Passive-dynamic ankle–foot orthosis replicates soleus but not gastrocnemius muscle function during stance in gait

Arch, Elisa S.; Stanhope, Steven J.; Higginson, Jill S.

doi:10.1177/0309364615592693

Cited by 33 publications

(33 citation statements)

References 47 publications

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“…These models can reveal insights that are difficult to discover via experiments alone; for example, we found that devices may substantially affect the metabolic rate of joint motions other than the one being assisted. Our findings support use of musculoskeletal modeling and simulation to predict how hypothetical devices may perform and to understand the performance of actual devices [22,28,60]. This work complements experiments, which are necessary to test the accuracy of the predictions made by simulations, improve musculoskeletal and metabolics models, and solve the practical challenges we ignored.…”

Section: Discussionsupporting

confidence: 70%

“…In particular, the optimal device torque profiles and the corresponding changes in muscle activity we observed were shaped by the presence of muscles that actuate multiple degrees of freedom (this includes biarticular muscles as well as muscles crossing a single joint that has multiple degrees of freedom). We found that a device torque may be less than the corresponding net joint moment if an assisted muscle also contributes to the required net joint moment about another joint motion (e.g., ankle plantarflexion device and medial gastrocnemius [60,61]; Fig 4A). Conversely, if a muscle crossing an assisted joint motion generates an undesired moment about another joint motion, then the device can largely take over for this muscle (e.g., hip flexion device and iliacus; Fig 6A).…”

Section: Discussionmentioning

confidence: 99%

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Simulating ideal assistive devices to reduce the metabolic cost of walking with heavy loads

et al. 2017

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Wearable robotic devices can restore and enhance mobility. There is growing interest in designing devices that reduce the metabolic cost of walking; however, designers lack guidelines for which joints to assist and when to provide the assistance. To help address this problem, we used musculoskeletal simulation to predict how hypothetical devices affect muscle activity and metabolic cost when walking with heavy loads. We explored 7 massless devices, each providing unrestricted torque at one degree of freedom in one direction (hip abduction, hip flexion, hip extension, knee flexion, knee extension, ankle plantarflexion, or ankle dorsiflexion). We used the Computed Muscle Control algorithm in OpenSim to find device torque profiles that minimized the sum of squared muscle activations while tracking measured kinematics of loaded walking without assistance. We then examined the metabolic savings provided by each device, the corresponding device torque profiles, and the resulting changes in muscle activity. We found that the hip flexion, knee flexion, and hip abduction devices provided greater metabolic savings than the ankle plantarflexion device. The hip abduction device had the greatest ratio of metabolic savings to peak instantaneous positive device power, suggesting that frontal-plane hip assistance may be an efficient way to reduce metabolic cost. Overall, the device torque profiles generally differed from the corresponding net joint moment generated by muscles without assistance, and occasionally exceeded the net joint moment to reduce muscle activity at other degrees of freedom. Many devices affected the activity of muscles elsewhere in the limb; for example, the hip flexion device affected muscles that span the ankle joint. Our results may help experimentalists decide which joint motions to target when building devices and can provide intuition for how devices may interact with the musculoskeletal system. The simulations are freely available online, allowing others to reproduce and extend our work.

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Section: Discussionsupporting

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Simulating ideal assistive devices to reduce the metabolic cost of walking with heavy loads

et al. 2017

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“…21 The spring-like properties of the DLS-AFO can also support ankle push-off by unleashing energy from the leaf in pre-swing that was loaded in the stance phase 1718 This energy takes over part of the ankle work during the gait cycle17 and lowers soleus activity,23 thereby reducing the need for inefficient compensation strategies by patients with weak calf muscles 24. In healthy individuals, an exoskeleton based on this mechanism of storing and unleashing energy reduced the walking EC by 7% 25…”

Section: Introductionmentioning

confidence: 99%

Precision orthotics: optimising ankle foot orthoses to improve gait in patients with neuromuscular diseases; protocol of the PROOF-AFO study, a prospective intervention study

et al. 2017

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IntroductionIn patients with neuromuscular disorders and subsequent calf muscle weakness, metabolic walking energy cost (EC) is nearly always increased, which may restrict walking activity in daily life. To reduce walking EC, a spring-like ankle-foot-orthosis (AFO) can be prescribed. However, the reduction in EC that can be obtained from these AFOs is stiffness dependent, and it is unknown which AFO stiffness would optimally support calf muscle weakness. The PROOF-AFO study aims to determine the effectiveness of stiffness-optimised AFOs on reducing walking EC, and improving gait biomechanics and walking speed in patients with calf muscle weakness, compared to standard, non-optimised AFOs. A second aim is to build a model to predict optimal AFO stiffness.Methods and analysisA prospective intervention study will be conducted. In total, 37 patients with calf muscle weakness who already use an AFO will be recruited. At study entry, participants will receive a new custom-made spring-like AFO of which the stiffness can be varied. For each patient, walking EC (primary outcome), gait biomechanics and walking speed (secondary outcomes) will be assessed for five stiffness configurations and the patient's own (standard) AFO. On the basis of walking EC and gait biomechanics outcomes, the optimal AFO stiffness will be determined. After wearing this optimal AFO for 3 months, walking EC, gait biomechanics and walking speed will be assessed again and compared to the standard AFO.Ethics and disseminationThe Medical Ethics Committee of the Academic Medical Centre in Amsterdam has approved the study protocol. The study is registered at the Dutch trial register (NTR 5170). The PROOF-AFO study is the first to compare stiffness-optimised AFOs with usual care AFOs in patients with calf muscle weakness. The results will also provide insight into factors that influence optimal AFO stiffness in these patients. The results are necessary for improving orthotic treatment and will be disseminated through international peer-reviewed journals and scientific conferences.

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“…However they do not replicate a completely physiologic gait. [17] The results of non-operative treatment compare poorly to those managed surgically, with only 55% satisfaction rate in the cases evaluated showing very slow improvement over the years. [16] Nevertheless, non-operative treatment with an AFO may be acceptable if the risks of surgery are deemed too high.…”

Section: Non-operative Treatmentmentioning

confidence: 99%

Management of chronic Achilles tendon ruptures—A review

2016

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Passive-dynamic ankle–foot orthosis replicates soleus but not gastrocnemius muscle function during stance in gait

Cited by 33 publications

References 47 publications

Simulating ideal assistive devices to reduce the metabolic cost of walking with heavy loads

Simulating ideal assistive devices to reduce the metabolic cost of walking with heavy loads

Precision orthotics: optimising ankle foot orthoses to improve gait in patients with neuromuscular diseases; protocol of the PROOF-AFO study, a prospective intervention study

Management of chronic Achilles tendon ruptures—A review

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