Novel Applications of Ultrasound Technology to Visualize and Characterize Myofascial Trigger Points and Surrounding Soft Tissue

Design for a vibration source that can be used for VSE imaging of the upper trapezius. This design can induce vibrations uniformly over a broad area both along the muscle fibers (A) and transverse to the muscle fibers (B).

PPTs (in lb) measured using pressure algometry demonstrated lower thresholds in A-MTrPs and L-MTrPs compared with palpably normal muscle (N>A, L; P<.007). The error bars correspond to SDs.

Gray-scale imaging of a trigger point in the upper trapezius. (A) An isolated MTrP appears as a well-defined focal hypoechoic nodule. (B) A series of 4 hypoechoic MTrPs in the upper trapezius.

3D imaging of trigger points. A mechanically scanned 3D probe (3D9-3v) was used for 3D imaging in a subject with a latent trigger point. The MTrP is clearly identified (arrows) in all 3 planes as well as in a multislice view.

Simultaneous 2D gray-scale and color variance imaging. (A and B) Normal upper trapezius muscle. The normal muscle appears isoechoic and has uniform color variance (TIS=0). (C and D) Muscle with a palpable MTrP. A hypoechoic region and a well-defined focal decrease of color variance indicating a localized stiffer region is visible (TIS=1). (E and F) Muscle with a palpable MTrP. Multiple hypoechoic regions and multiple focal nodules are visible (TIS=2). Abbreviation: TIS, tissue imaging score.

3D color Doppler imaging of blood vessels passing through trigger points. A mechanically scanned 3D probe (3D9-3v) was used for 3D imaging in a subject with a latent trigger point. The blood vessel is clearly visualized in all 3 planes.

(A) The main blood supply to the upper trapezius is through the ascending branch of the transverse cervical artery. Unless stated otherwise, this image is from the 20th U.S. edition of Gray's Anatomy of the Human Body, originally published in 1918 and therefore lapsed into the public domain. (B) The ascending branch can be visualized using color Doppler imaging. The blood flow waveform in the ascending branch or other branches arising from this vessel can provide an indication of the flow resistance in the perfused tissue. (C) A blood vessel passing through an A-MTrP.

(A) Subject with an A-MTrP visible as a hypoechoic region on the gray-scale image, and an artery running through the MTrP visible on color Doppler (the Doppler sample volume is placed inside the MTrP). High-resistance blood flow waveform with retrograde diastolic flow was observed in the artery. (B) The same subject had an L-MTrP on the contralateral side with an artery running through it, which showed elevated diastolic flow but no retrograde diastolic flow. (C) Four waveform shapes observed in our studies. C.1 shows arterial flow in muscle with no diastolic flow (BFS=0). C.2 shows elevated flow in diastole (BFS=1). C.3 shows oscillatory high-resistance flow with retrograde flow in early diastole (BFS=2). C.4 shows sustained retrograde flow in diastole (BFS=2). Abbreviation: BFS, blood flow score.

Distribution of scores based on US imaging for (A) active, (B) latent, and (C) normal sites in upper trapezius muscle. Muscle with palpable trigger points on clinical exam (either active or latent) had a significantly higher TIS compared with palpably normal muscle (P<.002). One-hundred percent of A-MTrPs and L-MTrPs had a TIS of 1 or 2, compared with 36% of normal sites. A-MTrPs had a significantly higher BFS compared with L-MTrPs (P<.029). Sixty-nine percent of active sites had a BFS of 2 compared with 16.7% of latent sites. Abbreviations: BFS, blood flow score; TIS, tissue imaging score.