Elsevier

Gait & Posture

Volume 60, February 2018, Pages 273-278
Gait & Posture

SIAMOC best paper 2016
Electromyographic activity of the vastus intermedius muscle in patients with stiff-knee gait after stroke. A retrospective observational study

https://doi.org/10.1016/j.gaitpost.2017.07.002Get rights and content

Highlights

  • VI activity was measured by fine wires during stiff-knee gait of stroke patients.

  • VI abnormal activity is frequent in stroke patients with SKG.

  • VI may affect the stance phase thus preventing knee flexion.

  • VI may affect the swing phase thus braking knee flexion.

  • VI activity should be assessed to assist in the clinical decision-making processes.

Abstract

Stiff-knee gait (SKG) in hemiplegic patients is often due to an inappropriate activity of the quadriceps femoris. However, there are no studies in literature addressing the vastus intermedius (VI) involvement in SKG. In this study, VI activity was analyzed in a sample of 46 chronic stroke patients with SKG, during spontaneous gait. VI activity was recorded by fine-wire electrodes inserted under ultrasound guidance then confirmed by electrical stimulation. The measured VI activity was compared to the normal reference pattern reported in literature and classified (e.g. premature, prolonged). The occurrences of abnormal activations during each sub-phase of the gait cycle were assessed.

VI activity presented an abnormal timing in 96% of the sample. The most common pathological pattern (in 46% of the sample) was the combination of premature and prolonged VI activation. Nearly 20% of patients presented a continuous activity. A pathological activation in patients was found for 91% in mid stance, for more than 50% in terminal stance and pre-swing and for 37% and 70% in initial- and mid-swing.

Results indicate that abnormal VI activity is frequent in patients with SKG. Hence, VI activity should be included in the assessment of SKG to assist in the clinical decision-making processes.

Introduction

Stiff-knee gait (SKG) is a common occurrence in hemiparetic stroke survivors characterized by both a limited and a delayed knee flexion during the swing phase of the gait cycle [1], [2]. Knee flexion (KF) can be totally absent in subjects with severe SKG, while less compromised patients can reach a peak of flexion of about 40°, with respect to the average normal reference of 56° during slow walking [3]. SKG compromises the foot clearance during swing, one of the prerequisites for normal gait [1] and may lead to toe dragging, which alters gait stability and increases the risk of falls [4]. Moreover, the compensatory movements required to move the foot forward during swing, such as ipsilateral hip circumduction, contralateral vaulting, upward pelvic tilt or pelvic lag [1], [5], [6], greatly increase the patients’ vertical shift of the body’s center of mass and consequently the energy expenditure during gait [7], [8].

SKG can be caused by either an insufficient or absent push off at the ankle, which is the main mechanism for knee flexion generation [3], or by the presence of an abnormal braking activity of the thigh muscles, which is typically triggered by the quick knee flexion at toe off when the push off is maintained [3], [9], [10], [11], [12]. In addition, hip flexor weakness can be a further cause for a limited knee flexion during swing [13].

Amongst abnormal muscle activities of the thigh, several causes are described in current literature, for example, the quadriceps femoris (QF) spasticity, or the QF premature and prolonged activity during gait [1], [10], [14]. The rectus femoris (RF) is often considered the main cause in limited knee flexion [15] because its prolonged activity in the swing-phase results in an unwanted knee extensor moment during swing [1], [16], [17].

SKG treatments include conservative approaches based on focal muscle inhibition by botulinum toxin, chemodenervation, and functional surgery consisting of muscle release or muscle transfer [14], [16], [18], [19]. As RF spasticity was considered the main cause of SKG, treatments focused mainly on reducing RF activity [18]. An average recovery of few degrees in KF was obtained by RF treatments, but with a very large spread in the amount of knee flexion recovery in the investigated sample [18], [19]. Such large between-subjects variability of the treatment efficacy suggests the need of a deeper assessment of QF muscles during the stiff-legged gait of stroke patients to improve the appropriateness of the interventions.

Quite surprisingly from a clinical point of view, the vastus intermedius (VI) is overlooked in literature, with 1 published study only on a very limited sample [20]. Presumably the reason being that VI is a deep muscle that cannot be measured by surface EMG. However, VI cross-sectional area is nearly four times that of RF and is similar to that of the vasti muscles [21]. For this reason its contribution to the process of knee extension mechanism should not be neglected.

To start filling the existing gap, we retrospectively analyzed VI activity acquired by fine-wire (fw) electrodes during spontaneous gait in a sample of chronic stroke patients covering a wide range of functional impairments. The aim of this study was to describe the patients’ VI activation patterns with respect to the normal reference pattern provided by Perry [1], and the occurrence of abnormal activities within the gait cycle (GC), and during each GC sub-phase.

Section snippets

Study design and settings

In this observational study, we retrospectively analyzed data from chronic hemiplegic stroke patients with SKG who had undergone VI electromyography (EMG) with fw electrodes over the period of time from February 2010 to May 2015. Data were recorded at the Laboratory of Motion Analysis and Biomechanics, at the Sol et Salus Hospital based in Rimini, Italy, and at the Laboratory of Motion Analysis, at the San Giorgio Rehabilitation Hospital based in Ferrara, Italy. The consistency for Gait

Results

In the investigated sample of 46 hemiplegic patients only two subjects showed a physiological pattern of VI EMG activity in terms of onset and offset. The remaining 44 patients presented VI abnormal timing: 21 patients (46%) presented a premature and prolonged activity; 11 patients (24%) had a prolonged activity; 9 patients (20%) presented a continuous activity; 2 patients (4%) had a premature activity, and 1 patient (2%) a prolonged and out-of-phase activity. Fig. 1 summarizes these results.

Discussion

For the first time in literature this study presents a descriptive analysis of VI activation during gait in a sample of stroke patients with SKG assessed by fw EMG. As illustrated in Fig. 1, for the vast majority of patients (96%), the indwelling EMG pattern resulted non physiological, when compared to the normal reference pattern reported by Perry [1]. The clinical relevance of this finding can be appreciated by considering that the VI cross-sectional area, and consequently its force, is about

Conclusion

Our results suggest that VI muscle can contribute to SKG in adult stroke patients. Therefore, the measurement of VI activity should be included in the standard clinical (retraction, spasticity, force) and instrumental (GA, surface EMG) assessment of SKG to correctly understand its physiopathology, to assist in the decision-making process, and to increase the appropriateness of the therapeutic protocols.

Conflict-of-interest statement

All the Authors have no conflict of interest associated with this manuscript.

Financial disclosure statement

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

Acknowledgments

The authors would like to acknowledge dr. Isabella Campanini, AUSL of Reggio Emilia, Italy, for her kind and insightful suggestions when discussing the study results.

References (36)

Cited by (17)

  • Differences in causes of stiff knee gait in knee extensor activity or ankle kinematics: A cross-sectional study

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    The rectus femoris-reflex excitability at toe-off is increased in stroke patients, negatively correlating with the peak knee flexion angle during the swing phase [10]. Moreover, the amplified activity of the vastus lateralis owing to multijoint heteronymous excitatory reflexes induced by hip extension and anomalous activity of the vastus intermedius contributes to SKG [11,12]. Hence, SKG treatment focuses on decreasing quadriceps activity during the swing phase.

  • EMG gait data from indwelling electrodes is attenuated over time and changes independent of any experimental effect

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    In the consensus project caution was advised when using fine-wire EMG to study dynamic contractions (Besomi et al., 2019). Nonetheless fine-wire EMG is currently used to study muscle activity in dynamic tasks like walking (Akuzawa et al., 2016; Allison et al., 2018; Barn et al., 2014; Farris et al., 2019; Kelly et al., 2015; Kelly et al., 2016; Lawrenson et al., 2019; Maharaj et al., 2016; Maharaj et al., 2017, 2018; Mazzoli et al., 2018; Murley et al., 2009, 2010, 2014; Zacharias et al., 2019). Whilst shank muscle activation patterns and onset times recorded using indwelling EMG and surface EMG sensors have been shown to be similar (Bogey et al., 2003; Bogey et al., 2000; Chimera et al., 2009; Peter et al., 2019), there are important theoretical differences that could affect the comparability of the signals over time.

  • Kinematic gait asymmetry assessment using joint angle data in patients with chronic stroke—A normalized cross-correlation approach

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    In addition, we discovered that kinematic gait asymmetry of the knee joint during walking is related to gait speed, balance ability, and activities of daily living. Stroke patients frequently experience decreased knee joint flexion angle during walking, as a result of a common gait disorder known as stiff-knee gait (SKG) [39–41]. Our knee joint angle waveform data shown in Fig. 1b indicates that in the swing phase, the knee joint flexion angle on the affected side decreases.

  • <sup>☆</sup>Impact of instrumental analysis of stiff knee gait on treatment appropriateness and associated costs in stroke patients

    2019, Gait and Posture
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    We recently presented an algorithm, based on instrumental gait analysis data, to differentiate among the causes of SKG - the inadequate APO and the presence of knee extensors braking activity - so as to identify a subset of patients who would benefit from focal inhibition [7]. A further increase in treatment appropriateness can be achieved by a direct measurement of the quadriceps muscles by dynamic electromyography (dEMG) [18,19]. The aim of the current study is to estimate the percentage of inappropriate SKG treatments by focal RF inhibition that can be avoided by adding an instrumental assessment of gait to the clinical evaluation.

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