Customized passive-dynamic ankle–foot orthoses can improve walking economy and speed for many individuals post-stroke

 But you didn't ask or answer the most important question! 

Does this get them recovered enough to not need the orthosis? 

Horrendous research, I'd have you all fired! Survivors don't want compensation, they want RECOVERY!

Customized passive-dynamic ankle–foot orthoses can improve walking economy and speed for many individuals post-stroke

• Jacob T. Skigen,
• Corey A. Koller,
• Luke Nigro,
• Darcy S. Reisman,
• Zahra McKee,
• Shay R. Pinhey,
• Adrienne Henderson,
• Jason M. Wilken &
• Elisa S. Arch 

Journal of NeuroEngineering and Rehabilitation volume 21, Article number: 126 (2024) Cite this article

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Abstract

Background

Passive-dynamic ankle–foot orthoses (PD-AFOs) are often prescribed to address plantar flexor weakness during gait, which is commonly observed after stroke. However, limited evidence is available to inform the prescription guidelines of PD-AFO bending stiffness. This study assessed the extent to which PD-AFOs customized to match an individual’s level of plantar flexor weakness influence walking function, as compared to No AFO and their standard of care (SOC) AFO.

Methods

Mechanical cost-of-transport, self-selected walking speed, and key biomechanical variables were measured while individuals greater than six months post-stroke walked with No AFO, with their SOC AFO, and with a stiffness-customized PD-AFO. Outcomes were compared across these conditions using a repeated measures ANOVA or Friedman test (depending on normality) for group-level analysis and simulation modeling analysis for individual-level analysis.

Results

Twenty participants completed study activities. Mechanical cost-of-transport and self-selected walking speed improved with the stiffness-customized PD-AFOs compared to No AFO and SOC AFO. However, this did not result in a consistent improvement in other biomechanical variables toward typical values. In line with the heterogeneous nature of the post-stroke population, the response to the PD-AFO was highly variable.

Conclusions

Stiffness-customized PD-AFOs can improve the mechanical cost-of-transport and self-selected walking speed in many individuals post-stroke, as compared to No AFO and participants’ standard of care AFO. This work provides initial efficacy data for stiffness-customized PD-AFOs in individuals post-stroke and lays the foundation for future studies to enable consistently effective prescription of PD-AFOs for patients post-stroke in clinical practice.

Trial Registration: NCT04619043.

Background

Stroke is one of the leading causes of long-term disability, with more than 795,000 individuals in the United States experiencing a stroke each year [1]. Weakened plantar flexor muscles on the paretic limb is a common impairment after stroke [2, 3]. This weakness compromises the individual’s ability to control the lower leg's forward rotation during mid-to-terminal stance [2, 4, 5] and to generate forward propulsion during push-off [2, 5]. This impaired ankle function can result in kinematic deviations during stance including excessive ankle dorsiflexion [6] or persistent knee extension/hyperextension [5, 7]. Impaired ankle function also inhibits forward progression [5] by causing decreased gait speed [2, 5], shorter and asymmetric step lengths [8], and an increased metabolic cost of walking [9,10,11,12]. Poor walking economy has been linked to decreases in mobility and participation in daily activities [13, 14], which in turn have been shown to negatively impact both the physical [15,16,17] and mental [18] well-being of chronic stroke survivors.

Passive-dynamic ankle–foot orthoses (PD-AFOs) are a type of unpowered orthotic device that are gaining popularity for patients with neuromuscular impairments. PD-AFOs can be used to mitigate the negative effects on gait caused by weakened plantar flexors because they have a spring-like bending stiffness [19,20,21,22] that provides resistance to help control shank forward rotation during stance-phase dorsiflexion [23]. Additionally, as the PD-AFO deflects during the stance phase, it acts like a torsional spring by storing mechanical energy, which is returned during push-off to aid in forward progression [22]. In this way, PD-AFOs mimic many of the functions of healthy plantar flexor muscles. However, achieving optimal patient outcomes with PD-AFOs likely requires customizing the PD-AFO stiffness to provide personalized support for each individual [19, 24,25,26].

Despite the recognized need to match AFO characteristics to a patient’s needs [21], there is a lack of objective prescription guidelines to drive this matching for most, if not all, currently prescribed “standard-of-care” (SOC) AFOs. The lack of guidelines often results in an iterative trial-and-error approach to achieve a suitable PD-AFO strut stiffness, and results in substantial inconsistencies in the SOC AFOs that are currently provided. Such inconsistencies lead to varied and often limited patient outcomes for AFO users [24] likely due to a mismatch between orthosis characteristics and a patient’s needs [21].

Prior studies have begun to investigate the effects of PD-AFO stiffness on gait and propose methods for matching PD-AFO stiffness to patients’ needs, but there are still gaps in the knowledge. Pilot studies by our group examined the immediate effects of wearing a PD-AFO with the stiffness customized to make up for each individual’s level of plantar flexor weakness after stroke[19, 27]. The findings suggest customized PD-AFOs can increase the peak paretic plantar flexion moment, but results of other biomechanical and walking performance parameters were inconsistent [27]. Further, the prior studies did not examine more global outcome measures like cost-of-transport (COT) or orthosis satisfaction, and sample sizes were small. Other researchers have demonstrated that customizing PD-AFO stiffness can improve metabolic cost and gait speed compared to walking shod without an AFO and wearing an SOC AFO [24, 25, 28,29,30]. However, this research used a qualitative decision scheme to select one of five predetermined AFO stiffness values for each participant, based primarily on metabolic cost and gait speed outcomes, rather than utilizing an a priori prescription model. Further, this research did not include individuals with stroke. Multiple studies evaluating the effect of PD-AFO stiffness have been conducted in individuals post-limb salvage [31,32,33]; however given the many differences between the limb-salvage and post-stroke populations, results cannot be generalized across these populations. Thus, there is still insufficient evidence evaluating efficacy of a standardized, objective method for customizing PD-AFO stiffness to meet the individual needs of persons post-stroke.

The purpose of this study was to evaluate efficacy of stiffness-customized PD-AFOs in reducing total mechanical COT, improving self-selected walking speed (SSWS), improving gait biomechanics, and improving orthosis satisfaction compared to walking shod with no AFO and walking with their SOC AFO for individuals post-stroke. We hypothesized that walking with the PD-AFO would significantly decrease total mechanical COT, increase gait speed, improve gait biomechanics (towards typical), compared to walking with no AFO or their SOC AFO; and increase orthosis satisfaction compared to their SOC AFO. The findings of this study could provide evidence to inform the selection of PD-AFO stiffness and an important step toward establishing a standardized, objective prescription guideline for customizing PD-AFO stiffness to improve outcomes for individuals post-stroke.

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