Passive material properties of stroke-impaired plantarflexor and dorsiflexor muscles

Abstract

Background Following a stroke, intrinsic muscle properties such as stiffness may be altered, which is accompanied by increased spasticity and contractures. Previously, quantification of muscle stiffness has been based off of indirect measurements. Using shear wave ultrasound elastography, direct measurements of muscle material properties can be made. Methods Our aim was to evaluate material properties, specifically passive stiffness, using shear wave ultrasound elastography across a range of muscle lengths, in the medial gastrocnemius and the tibialis anterior in chronic stroke survivors. Findings Our main results show significant increases of 27.7% and 26.9 % in shear wave velocity of stroke-impaired medial gastrocnemius compared to the unimpaired contralateral side at 90° ankle angle (P=0.033) and 15° plantarflexion (P=0.001), respectively. However, no significant difference was found in the tibialis anterior between the two sides. Relatively weak correlations were found between SW velocity in the medial gastrocnemius and joint stiffness for both the non-paretic (ρ=0.384, P=0.001), and paretic side (ρ=0.363, P=0.002). Additionally, muscle stiffness estimates of stroke-impaired tibialis anterior from joint torque and angle measurements were significantly greater by 23.1% (P=0.033) than the unimpaired contralateral side. However, no significant difference was found in the medial gastrocnemius. Interpretation These results indicate that there are non-uniform changes in passive stiffness of stroke-impaired muscle. Therefore, muscles need to be evaluated individually to access alterations. Additionally, interpretation of joint-based calculations of muscle stiffness should be made cautiously. Having the ability to non-invasively assess muscle stiffness adaptations in vivo would aid in prognosis, evaluation, and treatment following a stroke.

Effects of stroke injury on the shear modulus of the lower leg muscle during passive dorsiflexion

“…4). This is novel, since the few studies using SWE in stroke subjects were focused on one muscle thought to be representative of the studied muscle group (17,39,44,47,62). Our pictorial analyses highlight that stroke survivors' response is commonly observed at the same muscle regions within plantar flexors: the highest values for GM followed by GL (Fig.…”

“…3B, experiment 2). Of particular relevance, the studies of Mathevon et al (47) and Jakubowski et al (39) focused on GM and reported higher shear modulus on the affected side of stroke survivors. Although we measured the shear modulus during standardized dynamic stretches, these studies positioned the ankle in the targeted angle first, before scanning the GM with the transducer.…”

Loss of variable fascicle gearing during voluntary isometric contractions of paretic medial gastrocnemius muscles in male chronic stroke survivors

“…For example, previous studies have reported remarkable alterations in muscle architecture in chronic stroke survivors (Li et al 2007;Gao & Zhang, 2008;Gao et al 2009;Zhao et al 2015;Dias et al 2017;. Material properties of muscle and tendon tissues have also been reported to be different in chronic stroke survivors (Zhao et al 2009;Lee et al 2015;Zhao et al 2015;Jakubowski et al 2017). Moreover, contractile properties appear to change in chronic stroke survivors, supported by a narrower width of active force-length curve (Gao & Zhang, 2008) or a greater velocity-dependent concentric torque decay (Clark et al 2006).…”

Volume and intramuscular fat content of upper extremity muscles in individuals with chronic hemiparetic stroke

“…These deficits are attributed to a loss of corticofugal projections that occur post stroke and result in paresis, loss of independent joint control and hypertonicity (Dewald & Beer, 2001;Miller & Dewald, 2012). Associated with neural deficits and resulting disuse, changes in musculoskeletal properties (sarcomere length, fascicle length, stiffness) may also have a negative impact on function, with only a few studies focusing on characterizing these musculoskeletal changes (Jakubowski, Terman, Santana, & Lee, 2017;Landin, Hagenfeldt, Saltin, & Wahren, 1977;Zhao, Ren, Roth, Harvey, & Zhang, 2015). The inability to efficiently and fully activate muscles, combined with decreased use of the upper extremity, will lead to muscle atrophy defined here as a decrease in muscle contractile element volume, and potentially an increase in intramuscular fat.…”