Quantification of Myofascial Taut Bands

Abstract

Objective: To assess the correlation of clinician-identified myofascial taut bands with their presence and characteristics on magnetic resonance elastography (MRE) imaging.

Design: Cross-sectional study.

Setting: A magnetic resonance imaging (MRI) research laboratory.

Participants: A convenience sample of adults (N=65; 45 women, 20 men) identified by skilled musculoskeletal physicians as having upper trapezius myofascial pain-associated taut bands.

Interventions: Subjects had their taut bands outlined and were positioned within a 1.5T MRI machine. Shear waves were induced with a pneumatic transducer located over the belly of the involved muscle. Wave propagation was visualized with MRE images across a vibration cycle. Imaging data were assessed independently by 2 skilled MRE interpreters.

Main outcome measures: The primary outcome measure was the determination of the intra- and interrater reliabilities of MRE taut band identification and their correlation with clinician identification of band presence. Secondary outcomes consisted of the elucidation of the physical characteristics of taut bands and their surrounding muscle tissue.

Results: MRE intra- and interrater reliability was excellent, with kappa coefficients and 95% confidence intervals (CIs) of .86 (.68-1.00) and .93 (.79-1.00), respectively. Stiffness in MRE-identified taut bands was elevated at a mean ± SD of 11.5±2.4 kPa and fell to 5.8±0.9 kPa in surrounding muscle tissue (P<.001); muscular tone in trapezius muscles without a taut band was relatively uniform at 6.6±2.1 kPa. Agreement between the physicians and the MRE raters, however, was relatively poor (63.1%; 95% CI, 50.2%-74.7%).

Conclusions: Our findings suggest that while clinicians may overestimate, and current MRE techniques may underestimate, the presence of taut bands, these bands do exist, can be assessed quantitatively, and do represent localized areas of increased muscle stiffness.

Keywords: Elasticity imaging techniques; Magnetic resonance imaging; Muscles; Rehabilitation.

Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Apparatus setup for the MRE examination.

Figure 2

Scout planes that lead to the final MRE scan plane. (a) Oblique scout planes made on the axial images; (b) further scout planes made on an oblique axis. (c) The final scout image.

Figure 3

The automated thresholding process (ANALYZE®, Mayo Clinic, Rochester, MN) to determine the three maximum-likelihood thresholds that divide the stiffness range into four statistically significant classes. (a) Histogram of a typical case with taut band region and surrounding normal tissue region divided by the thresholding algorithm. (b) The division of stiffness classes in the region of interest for (a). (c) Histogram of a typical case which no threshed can be identified in the region of interest (ROI) that divides the stiffness range into any statistically significant classes. (d) The division of stiffness classes in the region of interest for (c). Based on the thresholding process, the whole ROI is one single class (excluding the image background), thus a homogenous region.

Figure 4

Typical MRE elastogram of region of interest (ROI) superimposed onto the regular MR image. I. Spine of scapula II. Taut band III. Surrounding muscle tissues IV. Cervical spine