Trigger Point TOP
Trigger points are discrete, focal, hyperirritable spots located in a taut band of skeletal muscle. They produce pain locally and in a referred pattern and often accompany chronic musculoskeletal disorders. Acute trauma or repetitive microtrauma may lead to the development of stress on muscle fibers and the formation of trigger points. Patients may have regional, persistent pain resulting in a decreased range of motion in the affected muscles. These include muscles used to maintain body posture, such as those in the neck, shoulders, and pelvic girdle. Trigger points may also manifest as tension headache, tinnitus, temporomandibular joint pain, decreased range of motion in the legs, and low back pain. Palpation of a hypersensitive bundle or nodule of muscle fiber of harder than normal consistency is the physical finding typically associated with a trigger point. Palpation of the trigger point will elicit pain directly over the affected area and/or cause radiation of pain toward a zone of reference and a local twitch response. Various modalities, such as the Spray and Stretch technique, ultrasonography, manipulative therapy and injection, are used to inactivate trigger points. Trigger-point injection has been shown to be one of the most effective treatment modalities to inactivate trigger points and provide prompt relief of symptoms.
About 23 million persons, or 10 percent of the U.S. population, have one or more chronic disorders of the musculoskeletal system.1 Musculoskeletal disorders are the main cause of disability in the working-age population and are among the leading causes of disability in other age groups.2 Myofascial pain syndrome is a common painful muscle disorder caused by myofascial trigger points.3 This must be differentiated from fibromyalgia syndrome, which involves multiple tender spots or tender points.3 These pain syndromes are often concomitant and may interact with one another.
Trigger points are discrete, focal, hyperirritable spots located in a taut band of skeletal muscle. The spots are painful on compression and can produce referred pain, referred tenderness, motor dysfunction, and autonomic phenomena.4
Trigger points are classified as being active or latent, depending on their clinical characteristics.5 An active trigger point causes pain at rest. It is tender to palpation with a referred pain pattern that is similar to the patient's pain complaint.3,5,6 This referred pain is felt not at the site of the trigger-point origin, but remote from it. The pain is often described as spreading or radiating.7 Referred pain is an important characteristic of a trigger point. It differentiates a trigger point from a tender point, which is associated with pain at the site of palpation only (Table 1).8
A latent trigger point does not cause spontaneous pain, but may restrict movement or cause muscle weakness.6 The patient presenting with muscle restrictions or weakness may become aware of pain originating from a latent trigger point only when pressure is applied directly over the point.9
Tender points, by comparison, are associated with pain at the site of palpation only, are not associated with referred pain, and occur in the insertion zone of muscles, not in taut bands in the muscle belly.8 Patients with fibromyalgia have tender points by definition. Concomitantly, patients may also have trigger points with myofascial pain syndrome. Thus, these two pain syndromes may overlap in symptoms and be difficult to differentiate without a thorough examination by a skilled physician.
There are several proposed histopathologic mechanisms to account for the development of trigger points and subsequent pain patterns, but scientific evidence is lacking. Many researchers agree that acute trauma or repetitive microtrauma may lead to the development of a trigger point. Lack of exercise, prolonged poor posture, vitamin deficiencies, sleep disturbances, and joint problems may all predispose to the development of micro-trauma.5 Occupational or recreational activities that produce repetitive stress on a specific muscle or muscle group commonly cause chronic stress in muscle fibers, leading to trigger points. Examples of predisposing activities include holding a telephone receiver between the ear and shoulder to free arms; prolonged bending over a table; sitting in chairs with poor back support, improper height of arm rests or none at all; and moving boxes using improper body mechanics.11
Acute sports injuries caused by acute sprain or repetitive stress (e.g., pitcher's or tennis elbow, golf shoulder), surgical scars, and tissues under tension frequently found after spinal surgery and hip replacement may also predispose a patient to the development of trigger points.12
Patients who have trigger points often report regional, persistent pain that usually results in a decreased range of motion of the muscle in question. Often, the muscles used to maintain body posture are affected, namely the muscles in the neck, shoulders, and pelvic girdle, including the upper trapezius, scalene, sternocleidomastoid, levator scapulae, and quadratus lumborum.13 Although the pain is usually related to muscle activity, it may be constant. It is reproducible and does not follow a dermatomal or nerve root distribution. Patients report few systemic symptoms, and associated signs such as joint swelling and neurologic deficits are generally absent on physical examination.14
In the head and neck region, myofascial pain syndrome with trigger points can manifest as tension headache, tinnitus, temporomandibular joint pain, eye symptoms, and torticollis.15 Upper limb pain is often referred and pain in the shoulders may resemble visceral pain or mimic tendonitis and bursitis.5,16 In the lower extremities, trigger points may involve pain in the quadriceps and calf muscles and may lead to a limited range of motion in the knee and ankle. Trigger-point hypersensitivity in the gluteus maximus and gluteus medius often produces intense pain in the low back region.15 Examples of trigger-point locations are illustrated in Figure 1.16
Palpation of a hypersensitive bundle or nodule of muscle fiber of harder than normal consistency is the physical finding most often associated with a trigger point.10 Localization of a trigger point is based on the physician's sense of feel, assisted by patient expressions of pain and by visual and palpable observations of local twitch response.10 This palpation will elicit pain over the palpated muscle and/or cause radiation of pain toward the zone of reference in addition to a twitch response. The commonly encountered locations of trigger points and their pain reference zones are consistent.8 Many of these sites and zones of referred pain have been illustrated in Figure 2.10
Nonpharmacologic treatment modalities include acupuncture, osteopathic manual medicine techniques, massage, acupressure, ultrasonography, application of heat or ice, diathermy, transcutaneous electrical nerve stimulation, ethyl chloride Spray and Stretch technique, dry needling, and trigger-point injections with local anesthetic, saline, or steroid. The long-term clinical efficacy of various therapies is not clear, because data that incorporate pre- and post-treatment assessments with control groups are not available.
The Spray and Stretch technique involves passively stretching the target muscle while simultaneously applying dichlorodifluoromethane-trichloromonofluoromethane (Fluori-Methane) or ethyl chloride spray topically.5 The sudden drop in skin temperature is thought to produce temporary anesthesia by blocking the spinal stretch reflex and the sensation of pain at a higher center.5,10 The decreased pain sensation allows the muscle to be passively stretched toward normal length, which then helps to inactivate trigger points, relieve muscle spasm, and reduce referred pain.5
The decision to treat trigger points by manual methods or by injection depends strongly on the training and skill of the physician as well as the nature of the trigger point itself.10 For trigger points in the acute stage of formation (before additional pathologic changes develop), effective treatment may be delivered through physical therapy. Furthermore, manual methods are indicated for patients who have an extreme fear of needles or when the trigger point is in the middle of a muscle belly not easily accessible by injection (i.e., psoas and iliacus muscles).10 The goal of manual therapy is to train the patient to effectively self-manage the pain and dysfunction. However, manual methods are more likely to require several treatments and the benefits may not be as fully apparent for a day or two when compared with injection.10
While relatively few controlled studies on trigger-point injection have been conducted, trigger-point injection and dry needling of trigger points have become widely accepted. This therapeutic approach is one of the most effective treatment options available and is cited repeatedly as a way to achieve the best results.5
Trigger-point injection is indicated for patients who have symptomatic active trigger points that produce a twitch response to pressure and create a pattern of referred pain. In comparative studies,17 dry needling was found to be as effective as injecting an anesthetic solution such as procaine (Novocain) or lidocaine (Xylocaine).10 However, post-injection soreness resulting from dry needling was found to be more intense and of longer duration than the soreness experienced by patients injected with lidocaine.10
Trigger-point injection can effectively inactivate trigger points and provide prompt, symptomatic relief. Table 210,18 outlines the necessary equipment for trigger-point injection. Contraindications to trigger-point injection are listed in Table 310,18 and possible complications are outlined in Table 4.
The choice of needle size depends on the location of the muscle being injected. The needle must be long enough to reach the contraction knots in the trigger point to disrupt them. A 22-gauge, 1.5-inch needle is usually adequate to reach most superficial muscles. For thick subcutaneous muscles such as the gluteus maximus or paraspinal muscles in persons who are not obese, a 21-gauge, 2.0-inch needle is usually necessary.10 A 21-gauge, 2.5-inch needle is required to reach the deepest muscles, such as the gluteus minimus and quadratus lumborum, and is available as a hypodermic needle. Using a needle with a smaller diameter may cause less discomfort; however, it may provide neither the required mechanical disruption of the trigger point nor adequate sensitivity to the physician when penetrating the overlying skin and subcutaneous tissue. A needle with a smaller gauge may also be deflected away from a very taut muscular band, thus preventing penetration of the trigger point. The needle should be long enough so that it never has to be inserted all the way to its hub, because the hub is the weakest part of the needle and breakage beneath the skin could occur.6 041b061a72