Trigger points are discrete, focal, hyperirritable sites located within bands of skeletal muscle. The points are painful on compression and can produce referred pain, referred tenderness, motor dysfunction, and autonomic phenomena. A “local twitch response” can usually be produced when firm “snapping” pressure is applied perpendicular to the muscle over the trigger point. Trigger points often accompany chronic musculoskeletal disorders.
An active trigger point often causes pain at rest and produces a referred pain pattern that is similar to the patient's pain complaint. This referred pain is felt not at the site of the trigger point origin, but remote from it, and it is often described as spreading or radiating. Referred pain differentiates a trigger point from a tender point, which is associated with pain at the site of palpation only. A latent trigger point does not cause spontaneous pain but may restrict movement or cause muscle weakness. The patient commonly presents with muscle restrictions or weakness and may become aware of pain originating from a latent trigger point only when pressure is applied directly over the point.
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 microtrauma. Activities that produce repetitive stress on specific muscles may lead to trigger points. Acute sports injuries, repetitive stress, surgical scars, and tissues under tension after surgery may also predispose a patient to the development of trigger points.
Patients with trigger points often report regional, persistent pain that usually results in a decreased range of motion. Often, the postural muscles of the neck, shoulders, and pelvic girdle are affected. The pain may be related to muscle activity, or it may be constant. It is reproducible and does not follow a dermatomal or nerve root distribution. Joint swelling and neurologic deficits are generally absent on physical examination. 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.
Trigger points are diagnosed by palpation of a hard, hypersensitive nodule within a muscle. Localization of a trigger point is based on the examiners sense of feel. Common locations of trigger points are shown in Figure 1. No laboratory test or imaging technique is helpful for diagnosing trigger points.
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(1) Examine the patient for trigger points. |
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When treating myofascial pain syndromes, try to eliminate predisposing and perpetuating factors. Pharmacologic treatment includes analgesics and medications, such as antidepressants, to help sleep. Nonpharmacologic treatment modalities include massage, ultrasonography, application of heat or ice, diathermy, transcutaneous electrical nerve stimulation, ethyl chloride spray and stretch technique, and dry needling. These methods are more likely to require several treatments, and the benefits may not be as fully apparent for days.
Trigger point injection with local anesthetic can effectively inactivate trigger points and provide prompt, symptomatic relief. It is the most studied, effective, and commonly used treatment modality. It has a naloxone-reversible mechanism of action, suggesting an endogenous opioid system as a mediator for the decreased pain and improved physical findings after injection with local anesthetic.
In comparative studies, dry needling was found to be as effective as injecting an anesthetic solution. However, soreness resulting from dry needling was found to be more intense and of longer duration than that experienced by patients injected with lidocaine.
An injectable solution of 1% lidocaine or 1% procaine typically is used, although saline is also used. Diclofenac (Voltaren) and botulinum toxin type A (Botox) have been used, but these substances may have significant myotoxicity. Procaine has the distinction of being the least myotoxic of all local injectable anesthetics. Injectable corticosteroids may also be added to the local anesthetic, but data supporting added efficacy for steroids are limited.
Postinjection soreness is common, but the patient's relief of the referred pain pattern measures the success of the injection. Reinjection of the trigger points is not recommended until the postinjection soreness resolves, usually after 3 or 4 days. If two or three previous attempts have been unsuccessful, do not continue injecting a site. Encourage patients to remain active, putting muscles through their full range of motion for a week after injection, but advise them to avoid strenuous activity, especially for 3 or 4 days.
Complications of trigger point injections include vasovagal syncope, local pain, needle breakage, hematoma formation, and skin infection. All needle injections have the risk of entering or administering medication to an inappropriate or unintended area. Pneumothorax may be avoided by never aiming a needle at an intercostal space. Ask about bleeding tendencies, because capillary hemorrhage increases postinjection soreness and ecchymosis. Have patients refrain from daily aspirin for at least 3 days before the procedure.
INDICATIONS
CONTRAINDICATIONS
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PROCEDURE
Common locations of trigger points. Place the patient in a comfortable position to assist with muscle relaxation. The prone or supine position is usually most effective and may also help to avoid injury if a vasovagal reaction occurs. Examine the patient for trigger points, especially in the areas where they most frequently occur. Choose a 23- to 25-gauge needle that is long enough to reach the trigger point; a ½- to 1½-inch needle usually is adequate.
PITFALL: Using a smaller-diameter needle may cause less discomfort, but it may be deflected away from a very taut muscular band.
PITFALL: Never insert the needle to its hub to minimize the risk of needle breakage.
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Cleanse the skin overlying the trigger point with alcohol. Use alternating pressure between index and middle finger to isolate the location of the trigger point (Figure 2A and 2B). Position the trigger point halfway between the fingers to keep it from sliding to one side during the injection (Figure 2C).
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(2) Cleanse the skin overlying the trigger point with alcohol, and isolate the location of the trigger point by alternating pressure between the index and middle fingers. |
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Using sterile technique, inject with the needle parallel to the fingers and away from the hand. Press firmly downward and apart with the fingers to maintain pressure for hemostasis and to ensure adequate tension of the muscle fibers to allow penetration of the trigger point.
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(3) Inject with the needle parallel to the fingers and away from the hand. |
PITFALL: Before advancing the needle into the trigger point, warn the patient of the possibility of pain or muscle twitching when the needle enters the muscle.
Insert the needle so that it may enter the trigger point at an angle of 30 degrees. Withdraw the plunger before injection to ensure that the needle is not within a blood vessel.
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(4) The needle should enter the trigger point at a 30-degree angle. |
PITFALL: Never aim a needle at an intercostal space to prevent the risk of pneumothorax.
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Inject a small amount (0.2 mL) of solution into the trigger point. Withdraw the needle to the level of the subcutaneous tissue, and then repeat the injection process superiorly, inferiorly, laterally, and medially until the local twitch response is eliminated or resisting muscle tautness is relieved. Immediately have the patient actively move each injected muscle through its full range of motion three times to stretch the injection site.
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(5) Inject a small amount of solution into the trigger point, withdraw the needle to the subcutaneous tissue, and then repeat injections superiorly, inferiorly, laterally, and medially until the local twitch response has stopped or the resisting muscle tautness is relieved. |
After injection, palpate the area for other trigger points. If found, they should be isolated and injected. Apply pressure to the injected area for 2 minutes to promote hemostasis. Apply an adhesive bandage.
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(6) Apply pressure to the injected area for 2 minutes to promote hemostasis, and apply an adhesive bandage. |
PITFALL: Failing to apply direct pressure for at least 2 minutes after injection makes hematoma formation much more likely.
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CODING INFORMATION
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INSTRUMENT AND MATERIALS ORDERING
Common materials for trigger point injection, including a 3- or 5-mL syringe, 1% lidocaine without epinephrine, or 1% procaine, and 22-, 25-, or 27-gauge needles of various lengths. A suggested tray for performing soft tissue aspirations and injections is listed in Appendix D. Skin preparation recommendations appear in Appendix H.
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