The effect of ankle foot orthosis alignment on walking in individuals treated for traumatic lower extremity injuries

Ankle osteoarthritis: Toward new understanding and opportunities for prevention and intervention

The ankle infrequently develops primary osteoarthritis (OA), especially when compared to the hip and the knee. Ankle OA instead generally develops only after trauma. The consequences of end-stage ankle OA can nonetheless be extremely debilitating, with impairment comparable to that of end-stage kidney disease or congestive heart failure. Disconcertingly, evidence suggests that ankle OA can develop more often than is generally appreciated after even low-energy rotational ankle fractures and chronic instability associated with recurrent ankle sprains, albeit at a slower rate than after more severe trauma. The mechanisms whereby ankle OA develops after trauma are poorly understood, but mechanical factors are implicated. A better understanding of the prevalence and mechanical etiology of post-traumatic ankle OA can lead to better prevention and mitigation. New surgical and conservative interventions, including improved ligamentous repair strategies and custom carbon fiber bracing, hold promise for advancing treatment that may prevent residual ankle instability and the development of ankle OA. Studies are needed to fill in key knowledge gaps here related to etiology so that the interventions can target key factors. New technologies, including weight bearing CT and biplane fluoroscopy, offer fresh opportunities to better understand the relationships between trauma, ankle alignment, residual ankle instability, OA development, and foot/ankle function. This paper begins by reviewing the epidemiology of post-traumatic ankle OA, presents evidence suggesting that new treatment options might be successful at preventing ankle OA, and then highlights recent technical advances in understanding of the origins of ankle OA to identify directions for future research.

Immediate changes in stroke patients' gait following the application of lower extremity elastic strap binding technique

OBJECTIVE

To ascertain the immediate changes in stroke patients' temporal and spatial parameters of gait and the joint angles of stroke patients throughout the entire gait cycle following the application of lower extremity elastic strap binding technique.

METHODS

Twenty-nine stroke patients were invited as the study participants. The patient seated, flexed the hip and knee, utilized a 5 cm-wide elastic strap, positioning its midpoint beneath the affected foot and crossing it anterior to the ankle joint. Upon standing, the strap encircled the posterior aspect of the lower leg, proceeded around the back of the knee, and ascended the thigh on the affected side. Crossing anteriorly over the thigh, it then encircled the back of the waist before being secured in place. Using Qualisys motion capture system to collect kinematic data of the lower extremities during walking while wearing shoes only or strapping. A paired sample t-test was used to analyze the effects of the technique on gait spatiotemporal parameters and joint angles in stroke patients.

RESULTS

The patients' step length decreased (P = 0.024), and step width increased (P = 0.008) during the gait cycle after the strapping. In the gait cycle between 0% and 2%, 7%-77%, and 95%-100%, the hip flexion angle on the affected side was significantly larger after the strapping (P < 0.05). In the gait cycle between 0% to 69% and 94%-100%, the knee flexion angle on the affected side was significantly larger after the strapping (P < 0.05). In the gait cycle between 0% to 57% and 67%-100%, the ankle dorsiflexion angle on the affected side was significantly smaller after the strapping (P < 0.05), and in the gait cycle between 0% to 35% and 68%-100%, the ankle inversion angle on the affected side was significantly smaller after the strapping (P < 0.05).

CONCLUSION

The lower extremity elastic strap binding technique can decrease the hip flexion and knee flexion limitations in stroke patients during walking, and reduce the ankle plantar flexion and ankle inversion angle of stroke patients. The lower extremity elastic strap binding technique enabled stroke patients to adopt a more stable gait pattern.

The effect of carbon fiber custom dynamic orthosis use and design on center of pressure progression and perceived smoothness in individuals with lower limb trauma

BACKGROUND

Carbon-fiber custom dynamic orthoses are used to improve gait and limb function following lower limb trauma in specialty centers. However, the effects of commercially available orthoses on center of pressure progression and patient perception of orthosis smoothness during walking are poorly understood.

METHODS

In total, 16 participants with a unilateral lower extremity traumatic injury underwent gait analysis when walking without an orthosis, and while wearing monolithic and modular devices, in a randomized order. Device alignment, stiffness, participant rating of perceived device smoothness, center of pressure velocity, and ankle zero moment crossing were assessed.

FINDINGS

The modular device was approximately twice as stiff as the monolithic device. Alignment, smoothness ratings, peak magnitude of center of pressure velocity, and zero moment crossing were not different between study devices. The time to peak center of pressure velocity occurred significantly later for the modular device compared to the monolithic and no orthosis conditions, with large effect sizes observed.

INTERPRETATION

Commercially available orthoses commonly used to treat limb trauma affect the timing of center of pressure progression relative to walking without an orthosis. Despite multiple design differences, monolithic and modular orthoses included in this study did not differ with respect to other measures of center of pressure progression. Perceived smoothness ratings were approximately 40% greater with the study orthoses as compared to previous studies in specialty centers, which may be due to a more gradual center of pressure progression, as indicted by lower peak magnitude of center of pressure velocity with both study orthoses.

Interacting effects of AFO stiffness, neutral angle and footplate stiffness on gait in case of plantarflexor weakness: A predictive simulation study

To maximize effects of dorsal leaf ankle foot orthoses (AFOs) on gait in people with bilateral plantarflexor weakness, the AFO properties should be matched to the individual. However, how AFO properties interact regarding their effect on gait function is unknown. We studied the interaction of AFO bending stiffness with neutral angle and footplate stiffness on the effect of bending stiffness on walking energy cost, gait kinematics and kinetics in people with plantarflexor weakness by employing predictive simulations. Our simulation framework consisted of a planar 11 degrees of freedom model, containing 11 muscles activated by a reflex-based neuromuscular controller. The controller was optimized by a comprehensive cost function, predominantly minimizing walking energy cost. The AFO bending and footplate stiffness were modelled as torsional springs around the ankle and metatarsal joint. The neutral angle of the AFO was defined as the angle in the sagittal plane at which the moment of the ankle torsional spring was zero. Simulations without AFO and with AFO for 9 bending stiffnesses (0-14 Nm/degree), 3 neutral angles (0-3-6 degrees dorsiflexion) and 3 footplate stiffnesses (0-0.5-2.0 Nm/degree) were performed. When changing neutral angle towards dorsiflexion, a higher AFO bending stiffness minimized energy cost of walking and normalized joint kinematics and kinetics. Footplate stiffness mainly affected MTP joint kinematics and kinetics, while no systematic and only marginal effects on energy cost were found. In conclusion, the interaction of the AFO bending stiffness and neutral angle in bilateral plantarflexor weakness, suggests that these should both be considered together when matching AFO properties to the individual patient.

Novel testing system to determine shoe mechanical properties

BACKGROUND

Shoes play an important role in ankle foot orthosis (AFO) function and alignment. Despite this, shoe mechanical testing systems are rarely colocated with gait analysis systems, limiting their availability and use during AFO-related studies.

OBJECTIVE

The purpose of this study was to evaluate a novel mechanical testing system used to measure shoe heel stiffness and change in height with loading using equipment available in most gait analysis laboratories. The novel testing system will allow for shoe assessment during AFO studies at little additional cost.

STUDY DESIGN

Shoes were tested to determine initial stiffness, terminal stiffness, and total stiffness, and whether these measures changed with repeated compressions (early vs. late).

TECHNIQUE

The novel testing system consists of a baseplate for counterweights, uprights that support a low-friction hinge, and a lever arm with a heel-shaped indenter to apply force to the shoe. Minimal detectable change values were calculated using the standard error of measurement. Intraclass correlation coefficients were calculated in SPSS using a (2, k) model.

RESULTS

No significant differences in mean values, or interactions, were observed between rounds of testing and early and late compressions (P > .05). Intraclass correlation coefficient values were greater than 0.98, and minimal detectable change values were less than 20% of the average for each measure.

CONCLUSIONS

The novel mechanical testing system, combined with pre-existing gait analysis equipment, can be used to reliably assess shoe stiffness and change in height.

Quantifying alignment bias during the fabrication and fitting of ankle-foot orthoses: A single center study

BACKGROUND

The sagittal plane alignment of ankle-foot orthoses (AFO) and AFO footwear combinations (AFO-FC) has been shown to influence gait outcomes. As such, clinicians often target a particular alignment during the fabricating and fitting of an AFO to maximize outcomes.

RESEARCH QUESTION

How does the alignment of an AFO change during the fabrication and fitting process with respect to the intended, benchmark sagittal plane alignment identified by the consulting orthotist?

STUDY DESIGN

Prospective METHODS: The assessment of AFO alignment was performed using a convenience sample of 125 custom molded AFOs from 68 individuals fabricated at our center (57 bilateral AFOs, 11 unilateral AFOs). The alignment of each AFO was measured at 5 distinct steps during the fabrication and fitting process using a recently validated method to measure AFO neutral angle using differential inclinometers.

RESULTS

Prior to fabrication, the intended, benchmark alignment set by the consulting orthotist was 90 degrees for 92% of AFOs, was between 1 and 7 degrees of dorsiflexion for 7% of AFOs and was 5 degrees of plantarflexion for 1% of AFOs. Repeated measures ANOVA showed that AFO alignment changed between all fabrication and fitting steps. Overall, paired t-tests confirmed that AFO alignment was consistently 2-5 degrees more dorsiflexed than the benchmark alignment. Prior to fitting shoes, 55% of fabricated AFOs measured more than 2 degrees from the benchmark alignment. After fitting shoes, nearly 87% of AFO-FCs were more than 2 degrees from the benchmark alignment.

SIGNIFICANCE

The finding of systematic dorsiflexion bias and changes in AFO alignment throughout the fabrication and fitting process indicates the need to improve AFO fabrication precision. The neutral angle measurement methodology - using differential inclinometers - provides a means to improve this precision by enabling orthotists to precisely quantify and make appropriate adjustments to AFO alignment throughout the entire fabrication and fitting process.

Alternative methods for measuring ankle-foot orthosis alignment in clinical care

BACKGROUND

Changes in gait due to an ankle foot orthosis (AFO) have been shown to be impacted by the sagittal plane alignment of the AFO, but there is variability in practice and lack of consensus as to how this alignment should be measured. The neutral angle is a measure of AFO alignment that has the potential to be used by various specialties that prescribe, provide, and analyze AFOs. Currently, a lack of validated measurement methods prevents the neutral angle from being used in various clinical settings. Two experimental neutral angle measurement methods are proposed to address this shortcoming: a portable low-cost method for use during AFO fabrication and fitting, and a laboratory-based method for use during dynamic three-dimensional gait analysis (3DGA).

RESEARCH QUESTION

What is the concurrent validity of the two experimental neutral angle measurement methods against the gold standard?

METHODS

The gold standard neutral angle measurement (NA_GOLD) was prospectively collected during a static 3DGA trial for 19 pediatric AFOs from 10 individuals. While NA_GOLD was being collected, the neutral angle was simultaneously measured using digital differential inclinometers (NA_INCL). Within the same 3DGA session, the neutral angle was also measured during the swing phase of gait (NA_SWING). The NA_INCL and NA_SWING measurements were compared to NA_GOLD using repeated measures ANOVA, ICC, and bootstrapped errors-in-variables regressions.

RESULTS

Repeated measures ANOVA indicated no differences between measurement methods (p = 0.43) and ICC analysis indicated good absolute agreement (ICC(A-1) = 0.85). Mean absolute deviations between the NA_INCL and NA_SWING with NA_GOLD measurements were 2.4 ° and 1.9 °, with standard deviations of 2.9 ° and 2.7 °, respectively. Maximum observed differences were less than 7 °. The NA_INCL and NA_SWING methods explained 74 % and 81 % of the variance in NA_GOLD, respectively.

SIGNIFICANCE

The concurrent validity of two new neutral angle measurement methods provides alternative means to assess AFO alignment in the clinic.

The effect of custom carbon ankle-foot orthosis alignment on roll-over shape and center of pressure velocity

BACKGROUND

Maintaining an optimal rolling of the foot over the ground is thought to increase the stability and efficiency of pathologic gait. Ankle-foot orthoses are often prescribed to improve gait mechanics in individuals with lower extremity injuries; however, their design may compromise how the foot rolls over the ground.

OBJECTIVES

The aim of this study was to investigate the effects of the sagittal plane ankle-foot orthosis alignment on roll-over shape and center of pressure velocity in individuals with lower limb reconstructions.

STUDY DESIGN

Randomized cross-over study with a control group comparison.

METHODS

In total, 12 individuals with lower limb reconstruction who used a custom carbon ankle-foot orthosis and 12 uninjured controls underwent gait analysis. Ankle-foot orthosis users were tested in their clinically-provided ankle-foot orthosis alignment, with an alignment that was 3° more plantarflexed, and with an alignment that was 3° more dorsiflexed. Components of roll-over shape and center of pressure velocity were calculated from heel strike on the ankle-foot orthosis limb to contralateral heel strike.

RESULTS

Roll-over shape radius was not affected by 3° changes to alignment and was not significantly different from controls. Aligning the ankle-foot orthosis in more dorsiflexion than clinically provided resulted in a smaller peak center of pressure velocity that occurred later in stance.

CONCLUSION

Individuals using custom carbon ankle-foot orthoses can accommodate 3° alterations in the dorsiflexion or plantarflexion alignment.

Ankle-foot orthosis alignment affects running mechanics in individuals with lower limb injuries

BACKGROUND

Individuals with severe lower extremity injuries often require ankle-foot orthoses to return to normal activities. Ankle-foot orthoses alignment is a key consideration during the clinical fitting process and may be particularly important during dynamic activities such as running.

OBJECTIVE

To investigate how 3° changes in sagittal plane ankle-foot orthoses alignment affect running mechanics.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve participants with unilateral lower limb injury ran overground and lower extremity running mechanics were assessed. Participants wore their passive-dynamic ankle-foot orthoses in three alignments: clinically fit neutral, 3° plantarflexed from clinically fit neutral, and 3° dorsiflexed from clinically fit neutral.

RESULTS

The 3° changes in sagittal alignment significantly influenced ankle mechanics during running. The plantarflexed alignment significantly decreased the peak ankle plantarflexor moment, peak knee extensor moment, and peak ankle and knee power absorption and generation compared to more dorsiflexed alignments. Alignment also altered footstrike angle, with dorsiflexed alignments associated with a more dorsiflexed footstrike pattern and plantarflexed alignments toward a more plantarflexed footstrike pattern. However, alignment did not influence loading rate.

CONCLUSION

Small changes in ankle-foot orthoses alignment significantly altered running mechanics, including footstrike angle, and knee extensor moments. Understanding how ankle-foot orthoses design parameters affect running mechanics may aid the development of evidence-based prescription guidelines and improve function for ankle-foot orthoses users who perform high-impact activities.

CLINICAL RELEVANCE

Understanding how ankle-foot orthoses alignment impacts biomechanics should be a consideration when fitting passive-dynamic devices for higher impact activities, such as running. Individual running styles, including footstrike patterns, may be affected by small changes in alignment.