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.
PATIENTS: Group 1: MPS
+ 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