The effect of rotational speed on ankle-foot orthosis properties

Totah, Deema; Barton, Kira; Gates, Deanna H.

doi:10.1016/j.jbiomech.2021.110483

Cited by 4 publications

(1 citation statement)

References 16 publications

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“…With the other four custom fixtures, three considerations were incorporated for consistency. First, AFO stiffnesses may be sensitive to rotational speed [ 22 – 24 ], thus, all test fixtures were operated at relatively slow speeds except the BRUCE which is manually controlled. Second, the heights of the rotation axes were either mechanically or numerically adjusted to be similar (75–81 mm), as rotation axis may impact stiffness [ 10 , 25 ].…”

Section: Discussionmentioning

confidence: 99%

Comparison of five different methodologies for evaluating ankle–foot orthosis stiffness

Shuman

Totah

Gates

et al. 2023

J NeuroEngineering Rehabil

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Background The mechanical properties of an ankle–foot orthosis (AFO) play an important role in the gait mechanics of the end user. However, testing methodologies for evaluating these mechanical properties are not standardized. The purpose of this study was to compare five different evaluation frameworks to assess AFO stiffness. Method The same 13 carbon composite AFOs were tested with five different methods. Four previously reported custom test fixtures (the BRUCE, KST, SMApp, and EMPIRE) rotated an AFO into dorsiflexion about a defined axis in the sagittal plane. The fifth method involved quasi-static deflection of AFOs into dorsiflexion by hanging weights (HW) from the footplate. AFO rotational stiffness was calculated as the linear fit of the AFO resistive torque and angular deflection. Differences between methods were assessed using descriptive statistics and a repeated measures Friedman with post-hoc Bonferroni–Holm adjusted Wilcoxon signed-rank tests. Results There were significant differences in measured AFO stiffnesses between test methods. Specifically, the BRUCE and HW methods measured lower stiffness than both the EMPIRE and the KST. Stiffnesses measured by the SMApp were not significantly different than any test method. Stiffnesses were lowest in the HW method, where motion was not constrained to a single plane. The median difference in absolute AFO stiffness across methods was 1.03 Nm/deg with a range of [0.40 to 2.35] Nm/deg. The median relative percent difference, measured as the range of measured stiffness from the five methods over the average measured stiffness was 62% [range 13% to 156%]. When the HW method was excluded, the four previously reported test fixtures produced a median difference in absolute AFO stiffness of 0.52 [range 0.38 to 2.17] Nm/deg with a relative percent difference between the methods of 27% [range 13% to 89%]. Conclusions This study demonstrates the importance of developing mechanical testing standards, similar to those that exist for lower limb prosthetics. Lacking standardization, differences in methodology can result in large differences in measured stiffness, particularly for different constraints on motion. Non-uniform measurement practices may limit the clinical utility of AFO stiffness as a metric in AFO prescription and future research.

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Section: Discussionmentioning

confidence: 99%

Comparison of five different methodologies for evaluating ankle–foot orthosis stiffness

Shuman

Totah

Gates

et al. 2023

J NeuroEngineering Rehabil

Self Cite

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Design and Experimental Evaluation of Passive Ankle-Foot Orthoses Hinges Using Superelastic NiTi Shape Memory Alloy

Menna,

Genikomsou,

Green

et al. 2024

Biomedical Materials & Devices

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Effect of Ankle-Foot Orthosis Stiffness on Muscle Force During Gait Through Mechanical Testing and Gait Simulation

et al. 2021

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Mechanical testing and gait measurement for ankle-foot orthosis (AFO) are crucial for determining the AFO stiffness magnitude in an individual. However, information on the effect of the stiffness magnitude on the muscle force during gait is limited. This study aimed to investigate the relationship between the AFO stiffness and ankle muscle force during gait. The AFO stiffness was mechanically tested using a sixaxis robot arm. The stiffness magnitude was adjusted using different spring constants. Five stiffness conditions were set for each plantarflexion resistive (PFR) and dorsiflexion resistive (DFR) function. The effect of the PFR and DFR on the ankle muscle force during gait were determined using musculoskeletal and AFO models. Tibialis anterior (TA) and triceps surae (TS) muscle forces were calculated through gait simulation. The angle-moment relationships display hysteresis loops for each condition. One of the PFR and DFR conditions differed significantly from the others (for all, p < 0.05). In order of lower stiffness, the each PFR contribution ratio to the peak TA muscle force normalized in the no-stiffness condition was 8.4%, 10.8%, 11.3%, 13.5%, and 15.3%; while the each DFR contribution ratio to the peak TS muscle force was 16.2%, 20.9%, 25.3%, 29.8%, and 30.5%, respectively. Through mechanical testing as well as gait simulation, it was demonstrated that the magnitude of the AFO stiffness decreased the required ankle muscle force during gait. This study can contribute to more effective gait rehabilitation using AFO as well as AFO fabrication with customized stiffness for individual gait function.

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The effect of rotational speed on ankle-foot orthosis properties

Cited by 4 publications

References 16 publications

Comparison of five different methodologies for evaluating ankle–foot orthosis stiffness

Comparison of five different methodologies for evaluating ankle–foot orthosis stiffness

Design and Experimental Evaluation of Passive Ankle-Foot Orthoses Hinges Using Superelastic NiTi Shape Memory Alloy

Effect of Ankle-Foot Orthosis Stiffness on Muscle Force During Gait Through Mechanical Testing and Gait Simulation

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