Soft Tissue Stiffness Before and after Trigger Point Injections in Neck–Shoulder Myofascial Pain Syndrome: A Double-Blind, Randomized, and Controlled Crossover Trial with Botulinum Toxin A and Saline Injections

ABSTRACTObjectives: To determine values of soft tissue stiffness [STS] before and after injection treatment in neck–shoulder myofascial pain and to correlate them with self-reported and clinically assessed pain and disability.Methods: Thirty-one patients recruited by newspaper advertisement were screened by a physician. The subjects received either botulinum toxin A [BTA] or saline injections on two occasions four weeks apart. The volume of each injection was 0.05 ml of either normal saline [without preservative] or saline containing five units of BTA. The total dose varied from 15 to 35 U of BTA [total volume 0.15 to 0.35 ml]. The follow-up measurements were performed at four weeks after each treatment. The STS of trigger points [TrPs] and a reference point was determined using the STS meter [STSM]. The pressure-pain threshold [PPT] was determined using the dolorimeter. The subjective severity of neck–shoulder pain [SSNP] and the neck pain and disability scale [NPDS] were assessed with questionnaires. Th...