Shear-Wave Elastography Supports that Muscle Stiffness Should NOT be Considered a Criterion to Determine the Presence of Myofascial Trigger Points in the Infraspinatus Muscle.

Abstract

Abstract: Objective: This study aimed to determine latent Myofascial trigger points (MTrPs) and asymptomatic surrounding areas differences in pain pressure thresholds (PPTs) and shear-wave elastography (SWE) metrics differences. Design: Latent MTrPs and asymptomatic control points were identified within the infraspinatus muscle. A blinded examiner assessed the PPTs and acquired three SWE images of each location. PPT and SWE scores were compared by location (MTrP and control) and gender. Finally, correlations among demographics, PPTs and SWE data were calculated. Results: Forty participants were analyzed. PPTs were significantly lower in latent MTrPs compared with control points in males (p=0.003) and females (p<0.001), and lower in females compared with males (MTrP p<0.001; control point p=0.006). No significant SWE differences were found between MTrPs and control points (p>0.05) nor between males and females (MTrP and control points, p>0.05). In contrast with the accepted MTrP definition, those areas with greater PPTs exhibited greater stiffness via SWE (p<0.01). Conclusion: Although PPT scores indicated significant differences in hyperirritability between latent MTrPs and control points, SWE measurements revealed no significant differences in muscle stiffness. Furthermore, muscle stiffness was significantly associated with greater PPT scores, challenging the hypothesis that stiffer areas can be identified as MTrPs or sources of pain.