title: Difference in pain relief after trigger point injections in myofascial pain patients with and without fibromyalgia.
abstract: 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.
  
  
  METHODS
  Prospective design blinded measurement, before- after trial.
  
  
  METHODS
  A pain control medical clinic.
  
  
  METHODS
  Group 1: MPS + FMS; Group 2: MPS only. All patients (9 in each group) had active TrPs in the upper trapezius muscle.
  
  
  METHODS
  Myofascial TrP injection with 0.5% xylocaine.
  
  
  METHODS
  Subjective pain intensity (PI), pain threshold (PT), and range of motion (ROM) were assessed before, immediately after, and 2 weeks after TrP injection.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of California, Irvine, USA.
authors.forename: C Z
authors.initials: CZ
authors.lastname: Hong
authors.forename: T C
authors.initials: TC
authors.lastname: Hsueh
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage*; D005260:Female; D005356:Fibromyalgia / Q000188:drug therapy* / Q000503:physiopathology; D006801:Humans; D007273:Injections, Intramuscular; D008012:Lidocaine / Q000008:administration & dosage*; D008875:Middle Aged; D009209:Myofascial Pain Syndromes / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement; D011446:Prospective Studies; D016059:Range of Motion, Articular; D012785:Shoulder Joint / Q000502:physiology
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine