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Richard R Neptune – One of the best experts on this subject based on the ideXlab platform.

  • hip recovery strategy used by below knee Amputees following mediolateral foot perturbations
    Journal of Biomechanics, 2018
    Co-Authors: Sarah E Miller, Ava D Segal, Glenn K Klute, Richard R Neptune

    Abstract:

    Abstract Lower-limb Amputees have a higher risk of falling compared to non-Amputees. Proper regulation of whole-body angular momentum is necessary to prevent falls, particularly in the frontal plane where individuals are most unstable. However, the balance recovery mechanisms used by lower-limb Amputees when recovering from a perturbation are not well-understood. This study sought to understand the balance recovery mechanisms used by lower-limb Amputees in response to mediolateral foot perturbations by examining changes to frontal plane whole-body angular momentum and hip joint work. These metrics provide a quantitative measure of frontal plane dynamic balance and associated joint contributions required to maintain balance during gait. Nine Amputees and 11 non-Amputees participated in this study where an unexpected medial or lateral foot placement perturbation occurred immediately prior to heel strike on the residual, sound or non-Amputee limbs. Lateral perturbations of all limbs resulted in a reduced range of whole-body angular momentum and increased positive frontal plane hip work in the first half of single limb support. Medial perturbations for all limbs resulted in increased range of whole-body angular momentum and decreased positive frontal plane hip work, also in the first half of single limb support. These results suggest that medial foot placement perturbations are particularly challenging and that hip strategies play an important role in balance recovery. Thus, rehabilitation interventions that focus on hip muscles that regulate mediolateral balance, particularly the hip abductors, and the use of prostheses with active ankle control, may reduce the risk of falls.

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  • optimization of prosthetic foot stiffness to reduce metabolic cost and intact knee loading during below knee Amputee walking a theoretical study
    Journal of Biomechanical Engineering-transactions of The Asme, 2012
    Co-Authors: Nicholas P Fey, Glenn K Klute, Richard R Neptune

    Abstract:

    Unilateral below-knee Amputees develop abnormal gait characteristics that include bilateral asymmetries and an elevated metabolic cost relative to non-Amputees. In addition, long-term prosthesis use has been linked to an increased prevalence of joint pain and osteoarthritis in the intact leg knee. To improve Amputee mobility, prosthetic feet that utilize elastic energy storage and return (ESAR) have been designed, which perform important biomechanical functions such as providing body support and forward propulsion. However, the prescription of appropriate design characteristics (e.g., stiffness) is not well-defined since its influence on foot function and important in vivo biomechanical quantities such as metabolic cost and joint loading remain unclear. The design of feet that improve these quantities could provide considerable advancements in Amputee care. Therefore, the purpose of this study was to couple design optimization with dynamic simulations of Amputee walking to identify the optimal foot stiffness that minimizes metabolic cost and intact knee joint loading. A musculoskeletal model and distributed stiffness ESAR prosthetic foot model were developed to generate muscle-actuated forward dynamics simulations of Amputee walking. Dynamic optimization was used to solve for the optimal muscle excitation patterns and foot stiffness profile that produced simulations that tracked experimental Amputee walking data while minimizing metabolic cost and intact leg internal knee contact forces. Muscle and foot function were evaluated by calculating their contributions to the important walking subtasks of body support, forward propulsion and leg swing. The analyses showed that altering a nominal prosthetic foot stiffness distribution by stiffening the toe and mid-foot while making the ankle and heel less stiff improved ESAR foot performance by offloading the intact knee during early to mid-stance of the intact leg and reducing metabolic cost. The optimal design also provided moderate braking and body support during the first half of residual leg stance, while increasing the prosthesis contributions to forward propulsion and body support during the second half of residual leg stance. Future work will be directed at experimentally validating these results, which have important implications for future designs of prosthetic feet that could significantly improve Amputee care.

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  • muscle and prosthesis contributions to Amputee walking mechanics a modeling study
    Journal of Biomechanics, 2012
    Co-Authors: Anne K. Silverman, Richard R Neptune

    Abstract:

    Unilateral, below-knee Amputees have altered gait mechanics, which can significantly affect their mobility. Below-knee Amputees lose the functional use of the ankle muscles, which are critical during walking to provide body support, forward propulsion, leg-swing initiation and mediolateral balance. Thus, either muscles must compensate or the prosthesis must provide the functional tasks normally provided by the ankle muscles. Three-dimensional (3D) forward dynamics simulations of Amputee and non-Amputee walking were generated to identify muscle and prosthesis contributions to Amputee walking mechanics, including the subtasks of body support, forward propulsion, leg-swing initiation and mediolateral balance. Results showed that the prosthesis provided body support in the absence of the ankle muscles. The prosthesis contributed to braking from early to mid-stance and propulsion in late stance. The prosthesis also functioned like the uniarticular soleus muscle by transferring energy from the residual leg to the trunk to provide trunk propulsion. The residual-leg vasti and rectus femoris reduced their contributions to braking in early stance, which mitigated braking from the prosthesis during this period. The prosthesis did not replace the function of the gastrocnemius, which normally generates energy to the leg to initiate swing. As a result, lower overall energy was delivered to the residual leg. The prosthesis also acted to accelerate the body laterally in the absence of the ankle muscles. These results provide further insight into muscle and prosthesis function in below-knee Amputee walking and can help guide rehabilitation methods and device designs to improve Amputee mobility.

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Glenn K Klute – One of the best experts on this subject based on the ideXlab platform.

  • hip recovery strategy used by below knee Amputees following mediolateral foot perturbations
    Journal of Biomechanics, 2018
    Co-Authors: Sarah E Miller, Ava D Segal, Glenn K Klute, Richard R Neptune

    Abstract:

    Abstract Lower-limb Amputees have a higher risk of falling compared to non-Amputees. Proper regulation of whole-body angular momentum is necessary to prevent falls, particularly in the frontal plane where individuals are most unstable. However, the balance recovery mechanisms used by lower-limb Amputees when recovering from a perturbation are not well-understood. This study sought to understand the balance recovery mechanisms used by lower-limb Amputees in response to mediolateral foot perturbations by examining changes to frontal plane whole-body angular momentum and hip joint work. These metrics provide a quantitative measure of frontal plane dynamic balance and associated joint contributions required to maintain balance during gait. Nine Amputees and 11 non-Amputees participated in this study where an unexpected medial or lateral foot placement perturbation occurred immediately prior to heel strike on the residual, sound or non-Amputee limbs. Lateral perturbations of all limbs resulted in a reduced range of whole-body angular momentum and increased positive frontal plane hip work in the first half of single limb support. Medial perturbations for all limbs resulted in increased range of whole-body angular momentum and decreased positive frontal plane hip work, also in the first half of single limb support. These results suggest that medial foot placement perturbations are particularly challenging and that hip strategies play an important role in balance recovery. Thus, rehabilitation interventions that focus on hip muscles that regulate mediolateral balance, particularly the hip abductors, and the use of prostheses with active ankle control, may reduce the risk of falls.

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  • lower limb Amputee recovery response to an imposed error in mediolateral foot placement
    Journal of Biomechanics, 2014
    Co-Authors: Ava D Segal, Glenn K Klute

    Abstract:

    Despite walking with a wider step width, Amputees remain 20% more likely to fall than non-Amputees. Since mediolateral (ML) balance is critical for ambulation and contingent on ML foot placement, we used a ML disturbance to perturb walking balance and explore the influence of prosthetic foot stiffness on balance recovery. Ten transtibial Amputees were fit with two commonly prescribed prosthetic feet with differing stiffness characteristics; 12 non-Amputees also participated. A perturbation device that released an air burst just before heel strike imposed a repeatable medial or lateral disturbance in foot placement. After a medial disturbance, the first recovery step width was narrowed (p<0.0001) for the prosthetic limb (−103%), the sound limb (−51%) and non-Amputees (−41%) and more than twice as variable. The ML inclination angle remained reduced (−109%) for the prosthetic limb, while the sound limb and non-Amputees approached undisturbed levels (p<0.0004). Amputees required five steps to return to undisturbed step width after a prosthetic medial disturbance versus two steps for the sound limb and for non-Amputees. After a lateral disturbance, the first recovery step was widened for the prosthetic limb (+82%), sound limb (+75%), and wider than non-Amputees (+51%; p<0.0001), with all participants requiring three steps to return to undisturbed step width. Amputees also exhibited a similar upper torso response compared to the non-Amputees for both disturbances. Prosthetic feet with different stiffness properties did not have a significant effect. In conclusion, Amputee balance was particularly challenged by medial disturbances to the prosthetic limb implying a need for improved interventions that address these balance deficits.

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  • optimization of prosthetic foot stiffness to reduce metabolic cost and intact knee loading during below knee Amputee walking a theoretical study
    Journal of Biomechanical Engineering-transactions of The Asme, 2012
    Co-Authors: Nicholas P Fey, Glenn K Klute, Richard R Neptune

    Abstract:

    Unilateral below-knee Amputees develop abnormal gait characteristics that include bilateral asymmetries and an elevated metabolic cost relative to non-Amputees. In addition, long-term prosthesis use has been linked to an increased prevalence of joint pain and osteoarthritis in the intact leg knee. To improve Amputee mobility, prosthetic feet that utilize elastic energy storage and return (ESAR) have been designed, which perform important biomechanical functions such as providing body support and forward propulsion. However, the prescription of appropriate design characteristics (e.g., stiffness) is not well-defined since its influence on foot function and important in vivo biomechanical quantities such as metabolic cost and joint loading remain unclear. The design of feet that improve these quantities could provide considerable advancements in Amputee care. Therefore, the purpose of this study was to couple design optimization with dynamic simulations of Amputee walking to identify the optimal foot stiffness that minimizes metabolic cost and intact knee joint loading. A musculoskeletal model and distributed stiffness ESAR prosthetic foot model were developed to generate muscle-actuated forward dynamics simulations of Amputee walking. Dynamic optimization was used to solve for the optimal muscle excitation patterns and foot stiffness profile that produced simulations that tracked experimental Amputee walking data while minimizing metabolic cost and intact leg internal knee contact forces. Muscle and foot function were evaluated by calculating their contributions to the important walking subtasks of body support, forward propulsion and leg swing. The analyses showed that altering a nominal prosthetic foot stiffness distribution by stiffening the toe and mid-foot while making the ankle and heel less stiff improved ESAR foot performance by offloading the intact knee during early to mid-stance of the intact leg and reducing metabolic cost. The optimal design also provided moderate braking and body support during the first half of residual leg stance, while increasing the prosthesis contributions to forward propulsion and body support during the second half of residual leg stance. Future work will be directed at experimentally validating these results, which have important implications for future designs of prosthetic feet that could significantly improve Amputee care.

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Joseph M. Czerniecki – One of the best experts on this subject based on the ideXlab platform.

  • transfemoral Amputee intact limb loading and compensatory gait mechanics during down slope ambulation and the effect of prosthetic knee mechanisms
    Clinical Biomechanics, 2018
    Co-Authors: David C Morgenroth, Michelle Roland, Alison L Pruziner, Joseph M. Czerniecki

    Abstract:

    Abstract Background Intact limb knee osteoarthritis is a prevalent secondary disability in transfemoral Amputees. Walking down a ramp may increase this risk due to excessive limb loading. We sought to determine whether intact limb loading differed between transfemoral Amputees and controls during down slope ambulation, and the compensatory strategies transfemoral Amputees used to modify intact limb loading. Secondarily, we sought to determine the effect of prosthetic knee type. Methods Five unilateral transfemoral Amputees and five non-Amputee controls walked down a ramp and the following outcome measures were compared between Amputees and controls and across prosthetic knee type (C-leg versus Power Knee): step length, walking speed, leading limb ground reaction forces, and trailing and leading limb ankle and knee energy absorption. Linear mixed effects regression was used to test for association between gait variables and limb. Findings There were no significant differences in intact limb loading between Amputees and controls or between prosthetic knee types. Transfemoral Amputees walked slower (C-leg – control = −0.29 m/s; P = 0.008, Power Knee – control = −0.38 m/s; P  Interpretation Intact limb loading in transfemoral Amputees is equivalent to controls during down ramp ambulation, in spite of reduced prosthetic trailing limb energy absorption. The primary compensatory strategies include a reduced ambulation speed and intact limb step length, which reduces center of mass velocity at heel contact.

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  • the development and validation of a novel outcome measure to quantify mobility in the dysvascular lower extremity Amputee the Amputee single item mobility measure
    Clinical Rehabilitation, 2016
    Co-Authors: Daniel C Norvell, Rhonda M. Williams, Aaron P Turner, Joseph M. Czerniecki

    Abstract:

    Objective:This study describes the development and psychometric evaluation of a novel patient-reported single-item mobility measure.Design:Prospective cohort study.Setting:Four Veteran’s Administration Medical Centers.Subjects:Individuals undergoing their first major unilateral lower extremity amputation; 198 met inclusion criteria; of these, 113 (57%) enrolled.Interventions:None.Main measures:The Amputee Single Item Mobility Measure, a single item measure with scores ranging from 0 to 6, was developed by an expert panel, and concurrently administered with the Locomotor Capabilities Index-5 (LCI-5) and other outcome measures at six weeks, four months, and 12 months post-amputation. Criterion and construct validity, responsiveness, and floor/ceiling effects were evaluated. Responsiveness was assessed using the standardized response mean.Results:The overall mean 12-month Amputee Single Item Mobility Measure score was 3.39 ±1.4. Scores for transmetatarsal, transtibial, and transfemoral Amputees were 4.2 (±1….

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  • the effects of a controlled energy storage and return prototype prosthetic foot on transtibial Amputee ambulation
    Human Movement Science, 2012
    Co-Authors: Ava D Segal, Glenn K Klute, Michael S. Orendurff, Karl E Zelik, David C Morgenroth, Michael E Hahn, Peter G Adamczyk, Steven H Collins, Arthur D Kuo, Joseph M. Czerniecki

    Abstract:

    The lack of functional ankle musculature in lower limb Amputees contributes to the reduced prosthetic ankle push-off, compensations at other joints and more energetically costly gait commonly observed in comparison to non-Amputees. A variety of energy storing and return prosthetic feet have been developed to address these issues but have not been shown to sufficiently improve Amputee biomechanics and energetic cost, perhaps because the timing and magnitude of energy return is not controlled. The goal of this study was to examine how a prototype microprocessor-controlled prosthetic foot designed to store some of the energy during loading and return it during push-off affects Amputee gait. Unilateral transtibial Amputees wore the Controlled Energy Storage and Return prosthetic foot (CESR), a conventional foot (CONV), and their previously prescribed foot (PRES) in random order. Three-dimensional gait analysis and net oxygen consumption were collected as participants walked at constant speed. The CESR foot demonstrated increased energy storage during early stance, increased prosthetic foot peak push-off power and work, increased prosthetic limb center of mass (COM) push-off work and decreased intact limb COM collision work compared to CONV and PRES. The biological contribution of the positive COM work for CESR was reduced compared to CONV and PRES. However, the net metabolic cost for CESR did not change compared to CONV and increased compared to PRES, which may partially reflect the greater weight, lack of individualized size and stiffness and relatively less familiarity for CESR and CONV. Controlled energy storage and return enhanced prosthetic push-off, but requires further design modifications to improve Amputee walking economy.

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