Impact of ankle foot orthosis stiffness on Achilles tendon and gastrocnemius function during unimpaired gait

Choi, Hwan; Peters, Keshia M.; MacConnell, Michael B.; Ly, Katie K.; Eckert, Eric S.; Steele, Katherine M.

doi:10.1016/j.jbiomech.2017.09.015

Cited by 27 publications

(28 citation statements)

References 40 publications

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“…Four different ankle stiffness values are considered for each quadrant of the angle vs. torque curve, as most of the patient-specific AFOs show a different behavior in plantarflexion compared to dorsiflexion due to their shape (Table 6). The magnitude of these stiffness values is in line with that used in other research studies for investigating 3D printed AFOs (Schrank et al 2013;Choi et al 2017). AFO A seems to be the stiffest in plantarflexion whereas in dorsiflexion, AFO A, B and C have similar values.…”

Section: Discussionsupporting

confidence: 89%

“…Ankle foot orthoses (AFOs) are external medical devices used to restore the natural gait pattern for patients with neurological and musculoskeletal disorders (Singer et al 2014;Kobayashi et al 2015;Ries et al 2015;Choi et al 2017). Depending on the design and the material, AFOs can be classified in different ways: currently, in the USA, the majority of the AFOs are custom fabricated (73%) and made of thermoplastic materials (83%) (American Board for Certification in Orthotics, Prosthetics & Pedorthics, Inc 2015).…”

Section: Introductionmentioning

confidence: 99%

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A validated computational framework to evaluate the stiffness of 3D printed ankle foot orthoses

Ielapi

Lammens

Paepegem

et al. 2019

Computer Methods in Biomechanics and Biomedical Engineering

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The purpose of this study was to create and validate a standardized framework for the evaluation of the ankle stiffness of two designs of 3D printed ankle foot orthoses (AFOs). The creation of four finite element (FE) models allowed patient-specific quantification of the stiffness and stress distribution over their specific range of motion during the second rocker of the gait. Validation was performed by comparing the model outputs with the results obtained from a dedicated experimental setup, which showed an overall good agreement with a maximum relative error of 10.38% in plantarflexion and 10.66% in dorsiflexion. The combination of advanced computer modelling algorithms and 3D printing techniques clearly shows potential to further improve the manufacturing process of AFOs.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

A validated computational framework to evaluate the stiffness of 3D printed ankle foot orthoses

Ielapi

Lammens

Paepegem

et al. 2019

Computer Methods in Biomechanics and Biomedical Engineering

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“…Musculoskeletal simulations of walking with a unilateral elastic exoskeleton have demonstrated that applying ankle exoskeleton torque to the ankle joint reduces muscle force requirements, which leads to decreased tendon stretch and increased fascicle strain 17 . This trend is also supported by a recent study that used ultrasound imaging to track the junction between the medial gastrocnemius and Achilles tendon during walking with a dynamic orthosis 35 . Together, these studies demonstrate that exoskeletons may disrupt the normal plantar flexor MT dynamics by limiting the ability of series-elastic tissues to keep plantar flexor muscles operating with contractile dynamics favorable for economical force production 30 .…”

supporting

confidence: 58%

Ultrasound imaging links soleus muscle neuromechanics and energetics during human walking with elastic ankle exoskeletons

Nuckols

Dick

Beck

et al. 2020

Sci Rep

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Unpowered exoskeletons with springs in parallel to human plantar flexor muscle-tendons can reduce the metabolic cost of walking. We used ultrasound imaging to look 'under the skin' and measure how exoskeleton stiffness alters soleus muscle contractile dynamics and shapes the user's metabolic rate during walking. Eleven participants (4F, 7M; age: 27.7 ± 3.3 years) walked on a treadmill at 1.25 m s −1 and 0% grade with elastic ankle exoskeletons (rotational stiffness: 0-250 Nm rad −1) in one training and two testing days. Metabolic savings were maximized (4.2%) at a stiffness of 50 Nm rad −1. As exoskeleton stiffness increased, the soleus muscle operated at longer lengths and improved economy (force/activation) during early stance, but this benefit was offset by faster shortening velocity and poorer economy in late stance. Changes in soleus activation rate correlated with changes in users' metabolic rate (p = 0.038, R 2 = 0.44), highlighting a crucial link between muscle neuromechanics and exoskeleton performance; perhaps informing future 'muscle-in-the loop' exoskeleton controllers designed to steer contractile dynamics toward more economical force production. The plantar flexors serve an essential role in human walking by providing more than 50% of the leg's total positive mechanical energy 1 and up to 60% of the mechanical power output for redirecting the body's center of mass during push-off 2. The importance of the ankle plantar flexors in legged locomotion is linked to their morphology. Muscle-tendons (MTs) with short pennate muscle fibers and long compliant in-series tendons are well suited for economical locomotion because the elastic tendons store and return mechanical energy over each step 3-5. During steady-state walking, the interaction of the plantar flexors and Achilles tendon is tuned. Throughout early stance, 0% (heel strike) to 40% stride, plantar flexor muscle fascicles generate force isometrically while the Achilles tendon stretches and stores mechanical energy 6. In late stance, 40% to 60% (toe-off) stride, the plantar flexors shorten and the tendon rapidly recoils, providing a burst of positive mechanical power 1,4,7. This coordinated MT interaction permits the plantar flexor muscle fascicles to operate over a narrow region of their force-length (F-L) curve and remain at slow shortening velocities which are favorable contractile conditions for economical force production 7-12. Any disruption to this 'catapult' like mechanism may decrease the ankle's efficient mechanical power production and worsen walking efficiency. Exoskeletons are a class of wearable devices that often act in parallel with human MTs to restore or augment human movement. An increasing number of studies 13 are establishing that both tethered 14-18 and portable 19-21 lower-limb exoskeletons can deliver mechanical power to the body to reduce metabolic demand during walking in young healthy individuals 14-22 , individuals post-stroke 23 , and older adults 24,25. Recently, our group has demonstrated that exoskeletons need not deli...

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“…However, users participation restrict to this phase is not enough to guarantee the satisfaction and efficacy of the device. When the study's proposal is to evaluate the influence of an orthotic device in a biomechanical aspect, the evaluation can be lead with healthy participants, as presented by Choi et al (2017) in the study named "Impact of ankle-foot orthosis stiffness on Achilles tendon and gastrocnemius function during unimpaired gait". In this case, although an evaluation had been conducted, it was not focused on a real user.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Orthosis Rapid Prototyping During the Design Process: Analysis of Verification Models

Ferrari

Santos

Bertolaccini

et al. 2019

Advances in Intelligent Systems and Computing

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Accessing physical prototypes is possible to test an idea quickly with models that look like the final product. Rapid Prototyping (RP) based on additive or subtractive technology permit to conduct trial tests of usability in order to avoid errors and failures before the final product production. Those technologies are increasingly in orthosis's production. Ergonomics field involved in the design process with RP can facilitate usability tests providing comfort, safety, and performance in the development of orthoses. The objective of this study is to review, accessing the specialized literature, the use of RP for prototypes' production for user's evaluation of orthoses. The results showed that the most common technique used was FDM. Half of the studies involved user's participation or evaluation in the design processes, although, only three out of thirty-eight studies used RP to proof of concept's production, indicating little use of proof-of-concepts models.

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Impact of ankle foot orthosis stiffness on Achilles tendon and gastrocnemius function during unimpaired gait

Cited by 27 publications

References 40 publications

A validated computational framework to evaluate the stiffness of 3D printed ankle foot orthoses

A validated computational framework to evaluate the stiffness of 3D printed ankle foot orthoses

Ultrasound imaging links soleus muscle neuromechanics and energetics during human walking with elastic ankle exoskeletons

Evaluation of Orthosis Rapid Prototyping During the Design Process: Analysis of Verification Models

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