Randomized controlled study of the antinociceptive effect of ultrasound on trigger point sensitivity: novel applications in myofascial therapy?

OBJECTIVE: To investigate whether therapeutic ultrasound modulates the pain sensitivity of myofascial trigger points. DESIGN: Repeated measures, single-blinded randomized controlled trial of ultrasound treatment of trigger points. SETTING: Outpatient injury rehabilitation clinic. SUBJECTS: Forty-four patients (22 males, 22 females) with trigger points identified within the trapezius muscle. INTERVENTIONS: Five-minute therapeutic intensity of ultrasound versus 5-min low-intensity application of ultrasound to a trapezius myofascial trigger point locus. MAIN MEASURES: Pain pressure threshold readings were measured at the trapezius trigger point site before and after exposure to the ultrasound intervention. RESULTS: Pain pressure threshold scores increased an average of 44.4 (14.2)% after therapeutic exposure to ultrasound (pre-ultrasound test 35.4 (8.5) N, post-ultrasound test 51.1 (12.8) N). No significant difference in pain pressure threshold scores was observed with low-intensity ultrasound exposures (pre-ultrasound 36.1 (6.1) N, post-ultrasound 36.6 (4.8) N). CONCLUSIONS: Therapeutic exposures to ultrasound reduce short-term trigger point sensitivity. Ultrasound may be a useful clinical tool for the treatment and management of trigger points and myofascial pain syndromes.