded. Compared with water, air was determined to be a better medium with a higher linear full-scale span (FSS) because of its compressible nature. Repeatable 0.5-mm vertical displacements yielded a linear (>0.99 R2) FSS of 4.5 mm and a sensitivity of 0.8 kPa/mm. The sensing system is highly precise, with as low as 1% FSS total error band and average hysteresis of 2.84% of FSS. Over 24 h, a 4% FSS drift was observed. Sensing system characteristics, coupled with low-cost, customizable fabrication, indicates promising performance for daily use to notify and alert transtibial prosthetic users of downward movement and/or pistoning.

Methodology of CAD design and CAM production of transtibial prosthetic sockets

The digitization of the design process of lower limb prosthetic sockets seems to be necessary. Using modern CAD procedures and CAM technologies, it is possible to produce functional, individual prosthetic aids that bring many benefits compared to commonly used methods. However, the disadvantage of using CAD/CAM procedures can be the input costs for production technology and software. The aim of this research is to propose a low-cost solution for individual transtibial socket design and production. Modern methods and technologies like 3D scanning, CAD design and additive manufacturing have been applied. As a result, a transtibial stump positive and custom socket design methodology is proposed. In conclusions a total value of a custom transtibial socket design and production was calculated.

Augmenting the flexural strength of polymer composites for stronger and more durable prosthetic sockets

AbstractThe objective of this study was to develop a novel approach to enhance the flexural strength of polymer composites used in the fabrication of prosthetic sockets. The effects of control factors such as nozzle hole diameter and internal filling pattern on the flexural behavior of three distinct composite materials were examined: poly lactic acid reinforced with carbon fiber (PLA‐CF), polyethylene terephthalate glycol reinforced with carbon fiber (PETG‐CF), and PLA reinforced with multi‐walled carbon nanotubes (PLA‐MWCNTs), fabricated through fused filament fabrication. During study, samples of each composite material were created using 3D printing technology and underwent flexural testing. Fractography was then performed on the samples, and statistical analysis techniques, including Taguchi's method and response surface methodology (RSM) were used to analyze the results. The study found that the flexural behavior of the prosthetic socket materials varied significantly based on the control factors used. Specifically, a nozzle hole diameter of 0.6 mm and a rectilinear internal filling pattern with PLA‐MWCNTs composite material had the highest flexural strength among the three materials tested. Through this study, the authors demonstrated the potential to improve the design and manufacture of prosthetic sockets, which can lead to better functionality and comfort for the user. The low‐cost transtibial prosthetic socket developed in this study using the optimized composite material and 3D printing technology shows promise as an application in the field of prosthetics. This research can pave the way for the development of even stronger and more durable prosthetic sockets in the future.

EFFECT OF NAOH TREATMENT ON THE TESILE PROPERTIES OF COCONUT FIBRE FOR POLYESTER RESIN TRANSTIBIAL PROSTHETIC SOCKET REINFORCEMENT

Recently, there is increase in the use of natural fiber in the reinforcement of polymer composites due to its low production cost, ease of fabrication and enhanced strength. In this study, the effect of NaOH treatment on the tensile properties of coconut fibre for polyester resin transtibial prosthetic socket reinforcement was investigated. The coconut fibres were extracted using hand pulling and water retting method; NaOH treatment was used to mercerize the fibres was carried out 5% to 25% at time interval of between 30Min. to 150Min. The result indicated that the effect of NaOH treatment on the Coconut fibre vary, depending on the concentration of NaOH and the treatment time. It is concluded that treatment of Coconut fibre in 15% NaOH for 150minutes is the best treatment protocol of Coconut fibre for polyester resin reinforcement.

Mechanical testing of transtibial prosthetic sockets: A discussion paper from the American Orthotic and Prosthetic Association Socket Guidance Workgroup.

The advent of novel manufacturing technologies, materials, and socket design concepts could introduce risks to prosthetic limb users, as the existing knowledge base for safe fabrication may not apply. Moreover, although structural test standards exist for mass-produced prosthetic components, they are not applicable to prosthetic sockets. The "AOPA Socket Guidance Workgroup" was formed in 2020 to provide the prosthetic community with evidence-based clinical best practices and methods in the field of prosthetic socket structural analysis. This multidisciplinary expert workgroup undertook a critical analysis of the knowledge gaps regarding the requirements for mechanical testing of lower limb prosthetic sockets. The Workgroup identified knowledge gaps in 4 domains. Domain 1 describes the shape and composition of a mock residual limb, required to support and generate in vivo representative loading within the socket. Domain 2 concerns prosthetic socket coordinate systems and alignment. Domain 3 regards the components and requirements of test specimens. Finally, Domain 4 considers test conditions, loading parameters, and acceptance criteria. This paper describes these knowledge gaps in detail and recommends potential solution approaches based on literature review, group consensus around existing knowledge, or the formation of new study groups to fill each knowledge gap. Our intent is for the recommendations arising from this paper to support the community (e.g., researchers in the clinic, academia, industry, and funders) in addressing these knowledge gaps.

A proper sequence of dynamic alignment in transtibial prosthesis: insight through socket reaction moments

Dynamic alignment in prosthetic fitting is important because it affects the user’s stability, kinematics, and kinetics such as socket reaction moments. It is performed by tuning the spatial relationship between the transtibial prosthetic socket and the foot following sequential observational gait analysis in the three anatomical planes. However, the order of planes in which the adjustment should be performed is still unclear. To investigate the appropriate sequence of dynamic alignment adjustment, ten participants with transtibial amputation were asked to walk in different alignment conditions (flexion, extension, adduction, abduction; lateral, medial, anterior, and posterior translation of the socket, and plantarflexion, dorsiflexion, inversion, and eversion of the foot) to measure socket reaction moments in the out-of-planes (e.g., the effect of sagittal alignment on the coronal moment). A significant difference was found only among socket posterior translation, socket flexion, and baseline alignment in the coronal moment (P = 0.02). The results of the current and previous studies suggest that moments in the coronal plane are affected by alignment changes in all three planes, whereas moments in the sagittal plane are affected only by sagittal alignment changes. It is suggested that the procedure of alignment adjustments should be finalized in the coronal plane.

Design and Production of Low-Cost 3D-Printed Transtibial Prosthetic Sockets

ABSTRACT Introduction Only 5% to 15% of individuals with amputation living in low- and middle-income countries (LMICs) have access to proper prostheses. Mainly, prosthetic costs are too high, and facilities are not within reach. Measurement and production of traditional prosthetic sockets are time-consuming, labor-intensive, and highly dependent on the experience and skills of the personnel involved. Materials and Methods This report describes the workflow to produce low-cost patella tendon bearing transtibial prosthetic sockets. Using computer-aided design (CAD) and computer-aided manufacturing (CAM), transtibial prostheses can be easily produced in rural areas. The size of the residual limb was scanned with a handheld 3D-scanner (Einscanner Pro Plus), and the sockets were printed using fused filament fabrication (FFF) with an Ultimaker S5. The foot was made locally, and the other prosthetic parts were imported. The 3D-printed socket costs US $20 (excluding value-added tax [VAT]). The total material cost of the prosthesis, including the other prosthetic materials, amounts to approximately US $100 (excluding VAT). Assuming the asset cost of the devices, the costs of one local employee, overhead expenses, a profit margin, and the VAT included, a 3D-printed prosthesis could be sold for US $170. Conclusions This report provides a blueprint to produce low-cost 3D-printed transtibial prosthetic sockets. Further research will be conducted to replace the imported prosthetic parts for local products and to automatize the digital design process. Clinical Relevance With this workflow, prosthetic sockets can be produced consistently, which makes it a suitable method in LMICs.

Design Evaluation of FFF-Printed Transtibial Prosthetic Sockets Using Follow-Up and Finite Element Analysis

Background: Participants in Sierra Leone received a Fused Filament Fabrication (FFF)-printed transtibial prosthetic socket. Follow-up was conducted on this group over a period of 21 months. To investigate the failure of some of the FFF-printed transtibial sockets, further strength investigation is desired. Methods: A finite element (FE) analysis provided an extensive overview of the strength of the socket. Using follow-up data and FE analyses, weak spots were identified, and the required optimization/reinforcement of the socket wall was determined. Results: Five sockets with a 4 mm wall thickness were tested by five participants. The strength of the 4 mm prosthetic socket seemed to be sufficient for people with limited activity. The 4 mm sockets used by active participants failed at the patella tendon or popliteal area. One socket with a wall thickness of 6 mm was used by an active user and remained intact after one year of use. An FE analysis of the socket showed high stresses in the patella tendon area. An increased wall thickness of 7 mm leads to a decrease of 26% in the stress corresponding to the observed failure in the patella tendon area, compared to the 4 mm socket. Conclusions: Follow-up in combination with an FE analysis can provide insight into the strength of the transtibial socket. In future designs, both the patella tendon and popliteal area will be reinforced by a thickened trim line of 7 mm. A design with a thickened trimline of 7 mm is expected to be sufficiently strong for active users. Another follow-up study will be performed to confirm this.

Transtibial prosthetic socket fitting: Australian prosthetist perspectives on primary challenges, management strategies, and opportunities for workflow and technological innovation.

Following transtibial amputation, a custom-built socket is the most common interface between the prosthesis and residual limb. Desire from both prosthetists and prosthesis users for improved socket fitting processes have been well documented. However, there is currently limited information available about prosthetists' experiences of how prosthetic manufacturing workflow can contribute to socket fit problems. This study aims to determine how socket fit problems are currently detected and managed by prosthetists and to identify challenges, management strategies, and opportunities for workflow and technological innovation during prosthesis manufacture and socket fitting. Mixed-method (quantitative and qualitative) survey. An online survey was developed and piloted in consultation with members of the Australian Orthotic Prosthetic Association. The final 25-question survey was distributed through their membership database. Mixed methods were used to analyze survey items. Qualitative items were grouped and coded under themes relating to challenges, management strategies, and opportunities. Quantitative data were analyzed using nonparametric descriptive methods. Twenty-three respondents with a range of experience completed the survey. Seven of eight major Australian states/territories were represented. Primary workflow stages presenting challenges with limited strategies/solutions available to the prosthetists were roll-on liner selection, mold or cast modifications, communication with the client, and check socket fitting. Suggested solutions included improved socket-limb interface monitoring technology. This study provides the first insights into prosthetist-identified challenges and limitations at different stages of the socket workflow and presents a starting point for more targeted research into innovation that may assist in these processes.

Pressure Reduction Management System in Three-Dimensional-Printed Transtibial Prosthetic Socket during Stance Phase

ABSTRACT Introduction High pressure on sensitive areas of the residual limb while wearing a prosthetic socket must be minimized to avoid injury and uncomfortable fitting. The purpose of this study was to reduce the peak pressures on sensitive regions within a three-dimensional (3D)-printed transtibial prosthetic socket. Materials and Methods This study proposed a 3D-printed socket with three built-in tiny air bladders integrated within the interface between the liner and socket and electronically managed by a pressure and volume control system. A pseudo-artificial residual limb was fabricated to mimic the transtibial residual limb. The interface pressure in the 3D-printed socket was evaluated using F-socket transducers during inflation and deflation of the air bladders in the stance phase through universal tensile machine load. Results Based on the statistical analysis, the highest significant pressure reduction (P < 0.05) was 5.71%, which was recorded at the posterior region, and 4.68% (P < 0.05) at the medial region during posterior and medial air bladders inflation, respectively. Conclusion Peak pressures were reduced at the lateral tibia condyle, tibia tuberosity, tibia crest, anterior distal end of tibia, fibula head, distal end of fibula, medial femoral condyle, lateral femur condyle, and patellar of the artificial residual limb. Clinical Relevance This system has the potential to minimize high pressures at the subregions of the residual limb in clinical settings and in day-to-day activities. Thus, this design could provide an excellent pressure and volume control at the bony areas, which improves satisfaction and socket fit for persons with amputation.

Angulation vs translation of transtibial prosthetic socket: their difference analyzed by socket reaction moments

BackgroundPrevious studies investigated the effects of alignment changes in transtibial prostheses on socket reaction moments. However, the effects of angular and translational alignment changes with equal displacement between the foot and the socket were not directly compared. Research questionsWhat are the different effects of angular and translational alignment changes in transtibial prostheses? MethodsTen individuals with transtibial prostheses participated in the measurement of temporo-spatial parameters, socket reaction moments, and their timings under nine alignment conditions (3° flexion/extension, anterior/posterior translation, 6° adduction/abduction, medial/lateral translation, and baseline). The displacement of the prosthetic feet was set to be equal between the angular and translational changes. ResultsNo significant changes in walking speed were found. Similar effects were observed in the magnitudes, but not in timing, of the moments under angular and translational changes in the sagittal plane (p < 0.01 for the differences in peak extension moment among anterior translation, baseline, and extension conditions, and in peak flexion moment among anterior translation, baseline, and extension conditions). In the coronal plane, similar effects were found in the magnitudes of the moments in the early stance (p < 0.01 at 5 %, 20 %, and 75 % stance). A significant difference in magnitude was observed in the late stance (p < 0.01 between adduction and medial translation conditions). SignificanceThe timing of the socket reaction moment may be different in the sagittal plane, while the magnitudes of the socket reaction moment in the late stance may be different in the coronal plane between the angular and translational alignment changes.

Air microfluidics-enabled soft robotic transtibial prosthesis socket liner toward dynamic management of residual limb contact pressure and volume fluctuation.

Residual limb volume fluctuation and the resulting contact pressures are some of the key factors leading to skin ulcerations, suboptimal prosthetic functioning, pain, and diminishing quality of life of transtibial amputees. Self-management of socket fit is complicated by peripheral neuropathy, reducing the perception of pressure and pain in the residual limb. We introduce a novel proof-of-concept for a transtibial prosthetic socket liner with the potential to dynamically adjust the fit between the limb and socket. The core of the technology is a small air microfluidic chip (10 cm3 and 10 g) with 10 on-chip valves that enable sequential pressurizing of 10 actuators in custom sizes to match the pressures required by the residual limb's unique anatomy. The microfluidic chip largely reduced the number of electromechanical solenoid valves needed for sequential control of 10 actuators (2 instead of 10 valves), resulting in the reduction of the required power, size, mass, and cost of the control box toward an affordable and wearable prosthetic socket. Proof-of-concept testing demonstrated that the applied pressures can be varied in the desired sequence and to redistribute pressure. Future work will focus on integrating the system with biofidelic prosthetic sockets and residual limb models to investigate the ability to redistribute pressure away from pressure-sensitive regions (e.g., fibular head) to pressure tolerant areas. Overall, the dynamic prosthesis socket liner is very encouraging for creating a dynamic socket fit system that can be seamlessly integrated with existing socket fabrication methods for managing residual limb volume fluctuations and contact pressure.

Determining educational assessment criteria for patellar-tendon-bearing impressions for transtibial prosthetic sockets: A Delphi study.

Validated criteria to guide assessment of student performance in clinical tasks in prosthetics and orthotics education have not been established. Lack of established criteria and assessment methods presents challenges in evaluating student performance on clinical tasks, such as taking impressions for patellar-tendon-bearing (PTB) sockets. To establish assessment criteria for the PTB impression process for use in educational settings. Delphi consensus process. Initial Delphi survey items were based on interviews with prosthetic instructors and focus groups with prosthetic students. Expert prosthetic educators were then identified by purposive sampling to complete multiple-round Internet-based Delphi surveys. The Delphi surveys asked experts to indicate their level of agreement on various assessment methods and criteria in PTB education. Consensus for survey items was reviewed after each survey round and used to determine the content of and need for subsequent rounds. Fourteen experts completed two Delphi survey rounds. Items were categorized into educational materials/strategies, impression stages/materials, measurement tools, measurements taken, assessment during impression, assessment after impression, feedback, student self-assessment, and grading. In two survey rounds, 40 items guiding assessment methods and criteria for PTB impressions achieved 80% consensus. A high level of consensus was achieved in two survey rounds. Lower levels of consensus were reached on specific objective criteria, such as use of measurement thresholds when evaluating student impressions. Standardized assessment of student performance on PTB impression-taking instead relies primarily on qualitative assessments based on instructor expertise.

Developing a control framework for self-adjusting prosthetic sockets incorporating tissue injury risk estimation and generalized predictive control.

To perform activities of daily living (ADL), people with lower limb amputation depend on the prosthetic socket for stability and proprioceptive feedback. Poorly fitting sockets can cause discomfort, pain, limb tissue injuries, limited device usage, and potential rejection. Semi-passively controlled adjustable socket technologies exist, but these depend upon the user's perception to determine safe interfacial pressure levels. This paper presents a framework for automatic control of an adjustable transtibial prosthetic socket that enables active adaptation of residuum-socket interfacial loading through localized actuators, based on soft tissue injury risk estimation. Using finite element analysis, local interfacial pressure vs. compressive tissue strain relationships were estimated for three discrete anatomical actuator locations, for tissue injury risk assessment within a control structure. Generalized Predictive Control of multiple actuators was implemented to maintain interfacial pressure within estimated safe and functional limits. Controller simulation predicted satisfactory dynamic performance in several scenarios. Actuation rates of 0.06-1.51kPa/s with 0.67% maximum overshoot, and 0.75-1.58kPa/s were estimated for continuous walking, and for a demonstrative loading sequence of ADL, respectively. The developed platform could be useful for extending recent efforts in adjustable lower limb prosthetic socket design, particularly for individuals with residuum sensory impairment.