Fatigue test of low-cost flexible-shank monolimb trans-tibial prosthesis

FATIGUE ANALYSIS OF POLYCENTRIC PROSTHETIC KNEE FOR TRANS-FEMORAL AMPUTATION

A prosthetic knee is predominantly subjected to cyclic action leading to fatigue failure during its operation. However, cyclic failure is more severe as it occurs below the yield strength and may happen even without prior indication. This study presents a cyclic structural analysis of an existing polycentric mechanical prosthetic knee by finite element simulation and its experimental validation as per the ISO 10328:2016 standard. The three-dimensional (3D) model is imported to the ANSYS 20.1 workbench to study stress distribution and fatigue life in the knee for ensuring its safety performance. The maximum von-Mises stresses developed at the front and back joint bars made of A390.0-T5 and A390.0-T6 cast aluminium are 100 and 89[Formula: see text]MPa, respectively, in both loading conditions compared to their mechanical fatigue strength of 89[Formula: see text]MPa. The maximum deformation and average number of cycles for fatigue failure are 2.66 and 2.53[Formula: see text]mm and [Formula: see text] and [Formula: see text] for simulation and experimental results, respectively. These results suggest that this polycentric knee unit has poor fatigue strength and thereby does not meet the ISO structural standard. A validation test has been performed with an average error of 4.75% between the simulation and experiments results showing higher reliability.

Mechanical Reinforcement of Polyamide 6 by Cold Hydrostatic Extrusion

This paper presents the effect of severe plastic deformation obtained using the cold hydrostatic extrusion (HE) method on the mechanical and structural properties of polyamide 6 (PA6). As a result of the plastic strain, a significant increase in ultimate tensile strength and tensile modulus were observed. Tensile strength rose by almost 500%, up to the level of 508 MPa, whereas the tensile modulus rose by about 65%. Flexural modulus increase was also observed to 3230 MPa, i.e., by approx. 160%. As a result of high plastic deformation, the structure of the polyamide 6 changed significantly, as evidenced by its fibrous nature as presented in the results of the scanning electron microscopy inspection (SEM). The surface quality of products investigated was tested using profilometry.

Multi-scale semi-analytical model for fatigue life prediction of trans-tibial prosthetic sockets

The trans-tibial socket is an essential component of the prosthesis that connects it to the residual limb. Socket misalignments and permanent deformations reduce the comfort of the amputee. In order to forestall such issues, sufficient information about the socket lifespan needs to be acquired, which is fairly difficult given the lack of calculation methods that estimate the fatigue life in the literature. In this paper a semi-analytical model is proposed based on experimental results. It highlights the effects of the amputee average daily walking time on the socket fatigue life. A proportionality relationship is demonstrated linking the Burgers model parameters at the structural scale to those at the macroscopic scale. Hence, it becomes possible to evaluate the permanent deformation that induces a misalignment in the socket. These results are useful for the designers to predict the fatigue life of the socket, and also for clinicians to monitor the mechanical degradation of the trans-tibial socket and schedule maintenance or replacement.

A scoping literature review of the provision of orthoses and prostheses in resource-limited environments 2000-2010. Part two: research and outcomes

BACKGROUND

Despite the activities of many orthotic and prosthetic provision organizations in resource-limited environments, there is still a great need and there are several areas for improvement, as identified in Part One of this series.

OBJECTIVES

Our goal was to examine outcomes and conclusions of research studies to produce an evidence base for determining factors that may lead to successful provision of orthoses and prostheses in resource-limited environments.

STUDY DESIGN

Literature review.

METHODS

We conducted a scoping literature review of all information related to orthotic and prosthetic provision in resource-limited environments published from 2000 to 2010. We extracted measured outcomes reported in all types of articles and analyzed conclusions from research studies.

RESULTS

Reported outcomes included durability, cost, satisfaction, use/nonuse of device, amount of utilization, walking speed, discomfort, pain, fit, misalignment, capacity for service provision, number of devices produced or delivered, and number of graduates from training programs.

CONCLUSIONS

There are many gaps in the evidence base, notably in measuring inclusion, participation, and quality of life for orthosis and prosthesis users in resource-limited environments. There is a paucity of reported outcomes for orthotics. Valid, reliable, and standard methods of data collection and reporting are needed to advance the field and enhance the evidence base.

A scoping literature review of the provision of orthoses and prostheses in resource-limited environments 2000-2010. Part one: considerations for success

STUDY DESIGN

Literature Review

BACKGROUND

We estimate that over 29 million people worldwide in resource-limited environments (RLEs) are in need of orthotic and prosthetic (O&P) devices and services.

OBJECTIVES

Our goal was to ascertain the current state of O&P provision in RLEs and identify factors that may lead to more successful O&P provision.

METHODS

We conducted a comprehensive scoping literature review of all information related to O&P provision in RLEs published from 2000 to 2010. We targeted Vietnam, Cambodia, Tanzania, Malawi, Colombia, and the Navajo Nation, but also included information about developing countries in general. We searched academic databases and grey literature. We extracted information from each article in the areas of design, manufacturing, distribution, service provision, and technology transfer.

RESULTS

We identified commonly reported considerations and strategies for O&P provision from 431 articles. Analysis of expert consensus documents revealed recurring themes for improving O&P provision. We found that some suggestions from the consensus documents are being followed, but many are overlooked or have not yet been implemented.

CONCLUSIONS

Areas for improvement include conducting field testing during the design process, providing services to rural environments, offering follow-up services, considering government collaboration, and encouraging an active role of the orthosis/prosthesis user. Outcomes and research studies will be further discussed in Part Two.

Lower-limb prosthetic technologies in the developing world: A review of literature from 1994-2010

In the mid-1990s, a number of key publications and meetings of experts identified major technical issues associated with prosthetic technologies intended for developing countries. These included inadequate durability of prosthetic feet, poor socket quality and prosthetic fit, improper alignment of prostheses, and inferior function of components. To examine the progress that has been made since then in addressing these issues, a comprehensive review of literature was performed. In total, 106 articles were selected and included in the review. The review examined prosthetic technologies categorized into feet and ankles, knees, sockets and suspension, and materials, structures, and alignment methods. Moreover, publications were categorized as technical development, clinical (lab-based) testing, or clinical field testing studies. The results reveal important work that has been carried out to develop and implement standardized outcome measures during field testing, allowing various existing prosthetic technologies to be evaluated in terms of their use, function, durability, and other factors. Progress has also been made toward addressing the aforementioned limitations of prosthetic technologies, however, more research and development is required. This includes improving the durability of the external cosmetic features of prosthetic feet, developing more functional prosthetic knee joints, and simplifying fabrication techniques to further improve outcomes associated with socket fit and prosthetic alignment. Research and development collaborations between developed and developing countries, and the dissemination of ongoing research, development, and evaluation activities are essential to the advancement of prosthetic technologies in these regions.