V. de Groot

The effect of ankle foot orthosis stiffness on the energy cost of walking: A simulation study

BACKGROUND In stroke and multiple sclerosis patients, gait is frequently hampered by a reduced ability to push-off with the ankle caused by weakness of the plantar-flexor muscles. To enhance ankle push-off and to decrease the high energy cost of walking, spring-like carbon-composite Ankle Foot Orthoses are frequently prescribed. However, it is unknown what Ankle Foot Orthoses stiffness should be used to obtain the most efficient gait. The aim of this simulation study was to gain insights into the effect of variation in Ankle Foot Orthosis stiffness on the amount of energy stored in the Ankle Foot Orthosis and the energy cost of walking. METHODS We developed a two-dimensional forward-dynamic walking model with a passive spring at the ankle representing the Ankle Foot Orthosis and two constant torques at the hip for propulsion. We varied Ankle Foot Orthosis stiffness while keeping speed and step length constant. FINDINGS We found an optimal stiffness, at which the energy delivered at the hip joint was minimal. Energy cost decreased with increasing energy storage in the ankle foot orthosis, but the most efficient gait did not occur with maximal energy storage. With maximum storage, push-off occurred too late to reduce the impact of the contralateral leg with the floor. Maximum return prior to foot strike was also suboptimal, as push-off occurred too early and its effects were subsequently counteracted by gravity. The optimal Ankle Foot Orthosis stiffness resulted in significant push-off timed just prior to foot strike and led to greater ankle plantar-flexion velocity just before contralateral foot strike. INTERPRETATION Our results suggest that patient energy cost might be reduced by the proper choice of Ankle Foot Orthosis stiffness.

A new method for evaluating ankle foot orthosis characteristics: BRUCE

The mechanical characteristics of ankle foot orthoses (AFOs), such as the stiffness and neutral angle around the ankle and metatarsal-phalangeal (MTP) joints, are rarely quantified. Paradoxically, it is expected that these characteristics determine the function of the AFO in pathological gait. Therefore a device to determine these AFO characteristics named BRUCE was designed based on multidisciplinary consensus. The design is based on a replicated human leg that is manually driven and continuously registers joint configuration and force exerted by the AFO onto the device. From this information, neutral angles and stiffnesses around the ankle and MTP joints are determined using a linear fit. The reliability of the stiffnesses and neutral angles was studied by repeatedly measuring the mechanical characteristics of four different AFOs, and evaluating the inter-session, intra-session, and inter-observer errors. The reliability study revealed that ankle and MTP stiffness could be measured with very high reliability (ICC=0.98-1.00). Ankle and MTP neutral angles showed reasonable reliability (ICC=0.79-0.92). Measurement error in the neutral angles could mainly be attributed to the difference in testers. With a fixed tester excellent reliability was obtained (ICC=0.99-0.99). The results derived using BRUCE can help to gain insight into the role of the mechanical characteristics of AFOs in correcting pathological gait. Objective information of AFO characteristics is expected to lead to a better founded prescription of AFOs, resulting in optimal functional benefit for the patient.

Spring-like Ankle Foot Orthoses reduce the energy cost of walking by taking over ankle work

In patients with central neurological disorders, gait is often limited by a reduced ability to push off with the ankle. To overcome this reduced ankle push-off, energy-storing, spring-like carbon-composite Ankle Foot Orthoses (AFO) can be prescribed. It is expected that the energy returned by the AFO in late stance will support ankle push-off, and reduce the energy cost of walking. In 10 patients with multiple sclerosis and stroke the energy cost of walking, 3D kinematics, joint power, and joint work were measured during gait, with and without the AFO. The mechanical characteristics of the AFO were measured separately, and used to calculate the contribution of the AFO to the ankle kinetics. We found a significant decrease of 9.8% in energy cost of walking when walking with the AFO. With the AFO, the range of motion of the ankle was reduced by 12.3°, and the net work around the ankle was reduced by 29%. The total net work in the affected leg remained unchanged. The AFO accounted for 60% of the positive ankle work, which reduced the total amount of work performed by the leg by 11.1% when walking with the AFO. The decrease in energy cost when walking with a spring-like energy-storing AFO in central neurological patients is not induced by an augmented net ankle push-off, but by the AFO partially taking over ankle work.

Multiple sclerosis functional composite: impact of reference population and interpretation of changes

The Multiple sclerosis functional composite (MSFC) has been recommended as a clinical outcome measure to be used in future MS trials. A specific characteristic of the MSFC is that it is defined as a measure of impairment relative to a reference population. Using different reference populations affects actual MSFC scores. If the selection of a reference population also has an effect on sensitivity to change of the MSFC, comparison of data from clinical trials will be almost impossible when different reference populations are used. We studied the effect of the selection of a reference population on the outcome of a trial by simulating 343 intervention trials and comparing results obtained by using three different reference populations: two previously published MS patient populations and a healthy population. Scores of the healthy population were collected in the first part of the study. The effects of sex, age and education level on test scores of healthy subjects were studied as well. In the healthy controls, sex, age and education level had a different impact on individual test scores of MSFC components and overall MSFC score. Our study shows that, with the use of the MSFC, the selection of different reference populations does not affect the trial statistics and significance, but it does affect comparability of results between different trials, and complicates the clinical interpretation of any observed change.

Regional brain atrophy development is related to specific aspects of clinical dysfunction in multiple sclerosis

Brain atrophy in multiple sclerosis (MS) is thought to reflect irreversible tissue damage leading to persistent clinical deficit. Little is known about the rate of atrophy in specific brain regions in relation to specific clinical deficits. We determined the displacement of the brain surface between two T1-weighted MRI images obtained at baseline and after a median follow-up time of 2.2 years for 79 recently diagnosed, mildly disabled MS patients. Voxel- and cluster-wise permutation-based statistics were used to identify brain regions in which atrophy development was significantly related to Expanded Disability Status Scale (EDSS), Timed Walk Test (TWT), Paced Auditory Serial Addition Test (PASAT) and 9-Hole Peg Test (HPT). Clusters were considered significant at a corrected cluster-wise p-value of 0.05. Worse EDSS change-score and worse follow-up EDSS were related to atrophy development of periventricular and brainstem regions and right-sided parietal, occipital and temporal regions. Worse PASAT at follow-up was significantly related to atrophy of the ventricles. A worse TWT change-score and worse follow-up TWT were exclusively related to atrophy around the ventricles and of the brainstem. Worse HPT change-score and worse follow-up HPT of either arm were significantly related to the atrophy of widely distributed peripheral regions, as well as atrophy of periventricular and brainstem regions. Our findings suggest that decline in ambulatory function is related to atrophy of central brain regions exclusively, whereas decline in neurologically more complex tasks for coordinated hand function is related to atrophy of both central and peripheral brain regions.

Community walking can be assessed using a 10-metre timed walk test

Background: A decline in mobility is a common feature of multiple sclerosis (MS). Community walking scales are used to categorize patients in their ability to move independently. The first purpose of this study was to determine which specific gait speed corresponded with the categories of the Modified Functional Walking Categories (MFWC). The second purpose was to determine the Minimally Important Change (MIC) in absolute gait speed using the MFWC and Expanded Disability Status Scale (EDSS) as external criteria. Method: MS patients were measured six times in 6 years. Gait velocity was measured with the 10-metre timed walk test (10-m TWT), the severity of MS was determined with the EDSS, and community walking was assessed with the MFWC. For each category of the MFWC, Receiver Operating Characteristic (ROC) curves were used to find the best possible cut-off point on the 10-m TWT. The MIC in absolute gait speed was determined using a change of one category on the MFWC or one point on the EDSS. Results: A strong relationship was found between gait speed and the MFWC; all areas under the ROC curves (AUCs) were between 0.74 and 0.86. The MIC in absolute gait speed could not be determined, because the AUCs were below the threshold of 0.70 and changes in gait speed were small. Conclusions: Gait speed is related to community walking, but an MIC in absolute gait speed could not be determined using a minimally important change on the MFWC or the EDSS as external criteria.

Vitality, perceived social support and disease activity determine the performance of social roles in recently diagnosed multiple sclerosis: a longitudinal analysis.

OBJECTIVE The aim of this study was to identify the principal determinants that are longitudinally associated with the performance of social roles in the first 3 years following a diagnosis of multiple sclerosis. DESIGN Inception cohort with 5 measurements over 3 years. PATIENTS A total of 156 patients recently diagnosed with multiple sclerosis. METHOD Performance of social roles was measured using the 2 role functioning and the social sub-scales of the Medical Outcome Study Short Form 36. Potential determinants (n = 43) were divided into the following clusters: patient and disease characteristics (n = 12), psychosocial characteristics (n = 10), basic functions (n = 18) and basic activities (n = 3). Multivariate longitudinal regression analyses were performed with generalized estimating equations. A backwards selection procedure for every cluster per outcome reduced the large number of potential determinants. In order to determine whether longitudinal associations are present the selected determinants were entered into an overall regression model. RESULTS Twenty-three candidate determinants were selected. Vitality, measured with the SF36 sub-scale vitality, the T2-weighted supratentorial lesion load and the perceived amount of social support, measured with the Social Support List Discrepancies, were longitudinally associated with the performance of social roles in 2 or 3 of the models. CONCLUSION Vitality, the perceived amount of social support, and disease activity, i.e. the T2-weighted supratentorial lesion load, determine the performance of social roles in the early stages of multiple sclerosis.

The initial course of daily functioning in multiple sclerosis : a three-year follow-up study

We studied the initial course of daily functioning in multiple sclerosis (MS). A cohort of 156 recently diagnosed patients was prospectively followed for three years (five measurements). Domains of interest were neurological deficits, physical functioning, mental health, social functioning and general health. An a priori distinction was made between a relapse onset group (n=128) and a non-relapse onset group (n=28). At baseline, neurological deficits are relatively minor for most patients, 26.3% have aberrant physical functioning scores, 38.5% have aberrant social functioning scores, 9% have aberrant mental health scores and 25% have aberrant general health scores. The neurological deficits and physical functioning deteriorated significantly over time. This deterioration was more pronounced and clinically relevant in the non-relapse onset group only. Mental health showed a significant, but not clinically relevant deterioration over time. Social functioning and general health showed non-significant effects for time. It is concluded that in the initial stage of MS, when neurological deficits are relatively minor and mental health is relatively unaffected, patients in both groups experience limitations in daily functioning. Patients in the non-relapse onset group have progressive neurological symptoms that are accompanied by progressive limitations in physical functioning, but not by progressive limitations in the other domains.

A cluster randomised controlled trial on the efficacy of client-centred occupational therapy in multiple sclerosis: good process, poor outcome.

Abstract Purpose: To assess the efficacy of client-centred occupational therapy (OT) according to a client-centred process framework, as compared to usual care OT, in patients with multiple sclerosis (MS). Method: A multicentre cluster randomised controlled trial with the institution (i.e. hospital or rehabilitation centre) as the unit of randomisation was performed. A total of 269 outpatients with MS, 13 hospitals and rehabilitation centres and 29 occupational therapists participated. Primary outcomes included measures of disability, participation and autonomy. Secondary outcomes included fatigue, generic health-related quality of life, quality and evaluation of therapy, therapy compliance and therapy frequency. Measurements were taken at baseline, four months and at eight months follow-up. Results: Primary outcome measures did not show significant differences between the two interventions. Secondary outcomes revealed significant differences in favour of the usual care OT on fatigue (physical scale and total scale) and health-related quality of life (bodily pain and vitality) at four months. After eight months only significant differences on mental health were found. Process outcomes (i.e. the information scale of therapy quality and the client-centredness of the organisation) were in favour of the client-centred intervention. Conclusion: Because the client-centred intervention resulted in no effects on the primary outcomes and small but negative effects on the secondary functional outcomes, we should seriously reconsider the application of client-centred practice. Implications for Rehabilitation An increasing number of interventions claim to incorporate client-centred practice. Client-centred practice is associated with improved satisfaction but the effects on functional health-related outcomes have not been fully evaluated. The findings of this study show that the process outcomes of therapy were in favour of the client-centred intervention, but no effects were found on the primary outcomes and negative effects on the secondary functional health outcomes. It is suggested that the implementation of client-centred practice should be adjusted in order to achieve optimal health outcomes.

Utilization of health care by patients with multiple sclerosis is based on professional and patient-defined health needs

Objective This cross-sectional study investigates healthcare utilization, and determines which predisposing, enabling, and health factors are associated with healthcare utilization among 121 patients with multiple sclerosis (MS). Methods Data on patient-related predisposing, enabling, and health factors were collected by means of written questionnaires and a home visit from a well-trained physiotherapist. Results Of the 121 patients with MS (mean age 43 years, mean score on the Expanded Disability Status Scale 3.5, disease duration 6 years), 16% were hospitalized in the previous year; 62% consulted their general practitioner, and 69% consulted their neurologist in the previous 6 months. Other medical specialists were consulted in the 6-month period by 50% of the study population. In a 4-week period preceding the home visit, 41% of the patients were treated by an allied healthcare professional. Multivariate logistic regression analyses showed that consulting the general practitioner, the neurologist, other medical specialists, and allied healthcare professionals, and the use of equipment/aids by MS patients is primarily related to their health, either as perceived by the patients themselves or defined by the professional. Conclusions MS patients in the Netherlands make appropriate use of healthcare facilities, because their utilization can predominantly be explained by health-related factors, and not by predisposing or enabling factors.