Detecting local twitch responses of myofascial trigger points in the lower-back muscles using ultrasonography.

OBJECTIVE: To evaluate the role of ultrasonography for detecting local twitch responses (LTRs) of myofascial trigger points (MTrPs) in deeply located lower-back muscles.

DESIGN: Case-control study. Active MTrP was diagnosed in all patients based on the criteria proposed by Travell and Simons in their upper-trapezius or lower-back muscles. One investigator administered trigger point injections while observing LTRs on ultrasonography. The other investigator observed LTRs visually during the procedure.

SETTING: University rehabilitation hospital.

PARTICIPANTS: Patients (n=41; mean age, 51.8 ± 11.8y) with MTrPs in the upper-trapezius muscles and patients (n=62; mean age, 56.8 ± 11.9y) with MTrPs in the erector spinae or quadratus lumborum were recruited from April 29 to October 31, 2010.

INTERVENTIONS: Ultrasound-guided trigger point injection.

MAIN OUTCOME MEASURES: LTR detection rate according to the depth of MTrPs; subjective pain intensity using a visual analog scale before and immediately after the trigger point injection.

RESULTS: In upper-trapezius muscles, all LTRs were detected by means of both ultrasonographic and visual inspection. In the lower-back muscles, many LTRs were detected only on ultrasonography during the trigger point injection. For deep muscles, ultrasound helped identify LTRs that were not detected by using visual assessment. Pain was alleviated more significantly in the group with LTRs during trigger point injections compared with the group without LTRs.

CONCLUSIONS: These findings suggest that ultrasonography was useful for detecting LTRs of MTrPs, especially for LTRs in the deep muscles. Ultrasound guidance may improve the therapeutic efficacy of trigger point injection for treating MTrPs in the deep muscles.