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. Objectives: 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. Study Design: Prospective observational study, approved by the local research ethics. Setting: 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. Limitations: The small number of patients and the short duration of follow-up. Key words: Neck pain, intramuscular innervation zone, myofascial trigger points, lidocaine

Anatomical Bases of the Temporal Muscle Trigger Points

“…Studies on the distribution map of nerve branching to the trapezius muscle suggested that dysfunction of the innervation zone was responsible for the emergence of MTPs [28,29]. This hypothesis is further supported by the physiopathological events following muscle injuries.…”

Rapid Improvement in Neck Disability, Mobility, and Sleep Quality with Chronic Neck Pain Treated by Fu’s Subcutaneous Needling: A Randomized Control Study

“…Furthermore, given that most people are high responders to needle pain [ 39 ], remote therapy and needle-less methods are the better options for health care. Remote injection with anesthetics has been demonstrated to be an effective treatment for chronic neck pain [ 40 ]. The analgesic effects of intramuscular lidocaine injection act on voltage-gated sodium channels to block nerve conduction and sensation in the peripheral nervous system [ 41 ].…”

Bases anatômicas dos pontos-gatilho do músculo temporal

“…Em nosso trabalho encontramos maior número de pontos de entrada do nervo no músculo próximos ao ponto de entrada do nervo no músculo, como no trabalho de Happak et al (1997). Assim como em pesquisas realizadas com o músculo trapézio, a posição dos PGMs segue os propostos por Travell e Simons (1983) (Fernández-de-las-Peñas et al, 2007Akamatsu et al, 2015;Xie et al, 2015), sugerindo que os pontos-gatilho têm uma relação com a ramificação nervosa (Xie et al, 2015).…”

“…Esta região é chamada de zona de inervação (IZ) (Simons, 2001;Barbero et al, 2013). Em trabalhos com o músculo trapézio, foi feito um mapeamento das ramificações dos nervos no interior do músculo e os autores sugeriram que o surgimento dos pontos-gatilho está relacionado com disfunção da zona de inervação (Barbero et al, 2013;Xie et al, 2015).…”

“…Os pontos-gatilho oferecem uma alta incidência de dor, sendo a principal fonte para 30% até 80% de pacientes atendidos em clínica de dor ou em atenção primária (Morihisa et al, 2016). Uma pesquisa realizada com a introdução de lidocaína nos pontos-gatilho no músculo trapézio, após o mapeamento da zona de inervação mostrou diminuição da dor miofascial (Xie et al, 2015).…”