title: Lidocaine Injection in the Intramuscular Innervation Zone Can Effectively Treat Chronic Neck Pain Caused by MTrPs in the Trapezius Muscle.
abstract: BACKGROUND
  An increasing number of people suffer from neck pain due to life style and prolonged use of computers. Research has revealed that myofascial trigger points (MTrPs) and the intramuscular innervation zone (IZ) are involved in neck pain. MTrPs are induced mainly by IZ dysfunction of the affected skeletal muscle and the 2 do not overlap in location. The question is whether injection treatment in MTrPs or in the IZ is more effective to relieve MTrPs-associated pains. The precise location and body-surface map of the intramuscular IZ in the trapezius muscle and a clinical injection study in the IZ may provide a useful answer to the question.
  
  
  OBJECTIVE
  This study aimed to investigate the efficacy of lidocaine injection in the intramuscular IZ for the treatment of chronic neck pain caused by MTrPs in the trapezius muscle.
  
  
  METHODS
  Prospective observational study, approved by the local research ethics.
  
  
  METHODS
  University hospital, departments of Anesthesiology and Anatomy.
  
  
  METHODS
  First, for the determination of IZ distribution and body-surface mapping, a modified intramuscular Sihler's neural staining technique was applied to elucidate nerve distribution patterns of the trapezius muscle. Then, 120 patients with myofascial pain syndrome (MPS) of the trapezius muscle were randomly divided into 5 groups for analysis. Group 1 (n = 24) received injections of saline (0.9% NaCl) at the MTrPs. Group 2 (n = 24) received injections of 0.5% lidocaine at the MTrPs. Group 3 (n = 24) received injections of saline (0.9% NaCl) at the mid-upper trapezius (Point E). Group 4 (n = 24) received injections of 0.5% lidocaine at Point E. Group 5 (n = 24) received a combined injection of 0.5% lidocaine treatment at both Point E and the lower trapezius (Point F). The injection dose was 4 mL at each injection site. All patients received injections once a week for 4 weeks. The visual analogue scale (VAS) and the frequency of painful days per month (FPD) were obtained before treatment and at 2, 4, and 6 months after treatment.
  
  
  RESULTS
  The intramuscular terminal nerve branches presented a "dendritic" distribution in the trapezius muscle and were connected with each other to form an S-shaped IZ belt in the middle of the muscle belly. Compared with the MTrP injection group, lidocaine-injection therapy in the IZ significantly reduced the degree and frequency of neck pain in patients at 6 months after treatment, especially the combined lidocaine-injection therapy in the IZ of both the mid-upper trapezius and the lower trapezius are more effective (all P < 0.05).
  
  
  CONCLUSIONS
  This study confirms that lidocaine-injection therapy in the IZ significantly reduces the degree and frequency of neck pain in patients at 6 months after treatment. The combined lidocaine-injection therapy in the IZ of both the mid-upper trapezius and the lower trapezius is more effective. In addition, this study establishes a clear distribution map of intramuscular nerves that will be conducive to the future use of chemical blockers and electrical stimulation in the nervous system in treating MPS of the trapezius muscle.
  
  
  CONCLUSIONS
  The small number of patients and the short duration of follow-up.
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Xie
authors.affiliation: Department of Anesthesiology, Zunyi Medical College, Zunyi, Guizhou, China.
authors.forename: Bangyong
authors.initials: B
authors.lastname: Qin
authors.affiliation: Department of Anatomy, Zunyi Medical College, Zunyi, Guizhou, China.
authors.forename: Fangjiu
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Anesthesiology, Zunyi Medical College, Zunyi, Guizhou, China.
authors.forename: Tian
authors.initials: T
authors.lastname: Yu
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Zheng
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D059350:Chronic Pain / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007267:Injections; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009209:Myofascial Pain Syndromes / Q000188:drug therapy*; D019547:Neck Pain / Q000188:drug therapy*; D064171:Superficial Back Muscles / Q000187:drug effects / Q000294:innervation*; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine