Difference in pain relief after trigger point injections in myofascial pain patients with & without fibromyalgia (FM)

OBJECTIVE: To compare responses to trigger point (TrP) injection

between patients having both myofascial pain syndrome (MPS)

caused by active TrPs and fibromyalgia syndrome (FMS) and

patients with MPS due to TrPs but without FMS.


Prospective design blinded measurement, before- after trial.

SETTING: A pain control medical clinic.


+ FMS; Group 2: MPS only. All patients (9 in each group) had

active TrPs in the upper trapezius muscle.


Myofascial TrP injection with 0.5% xylocaine.

MAIN OUTCOME MEASURES: Subjective pain intensity (PI), pain threshold

(PT), and range of motion (ROM) were assessed before,

immediately after, and 2 weeks after TrP injection.


In a comparison of preinjection measures to immediate

postinjection measures, only ROM was significantly improved

(p < .05) in Group 1 patients; all three parameters were

significantly improved (p < .05) in the Group 2 patients who

had only MPS. Two weeks after injection, both groups showed

significant improvement (p < .05) in all three measured

parameters as compared to preinjection measurements. In a

comparison of the two groups, the immediate effectiveness of

TrP injection was significantly less (p < .05) in Group 1

than in Group 2 for all three parameters. Two weeks after

injection, the degree of improvement in PT or ROM (but not

PI) was not significantly different between two groups.

Postinjection soreness (different from myofascial pain) was

more severe, developed sooner, and lasted longer in Group 1

than in Group 2.

CONCLUSION: Trigger point injection is a

valuable procedure for pain relief for patients in both

group. Patients with FMS are likely to experience significant

but delayed and attenuated pain relief following injection of

their active TrPs compared to myofascial pain patients with

similar TrPs but without FMS. Also, FMS patients are likely

to experience significantly more postinjection soreness for a

longer period of time.

Hong CZ, Hsueh TC

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