Sci Robot

Robotic leg prostheses promise to improve the mobility and quality of life of millions of individuals with lower-limb amputations by imitating the biomechanics of the missing biological leg. Unfortunately, existing powered prostheses are much heavier and bigger and have shorter battery life than conventional passive prostheses, severely limiting their clinical viability and utility in the daily life of amputees. Here, we present a robotic leg prosthesis that replicates the key biomechanical functions of the biological knee, ankle, and toe in the sagittal plane while matching the weight, size, and battery life of conventional microprocessor-controlled prostheses. The powered knee joint uses a unique torque-sensitive mechanism combining the benefits of elastic actuators with that of variable transmissions. A single actuator powers the ankle and toe joints through a compliant, underactuated mechanism. Because the biological toe dissipates energy while the biological ankle injects energy into the gait cycle, this underactuated system regenerates substantial mechanical energy and replicates the key biomechanical functions of the ankle/foot complex during walking. A compact prosthesis frame encloses all mechanical and electrical components for increased robustness and efficiency. Preclinical tests with three individuals with above-knee amputation show that the proposed robotic leg prosthesis allows for common ambulation activities with close to normative kinematics and kinetics. Using an optional passive mode, users can walk on level ground indefinitely without charging the battery, which has not been shown with any other powered or microprocessor-controlled prostheses. A prosthesis with these characteristics has the potential to improve real-world mobility in individuals with above-knee amputation.R01 HD098154/HD/NICHD NIH HHSUnited States/T42 OH008414/OH/NIOSH CDC HHSUnited States

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

The Design, Prototype, and Testing of a Robotic Prosthetic Leg

Since antiquity, health professionals have sought ways to provide and improve prosthetic devices to ease the suffering of those living with limb loss. Mid-century modern engineering techniques, in part, developed and funded by the American industrial war effort, led to numerous innovations and standardization of mass-customized products. Followed by the Digital Revolution, we are now experiencing the roboticization of prosthetic limbs. As innovations have come and gone, some essential technologies have been forgotten or ignored. Many successful products have been commercialized, but unfortunately, they are often rationed to those who need them most. Here we present a prototype device based on many prior discoveries, utilizing commercially available parts when possible. This device has the potential to reduce the overall costs of powered robotic prosthetics, making them accessible to those with knee instability or the fear of falling. Additional benefits of this device are that it is designed to improve the kinematic and kinetic symmetry of the lower extremities, including the hips. We will design, prototype, and test this robotic prosthetic leg for feasibility and safe performance. KEYWORDS: ENGINEERING, LIMB LOSS, FEAR OF FALLING, POWERED ROBOTIC PROSTHETIC LEG, PROTOTYP

Simulated performance of an energy storage and return prosthetic ankle based on cams and miniature hydraulics

Prosthetic feet are limited in their ability to mimic the energy-recycling behaviour of an intact ankle, negatively affecting lower-limb amputees’ gait in terms of metabolic cost and walking speed. To overcome these weaknesses, a novel prosthetic ankle based on hydraulics is described here. The ankle joint drives two cams, which in turn drive two hydraulic rams. One cam-ram system captures the negative work done from foot-flat until maximum dorsiflexion, by pumping oil into an accumulator, while the other returns positive work during push-off providing forward propulsion through fluid flowing from the accumulator to the ram. Simulation results are promising: of the total negative work done by the prosthetic ankle over the gait cycle (i.e., the maximum amount of energy available to be stored), 78% is returned, mainly during push-off; 14% is carried forward for future gait cycles; and 8% is lost. The estimated prosthesis height and mass are approximately 26.5cm and 2.3kg. Nonetheless, further work is necessary to realise a prototype for bench and in-vivo testing. By mimicking intact ankle torque and efficiently storing and returning energy at the ankle joint, this new design may contribute to reducing amputees’ metabolic cost of walking

Mechanisms and component design of prosthetic knees : a review from a biomechanical function perspective

Prosthetic knees are state-of-the-art medical devices that use mechanical mechanisms and components to simulate the normal biological knee function for individuals with transfemoral amputation. A large variety of complicated mechanical mechanisms and components have been employed; however, they lack clear relevance to the walking biomechanics of users in the design process. This article aims to bridge this knowledge gap by providing a review of prosthetic knees from a biomechanical perspective and includes stance stability, early-stance flexion and swing resistance, which directly relate the mechanical mechanisms to the perceived walking performance, i.e., fall avoidance, shock absorption, and gait symmetry. The prescription criteria and selection of prosthetic knees depend on the interaction between the user and prosthesis, which includes five functional levels from K0 to K4. Misunderstood functions and the improper adjustment of knee prostheses may lead to reduced stability, restricted stance flexion, and unnatural gait for users. Our review identifies current commercial and recent studied prosthetic knees to provide a new paradigm for prosthetic knee analysis and facilitates the standardization and optimization of prosthetic knee design. This may also enable the design of functional mechanisms and components tailored to regaining lost functions of a specific person, hence providing individualized product design

An Underactuated Active Transfemoral Prosthesis With Series Elastic Actuators Enables Multiple Locomotion Tasks

Robotic lower limb prostheses have the power to revolutionize mobility by enhancing gait efficiency and facilitating movement. While several design approaches have been explored to create lightweight and energy-efficient devices, the potential of underactuation remains largely untapped in lower limb prosthetics. Taking inspiration from the natural harmony of walking, in this article, we have developed an innovative active transfemoral prosthesis. By incorporating underactuation, our design uses a single power actuator placed near the knee joint and connected to a differential mechanism to drive both the knee and ankle joints. We conduct comprehensive benchtop tests and evaluate the prosthesis with three individuals who have above-knee amputations, assessing its performance in walking, stair climbing, and transitions between sitting and standing. Our evaluation focuses on gathering position and torque data recorded from sensors integrated into the prosthesis and comparing these measurements to biomechanical data of able-bodied locomotion. Our findings highlight the promise of underactuation in advancing lower limb prosthetics and demonstrate the feasibility of our knee–ankle underactuated design in various tasks, showcasing its ability to replicate natural movement

The effect of prefabricated wrist-hand orthoses on grip strength

Prefabricated wrist-hand orthoses (WHOs) are commonly prescribed to manage the functional deficit and compromised grip strength as a result of rheumatoid changes. It is thought that an orthosis which improves wrist extension, reduces synovitis and increases the mechanical advantage of the flexor muscles will improve hand function. Previous studies report an initial reduction in grip strength with WHO use which may increase following prolonged use. Using normal subjects, and thus in the absence of pain as a limiting factor, the impact of ten WHOs on grip strength was measured using a Jamar dynamometer. Tests were performed with and without WHOs by right-handed, female subjects, aged 20-50 years over a ten week period. During each test, a wrist goniometer and a forearm torsiometer were used to measure wrist joint position when maximum grip strength was achieved. The majority of participants achieved maximum grip strength with no orthosis at 30° extension. All the orthoses reduced initial grip strength but surprisingly the restriction of wrist extension did not appear to contribute in a significant way to this. Reduction in grip must therefore also be attributable to WHO design characteristics or the quality of fit. The authors recognize the need for research into the long term effect of WHOs on grip strength. However if grip is initially adversely affected, patients may be unlikely to persevere with treatment thereby negating all therapeutic benefits. In studies investigating patient opinions on WHO use, it was a stable wrist rather than a stronger grip reported to have facilitated task performance. This may explain why orthoses that interfere with maximum grip strength can improve functional task performance. Therefore while it is important to measure grip strength, it is only one factor to be considered when evaluating the efficacy of WHOs

Use of stance control knee-ankle-foot orthoses : a review of the literature

The use of stance control orthotic knee joints are becoming increasingly popular as unlike locked knee-ankle-foot orthoses, these joints allow the limb to swing freely in swing phase while providing stance phase stability, thus aiming to promote a more physiological and energy efficient gait. It is of paramount importance that all aspects of this technology is monitored and evaluated as the demand for evidence based practice and cost effective rehabilitation increases. A robust and thorough literature review was conducted to retrieve all articles which evaluated the use of stance control orthotic knee joints. All relevant databases were searched, including The Knowledge Network, ProQuest, Web of Knowledge, RECAL Legacy, PubMed and Engineering Village. Papers were selected for review if they addressed the use and effectiveness of commercially available stance control orthotic knee joints and included participant(s) trialling the SCKAFO. A total of 11 publications were reviewed and the following questions were developed and answered according to the best available evidence: 1. The effect SCKAFO (stance control knee-ankle-foot orthoses) systems have on kinetic and kinematic gait parameters 2. The effect SCKAFO systems have on the temporal and spatial parameters of gait 3. The effect SCKAFO systems have on the cardiopulmonary and metabolic cost of walking. 4. The effect SCKAFO systems have on muscle power/generation 5. Patient’s perceptions/ compliance of SCKAFO systems Although current research is limited and lacks in methodological quality the evidence available does, on a whole, indicate a positive benefit in the use of SCKAFOs. This is with respect to increased knee flexion during swing phase resulting in sufficient ground clearance, decreased compensatory movements to facilitate swing phase clearance and improved temporal and spatial gait parameters. With the right methodological approach, the benefits of using a SCKAFO system can be evidenced and the research more effectively converted into clinical practice

The effect of prefabricated wrist-hand orthoses on performing activities of daily living

Wrist-hand orthoses (WHOs) are commonly prescribed to manage the functional deficit associated with the wrist as a result of rheumatoid changes. The common presentation of the wrist is one of flexion and radial deviation with ulnar deviation of the fingers. This wrist position Results in altered biomechanics compromising hand function during activities of daily living (ADL). A paucity of evidence exists which suggests that improvements in ADL with WHO use are very task specific. Using normal subjects, and thus in the absence of pain as a limiting factor, the impact of ten WHOs on performing five ADLs tasks was investigated. The tasks were selected to represent common grip patterns and tests were performed with and without WHOs by right-handed, females, aged 20-50 years over a ten week period. The time taken to complete each task was recorded and a wrist goniometer, elbow goniometer and a forearm torsiometer were used to measure joint motion. Results show that, although orthoses may restrict the motion required to perform a task, participants do not use the full range of motion which the orthoses permit. The altered wrist position measured may be attributable to a modified method of performing the task or to a necessary change in grip pattern, resulting in an increased time in task performance. The effect of WHO use on ADL is task specific and may initially impede function. This could have an effect on WHO compliance if there appears to be no immediate benefits. This orthotic effect may be related to restriction of wrist motion or an inability to achieve the necessary grip patterns due to the designs of the orthoses