Gait patterns in association with underlying impairments in polio survivors with calf muscle weakness

Physical strain of walking in people with neuromuscular diseases is high and relates to step activity in daily life

OBJECTIVE

To determine the physical strain of walking and assess its relationship with daily steps and intensity of daily activity in people with neuromuscular diseases.

DESIGN

Cross-sectional study.

SUBJECTS/PATIENTS

Sixty-one adults with neuromuscular diseases.

METHODS

Physical strain of walking, defined as oxygen consumption during comfortable walking relative to peak oxygen uptake. Daily step count and daily time spent in moderate and vigorous physical activity were assessed using accelerometry and heart rate measurements, respectively. Regression analyses assessed the relationships between log daily step count and log daily time spent in moderate and vigorous physical activity, and physical strain of walking.

RESULTS

The mean (standard deviation) physical strain of walking was 73 (20)% Log daily step count and physical strain were negatively associated (β = -0.47). No association was found with log daily time spent in moderate and vigorous physical activity.

CONCLUSIONS

The highly increased physical strain of comfortable walking indicates that walking is very demanding for people with neuromuscular diseases and is associated with a reduction in daily step activity. The absence of a relationship between intensity of activities and physical strain indicates that, despite a reduction in daily step activity, strenuous daily activities may still be performed.

Minimization of metabolic cost of transport predicts changes in gait mechanics over a range of ankle-foot orthosis stiffnesses in individuals with bilateral plantar flexor weakness

Neuromuscular disorders often lead to ankle plantar flexor muscle weakness, which impairs ankle push-off power and forward propulsion during gait. To improve walking speed and reduce metabolic cost of transport (mCoT), patients with plantar flexor weakness are provided dorsal-leaf spring ankle-foot orthoses (AFOs). It is widely believed that mCoT during gait depends on the AFO stiffness and an optimal AFO stiffness that minimizes mCoT exists. The biomechanics behind why and how an optimal stiffness exists and benefits individuals with plantar flexor weakness are not well understood. We hypothesized that the AFO would reduce the required support moment and, hence, metabolic cost contributions of the ankle plantar flexor and knee extensor muscles during stance, and reduce hip flexor metabolic cost to initiate swing. To test these hypotheses, we generated neuromusculoskeletal simulations to represent gait of an individual with bilateral plantar flexor weakness wearing an AFO with varying stiffness. Predictions were based on the objective of minimizing mCoT, loading rates at impact and head accelerations at each stiffness level, and the motor patterns were determined via dynamic optimization. The predictive gait simulation results were compared to experimental data from subjects with bilateral plantar flexor weakness walking with varying AFO stiffness. Our simulations demonstrated that reductions in mCoT with increasing stiffness were attributed to reductions in quadriceps metabolic cost during midstance. Increases in mCoT above optimum stiffness were attributed to the increasing metabolic cost of both hip flexor and hamstrings muscles. The insights gained from our predictive gait simulations could inform clinicians on the prescription of personalized AFOs. With further model individualization, simulations based on mCoT minimization may sufficiently predict adaptations to an AFO in individuals with plantar flexor weakness.

Gait stability and the relationship with energy cost of walking in polio survivors with unilateral plantarflexor weakness

BACKGROUND

Polio survivors often exhibit plantarflexor weakness, which impairs gait stability, and increases energy cost of walking. Quantifying gait stability could provide insights in the control mechanisms polio survivors use to maintain gait stability and in whether impaired gait stability is related to the increased energy cost of walking.

RESEARCH QUESTION

Is gait stability impaired in polio survivors with plantarflexor weakness compared to able-bodied individuals, and does gait stability relate to energy cost of walking?

METHODS

We retrospectively analyzed barefoot biomechanical gait data of 31 polio survivors with unilateral plantarflexor weakness and of 24 able-bodied individuals. We estimated gait stability by calculating variability (SD) of step width, step length, double support time, and stance time, and by the mean and variability (SD) of the mediolateral and anteroposterior margin of stability (MoSML and MoSAP). In addition, energy cost of walking (polio survivors only) at comfortable speed was analyzed.

RESULTS

Comfortable speed was 31% lower in polio survivors compared to able-bodied individuals (p < 0.001). Corrected for speed differences, step width variability was significantly larger in polio survivors (+41%), double support time variability was significantly smaller (-27%), MoSML (affected leg) was significantly larger (+80%), and MoSAP was significantly smaller (affected leg:-17% and non-affected leg:-15%). Step width and step length variability (affected leg) were positively correlated with energy cost of walking (r = 0.502 and r = 0.552). MoSAP (non-affected leg) was negatively correlated with energy cost of walking (r = -0.530).

SIGNIFICANCE

Polio survivors with unilateral plantarflexor weakness demonstrated an impaired gait stability. Increased step width and step length variability and lower MoSAP could be factors related to the elevated energy cost of walking in polio survivors. These findings increase our understanding of stability problems due to plantarflexor weakness, which could be used for the improvement of (orthotic) interventions to enhance gait stability and reduce energy cost in polio survivors.

The interaction between muscle pathophysiology, body mass, walking speed and ankle foot orthosis stiffness on walking energy cost: a predictive simulation study

BACKGROUND

The stiffness of a dorsal leaf AFO that minimizes walking energy cost in people with plantarflexor weakness varies between individuals. Using predictive simulations, we studied the effects of plantarflexor weakness, passive plantarflexor stiffness, body mass, and walking speed on the optimal AFO stiffness for energy cost reduction.

METHODS

We employed a planar, nine degrees-of-freedom musculoskeletal model, in which for validation maximal strength of the plantar flexors was reduced by 80%. Walking simulations, driven by minimizing a comprehensive cost function of which energy cost was the main contributor, were generated using a reflex-based controller. Simulations of walking without and with an AFO with stiffnesses between 0.9 and 8.7 Nm/degree were generated. After validation against experimental data of 11 people with plantarflexor weakness using the Root-mean-square error (RMSE), we systematically changed plantarflexor weakness (range 40-90% weakness), passive plantarflexor stiffness (range: 20-200% of normal), body mass (+ 30%) and walking speed (range: 0.8-1.2 m/s) in our baseline model to evaluate their effect on the optimal AFO stiffness for energy cost minimization.

RESULTS

Our simulations had a RMSE < 2 for all lower limb joint kinetics and kinematics except the knee and hip power for walking without AFO. When systematically varying model parameters, more severe plantarflexor weakness, lower passive plantarflexor stiffness, higher body mass and walking speed increased the optimal AFO stiffness for energy cost minimization, with the largest effects for severity of plantarflexor weakness.

CONCLUSIONS

Our forward simulations demonstrate that in individuals with bilateral plantarflexor the necessary AFO stiffness for walking energy cost minimization is largely affected by severity of plantarflexor weakness, while variation in walking speed, passive muscle stiffness and body mass influence the optimal stiffness to a lesser extent. That gait deviations without AFO are overestimated may have exaggerated the required support of the AFO to minimize walking energy cost. Future research should focus on improving predictive simulations in order to implement personalized predictions in usual care. Trial Registration Nederlands Trial Register 5170. Registration date: May 7th 2015.  http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170.

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.

Semi-supervised clustering of quaternion time series: Application to gait analysis in multiple sclerosis using motion sensor data

Recent approaches in gait analysis involve the use of wearable motion sensors to extract spatio-temporal parameters that characterize multiple aspects of an individual's gait. In particular, the medical community could largely benefit from this type of devices as they could provide the clinicians with a valuable tool for assessing gait impairment. Motion sensor data are however complex and there is an urgent unmet need to develop sound statistical methods for analyzing such data and extracting clinically relevant information. In this article, we measure gait by following the hip rotation over time and the resulting statistical unit is a time series of unit quaternions. We explore the possibility to form groups of patients with similar walking impairment by taking into account their walking data and their global decease severity with semi-supervised clustering. We generalize a compromise-based method named hclustcompro to unit quaternion time series by combining it with the proper dissimilarity quaternion dynamic time warping. We apply this method on patients diagnosed with multiple sclerosis to form groups of patients with similar walking deficiencies while accounting for the clinical assessment of their overall disability. We also compare the compromise-based clustering approach with the method mergeTrees that falls into a sub-class of ensemble clustering named collaborative clustering. The results provide a first proof of both the interest of using wearable motion sensors for assessing gait impairment and the use of prior knowledge to guide the clustering process. It also demonstrates that compromise-based clustering is a more appropriate approach in this context.

A Systematic Review of Non-Pharmacological Interventions to Improve Gait Asymmetries in Neurological Populations

Gait asymmetries are commonly observed in neurological populations and linked to decreased gait velocity, balance decrements, increased fall risk, and heightened metabolic cost. Interventions designed to improve gait asymmetries have varying methods and results. The purpose of this systematic review was to investigate non-pharmacological interventions to improve gait asymmetries in neurological populations. Keyword searches were conducted using PubMed, CINAHL, and Academic Search Complete. The search yielded 14 studies for inclusion. Gait was assessed using 3D motion capture systems (n = 7), pressure-sensitive mats (e.g., GAITRite; n = 5), and positional sensors (n = 2). The gait variables most commonly analyzed for asymmetry were step length (n = 11), stance time (n = 9), and swing time (n = 5). Interventions to improve gait asymmetries predominantly used gait training techniques via a split-belt treadmill (n = 6), followed by insoles/orthoses (n = 3). The literature suggests that a wide range of methods can be used to improve spatiotemporal asymmetries. However, future research should further examine kinematic and kinetic gait asymmetries. Additionally, researchers should explore the necessary frequency and duration of various intervention strategies to achieve the greatest improvement in gait asymmetries, and to determine the best symmetry equation for quantifying gait asymmetries.

The effects of footplate stiffness on push-off power when walking with posterior leaf spring ankle-foot orthoses

BACKGROUND

Many studies on ankle-foot orthoses investigated the optimal stiffness around the ankle, while the effect of footplate stiffness has been largely ignored. This study investigated the effects of ankle-foot orthosis footplate stiffness on ankle-foot push-off power during walking in able-bodied persons.

METHODS

Twelve healthy participants walked at a fixed speed (1.25 m·s^-1) on an instrumented treadmill in four conditions: shod and with a posterior leaf-spring orthosis with a flexible, stiff or rigid footplate. For each trial, ankle kinematics and kinetics were averaged over one-minute walking. Separate contributions of the ankle joint complex and distal hindfoot to total ankle-foot power and work were calculated using a deformable foot model.

FINDINGS

Peak ankle joint power was significantly higher with the rigid footplate compared to the flexible and stiff footplate and not different from shod walking. The stiff footplate increased peak hindfoot power compared to the flexible and rigid footplate and shod walking. Total ankle-foot power showed a significant increase with increasing footplate stiffness, where walking with the rigid footplate was comparable to shod walking. Similar effects were found for positive mechanical work.

INTERPRETATION

A rigid footplate increases the lever of the foot, resulting in an increased ankle moment and energy storage and release of the orthosis' posterior leaf-spring as reflected in higher ankle joint power. This effect dominates the power generation of the foot, which was highest with the intermediate footplate stiffness. Future studies should focus on how tuning footplate stiffness could contribute to optimizing ankle-foot orthosis efficacy in clinical populations.

Individual stiffness optimization of dorsal leaf spring ankle-foot orthoses in people with calf muscle weakness is superior to standard bodyweight-based recommendations

BACKGROUND

In people with calf muscle weakness, the stiffness of dorsal leaf spring ankle-foot orthoses (DLS-AFO) needs to be individualized to maximize its effect on walking. Orthotic suppliers may recommend a certain stiffness based on body weight and activity level. However, it is unknown whether these recommendations are sufficient to yield the optimal stiffness for the individual. Therefore, we assessed whether the stiffness following the supplier's recommendation of the Carbon Ankle7 (CA7) dorsal leaf matched the experimentally optimized AFO stiffness.

METHODS

Thirty-four persons with calf muscle weakness were included and provided a new DLS-AFO of which the stiffness could be varied by changing the CA7® (Ottobock, Duderstadt, Germany) dorsal leaf. For five different stiffness levels, including the supplier recommended stiffness, gait biomechanics, walking energy cost and speed were assessed. Based on these measures, the individual experimentally optimal AFO stiffness was selected.

RESULTS

In only 8 of 34 (23%) participants, the supplier recommended stiffness matched the experimentally optimized AFO stiffness, the latter being on average 1.2 ± 1.3 Nm/degree more flexible. The DLS-AFO with an experimentally optimized stiffness resulted in a significantly lower walking energy cost (- 0.21 ± 0.26 J/kg/m, p < 0.001) and a higher speed (+ 0.02 m/s, p = 0.003). Additionally, a larger ankle range of motion (+ 1.3 ± 0.3 degrees, p < 0.001) and higher ankle power (+ 0.16 ± 0.04 W/kg, p < 0.001) were found with the experimentally optimized stiffness compared to the supplier recommended stiffness.

CONCLUSIONS

In people with calf muscle weakness, current supplier's recommendations for the CA7 stiffness level result in the provision of DLS-AFOs that are too stiff and only achieve 80% of the reduction in energy cost achieved with an individual optimized stiffness. It is recommended to experimentally optimize the CA7 stiffness in people with calf muscle weakness in order to maximize treatment outcomes. Trial registration Nederlands Trial Register 5170. Registration date: May 7th 2015. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170 .

Polio survivors have poorer walking adaptability than healthy individuals

BACKGROUND

Falling is a major health problem in polio survivors, often occurring as a result of tripping, slipping or misplaced steps. Therefore, reduced walking adaptability possibly plays an important role.

RESEARCH QUESTION

Does walking adaptability, assessed on an interactive treadmill, differ between polio survivors and healthy individuals?

METHODS

In this cross-sectional study, 48 polio survivors with at least one reported fall in the past year and/or fear of falling and 25 healthy individuals of similar age walked at self-selected comfortable fixed speed on an instrumented treadmill. Walking adaptability was measured as i) target-stepping accuracy (determined as variable error [VE] in mm independent of speed) in three conditions; 0 %, 20 % and 30 % variation in step length and width, and ii) anticipatory and reactive obstacle avoidance (ObA and ObR, in percentage successfully avoided). All trials were checked for valid step detection.

RESULTS

46 polio survivors (mean ± SD age: 63.2 ± 8.7 years) and 25 healthy individuals (64.3 ± 6.6 years, p = 0.585) showed valid step detection. Compared to healthy individuals (mean±SE VE: 30.6±1.2 mm), polio survivors stepped less accurately onto targets (36.4±0.9 mm, p = 0.001), especially with their least-affected leg. Polio survivors avoided fewer obstacles successfully (mean±SE ObA: 83±3 %, ObR: 59±4 %) than healthy individuals (100±0.3 %, p < 0.001 and 94±3 %, p < 0.001, respectively), with a stronger decline in success rates from anticipatory to reactive obstacle avoidance for polio survivors (p < 0.001).

SIGNIFICANCE

Polio survivors reporting falls and/or fear of falling had a demonstrably reduced walking adaptability, especially so for reactive obstacle avoidance, which requires step adjustments under high time-pressure demands. Future research should study the merit of walking-adaptability assessment to currently used clinical methods of fall-risk assessment within this population.

Validation of forward simulations to predict the effects of bilateral plantarflexor weakness on gait

BACKGROUND

Bilateral plantarflexor muscle weakness is a common impairment in many neuromuscular diseases. However, the way in which severity of plantarflexor weakness affects gait in terms of walking energy cost and speed is not fully understood. Predictive simulations are an attractive alternative to human experiments as simulations allow systematic alterations in muscle weakness. However, simulations of pathological gait have not yet been validated against experimental data, limiting their applicability.

RESEARCH QUESTION

Our first aim was to validate a predictive simulation framework for walking with bilateral plantarflexor weakness by comparing predicted gait against experimental gait data of patients with bilateral plantarflexor weakness. Secondly, we aimed to evaluate how incremental levels of bilateral plantarflexor weakness affect gait.

METHODS

We used a planar musculoskeletal model with 9 degrees of freedom and 9 Hill-type muscle-tendon units per leg. A state-dependent reflex-based controller optimized for a function combining energy cost, muscle activation squared and head acceleration was used to simulate gait. For validation, strength of the plantarflexors was reduced by 80 % and simulated gait compared with experimental data of 16 subjects with bilateral plantarflexor weakness. Subsequently, strength of the plantarflexors was reduced stepwise to evaluate its effect on gait kinematics and kinetics, walking energy cost and speed.

RESULTS

Simulations with 80 % weakness matched well with experimental hip and ankle kinematics and kinetics (R > 0.64), but less for knee kinetics (R < 0.55). With incremental strength reduction, especially beyond a reduction of 60 %, the maximal ankle moment and power decreased. Walking energy cost and speed showed a strong quadratic relation (R²>0.82) with plantarflexor strength.

SIGNIFICANCE

Our simulation framework predicted most gait changes due to bilateral plantarflexor weakness, and indicates that pathological gait features emerge especially when bilateral plantarflexor weakness exceeds 60 %. Our framework may support future research into the effect of pathologies or assistive devices on gait.

Increased cerebral integrity metrics in poliomyelitis survivors: putative adaptation to longstanding lower motor neuron degeneration

BACKGROUND

Post-polio syndrome (PPS) has been traditionally considered a slowly progressive condition that affects poliomyelitis survivors decades after their initial infection. Cerebral changes in poliomyelitis survivors are poorly characterised and the few existing studies are strikingly conflicting.

OBJECTIVE

The overarching aim of this study is the comprehensive characterisation of cerebral grey and white matter alterations in poliomyelitis survivors with reference to healthy- and disease-controls using quantitative imaging metrics.

METHODS

Thirty-six poliomyelitis survivors, 88 patients with ALS and 117 healthy individuals were recruited in a prospective, single-centre neuroimaging study using uniform MRI acquisition parameters. All participants underwent standardised clinical assessments, T1-weighted structural and diffusion tensor imaging. Whole-brain and region-of-interest morphometric analyses were undertaken to evaluate patterns of grey matter changes. Tract-based spatial statistics were performed to evaluate diffusivity alterations in a study-specific whiter matter skeleton.

RESULTS

In contrast to healthy controls, poliomyelitis survivors exhibited increased grey matter partial volumes in the brainstem, cerebellum and occipital lobe, accompanied by increased FA in the corticospinal tracts, cerebellum, bilateral mesial temporal lobes and inferior frontal tracts. Polio survivors exhibited increased integrity metrics in the same anatomical regions where ALS patients showed degenerative changes.

CONCLUSIONS

Our findings indicate considerable cortical and white matter reorganisation in poliomyelitis survivors which may be interpreted as compensatory, adaptive change in response to severe lower motor neuron injury in infancy.

Adaptive predictive systems applied to gait analysis: A systematic review

BACKGROUND

Due to the high susceptivity of the walking pattern to be affected by several disorders, accurate analysis methods are necessary. Given the complexity and relevance of such assessment, the utilization of methods to facilitate it plays a significant role, provided that they do not compromise the outcomes.

RESEARCH QUESTIONS

This paper aimed at identifying the standards for the application of adaptive predictive systems to gait analysis, given the extensive research on this field. Furthermore, we also intended to check whether such methods can effectively support clinicians in determining the number of physiotherapy sessions necessary to recover gait-related dysfunctions.

METHODS

Through a screening process of scientific databases, we considered studies encompassed from 1968 to April 2019. Within these 50 years, we found 24 papers that met our inclusion criteria. They were analyzed according to their data acquisition and processing methods via ad hoc questionnaires. Additionally, we examined quantitatively the adaptive approaches.

RESULTS

Concerning data acquisition, the included papers presented a mean score of 6.1 SD 1.0, most of them applying optoelectronic systems, and the ground reaction force (GRF) was the most used parameter. The AI quality assessment showed an above-average rate of 7.8 SD 1.0, and artificial neural networks (ANN) being the paradigm most frequently utilized. Our systematic review identified only one study that addressed therapeutics including a predictive method.

SIGNIFICANCE

While much progress has been identified to predict assessment aspects, there is little effort to assist healthcare professionals in establishing the rehabilitation duration and prognostics. Therefore, future studies should focus on accomplishing the production of applications of predictive methods to therapeutics and prognosis, not lingering extremely on the analysis of gait features.

Modifying ankle foot orthosis stiffness in patients with calf muscle weakness: gait responses on group and individual level

Background

To improve gait, persons with calf muscle weakness can be provided with a dorsal leaf spring ankle foot orthosis (DLS-AFO). These AFOs can store energy during stance and return this energy during push-off, which, in turn, reduces walking energy cost. Simulations indicate that the effect of the DLS-AFO on walking energy cost and gait biomechanics depends on its stiffness and on patient characteristics. We therefore studied the effect of varying DLS-AFO stiffness on reducing walking energy cost, and improving gait biomechanics and AFO generated power in persons with non-spastic calf muscle weakness, and whether the optimal AFO stiffness for maximally reducing walking energy cost varies between persons.

Methods

Thirty-seven individuals with neuromuscular disorders and non-spastic calf muscle weakness were included. Participants were provided with a DLS-AFO of which the stiffness could be varied. For 5 stiffness configurations (ranging from 2.8 to 6.6 Nm/degree), walking energy cost (J/kg/m) was assessed using a 6-min comfortable walk test. Selected gait parameters, e.g. maximal dorsiflexion angle, ankle power, knee angle, knee moment and AFO generated power, were derived from 3D gait analysis.

Results

On group level, no significant effect of DLS-AFO stiffness on reducing walking energy cost was found (p = 0.059, largest difference: 0.14 J/kg/m). The AFO stiffness that reduced energy cost the most varied between persons. The difference in energy cost between the least and most efficient AFO stiffness was on average 10.7%. Regarding gait biomechanics, increasing AFO stiffness significantly decreased maximal ankle dorsiflexion angle (− 1.1 ± 0.1 degrees per 1 Nm/degree, p < 0.001) and peak ankle power (− 0.09 ± 0.01 W/kg, p < 0.001). The reduction in minimal knee angle (− 0.3 ± 0.1 degrees, p = 0.034), and increment in external knee extension moment in stance (− 0.01 ± 0.01 Nm/kg, p = 0.016) were small, although all stiffness’ substantially affected knee angle and knee moment compared to shoes only. No effect of stiffness on AFO generated power was found (p = 0.900).

Conclusions

The optimal efficient DLS-AFO stiffness varied largely between persons with non-spastic calf muscle weakness. Results indicate this is caused by an individual trade-off between ankle angle and ankle power affected differently by AFO stiffness. We therefore recommend that the AFO stiffness should be individually optimized to best improve gait.

Trial registration number

Nederlands Trial Register 5170. Registration date: May 7th 2015. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170

Stiffness modification of two ankle-foot orthosis types to optimize gait in individuals with non-spastic calf muscle weakness - a proof-of-concept study

Background

To reduce gait problems in individuals with non-spastic calf muscle weakness, spring-like ankle-foot orthoses (AFOs) are often applied, but they are not individually optimized to treatment outcome. The aim of this proof-of-concept study was to evaluate the effects of modifying the stiffness for two spring-like AFO types with shoes-only as reference on gait outcomes in three individuals with calf muscle weakness due to polio.

Methods

We assessed 3D gait biomechanics, walking speed and walking energy cost for shoes-only and five stiffness conditions of a dorsal-leaf-spring AFO and a spring-hinged AFO. Outcomes were compared between stiffness conditions in the two AFOs and three subjects.

Results

Maximum ankle dorsiflexion angle decreased with increasing stiffness in both AFOs (up to 6–8°) and all subjects. Maximum knee extension angle changed little between stiffness conditions, however different responses between the AFOs and subjects were observed compared to shoes-only. Walking speed remained unchanged across conditions. For walking energy cost, we found fairly large differences across stiffness conditions with both AFOs and between subjects (range 3–15%).

Conclusions

Modifying AFO stiffness in individuals with non-spastic calf muscle weakness resulted in substantial differences in ankle biomechanics and walking energy cost with no effect on speed. Our results provide proof-of-concept that individually optimizing AFO stiffness can clinically beneficially improve gait performance.

Electronic supplementary material

The online version of this article (10.1186/s13047-019-0348-8) contains supplementary material, which is available to authorized users.

[Limited orthopaedic surgery combined with external fixation for the treatment of lower extremity sequelae of middle and old aged post-poliomyelitis]

Objective

To summarize the effectiveness of limited orthopedic surgery combined with external fixation for the treatment of lower extremity sequelae of middle and old aged post-poliomyelitis, and then to explore the strategy of surgical correction and functional reconstruction method.

Methods

From the database of 23 310 cases of poliomyelitis sequelae treated by QIN Sihe Orthopaedic Surgical team between September 1982 and December 2017, 629 patients over 41 years old were retrieved and the epidemiological characteristics of the patients were analyzed. Between March 2011 and June 2015, 57 patients with poliomyelitis sequelae treated with limited operation and external fixation were followed up 2-6 years, and the history of poliomyelitis sequelae was 41-67 years (mean, 47.1 years). Preoperative histopathological gait included 29 cases of quadriceps gait, 17 cases of walking with crutch, and 11 cases of claudication only. The operative methods included Achilles tendon lengthening in 52 cases, supracondylar osteotomy in 39 cases, knee flexion release in 36 cases, calcaneal arthrodesis in 27 cases, flexion and hip arthrodesis in 21 cases, tibia and fibula osteotomy in 19 cases, triple arthrodesis in 11 cases, and tendon transposition in 1 case. After operation, 18 cases were treated with combined external fixator and 39 cases with Ilizarov ring external fixator.

Results

Of the 629 cases, 481 cases were less than 50 years old (76.47%), accounting for 144 cases between 51 and 65 years old (22.89%). Among them, 495 cases (78.70%) were diagnosed after 2003. Of the 57 patients obtained complete follow-up information, 7 had slight infection of needle path during traction orthopaedics, 2 had early postoperative venous thrombosis of lower extremities, and 2 had incomplete paralysis of the common peroneal nerve. There was no complications such as skin incision infection, vascular injury, and bone nonunion. According to the evaluation standard of postoperative efficacy standard in correction of lower extremity deformities, the results were excellent in 23 cases, good in 20 cases, fair in 12 cases, and poor in 2 cases, with an excellent and good rate of 75.44%. The 2 patients with poor effectiveness were reoperated to improve their function.

Conclusion

Limited orthopedic surgery combined with external fixation for the treatment of lower extremity sequelae of middle and old aged post-poliomyelitis can effectively correct deformities of lower limbs, improve function, delay the disability aggravated by decay, and avoid serious complications.

Post-polio syndrome and the late effects of poliomyelitis: Part 2. treatment, management, and prognosis

Post-polio syndrome (PPS) is characterized by new muscle weakness and/or muscle fatigability that occurs many years after the initial poliomyelitis illness. An individualized approach to rehabilitation management is critical. Interventions may include rehabilitation management strategies, adaptive equipment, orthotic equipment, gait/mobility aids, and a variety of therapeutic exercises. The progression of muscle weakness in PPS is typically slow and gradual; however, there is also variability in both the natural history of weakness and functional prognosis. Further research is required to determine the effectiveness of selected medical treatment. Muscle Nerve 58:760-769, 2018.