Determination of the center of mass in a heterogeneous population of dogs

The center of mass (CoM) is the location in a body where mass distribution is balanced. It has a fundamental role in balance and motion which has been poorly described in the dog. The objective of this study was to estimate the variance of the center of mass (CoM) in a heterogeneous population of client-owned dogs and to describe the relationship between CoM, subject morphometrics and an inertial measurement unit (IMU) box positioned ventrally on a neck collar. A single force platform and a reaction board were used to determine CoM in the transverse, sagittal and dorsal planes in thirty-one healthy adult dogs. A series of morphometric measurements were acquired with each dog standing, including distances relative to an IMU box positioned ventrally on a neck collar. Mean transverse plane CoM was 48% the distance from ischium to the IMU box, near the xiphoid process. Mean sagittal place CoM was 59% the width of the chest on the left side. Mean dorsal plane CoM was 41% the distance from the most dorsal to the most ventral aspect of the body. Dog length was the primary variable required to maximize the relationship between three-dimensional CoM and identifiable variables measured. A CoM based normalization procedure should be considered to normalize mass or motion based outcome measure output (e.g., ground reaction forces, vector acceleration) in a heterogeneous population of dogs. Future research will be needed to determine if CoM-based normalization procedures reduce variance in outcome measures affected by subject morphometrics.

Influencing kinetic energy using ankle-foot orthoses to help improve walking after stroke: a pilot study

BACKGROUND

An ankle-foot orthosis with an oil damper (AFO-OD) may improve kinetics and kinematics for efficient walking after stroke. Yet it is unknown whether hemiplegic walking behaves like "inverted-pendulum" gait and how it is modulated by using AFO-ODs for efficiency.

OBJECTIVES

This study examined whether the use of AFO-ODs improves the kinetics of total vertical ground reaction force (vGRF) and kinematics of vertical pelvic displacement (vPD) in different walking phases, and gait speed following stroke. Also, the relationship between those gait parameters was examined to assess efficient walking.

STUDY DESIGN

Observational study within subject.

METHODS

Eight participants with hemiplegia walked at self-selected speed without and with AFO-ODs over the walkway and gait speed was measured. Force plates were used to measure total vGRF during the double-limb support phase with the paretic leading limb and with the paretic trailing limb (DSPT). The vPD in the paretic and nonparetic stance phases was measured by a three-dimensional motion analysis system.

RESULTS

Without AFO-ODs, reduced total vGRF during DSPT was related to greater vPD in the subsequent nonparetic stance. Using AFO-ODs significantly increased gait speed and total vGRF during double-limb support phase with the paretic leading limb and during DSPT, which were significantly correlated. Vertical pelvic displacement in the nonparetic stance was higher than the paretic stance in both conditions.

CONCLUSIONS

Decreased total vGRF during DSPT was compensated by excessive vPD in the nonparetic stance phase without AFO-ODs, indicating inefficient walking. However, the use of AFO-ODs improved the kinetic energy of total vGRF during the double-limb support phase, contributing to efficient walking.

CLINICAL RELEVANCE STATEMENT

The AFO-ODs can be used to improve kinetic energy and to modulate functions in the weight transition during the double-limb support phase, with faster walking speed. Thus, AFO-ODs can be considered to be therapeutic AFOs to acquire efficient walking performance in poststroke rehabilitation.

A Clinical Practice Guideline for the Use of Ankle-Foot Orthoses and Functional Electrical Stimulation Post-Stroke

BACKGROUND

Level of ambulation following stroke is a long-term predictor of participation and disability. Decreased lower extremity motor control can impact ambulation and overall mobility. The purpose of this clinical practice guideline (CPG) is to provide evidence to guide clinical decision-making for the use of either ankle-foot orthosis (AFO) or functional electrical stimulation (FES) as an intervention to improve body function and structure, activity, and participation as defined by the International Classification of Functioning, Disability and Health (ICF) for individuals with poststroke hemiplegia with decreased lower extremity motor control.

METHODS

A review of literature published through November 2019 was performed across 7 databases for all studies involving stroke and AFO or FES. Data extracted included time post-stroke, participant characteristics, device types, outcomes assessed, and intervention parameters. Outcomes were examined upon initial application and after training. Recommendations were determined on the basis of the strength of the evidence and the potential benefits, harm, risks, or costs of providing AFO or FES.

RESULTS/DISCUSSION

One-hundred twenty-two meta-analyses, systematic reviews, randomized controlled trials, and cohort studies were included. Strong evidence exists that AFO and FES can each increase gait speed, mobility, and dynamic balance. Moderate evidence exists that AFO and FES increase quality of life, walking endurance, and muscle activation, and weak evidence exists for improving gait kinematics. AFO or FES should not be used to decrease plantarflexor spasticity. Studies that directly compare AFO and FES do not indicate overall superiority of one over the other. But evidence suggests that AFO may lead to more compensatory effects while FES may lead to more therapeutic effects. Due to the potential for gains at any phase post-stroke, the most appropriate device for an individual may change, and reassessments should be completed to ensure the device is meeting the individual's needs.

LIMITATIONS

This CPG cannot address the effects of one type of AFO over another for the majority of outcomes, as studies used a variety of AFO types and rarely differentiated effects. The recommendations also do not address the severity of hemiparesis, and most studies included participants with varied baseline ambulation ability.

SUMMARY

This CPG suggests that AFO and FES both lead to improvements post-stroke. Future studies should examine timing of provision, device types, intervention duration and delivery, longer term follow-up, responders versus nonresponders, and individuals with greater impairments.

DISCLAIMER

These recommendations are intended as a guide for clinicians to optimize rehabilitation outcomes for people with poststroke hemiplegia who have decreased lower extremity motor control that impacts ambulation and overall mobility.A Video Abstract is available as supplemental digital content from the authors (available at: http://links.lww.com/JNPT/A335).

Ankle-foot orthoses improve walking but do not reduce dual-task costs after stroke

BACKGROUND

Cognitive-motor interference, as measured by dual-task walking (performing a mental task while walking), affects many clinical populations. Ankle-foot orthoses (AFOs) are lower-leg splints prescribed to provide stability to the foot and ankle, as well as prevent foot drop, a gait deficit common after stroke. AFO use has been shown to improve gait parameters such as speed and step time, which are often negatively impacted by dual-task walking.

OBJECTIVES

Our objective was to establish whether AFOs could protect against cognitive-motor interference, as measured by dual-task walking, following post-stroke hemiplegia.

METHODS

A total of 21 individuals with post-stroke hemiplegia that use an AFO completed a dual-task walking paradigm in the form of a 2 (walking with vs. without a concurrent cognitive task) by 2 (walking with vs. without an AFO) repeated-measures design. Changes to both motor and cognitive performance were analyzed.

RESULTS

The results suggest that the use of an AFO improves gait overall in both single- and dual-task walking, particularly with respect to stride regularity, but there were no interactions to suggest that AFOs reduce the cognitive-motor dual-task costs themselves. A lack of differences in cognitive performance during dual-task walking with and without the AFO suggests that the AFO's benefit to motor performance cannot be attributed to task prioritization.

CONCLUSIONS

These data support the use of AFOs to improve certain gait parameters for post-stroke hemiplegia, but AFOs do not appear to protect against cognitive-motor interference during dual-task walking. Future research should pursue alternate therapeutics for ameliorating task-specific declines under cognitively demanding circumstances.

Kinematic on Ankle and Knee Joint of Post-Stroke Elderly Patients by Wearing Newly Elastic Band-Type Ankle-Foot Orthosis in Gait

Purpose

The post-stroke elderly was increased caused by increasing stroke and advanced medical. However, ankle–foot orthoses (AFOs) can be uncomfortable for hemiplegic patients; therefore, the usability is not good. In this study, we analyzed ankle and knee joint angles in post-stroke elderly patients to assess the functional effectiveness (specifically prevention of back knee and drop-foot) of a new elastic band-type AFO (New Product: NP) during gait.

Patients and methods

Nine elderly post-stroke patients (eight males, one female; 55.7±8.4 years; 165.8±9.2 cm; 68.8±11.5 kg; five with right hemiplegia, four with left hemiplegia; onset period: 6.6 years) were selected for participation in this study. We captured gait motion using 12 cameras (MX-T20, Vicon, Inc., Oxford, UK) under three different conditions [wearing nothing (WI), using existing ordinary AFOs made from hard plastic material (EP), and using NP]. The angle variation and maximum–minimum angle of the lower body joints were analyzed during dorsi-plantar flexion of the ankle joint and flexion–extension of knee joint. A one-way ANOVA test for multiple comparisons was performed, followed by a Tukey’s b test to identify statistical significance, which was set at 0.005.

Results

Regarding the ankle joint, the maximum plantar flexion (drop-foot) value decreased with the NP, and the maximum dorsiflexion value increased. Regarding the knee joint, the maximum extension (back knee) value decreased, and the maximum flexion value increased (p < 0.005).

Conclusion

Using analysis of the kinematics of the ankles and knees during walking, this research confirmed the effectiveness of the NP, an elastic band-type AFO, for use in ordinary post-stroke elderly patients.

Center of mass in analysis of dynamic stability during gait following stroke: A systematic review

BACKGROUND

The Center of mass (CoM) analysis reveals important aspects of gait dynamic stability of stroke patients, but the variety of methods and measures represents a challenge for planning new studies.

RESEARCH QUESTION

How have the CoM measures been calculated and employed to investigate gait stability after a stroke? Three issues were addressed: (i) the methodological aspects of the calculation of CoM measures; (ii) the purposes and (iii) the conclusions of the studies on gait stability that employed those measures.

METHODS

PubMed and Science Direct databases have been searched to collect original articles produced until July 2017. A set of 26 studies were selected according to criteria involving their methodological quality.

RESULTS

A compromise between accuracy and feasibility in CoM calculation could be reached using the segmental method with 7-9 segments. Regarding their purposes, two types of studies were identified: clinical and research oriented. From the first ones, we highlighted: the margin of stability (MoS) in the mediolateral (ML) direction, and the angular momentum in the frontal plane could be indicators of dynamical stability; the MoS in the anteroposterior (AP) direction might be able to detect the risk of falls and the symmetry of vertical CoM displacement could be used to analyze energy expenditure during gait. These and other CoM measures are potentially useful in clinical settings, but their psychometric properties are still to be determined. The research oriented studies allowed to clarify that stability is not improved by widening the step in stroke patients and that the impaired control of the non-paretic limb might be the main source of instability.

SIGNIFICANCE

This review provides recommendations on the methods for estimating CoM and its measures, identifies the potential usefulness of CoM parameters and indicates issues that could be addressed in future studies.

The effects of alignment of an articulated ankle-foot orthosis on lower limb joint kinematics and kinetics during gait in individuals post-stroke

Mechanical tuning of an ankle-foot orthosis (AFO) is important in improving gait in individuals post-stroke. Alignment and resistance are two factors that are tunable in articulated AFOs. The aim of this study was to investigate the effects of changing AFO ankle alignment on lower limb joint kinematics and kinetics with constant dorsiflexion and plantarflexion resistance in individuals post-stroke. Gait analysis was performed on 10 individuals post-stroke under four distinct alignment conditions using an articulated AFO with an ankle joint whose alignment is adjustable in the sagittal plane. Kinematic and kinetic data of lower limb joints were recorded using a Vicon 3-dimensional motion capture system and Bertec split-belt instrumented treadmill. The incremental changes in the alignment of the articulated AFO toward dorsiflexion angles significantly affected ankle and knee joint angles and knee joint moments while walking in individuals post-stroke. No significant differences were found in the hip joint parameters. The alignment of the articulated AFO was suggested to play an important role in improving knee joint kinematics and kinetics in stance through improvement of ankle joint kinematics while walking in individuals post-stroke. Future studies should investigate long-term effects of AFO alignment on gait in the community in individuals post-stroke.

The influence of an ankle-foot orthosis on the spatiotemporal gait parameters and functional balance in chronic stroke patients

[Purpose] Observational study investigating the influence of various ankle-foot orthoses on the spatiotemporal gait parameters and functional balance in chronic stroke patients. [Subjects and Methods] Fifteen chronic stroke patients participated in this study after providing informed consent. Two groups of patients were differentiated based on the Timed Up and Go Test. Patients were tested in three different conditions: with standard prefabricated ankle-foot orthosis (Maramed), with individualized ankle-foot orthosis (Y-tech), and without any ankle-foot orthrosis. Spatiotemporal gait parameters were obtained by walking on an instrumented walkway (GAITRite(®)) at usual and fastest speed. Balance was assessed with Timed Up and Go Test, Step Test, and Four Square Step Test. [Results] Maramed and Y-tech significantly improved the spatiotemporal parameters while walking at usual and maximal speed (single support time affected side; double support time affected side and step length unaffected side). The Y-tech in addition improved velocity and cadence. Among the balance tests, only the Timed Up and Go test showed improvements in favor of Maramed and Y-tech. [Conclusion] Patients benefited from wearing orthosis at both usual and maximal speed, irrespective of whether they wore Maramed or Y-tech. Only severe stroke patients benefited from wearing an orthoses compared to mild impaired group.

The effect of changing plantarflexion resistive moment of an articulated ankle-foot orthosis on ankle and knee joint angles and moments while walking in patients post stroke

BACKGROUND

The adjustment of plantarflexion resistive moment of an articulated ankle-foot orthosis is considered important in patients post stroke, but the evidence is still limited. Therefore, the aim of this study was to investigate the effect of changing the plantarflexion resistive moment of an articulated ankle-foot orthosis on ankle and knee joint angles and moments in patients post stroke.

METHODS

Gait analysis was performed on 10 subjects post stroke under four different plantarflexion resistive moment conditions using a newly designed articulated ankle-foot orthosis. Data were recorded using a Bertec split-belt instrumented treadmill in a 3-dimensional motion analysis laboratory.

FINDINGS

The ankle and knee sagittal joint angles and moments were significantly affected by the amount of plantarflexion resistive moment of the ankle-foot orthosis. Increasing the plantarflexion resistive moment of the ankle-foot orthosis induced significant decreases both in the peak ankle plantarflexion angle (P<0.01) and the peak knee extension angle (P<0.05). Also, the increase induced significant increases in the internal dorsiflexion moment of the ankle joint (P<0.01) and significantly decreased the internal flexion moment of the knee joint (P<0.01).

INTERPRETATION

These results suggest an important link between the kinematic/kinetic parameters of the lower-limb joints and the plantarflexion resistive moment of an articulated ankle-foot orthosis. A future study should be performed to clarify their relationship further so that the practitioners may be able to use these parameters as objective data to determine an optimal plantarflexion resistive moment of an articulated ankle-foot orthosis for improved orthotic care in individual patients.

Alteration in the center of mass trajectory of patients after stroke

BACKGROUND

The movement disorders due to stroke can alter the motion of the Center of Mass (CoM) of the body. Thus, the analysis of the CoM motion can be an alternative to diagnostic the stroke gait disturbances and has not been widely explored.

OBJECTIVE

To identify and to analyze the alterations of CoM trajectory during both of gait cycles, affected and unaffected, of post-stroke patients comparing to healthy subjects.

METHODS

The CoM trajectory was obtained using a gold standard method, the three-dimensional (3D) kinematics associate to anthropometry. Two experimental groups were compared: Hemiparetic Group (HG) consisted of fourteen chronic hemiparetic patients and Control Group (CG) by fourteen able-bodied subjects.

RESULTS

The statistical analysis (P ≤ 0.05) revealed the following average gait alterations in the HG, in the stance phase of the affected side: higher lateral (midstance), lower vertical (midstance and terminal stance), and lower forward displacement (heel strike until terminal stance). In the swing phase of the affected side, HG showed higher lateral (preswing and initial swing) and vertical displacement (preswing until terminal swing), and lower forward (preswing until terminal swing) displacement of the CoM. There was also anticipation of the instants of maximum displacements in the lateral and vertical directions and lower total range in the forward direction.

CONCLUSION

The CoM trajectory analysis pointed out that the gait after stroke was altered such in the affected as in the unaffected lower limbs, mainly in the single support phase of the affected side, but also in the swing phase of the gait cycle.

A systematic review and meta-analysis of the effect of an ankle-foot orthosis on gait biomechanics after stroke

OBJECTIVE

To systematically review the evidence on the effects of an ankle-foot orthosis on gait biomechanics after stroke.

DATA SOURCES

The following databases were searched; AMED, CINHAL, Cochrane Library (Stroke section), Medline, PubMed, Science Direct and Scopus. Previous reviews, reference lists and citation tracking of the selected articles were screened and the authors of selected trials contacted for any further unpublished data.

REVIEW METHODS

Controlled trials of an ankle-foot orthosis on gait biomechanics in stroke survivors were identified. A modified PEDro score evaluated trial quality; those scoring 4/8 or more were selected. Information on the trial design, population, intervention, outcomes, and mean and standard deviation values for the treatment and control groups were extracted. Continuous outcomes were pooled according to their mean difference and 95% confidence intervals in a fixed-effect model.

RESULTS

Twenty trials involving 314 participants were selected. An ankle-foot orthosis had a positive effect on ankle kinematics (P < 0.00001-0.0002); knee kinematics in stance phase (P < 0.0001-0.01); kinetics (P = 0.0001) and energy cost (P = 0.004), but not on knee kinematics in swing phase (P = 0.84), hip kinematics (P < 0.18-0.89) or energy expenditure (P = 0.43). There were insufficient data for pooled analysis of individual joint moments, muscle activity or spasticity. All trials, except one, evaluated immediate effects only.

CONCLUSIONS

An ankle-foot orthosis can improve the ankle and knee kinematics, kinetics and energy cost of walking in stroke survivors.

The effect of varying the plantarflexion resistance of an ankle-foot orthosis on knee joint kinematics in patients with stroke

Ankle-foot orthoses (AFOs) can improve gait in patients with hemiplegia. However, it is anecdotally known that excessive plantarflexion resistance of an AFO could induce undesired knee flexion at early stance. The aim of this study was to systematically investigate the effect of varying the degrees of plantarflexion resistance of an AFO on knee flexion angles at early stance in five subjects with chronic stroke who demonstrated two clear knee flexion peaks at early stance and swing. Each subject wore an experimental AFO constructed with an oil-damper type ankle joint and was instructed to walk at their self-selected walking speed under five plantarflexion resistance conditions. The sagittal plane ankle and knee joint kinematics and gait speed were analyzed using a 3-D Motion Analysis System. A number of significant differences (P<0.005) in maximum knee flexion angles at early stance amongst different plantarflexion resistance conditions were revealed. The knee flexion angle was 23.80 (3.25) degrees under the free hinge joint condition (condition 1), while that was 26.09 (3.79) degrees under the largest resistance condition (condition 5). It was therefore demonstrated that increasing the plantarflexion resistance of an AFO would induce more knee flexion at early stance phase in patients with stroke.