Elsevier

Gait & Posture

Volume 58, October 2017, Pages 146-153
Gait & Posture

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

https://doi.org/10.1016/j.gaitpost.2017.07.107Get rights and content

Highlights

  • In polio survivors, gait pattern characteristics due to calf muscle weakness have not been fully described.

  • We examined gait pattern characteristics in association with underlying impairments.

  • We found 7 different gait patterns with two dominant patterns present.

  • Patients with a similar presentation of impairments did not necessarily walk alike.

  • The gait pattern could not be accurately predicted from underlying impairments.

Abstract

The objective was to identify gait patterns in polio survivors with calf muscle weakness and associate them to underlying lower extremity impairments, which are expected to help in the search for an optimal orthosis.

Unilaterally affected patients underwent barefoot 3D-gait analyses. Gait pattern clusters were created based on the ankle and knee angle and ankle moment shown in midstance of the affected limb. Impairment clusters were created based on plantarflexor and knee-extensor strength, and ankle and knee joint range-of-motion. The association between gait patterns and underlying impairments were examined descriptively. The Random Forest Algorithm and regression analyses were used to predict gait patterns and parameters.

Seven gait patterns in 73 polio survivors were identified, with two dominant patterns: one with a mildly/non-deviant ankle angle, ankle moment and knee angle (n = 23), and one with a strongly deviant ankle angle and a mildly/non-deviant ankle moment and knee angle (n = 18). Gait pattern prediction from underlying impairments was 49% accurate with best prediction performance for the second dominant gait pattern (sensitivity 78% and positive predictive value 74%). The underlying impairments explained between 20 and 32% of the variance in individual gait parameters.

Polio survivors with calf muscle weakness who present a similar impairment profile do not necessarily walk the same. From physical examination alone, the gait pattern nor the individual gait parameters could be accurately predicted. The patient’s gait should therefore be measured to help in the prescription and evaluation of orthoses for these patients.

Introduction

Poliomyelitis is a highly infectious viral disease that has left many polio survivors with permanent muscle weakness [1], often including the calf muscles. Gait in calf muscle weakness is typically characterized by instability of the ankle and knee [2], [3] and by an increased walking effort [2], [4], [5], which may hamper daily-life activities [6].

To compensate for loss of calf muscle function and improve gait, a dorsiflexion restricting ankle-foot orthosis (DR-AFO) can be provided. Dorsiflexion restriction aims to allow an external dorsiflexion moment around the ankle without causing instability [7], [8], [9], and it may reduce walking effort [10]. Previous research in polio survivors with calf muscle weakness, however, suggests that the efficacy of DR-AFOs to improve stability and reduce walking effort is partly dependent on the patients’ gait deviations when walking without an orthosis [10]. Hence, when prescribing a DR-AFO for calf muscle weakness, a clear understanding of the gait pattern deviations is important.

Gait pattern deviations due to calf muscle weakness have been previously investigated [7], [11], [12], [13], [14]. Yet, available studies lack a complete description of the joint kinetics of gait in addition to joint kinematics, while both contain important information of the resultant gait deviations and compensatory strategies. Furthermore, in most studies [11], [12], [13] gait was assessed in healthy subjects with a temporarily induced isolated calf muscle paralysis, while in polio survivors calf muscle weakness is rarely isolated, often not fully paralytic, and almost always accompanied with other lower extremity impairments such as muscle and joint contractures and bony deformities. Available gait descriptions in polio survivors have not yet been related to underlying impairments of the lower extremities, although the gait pattern may depend on these [4], [10]. Better insight in the gait pattern characteristics associated with calf muscle weakness is expected to help in the search for an optimal effective DR-AFO [7], [15].

The aims of this study in polio survivors with calf muscle weakness were to identify discrete gait patterns; relate the identified gait patterns to underlying impairments of the lower extremities; and determine whether, based on these underlying impairments, the gait pattern and single gait parameters could be predicted.

Section snippets

Study population

A retrospective search of the gait laboratory database at our university hospital outpatient Rehabilitation and Polio Expertise Center was conducted for selecting polio patients who had undergone barefoot three-dimensional (3D) gait analyses within a patient-care setting. Inclusion criteria for selecting patients were presence of muscle weakness in a single limb, presence of calf muscle weakness in that limb (defined as a score <5 according to the Medical Research Council (MRC) scale, and/or

Identification of gait patterns and impairment clusters

Seven of the eight possible gait patterns and all eight impairment clusters were identified (Fig. 1, Fig. 2). Five gait patterns contained the data of eight or more limbs, and each of these was connected to at least three impairment clusters. Most frequently identified (n = 23) was the least deviant gait pattern (gait pattern 1), to which seven impairment clusters were connected (Fig. 1). Next, gait pattern 5 (strongly deviant ankle angle and mildly/non-deviant ankle moment and knee angle) was

Discussion

In total, seven gait patterns were identified, with two dominant gait patterns present. These included the least deviant gait pattern 1 (32%), with patients presenting a mildly/non-deviant ankle angle, ankle moment and knee angle in midstance, and gait pattern 5 (25%), characterized by a strongly deviant ankle angle, and a mildly/non-deviant ankle moment and knee angle in midstance. There was a great variety in underlying impairments, both in degree and distribution of muscle weakness and

Conclusion

We observed a large heterogeneity in gait patterns and impairment profiles in polio survivors with calf muscle weakness. Polio survivors with a rather homogenous presentation of impairments do not necessarily walk in the same manner. From physical examination data, the gait pattern and single gait parameters could not be accurately predicted. Therefore, in the process of prescribing orthoses in polio survivors with calf muscle weakness, we propose that gait kinematics and kinetics should always

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflicts of interest statement

All authors declare that they have no conflict of interests with this publication.

Acknowledgements

We would like to thank the Dutch International Society of Prosthetics and Orthotics for a travel grant for H.E. Ploeger to visit Gillette Children's Specialty Healthcare in St Paul, MN in the USA (director of Bioengineering Research M.H. Schwartz) to train in the Random Forest Algorithm used in this paper.

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