Lidocaine-injection therapy in the intramuscular innervation zone effectively treats neck pain caused by myofascial trigger points in the trapezius muscle, according to research published in Pain Physician.

Previous research has shown that myofascial trigger points (MTrPs) are involved in neck pain. MTrPs are highly localized, irritable spots that are indurated and cord-shaped and can be palpated in the skeletal muscle. These points are fine and hypersensitive, and pain may be triggered when they are stretched, pressed, or contracted.

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Long hours hunching over a computer or other adverse postures of the neck and shoulder can cause MTrPs. One of the most vulnerable muscles in people who work long hours in these positions is the trapezius muscle.

MTrPs are induced mainly by dysfunction in the intramuscular innervation zone (IZ) and the location of the two does not overlap. This often leads to the question of whether lidocaine injection is a reasonable treatment method. The results from this study reveal that injection to the IZ zone for chronic neck pain originating from MTrPs in the trapezius muscle is more effective than injections administered to directly to the MTrPs.

“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,” wrote the study authors.

In order to determine the IZ distribution and map the body-surface, researchers applied a modified intramuscular Sihler’s neural staining technique on cadavers to find the nerve distribution patterns of the trapezius muscle.