Abstract
In stroke survivors, rectus femoris (RF) spasticity is often implicated in gait pattern alterations such as stiff knee gait (SKG). Botulinum toxin type A (BoNT-A) is considered the gold standard for focal spasticity treatment. However—even if the accuracy of injection is crucial for BoNT-A efficacy—instrumented guidance for BoNT-A injection is not routinely applied in clinical settings. In order to investigate the possible implications of an inadequate BoNT-A injection on patients’ clinical outcome, we evaluated the ultrasound-derived RF characteristics (muscle depth, muscle thickness, cross-sectional area and mean echo intensity) in 47 stroke survivors. In our sample, we observed wide variability of RF depth in both hemiparetic and unaffected side of included patients (0.44 and 3.54 cm and between 0.25 and 3.16 cm, respectively). Moreover, our analysis did not show significant differences between treated and non-treated RF in stroke survivors. These results suggest that considering the inter-individual variability in RF muscle depth and thickness, injection guidance should be considered for BoNT-A treatment in order to optimize the clinical outcome of treated patients. In particular, ultrasound guidance may help the clinicians in the long-term follow-up of muscle quality.
Highlights
Spasticity was first defined by Lance in 1980 as a motor disorder characterized by a speed-dependent increase in tonic stretch reflexes with exaggerated tendon reflexes, secondary to hyperexcitability of the stretch reflex as a component of the upper motor neurons [1].Hyperactivity of the rectus femoris (RF) due to spasticity can modify the gait pattern with a reduction of the peak knee flexion and consequent stiff knee gait (SKG) [2]
MD range observed in our patients, combined with inter individual physiological variability and possible muscle changes induced by spasticity, suggests that those aspects may severely affect the precision of Botulinum toxin type A (BoNT-A) injection, potentially reducing the clinical effect of BoNT-A treatment
Picelli et al analyzed the accuracy of anatomic-landmark guided and electrical stimulation-guided injections in gastrocnemius muscle, measured using ultrasonography and found that the accuracy was significantly higher for the medial gastrocnemius than for the lateral, observing that the medial gastrocnemius was significantly thicker than lateral [19]
Summary
Spasticity was first defined by Lance in 1980 as a motor disorder characterized by a speed-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon reflexes, secondary to hyperexcitability of the stretch reflex as a component of the upper motor neurons [1]. Hyperactivity of the rectus femoris (RF) due to spasticity can modify the gait pattern with a reduction of the peak knee flexion and consequent stiff knee gait (SKG) [2]. The compensation strategies to advance the limb in space, such as ipsilateral hip circumduction or contralateral vaulting, determine a less efficient gait pattern and increased energy expenditure [4]. Dynamic simulation studies showed that knee torque affects the swing phase more than hip torque, suggesting that inappropriate RF activity should reduce knee flexion [5].
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