Prosthetic Socket Research Articles

Исследование методов предварительной обработки электронно-геометрической модели культи нижней конечности

We analyze available methods for representing and visualizing three-dimensional models as applied to the problem of preliminary processing of digital geometric models of the lower limb stump in the creation of a prosthetic socket model. The research methodology involved the methods of processing three-dimensional images, classification, and clustering. As a result of the conducted research, the methods suitable for developing an algorithm for preliminary processing of a digital geometric model of the lower limb stump in the creation of a prosthetic socket model. Such an algorithm automates segmentation and visualization processes for 3D point clouds.

Повышение устойчивости полного протеза слуховых косточек

When performing tympanoplasty, one of the key stages is ossiculoplasty – reconstruction of the chain of auditory ossicles through prosthetics. When the chain of auditory ossicles, including the superstructure of the stapes, is destroyed, complete ossicular prostheses are used. The main task of the surgeon when performing ossiculoplasty is to achieve a balance of reliable functional position of the prosthesis ensured by lateral stability, on the one hand, and the exclusion of its contact with surrounding immobile anatomical elements, on the other. According to the literature, the frequency of dislocation of a total prosthesis reaches 13%. The study included 159 patients divided into a study group (72 patients) and a comparison group (87 patients) who underwent ossiculoplasty using a total ossicular prosthesis between 2017 and 2021. In the comparison group, the stability of the prosthesis was ensured by fragments of highly purified gelatin sponge. In the study group, an oval plate of autologous cartilage graft measuring 2,5 and 3,5 mm was additionally used, attached to the prosthetic socket. The results of postoperative observation showed a statistically significant (p < 0,05) reduction in the incidence of prosthesis dislocation to 4,2% compared to the comparison group (10,8%). Functional results were also statistically better when comparing subgroups of patients who underwent tympanoplasty with a first stage using a closed technique.

A Review of some Characteristics of a Composite Hybrid Socket for Prosthetics Derived from Plant Fibers

According to the ICF (International Classification of Functioning, Disability, and Health), a prosthetic is a device used to restore or replace the function of a missing limb as a result of a rare genetic defect, dangerous incident, surgical trauma, or disease that limits the amputee's ability to participate in daily life. Prosthetic limb sockets were formerly made out of a wide variety of materials before the development of thermoplastics and composites. Plant fibers are favored due to their low density. Both their strength and rigidity are remarkably high considering their low weight and inexpensiveness. Plant fiber is one of the most popular ways to give polymer composites more strength because of its low production costs and stretchability. Following a brief introduction to the many types of natural fibers (both plant and animal), this article provides a comprehensive assessment of the literature from the past decade that focuses on the mechanical characteristics of plant materials. Reinforced polymers are made with fibers. This literature study will focus on the mechanical properties and behavior of plant fibers used to create sockets for prosthetic limbs. If an article is written about the overall features of composites made with fibers made from the plant, it is expected to be of great use to the research community in the field of composites.

Additive Manufacturing of Short Silk Fiber Reinforced PETG Composites

The growing demand for customized medical devices like prostheses, orthoses, and implants is the prime motive for a surge in the investigation of 3D printable biocomposites. PETG (Polyethylene terephthalate glycol) based composites can be a good choice for biomedical applications. Specific characteristics of this material like biocompatibility, ease of formability, stable thermomechanical properties, and high chemical, and abrasion resistance make it suitable for biomedical applications. However, there are very few studies on the 3D printing of PETG-based composites. Development of a robust 3D printing protocol is required for any novel natural fiber reinforced PETG composites. This study presents natural fiber-reinforced PETG biocomposite filament preparation and 3D printing with the developed composite filaments. Silk was used as a filler material due to its high thermal stability and high tensile strength. Composite filaments with 2 wt%, 5 wt%, and 10 wt% silk were prepared using the extrusion process. Further, we developed a protocol for 3D printing with the developed composites to fabricate various 3D structure. Both filaments and printed specimens were characterized morphologically, structurally, and mechanically. The melt flow rate of the filaments decreased with an increase in fiber content which was a bottleneck for printing 10% silk-PETG composites. Micro-CT results validate an increase in void content in filaments on filler addition. The highest flexural modulus and flexural strength were exhibited by 2% silk-PETG printed parts and a 60% increase in compressive modulus compared to pure PETG. Tensile tests show that 2 wt% fiber addition significantly increased elastic modulus (2466.72 MPa) compared to pure PETG (902.81 MPa), whereas the surface roughness of printed composites increased with filler content. Finally, a lower limb prosthetic socket prototype was printed with a desktop 3D printer to demonstrate its potential for biomedical applications.

Extra-wide deposition in extrusion additive manufacturing: A new convention for improved interlayer mechanical performance

Recent studies have contested long-standing assumptions that mechanical anisotropy is caused by weak interlayer bonding and demonstrated that microscale geometry (the groove between extruded filaments) is the major cause of anisotropy in extrusion additive manufacturing (AM). Inspired by those finding, this study investigates the potential for a new convention for print-path design to improve mechanical properties by setting extrusion width to be at least 250 % of nozzle diameter. The new convention enabled an almost 50 % improvement in mechanical performance, which was supported by finite element analysis data, whilst simultaneously reducing the printing time by 67 %. Whereas a typical extrusion AM part uses several side-by-side extrusions, here, three 0.4-mm-wide extrusions are replaced with a single extra-wide 1.2-mm extrusion; two 0.6-mm-wide extrusions are also studied. The contact area between layers of the extra-wide extrusion was 90 % as opposed to 63 % for the conventional approach. The improved contact area led to a 40–48 % enhancement of strength, strain-at-fracture and toughness. This study presents a compelling case for a methodological shift to extra-wide extruded-filament deposition and explains the underlying cause of anisotropic strength observed in previous studies. Two case studies demonstrate practical applicability for a print run of 1000 nylon visors and lower-limb polylactide prosthetic sockets, for which extra-wide filaments more than doubled load-bearing capabilities. Polylactide material was used for most of the study; potential for translation to other materials is discussed.

The relationship between residual limb health, motion within the socket, and prosthetic suspension.

Residual limb health is critical for continued prosthesis use; however, many prosthesis users experience skin-related breakdown. The interface between the residual limb and the prosthetic socket sets the local mechanical environment and plays a role in skin stresses. Motion of the residual limb in the socket adds additional mechanical strain on the limb. This article explores the relationship between motion of the limb in the socket and residual limb health. We evaluated current methods for assessing residual limb health and motion of the residual limb in the socket and compared these evaluations across different prosthetic suspension systems. While few direct studies comparing residual limb health and motion exist, it has been shown that elevated vacuum suspension systems result in both improved residual limb health compared to passive suction and pin-lock systems and decreased motion compared to passive suction, pin-lock, knee sleeve, and anatomical suspension systems. While motion and health have not been directly linked, elevated vacuum suspension may demonstrate a relationship that reduced motion of the residual limb in the socket improves residual limb health. Further evaluation in this area is necessary to more completely and directly understand the relationship between residual limb motion and residual limb health.

MECHANICAL ANALYSIS OF THE NEWLY DEVELOPED 3D PRINTED PROSTHETIC SOCKET FROM PA12GB

This paper is focused on the complex evaluation of the prosthetic socket (of a hand) manufactured by the usage of additive technologies. Main advantage of this method is a significantly shorter production time and lower production cost. The durability of the socket is generally between 12 and 24 months. It is caused by the atrophy of the patient's tissues and also by the mechanical loading during the usage. The laminating of the carbon fibers on the model of the internal socket is used nowadays. This method is technologically and time demanding. The newly developed production process is using the 3D printing method by the HP MultiJet Fusion 4200 printer. The considered material is HP PA12GB. It is the thermoplastic material (polyamide) with 40% of glass beads. Production of the socket is reduced to few hours. This paper consists the mechanical comparison of the laminated (old design) and the 3D printed (new design) socket. The real mechanical testing is simulating the most critical loading by impact to the edge of the table. The evaluation in terms of durability and fatigue is performed also using the software nCode and Siemens NX.

A Wearable Ultrasound Interface for Prosthetic Hand Control

Ultrasound can non-invasively detect muscle deformations and has great potential applications in prosthetic hand control. Traditional ultrasound equipment was usually too bulky to be applied in wearable scenarios. This research presented a compact ultrasound device that could be integrated into a prosthetic hand socket. The miniaturized ultrasound system included four A-mode ultrasound transducers for sensing musculature deformations, a signal excitation/acquisition module, and a prosthetic hand control module. The size of the ultrasound system was 65*75*25 mm, weighing only 85 g. For the first time, we integrated the ultrasound system into a prosthetic hand socket to evaluate its performance in practical prosthetic hand control. We designed an experiment requiring twenty subjects to perform six commonly used gestures. The performance of decoding ultrasound signals was analyzed offline using four classification algorithms and then was assessed in online control. The average values of online classification accuracy with and without wearing the physical prosthetic were 91.5 [Formula: see text] and 96.5 [Formula: see text], respectively. We found that wearing the prosthetic hand influenced the ultrasound gestures classification accuracy, but remarkable online classification performance could still be maintained. These experimental results demonstrated the efficacy of the designed integrated ultrasound system for practical use, paving the way for an effective HMI system that could be widely used in prosthetic hand control.

Constitutive parameter identification of transtibial residual limb soft tissue using ultrasound indentation and shear wave elastography

Finite element analysis (FEA) can be used to evaluate applied interface pressures and internal tissue strains for computational prosthetic socket design. This type of framework requires realistic patient-specific limb geometry and constitutive properties. In recent studies, indentations and inverse FEA with MRI-derived 3D patient geometries were used for constitutive parameter identification. However, long computational times and use of specialized equipment presents challenges for clinical, deployment. In this study, we present a novel approach for constitutive parameter identification using a combination of FEA, ultrasound indentation, and shear wave elastography. Local shear modulus measurement using elastography during an ultrasound indentation experiment has particular significance for biomechanical modeling of the residual limb since there are known regional dependencies of soft tissue properties such as varying levels of scarring and atrophy. Beyond prosthesis design, this work has broader implications to the fields of muscle health and monitoring of disease progression.

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.

Thermo-mechanical and degradation properties of naturally derived biocomposites for prosthesis applications: Analysis of the interface pressure and stress distribution on the developed socket

Nowadays, the reduction of petroleum products has been aggressively studied due to their environmental concerns and for finding alternative synthetic materials for sustainable development. Thus, naturally derived biocomposites have great potential for creating a sustainable economy with reduced environmental pollution. The present study deals in two major parts; first, the fabrication of the knee prosthetic socket from different laminate biocomposites (FFF, KKK, and RRR) and examined their mechanical performance, thermal stability and degradation behaviour. The interface pressure between the developed socket and residual limb has been examined using the F-socket sensor. Second, the output data of experiential tests and measured interface pressure have been used for numerical analysis to examine the equivalent stress, deformation and safety factor of the sockets at different loading conditions (500 N, 700 N and 900 N). The results observed that FFF biocomposites have maximum compressive strength (121.0 6MPa), impact strength (36.86 kJ/m2), and shear strength (28.51 MPa) which is 8.15%, 49.53%, and 58.88% higher than RRR biocomposites and 2.74%, 34.62%, and 39.28% higher compared to KKK biocomposites, respectively. RRR biocomposites recorded higher hardness (68.42) and fatigue endurance stress (82.86 MPa) due to higher brittleness properties. The thermogravimetric analysis and degradation behaviour have been analyzed to examine thermal stability, degradation temperature, and degradation weight loss behaviour of biocomposites. Finally, the stress generation on the developed socket during the gait cycle is much lower than its calculated strength that did not affect the performance of the socket. Therefore, laminated biocomposites can be an alternative biomaterial to plastics and conventional materials due to their lighter weight, higher flexibility, and economical to provide greater comfort to the users for knee prosthesis applications.

3D printed transtibial prosthetic sockets: A systematic review.

The prosthetic socket, which transfers load from the residual limb to the prosthesis, is an integral part of the prosthesis. 3D printing has emerged as a potentially viable alternative to traditional fabrication for producing sockets that effectively transfer loads. We conducted a systematic review to better understand the current state of this newer fabrication method, with a focus on the structural integrity of 3D printed sockets and factors that can affect the strength of 3D printed sockets when tested using ISO 10328 standards. Literature searches were carried out in five databases (PubMed, Scopus, CINAHL, Web of Science and Google Scholar). Two reviewers independently performed the literature selection, quality assessment, and data extraction. A total of 1023 unique studies were screened in accordance with inclusion and exclusion criteria. Of 1023 studies, 12 studies met all inclusion criteria, with failure data for 15 3D-printed sockets and 26 standard laminated sockets. Within 3D printed sockets, the addition of composite materials such as carbon fiber particles and distal reinforcement using a compositing infill technique appears to improve socket strength. In light of the considerable amount of heterogeneity between studies in terms of materials and alignment used, the absolute values for failure could not be established for 3DS nor directly compared between 3DS and LCS. However, there is some evidence that the probability of a failure at a given load may be comparable between 3DS and LCS up to the P8 level. For all sockets, whether a laminated composite socket or a 3D printed socket, failure mainly occurred at the distal end of the socket or the pyramid attachment, which is consistent with the ISO testing protocol. Improving the strength of the 3D printed sockets through design modifications at the distal end and implementing emerging printing technologies could help to promote 3D printed sockets as a viable option, particularly when cost or access to care is limited.

A Survey of Prosthetists' Perspectives on Adjustable-Volume Lower-Limb Prosthetic Sockets

ABSTRACT Introduction Adjustable-volume prosthetic sockets have been available for many years to address residual limb volume changes, although little research has been conducted regarding their efficacy. As such, prosthetists are guided by patient preference, personal experience, and professional perception. The purpose of this study was to explore clinician perceptions and experiences fitting adjustable-volume prosthetic sockets. Materials and Methods An anonymous online survey was distributed to certified prosthetists. The survey contained questions about prosthetists' demographics, whether they had previously fit an adjustable-volume prosthetic socket, whether these fittings were successful, and what challenges they experienced. Those who had not previously fit adjustable sockets were asked what barriers had prevented them from doing so. Results A total of 221 certified prosthetists completed the survey. Of the 195 eligible respondents, 82% had experience in fitting adjustable prosthetic sockets. The most commonly fit socket styles were the RevoFit (n = 123), Socket-less (n = 67), and Infinite (n = 66) sockets. Prosthetists had varied success with the different socket styles, with the RevoFit being the most successful, and the Infinite and Socket-less sockets the least successful. Respondents most frequently noted increased bulk (93% of respondents; n = 181), complicated fabrication (72%; n = 141), and poor cosmesis (65%; n = 127) as challenges faced when fitting adjustable-volume sockets. Some respondents felt these sockets were a useful clinical tool; however, common themes regarding clinical perception of adjustable sockets included issues with cost/reimbursement and appropriateness for only a subset of the population of individuals with amputation only. Other respondents felt that adjustable sockets were either not adequate for clinical use or required improvements before their use would be beneficial. Conclusions There is no majority opinion regarding the benefits and challenges of adjustable sockets among prosthetists. In general, prosthetists feel that adjustable sockets can be used as one of the various tools to accommodate complicated lower-limb fittings. Additional work is needed to provide clinicians with a best practice guideline for providing adjustability within lower-limb sockets. Clinical Relevance The study showed that prosthetists feel that adjustable sockets can be one of the tools used for complicated lower-limb fittings. Additional work is needed to develop a best practice guideline for providing adjustability in lower-limb sockets.

A Modified Scapular-Parascapular Flap Design for Optimal Coverage of the Residual Limb.

Large soft tissue defects associated with major limb amputation pose a challenge to the reconstructive surgeon due to the 3-dimensional contour of the residual limb and the need to withstand the unnatural shear forces imparted by prosthetic sockets. Fasciocutaneous flaps based on the circumflex scapular system have proven useful for residual limb coverage due to the durability of the tissue provided, the absence of functional morbidity, and the ease of reelevation. A modified, bilobed flap design that incorporates large Burrow triangles into each limb serves to leverage the perforasome anatomy of the posterior trunk to provide maximal 3-dimensional coverage and favorable flap geometry while also facilitating donor site closure. A retrospective medical record review was performed for all patients who underwent reconstruction of a residual limb after major amputation using the modified, bilobed scapular-parascapular free flap design at Walter Reed National Military Medical Center between 2018 and 2021. A computer-based application was used to calculate flap area and dimensions based on photographs of preoperative and intraoperative markings. Six patients with varying amputation levels (2 transtibial, 1 transfemoral, 1 hip-disarticulation, 1 hemipelvectomy, 1 transradial) underwent soft tissue coverage using the modified flap design. Mean flap area was 318.4 cm 2 with 51.1 cm 2 attributable to the modified design. This represents a 16% increase over a conventional bilobed design. There were no partial or complete flap failures. The modified scapular-parascapular flap design enables harvest of a larger and more versatile fasciocutaneous flap with geometry that is well suited for coverage of the residual limb.

Optimisation-driven design to explore and exploit the process–structure–property–performance linkages in digital manufacturing

An intelligent manufacturing paradigm requires material systems, manufacturing systems, and design engineering to be better connected. Surrogate models are used to couple product-design choices with manufacturing process variables and material systems, hence, to connect and capture knowledge and embed intelligence in the system. Later, optimisation-driven design provides the ability to enhance the human cognitive abilities in decision-making in complex systems. This research proposes a multidisciplinary design optimisation problem to explore and exploit the interactions between different engineering disciplines using a socket prosthetic device as a case study. The originality of this research is in the conceptualisation of a computer-aided expert system capable of exploring process–structure–property–performance linkages in digital manufacturing. Thus, trade-off exploration and optimisation are enabled of competing objectives, including prosthetic socket mass, manufacturing time, and performance-tailored socket stiffness for patient comfort. The material system is modelled by experimental characterisation—the manufacturing time by computer simulations, and the product-design subsystem is simulated using a finite element analysis (FEA) surrogate model. We used polynomial surface response-based surrogate models and a Bayesian Network for design space exploration at the embodiment design stage. Next, at detail design, a gradient descent algorithm-based optimisation exploits the results using desirability functions to isolate Pareto non-dominated solutions. This work demonstrates how advanced engineering design synthesis methods can enhance designers’ cognitive ability to explore and exploit multiple disciplines concurrently and improve overall system performance, thus paving the way for the next generation of computer systems with highly intertwined material, digital design and manufacturing workflows.Graphical abstract

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.

Numerical and Experimental Assessment of Mechanical Properties of Biobased Epoxy Reinforced by Flax Fibres and Seashell Nanoparticles for Prosthetic Socket

Chronic diseases such as peripheral vascular and arteriosclerosis, wars, terrorist attacks, natural disasters, and traffic collisions are the major causes of the high demand for prostheses. The inadequacy of the typically used materials at reasonable prices and the high stiffness of these materials, which can negatively influence socket-limb load transfer, imply an urgent need to find alternatives to the existing prosthetic sockets. This work aims to use renewable, low-hazard, and low-cost natural flax fibres and seashell nanoparticles as substitutes for conventional reinforcement materials for prosthetic sockets. Seashell nanoparticles of 1, 3, and 5 weight fractions and 3 layers of flax fibres were integrated into biobased epoxy. Tensile and flexural properties of modified and unmodified specimens were assessed, and the finite element technique (ANSYS-20) was utilised to analyse and evaluate the mechanical characteristics of the specimens by observing the stress and total deformation. Here, all fabricated nanocomposites provided tensile and flexural strength higher than that of additive-free biobased epoxy. In addition, hybrid nanocomposites fabricated from 3 layers of flax fibres and 3 wt% of seashell nanoparticles were revealed to have the highest mechanical properties compared with unmodified resin and biobased epoxy filled with other percentages of the reinforcement. These findings were further validated numerically in which the total deformation was shown to decrease after the addition of 3 wt% of these nanoparticles within the nanocomposites. Moreover, the antibacterial activity proved its superb antimicrobial performance against various pathogenic microorganisms, namely, Staphylococcus aureus and E. coli. Accordingly, the fabricated composite systems are suggested to be an appropriate candidate for forming prosthetic sockets. These composites have promising mechanical and antibacterial properties, and they are made of affordable and available materials, which can be a suitable option, particularly in poor countries due to the fact that advanced technologies may require a substantial amount of money for equipment, surgery fees, and medical care.

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.

Design of Adjustable Frame-Type Prosthetic Socket for Lower Limb

ObjectivesProsthetic socket is the contact interface between the stump and the prosthesis, and also the interface component that transmits forces from the stump to the prosthesis distal. The current prosthetic socket fit is a major factor affecting rehabilitation, especially with the stump volume fluctuations. The main goal of this article is to design an adjustable frame-type prosthetic socket with constant force to adapt to the stump volume fluctuations. Materials and methodsIn this paper, an adjustable frame-type prosthetic socket with constant force is designed. The constant force device is designed based on the superelasticity of the shape memory alloy for maintaining constant stump-socket interface stress and automatically adapting to certain volume fluctuations. The constant force extrusion performance of this prosthetic socket was verified and optimized by finite element analysis. ResultsThe results suggest that the constant force unit may maintain constant interface stress. According to the optimization results, the shape memory alloy dimensional parameters could be selected according to different requirements. ConclusionThe adjustable frame-type prosthetic socket allows the user to adjust the socket volume through the cable system and has a large heat dissipation area. The constant force unit maintains constant interface stress and automatically adapts to stump volume fluctuations.

Медицинские аспекты протезирования пациентов после ампутации на уровне голени с использованием цифровых технологий

Introduction Digital technologies used for lower limb amputation patients wearing prostheses are mostly experimental due to the complexity involved in model development of the stump socket. The objective was to develop a technique for additive manufacturing of lower limb prosthetic sockets to minimize negative results using a three-dimensional model of a prosthetic socket and considering anatomy and functionality of the stump. Methods The review included 20 lower limb amputees who were assigned to 3 groups depending on the method of stump scanning. Results The results of prosthetics were evaluated with the stump scanned naked (n = 9), covered with a silicone cloth (n=6) and with the use of embedded components (n = 5). The results of clinical and instrumental examination showed the advantage of the scanning method offered. The symmetry index for the time of foot roll-over was 0.55 ± 0.14 in the first group, 0.63 ± 0.07 in the second group, and 0.85 ± 0.04 in the third group. Discussion The best results of prosthetics in third group were associated with the most favorable load distribution in the receiving cavity of the prosthetic socket due to embedded components. In these cases, processing the digital model was simplified with no need to unload bone prominences. With scanning of a naked stump, processing a digital model was complicated and required professional skills. This solution had the potential to prevent any sort of direct physical contact to avoid inadequate modeling of the computer model of the prosthetic socket. The use of a silicone liner allowed reducing the pressure on the bone prominences. With a sharply skeletonized stump, the elastic properties of the liner were not enough and could cause injury to the tissues. Conclusions The findings suggested that improved quality of prosthetics was dependent on the technique used to scan the stump. The use of pre-installed embedded components allowed for effective load distribution in the prosthetic socket and created favorable conditions for prosthetic use.