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Musculoskeletal pain is a significant health problem for the North American population.1–9 Such pain affects between 10% and 20% of the population and is a major cause of morbidity.1 It is estimated that approximately half of the chronic pain complaints result from a musculoskeletal origin.2 It is hypothesized that myofascial trigger point (MTrP) injections may alleviate much of this pain. It is imperative that the Emergency Physician perform a thorough history and physical examination, with an emphasis on the neurological and orthopedic examination to exclude other causes of musculoskeletal pain.3
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The etiology and pathogenesis of MTrPs have yet to be elucidated. Likewise, the precise mechanism by which MTrP injections inactivate the trigger point is unknown. Researchers do agree that acute trauma or repetitive microtrauma appears to lead to the development of a MTrP.6 The risk for a MTrP is increased when other factors are present, including poor physical conditioning, poor posture, and prolonged bending.7 MTrPs mostly affect the muscle groups used to maintain posture (i.e., muscles of the neck, shoulders, and back). When the head and neck region is affected, the patient may present with a tension headache or temporomandibular joint pain.6
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MTrPs are hyperirritable points located within a taut band of skeletal muscle or fascia.2 When these points are compressed, they may cause referred pain, local tenderness, and autonomic changes.2 Pain may be localized or diffuse. It can be described as burning, dull, sharp, or some combination of these. Autonomic changes associated with a MTrP include dizziness, edema at the site, lacrimation, piloerection, salivation, and tinnitus. The compression of a MTrP can further lead to muscle spasm, stiffness, shortening, and fatigue.1 This may progress to impaired muscle coordination, reduced muscle strength, and decreased range of motion.1
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The diagnosis of a MTrP relies on the following criteria: a tender spot with an underlying taught band, pain on palpation of the tender spot, and a local twitch response (i.e., a transient local contraction of skeletal muscle fibers in response to palpation or needling).3 While the data on clinical outcomes provide no definitive answer, the best outcomes appear to occur in patients who exhibit a local twitch response with palpation.4 The current literature provides no pathophysiologic explanation for this result. There are no laboratory, pathology, or radiology studies to identify or verify a MTrP.
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Identifying the palpable, taut band is critical in locating the MTrP. The MTrP can be identified by flat palpation, snapping palpation, pincer palpation, and/or deep palpation. Flat palpation uses a fingertip to slide across the skin over the affected muscle to find the MTrP (Figure 113-1). The taut band may be felt under the sliding fingertip. Snapping palpation uses the tip of the index finger to pluck the skin in an attempt to feel the underlying taut band. This ...