Foot/Ankle Prostheses Design Approach Based on Scientometric and Patentometric Analyses

There are different alternatives when selecting removable prostheses for below the knee amputated patients. The designs of these prostheses vary according to their different functions. These prostheses designs can be classified into Energy Storing and Return (ESAR), Controlled Energy Storing and Return (CESR), active, and hybrid. This paper aims to identify the state of the art related to the design of these prostheses of which ESAR prostheses are grouped into five types, and active and CESR are categorized into four groups. Regarding patent analysis, 324 were analyzed over the last six years. For scientific communications, a bibliometric analysis was performed using 104 scientific reports from the Web of Science in the same period. The results show a tendency of ESAR prostheses designs for patents (68%) and active prostheses designs for scientific documentation (40%).Beca Conacyt Doctorad

Advancements in Prosthetics and Joint Mechanisms

abstract: Robotic joints can be either powered or passive. This work will discuss the creation of a passive and a powered joint system as well as the combination system being both powered and passive along with its benefits. A novel approach of analysis and control of the combination system is presented. A passive and a powered ankle joint system is developed and fit to the field of prosthetics, specifically ankle joint replacement for able bodied gait. The general 1 DOF robotic joint designs are examined and the results from testing are discussed. Achievements in this area include the able bodied gait like behavior of passive systems for slow walking speeds. For higher walking speeds the powered ankle system is capable of adding the necessary energy to propel the user forward and remain similar to able bodied gait, effectively replacing the calf muscle. While running has not fully been achieved through past powered ankle devices the full power necessary is reached in this work for running and sprinting while achieving 4x’s power amplification through the powered ankle mechanism. A theoretical approach to robotic joints is then analyzed in order to combine the advantages of both passive and powered systems. Energy methods are shown to provide a correct behavioral analysis of any robotic joint system. Manipulation of the energy curves and mechanism coupler curves allows real time joint behavioral adjustment. Such a powered joint can be adjusted to passively achieve desired behavior for different speeds and environmental needs. The effects on joint moment and stiffness from adjusting one type of mechanism is presented.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201

Design of a Lightweight Modular Powered Transfemoral Prosthesis

Rehabilitation options for transfemoral amputees are limited, and no product today can mimic the full functionality of a human limb. Powered prosthetics have potential to close this gap but contain major drawbacks which ultimately increase the energy expenditure of the user. This thesis explores the viability of new designs and methods to reduce energy expenditure. In doing so a prototype containing many of the explored concepts is also being constructed to replace the laboratory’s current powered prosthetic, AMPRO II. This goal is accomplished by reducing weight through optimizing structural components, using lightweight motors and gearing, and reducing the energy requirements through novel passive spring sub-assemblies. Adjustable and modular components also enable a wider range of use and are explored. The main objective of this thesis is to investigate these design improvements and create the next-generation prosthetic for the Human Rehabilitation Lab. This thesis explores using a combination of passive and powered components to reduce the need for heavy actuators. Methods involve coding walking simulations based on an inverse dynamics study. By simulating design concepts with elastic elements the resulting power requirements of the motors have been estimated to evaluate each concept. Motors and gearing options have also been investigated with an optimization-based approach; gearing ratio was minimized in a test comparing discrete off-the-shelf motor options to biomechanical requirements. For the structural components, the mass of each part has been minimized through an iterative approach in FEA. Elements selected for further investigation from this thesis are being constructed with a prototype. Improvements over AMPRO II include adjustable height, functionality on both legs, a flexible foot, modularity, capabilities of passive elastic elements, and a mass estimated to be 20% lighter. Components include flat motors with harmonic drives, adjustable pylons for height, a low-profile mounting frame, passive pre-loaded springs, and a rotary series elastic actuator (RSEA). Unproven concepts such as the springs and RSEA have been designed as modular and optional to reduce risk. Moving forward, the first prototype is currently being built without the optional components to test the biomechanics. Future tests will incorporate the designed elastic elements to validate simulation concepts

Study of composite elastic elements for transfemoral prostheses: the MyLeg Project

In this thesis, the work on the design and realization of a semi-active foot prosthesis with variable stiffness system is presented. The final prosthesis was the result of a path started by the design of the elastic composite elements of an ESR prosthesis, a passive prosthetic device, generally prescribed to amputees with K3 and K4 of level of ambulation. The design of both the ESR prosthesis and the final variable stiffness prosthesis was carried out using a new systematic methodology of prosthesis design. This methodology has been developed and then presented in the same thesis by the author. Modelling and simulation techniques are illustrated step by step. With the variable stiffness prosthesis, the aim is to allow future users to perform more daily activities without being restricted by the conditions of the ground. It has been chosen to develop a semi-active prosthesis rather than a bionic foot for two main reasons: a bionic foot may be too expensive for most future users; and a bionic foot may be undesirable for too much weight; the much weight can be due to the motor and batteries, in addition to the structure that will certainly be much more complex than the structure of a semi-active prosthesis. To investigate the effectiveness of the variable stiffness, human subjects with amputees will be carried out

Biomechanics of Prosthetic Knee Systems : Role of Dampening and Energy Storage Systems

One significant drawback of the commercial passive and microprocessored prosthetic devices, the inability of delivering positive energy when needed, is due to the absence of the knee flexion during stance phase. Moreover, consequences such as circumduction and disturbed gait pattern take place due to the improper energy flow at the knee and the absence of the positive energy delivery during the swing phase. Current generation powered design has solved these problems by delivering the needed energy with heavy battery demanding motors, which increase the mass of the device significantly. Hence, the gait quality of transfemoral amputees has not improved significantly in the last 50 years due to the inefficient energy flow distribution causing the patient to hike his/her pelvis, which leads to back pain in the long run. In this context, state-of-art prosthetics technology is trending toward creating energy regenerative devices, which are able to harvest/ return energy during ambulation by a spring mechanism, since a spring not only permits significant power demand reduction but also provides high power-to-weight ratio. This study will examine the sagittal plane knee moment versus knee flexion angle properties robotically, clinically and theoretically to explore the functional stiffness of a healthy knee as well as a prosthetic knee during the energy return and harvest phases of gait. With this intention, a prosthetic knee test method will be developed for investigating the torque-angle properties of the knee by iteratively modifying the hip trajectory until achieving the closest to healthy knee biomechanics by a 3-Degree of Freedom (DOF) Simulator. This research reveals that constant spring stiffness is suboptimal to varying gait requirements for different types of activity, due to the variability of the power requirements of the knee caused by the passive, viscous and elastic characteristics and the activation dependent properties of the muscles. Exploring this variation is crucial for the design of tran

Biomechanics of Prosthetic Knee Systems : Role of Dampening and Energy Storage Systems

One significant drawback of the commercial passive and microprocessored prosthetic devices, the inability of delivering positive energy when needed, is due to the absence of the knee flexion during stance phase. Moreover, consequences such as circumduction and disturbed gait pattern take place due to the improper energy flow at the knee and the absence of the positive energy delivery during the swing phase. Current generation powered design has solved these problems by delivering the needed energy with heavy battery demanding motors, which increase the mass of the device significantly. Hence, the gait quality of transfemoral amputees has not improved significantly in the last 50 years due to the inefficient energy flow distribution causing the patient to hike his/her pelvis, which leads to back pain in the long run. In this context, state-of-art prosthetics technology is trending toward creating energy regenerative devices, which are able to harvest/ return energy during ambulation by a spring mechanism, since a spring not only permits significant power demand reduction but also provides high power-to-weight ratio. This study will examine the sagittal plane knee moment versus knee flexion angle properties robotically, clinically and theoretically to explore the functional stiffness of a healthy knee as well as a prosthetic knee during the energy return and harvest phases of gait. With this intention, a prosthetic knee test method will be developed for investigating the torque-angle properties of the knee by iteratively modifying the hip trajectory until achieving the closest to healthy knee biomechanics by a 3-Degree of Freedom (DOF) Simulator. This research reveals that constant spring stiffness is suboptimal to varying gait requirements for different types of activity, due to the variability of the power requirements of the knee caused by the passive, viscous and elastic characteristics and the activation dependent properties of the muscles. Exploring this variation is crucial for the design of tran

The Functionality Verification through Pilot Human Subject Testing of MyFlex-δ: An ESR Foot Prosthesis with Spherical Ankle Joint

Most biomechanical research has focused on level-ground walking giving less attention to other conditions. As a result, most lower limb prosthesis studies have focused on sagittal plane movements. In this paper, an ESR foot is presented, of which five different stiffnesses were optimized for as many weight categories of users. It is characterized by a spherical ankle joint, with which, combined with the elastic elements, the authors wanted to create a prosthesis that gives the desired stiffness in the sagittal plane but at the same time, gives flexibility in the other planes to allow the adaptation of the foot prosthesis to the ground conditions. The ESR foot was preliminarily tested by participants with transfemoral amputation. After a brief familiarization with the device, each participant was asked to wear markers and to walk on a sensorized treadmill to measure their kinematics and kinetics. Then, each participant was asked to leave feedback via an evaluation questionnaire. The measurements and feedback allowed us to evaluate the performance of the prosthesis quantitatively and qualitatively. Although there were no significant improvements on the symmetry of the gait, due also to very limited familiarization time, the participants perceived an improvement brought by the spherical ankle joint

The Functionality Verification through Pilot Human Subject Testing of MyFlex-δ: An ESR Foot Prosthesis with Spherical Ankle Joint

Most biomechanical research has focused on level-ground walking giving less attention to other conditions. As a result, most lower limb prosthesis studies have focused on sagittal plane movements. In this paper, an ESR foot is presented, of which five different stiffnesses were optimized for as many weight categories of users. It is characterized by a spherical ankle joint, with which, combined with the elastic elements, the authors wanted to create a prosthesis that gives the desired stiffness in the sagittal plane but at the same time, gives flexibility in the other planes to allow the adaptation of the foot prosthesis to the ground conditions. The ESR foot was preliminarily tested by participants with transfemoral amputation. After a brief familiarization with the device, each participant was asked to wear markers and to walk on a sensorized treadmill to measure their kinematics and kinetics. Then, each participant was asked to leave feedback via an evaluation questionnaire. The measurements and feedback allowed us to evaluate the performance of the prosthesis quantitatively and qualitatively. Although there were no significant improvements on the symmetry of the gait, due also to very limited familiarization time, the participants perceived an improvement brought by the spherical ankle joint

Design of a Passive Ankle Prosthesis with Energy Return That Increases with Increasing Walking Velocity

Patients who undergo a transtibial (below the knee) amputation are often met with a difficult decision: selection of a prosthesis. Limitations of currently available prostheses motivate work on a new solution, the EaSY Walk, a passive device that mimics two key aspects of the natural ankle: non-linear rotational stiffness through implementation of a stiffening flexure mechanism and rotational work output that varies as a function of walking velocity to propel the user forward. To achieve the latter, a strategy to convert the maximum available translational energy acquired from deflection along the leg into rotational energy about the ankle joint through coupling of these two degrees of freedom is used. This strategy utilizes maxima/minima of known ankle profiles to control timing of critical device functions as well as the quantity of energy input from leg deflection. In doing so, both consistent operation of the device and maximal energy output at a given walking velocity are theoretically obtained. Optimizing for both aforementioned ankle criteria, 25.1% of the work of the average natural ankle was achieved for 15 mm of leg deflection, less deflection than is exhibited by many shock absorbing pylon prostheses. After fabricating and testing the optimized design using a repeatable robot trajectory, the device was found to convert 26.6% of input translational work as rotational work, accounting for 63.1% of modeled rotational work. Through human subject testing, the device was found to function inconsistently due to the large impact loadings associated with human gait. In order to achieve proper functionality with human gait, design modifications to the energy storage and release devices are recommended