Prosthetic sockets stabilized by alternating areas of tissue compression and release

There is a rapid growth in limb amputation, particularly of the lower limb has been observed over the years due to road traffic accidents (TRA), infections and uncontrolled diabetes in developing countries. Peripheral vascular diseases are the leading cause of amputation in the developed countries. The prosthetic socket design aims to maximize comfort and functionality for an amputee towards ambulation. Prosthetic socket fit has a great impact on the amputee’s quality of life. The body-weight of an amputee transfers optimally through the socket to the ground during the different phases of the gait pattern/cycle and is directly is in contact with the human residual limb while prosthesis is on. Thus, socket designs play an important role in prosthetic rehabilitation; encapsulating the residual limb becomes the weight-bearing structure within the residuum–prosthesis complex. Additionally, biomechanical considerations in the socket design with pressure distribution to tolerant areas and relief to the sensitive part of the stump/residuum promote greater comfort. It acts as an interface between the residual limb and the prosthesis. The socket fit cannot be the same for all, as it differs with the individual level of amputation, shape, and dimension of the residual limb. The goal of prosthetic socket must fulfill the user's needs of increased Range of Motion (ROM) and total suspension to achieve near-normal gait pattern and optimal functioning. The knowledge of socket biomechanics, materials, and residual limb behavior improve the function, comfort, and satisfaction of the end-users. Currently, the Patellar Tendon Bearing (PTB), Total Surface Bearing (TSB), Silicone Socket Suspension (3S), and Vacuum-assisted Socket Suspension (VASS) socket designs are being used globally to optimize the amputee functioning. The clinician's expertise plays an important role in deciding the type of socket. Prosthetic socket design with the feature of self-adaptation in real time during various gait phases is one of the challenges for future research.KeywordsProsthesisSocketRehabilitationTranstibialHealthcareAmputeeTechnologyDesignBiomechanics

Limb movement between the residuum and socket continues to be an underlying factor in limb health, prosthetic comfort, and gait performance yet techniques to measure this have been underdeveloped. Develop a method to measure motion between the residual limb and a transtibial prosthetic socket. Single subject, repeated measures with mathematical modeling. The gait of a participant with transtibial amputation was recorded using a motion capture system using a marker set that included arrays on the anterior distal tibia and the lateral epicondyle of the femur. The proximal or distal translation, anterior or posterior translation, and angular movements were quantified. A random Monte Carlo simulation based on the precision of the motion capture system and a model of the bone moving under the skin explored the technique's accuracy. Residual limb tissue stiffness was modeled as a linear spring based on data from Papaioannou et al. Residuum movement relative to the socket went through ~30 mm, 18 mm, and 15° range of motion. Root mean squared errors were 5.47 mm, 1.86 mm, and 0.75° when considering the modeled bone-skin movement in the proximal or distal, anterior or posterior, and angular directions, respectively. The measured movement was greater than the root mean squared error, indicating that this method can measure motion between the residuum and socket. The ability to quantify movement between the residual limb and the prosthetic socket will improve prosthetic treatment through the evaluation of different prosthetic suspensions, socket designs, and motor control of the prosthetic interface.

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.

Between 60 and 80 percent of amputees typically report inadequate fit between their residual limb and their prosthetic socket. Inadequate fit of a prosthetic socket can result not only in secondary medical problems, but can also lead to increased financial burden as the patient is forced to undergo repeated adjustment of the prosthesis. To address this problem, studies have been undertaken to investigate the feasibility of adjustable prosthetic sockets using embedded shape-memory alloy (SMA) wire. Embedded SMA actuators will allow the socket to be adjusted to the patient’s stump as needed for a better fit. It is believed that this method will not only reduce replacement costs (excluding normal wear and tear), but will minimize secondary medical problems due to poor fit. and improve overall patient satisfaction with the prosthesis. Preliminary tests using Nitinol SMA wire on a surrogate socket have shown that a diametral reduction of 4 percent is possible. Present research entails SMA characterization; selection of the appropriate SMA for clinical use; experimentation with location, orientation, and connection of the SMA within the socket wall; and heating of the SMA within the polyethylene matrix.

Experimental thermal analysis of a novel prosthetic socket along with silicone and PCM liners

The large numbers of terrorist attacks and wars in Iraq led to increase the numbers of amputees. However, typically a large number of the amputations are trans-femoral or above knee (AK). In this work, manufacturing a socket by using new method (REVO FIT SOLUTION) for manufacturing trans-femoral prosthetic socket by two molding. The main objectives of this work is to design and manufacturing of above knee prosthetic socket by revo fit solution method to increase suspension, decrease weight of socket and easier to doffing and donning especially for the elderly. The experimental work included subjecting the socket materials to tensile and fatigue testing. The results show that the mechanical properties for (4 layers of carbon fiber) are бult =213MPa, бy =135MPa and E=3.5GPa. The Fatigue life equation for carbon fiber are б=739.6 (Nf)-0.13 and The fatigue limit are 90 MPa The data of gait cycle (force plate) and Interface pressure between the socket and the residual limb was calculated using F-Socket device, the pressure in anterior region equal to (222Kpa)between the socket and the residual limb for patient(male) suffering from above knee right leg amputation and age(42)year. The finite element technique (ANSYS) is used to analyze the model of prosthetic socket and calculate the safety factor, equivalent (Von Mises) stress, and total deformation. The obtained results from ANSYS gave the profile of safety factor of fatigue, for AK with carbon fiber is (1.26).

Moderatorsʼ Summary: Amputee Care

The purpose of this research is to manufacture and test adjustable sockets for below-knee amputation. This article studies using the pnuematic–pads for adjustable sockets. The manufacturing of an adjustable socket with pneumatic pads goes through several stages: In the theoretical design of the adjustable socket, the suggested materials were studied for the pneumatic pads, tubes, and pneumatic pump which should be suitable for the suggested application. In the experimental work, using composite materials for manufacturing the socket consisting of perlon and resin to achieve the rigid shape and required flexibility for the prosthetic user with the pneumatic pads. After assembling the adjustable socket parts, the pneumatic pads, the pump and the tubes, the socket were tested for several times on the patient. In the last stage, the pressure between the socket and the residual limb was measured using F-socket, and it was found that the results were: anterior (160kPa), lateral (167kPa), posterior (153kPa) and medial (348kPa). By comparing these results with what was previously studied, the pressure between the socket and the residual limb is within the acceptable range. The design provides good suspension and more adaptability to the change in stump volume. A posative feedback was given by the patient who used the prosthetic patient for several days as a trial to measure its safety and comfortablty.

Prosthetic socket for lower limb amputation needs to be customized based on the residual limb characteristics to satisfy functional and comfort requirements. One of the main causes for ill-fitting socket is the lack of appropriate application of material properties that match the characteristics of the amputee’s biological tissue. Additive manufacturing has the ability to confer inhomogeneous properties to the printed object. This paper presents a digital workflow for the design and fabrication of a prosthetic socket based on the results of numerical simulations and the use of multi-material voxel printing. A voxel model of the socket is generated and the contact pressure between the residual limb and the socket derived from FEA is mapped to the voxels, which were correspondingly assigned a material. This allow to define a material distribution at the voxel level and to generate printing instructions as a stack of bitmap images for voxel printing. The goal is to obtain a socket characterized by a spatial variation of material stiffness, according to the pressure map extracted from simulation, in order to adapt the socket to the patient’s anatomy and, consequently, to reduce contact pressure and discomfort.

In lower-limb prosthesis, the most important aspect is the adequate design and fit of the socket which serves as an interface between the residual limb and the prosthesis. Optimal socket design requires the knowledge of the external shape of the limb, the bone position, and the mechanical properties of the limb tissue. Using the current plaster casting methods, only the external shape of the limb can be acquired. In this paper, we describe methods to obtain the internal structural information as well as the external shape of a limb using ultrasound compound B-scan imaging technique. The methods can be eventually used to develop a complete CAD/CAM system for lower-limb prosthesis.

Numerical simulation and experimental testing for static failure prediction in additively manufactured below-knee prosthetic sockets.

The prosthetic socket serves as a critical interface between the human body and the prosthesis; however, conventional sockets are associated with a skin breakdown risk exceeding 60%. To address this issue, we conducted a biomechanical analysis of the limb-socket interface aiming to enhance both comfort and functional performance. Medical imaging scans of three hip disarticulation amputees were combined with reverse engineering techniques and finite element analysis to reconstruct a 3D model of the residual limb and socket, enabling stress distribution assessment. A novel socket design was proposed, leveraging computer-aided digital modeling and 3D printing to replace conventional manual fabrication, thereby enhancing fit, comfort, and manufacturing precision. The novel socket reduced stress concentrations at the limb-socket interface by 16.97% overall, with nearly a 25% reduction observed at the bottom of the residual limb. Experimental pressure distribution measurements exhibited a high degree of consistency with finite element analysis simulations ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mover> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mo stretchy="true">¯</mml:mo> </mml:mover> </mml:mrow> </mml:math> = 0.991). Furthermore, the socket significantly improved gait symmetry in prosthesis users. The inverse design methodology based on digital modeling, coupled with biomechanical analysis, offers an effective strategy for optimizing the structural design and fabrication process of hip prosthetic sockets.

Prosthetic hands have significant potential to restore the manipulative capabilities and self-confidence of amputees and enhance their quality of life. However, incompatibility between prosthetic devices and residual limbs can lead to secondary injuries such as skin pressure ulcers and restricted joint motion, contributing to a high prosthesis abandonment rate. To address these challenges, this study introduces a data-driven design framework (D3Frame) utilizing a multi-index optimization method. By incorporating motion/ pressure data, as well as clinical criteria such as pain threshold/ tolerance, from various anatomical sites on the residual limbs of amputees, this framework aims to optimize the structural design of the prosthetic socket, including the Antecubital Channel (AC), Lateral Epicondylar Region Contour (LC), Medial Epicondylar Region Contour (MC), Olecranon Region Contour (OC), Lateral Flexor/ Extensor Region (LR), and Medial Flexor/ Extensor Region (MR). Experiments on five forearm amputees verified the improved adaptability of the optimized socket compared to traditional sockets under three load conditions. The experimental results revealed a modest score enhancement on standard clinical scales and reduced muscle fatigue levels. Specifically, the percent effort of muscles and slope value of mean/ median frequency decreased by 19%, 70%, and 99% on average, respectively, and the average values of mean/ median frequency in the motion cycle both increased by approximately 5%. The proposed D3Frame in this study was applied to optimize the structural aspects of designated regions of the prosthetic socket, offering the potential to aid prosthetists in prosthesis design and, consequently, augmenting the adaptability of prosthetic devices.

Achieving a best-fit prosthetic socket is essential to comfort, functional performance, and long-term residual limb health in lower-limb amputees. To our knowledge, no previous study has quantitatively compared in vivo residual limb geometry under vacuum versus non-vacuum conditions using high-resolution computed tomography (CT). In this patient-specific case study of a bilateral knee-disarticulation (KD) amputee, both residual limbs were scanned under standardized conditions: one enclosed in a vacuum-compressed sleeve and the contralateral limb untreated as a natural control, thereby minimizing inter-subject variability. CT-based 3D reconstructions enabled volumetric and cross-sectional quantification, including symmetry/asymmetry analysis of paired limbs, while finite element analysis (FEA) assessed the biomechanical consequences for socket performance. Vacuum application resulted in a 4.1% reduction in total limb volume and a 5.3% reduction in mid-thigh cross-sectional area, with regionally asymmetric displacement of soft tissues. FEA demonstrated that vacuum-induced geometry reduced peak Von Mises stresses (27.43 MPa to 15.83 MPa), minimized maximum displacement (1.72 mm to 0.88 mm), and improved minimum factor of safety (~2.0 to ~3.0), while homogenizing contact pressure distribution (peak fell from 2.42 to 1.28 N/mm2). These findings provide preliminary CT-based evidence that vacuum application induces measurable morphological adaptations with implications for socket conformity, comfort, and load transfer. While limited to a single patient, this study highlights the potential of vacuum-induced modeling to inform personalized prosthetic socket design.

Automatic segmentation of magnetic resonance images of the trans-femoral residual limb