Methods of quantifying muscle properties in cervical pain via sonoelastography and tactile imaging.

Abstract

Myofascial trigger points (MTrPs) are a very common, yet poorly understood and overlooked, cause of nonarticular musculoskeletal pain. MTrPs are localized, stiff, hyperirritable tender nodules, palpated in taut bands of skeletal muscle. We are investigating sonoelastography and tactile imaging as complementary objective methods to measure the physical and mechanical properties of MTrPs. Sonoelastography was performed with an external 92-Hz vibration in the upper trapezius muscles in patients with acute neck pain (n=45). The area of reduced vibration amplitude was measured as an estimate of the size of the stiff MTrPs. A subset of patients (n=3) was studied via tactile imaging, using an array of pressure sensors mimicking a physical examination. Young’s modulus of MTrPs was estimated using a previously developed technique for breast lesion characterization. Using sonoelastography, active sites (spontaneously painful with palpable MTrPs) had larger MTrPs (0.57±0.20 cm2) compared to latent (MTrPs painful on palpation) sites (0.36±0.16 cm2), or palpably normal (0.17±0.22 cm2) sites [P<0.01, one-way analysis of variance (ANOVA)]. Using tactile imaging, preliminary trends show that active sites are likely to be stiffer (61±25 kPa) than latent sites (38±18 kPa). These results demonstrate that MTrPs may be objectively imaged and quantitatively characterized. Further studies are needed to confirm these preliminary results.