Quantification of dry needling and posture effects on myofascial trigger points using ultrasound shear-wave elastography.

Objectives: To determine (1) whether the shear modulus in upper trapezius muscle myofascial trigger points (MTrPs) reduces acutely after dry needling (DN), and (2) whether a change in posture from sitting to prone affects the shear modulus.

Design: Ultrasound images were acquired in B mode with a linear transducer oriented in the transverse plane, followed by performance of shear-wave elastography (SWE) before and after DN and while sitting and prone.

Setting: University.

Participants: Women (N=7; mean age ± SD, 46±17y) with palpable MTrPs were recruited.

Intervention: All participants were dry needled in the prone position using solid filament needles that were inserted and manipulated inside the MTrPs. SWE was performed before and after DN in the sitting and prone positions.

Main Outcome Measure: MTrPs were evaluated by shear modulus using SWE.

Results: Palpable reductions in stiffness were noted after DN and in the prone position. These changes were apparent in the shear modulus map obtained with ultrasound SWE. With significant main effects, the shear modulus reduced from before to after DN (P<.01) and from the sitting to the prone position (P<.05). No significant interaction effect between time and posture was observed.

Conclusions: The shear modulus measured with ultrasound SWE reduced after DN and in the prone position compared with sitting, in agreement with reductions in palpable stiffness. These findings suggest that DN and posture have significant effects on the shear modulus of MTrPs, and that shear modulus measurement with ultrasound SWE may be sensitive enough to detect these effects.