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Garrett Lee, M.D., James Zucherman, M.D., and Dean T. Mason, M.D.
St. Mary's Spine Center, San Francisco, CA
The low power laser, deemed to be a nonsignificant risk device by the Food and Drug Administration, has been used successfully for more than two decades in anesthesia and wound healing 1-4. It also has been applied for the relief of pain in a variety of conditions including rheumatoid arthritis, post-herpetic neuralgia, etc. 5-9. Zhou had used low level laser as acupuncture anesthesia in more than 7000 patients for tooth extractions and minor maxillofacial surgery 1,2. Mester had treated more than 1300 patients with open wounds and ulcers, which would not heal with conventional methods and plastic surgery 3,4. The low power laser is believed to stimulate fibroblastic production of collagen, accelerate neovascularization, enhance anti-inflammatory and immunosuppressive activity, and reduce pain and edema 10. In this study, we examined whether the laser had any propitious effects in patients with common musculoskeletal pains of the head, neck and shoulders.
Methods
Forty patients with pain of musculoskeletal origin were evaluated. There were 22 females and 18 males, mean age 52 years. The great majority of these patients had been evaluated and treated by their own physicians but continued to have pain. Many had pain in more than one site; some had concomitant pain in sites other than the head, neck and shoulders. The symptoms included headache pain (12), neck pain (23), jaw pain (3), arm pain (12), shoulder pain (18), musculoskeletal chest pain (1), wrist pain (1), tingling/numbness of the hands (3), back pain (20), hip pain (7), groin pain (1), and leg pain (8).
The primary diagnoses in the 40 patients were: cervical spine strains (25), shoulder strains (2), thoracic spine strains (2), lumbar spine strains (8), TMJ dysfunction (2), and strain of the groin (1).
Patients were examined for pain and tenderness and were treated with the low level infrared laser. The latter is a low power laser light which emitted 100 - 300mW at 830 nm wavelength and was directed to the soft tissue injury and lesion sites at the periosteal-osseous junction usually at the attachment sites of the tendons, muscles and ligaments where such injuries occurred.
Following treatment, patients were asked if they had some relief (i.e., less pain), complete relief (i.e., no pain), no relief (no change), or the pain was worse.
Results
All 40 patients indicated they either were completely relieved (6/40) or had less pain (34/40) after low power laser therapy. None reported worsening of pain or no pain relief after therapy. No patients had any adverse side effects from the treatment.
Of the patients who had complete relief, 5 returned for follow-up (average about 12 weeks) and all 5 continued to have no pain. In patients who had some or partial relief of pain, 29 returned for follow-up; 23 continued to have less pain than before and 6 reported having no pain.
Discussion
Although further controlled double-blind studies are needed and will soon be underway to substantiate these initial findings, the low power laser therapy appears to have salutary effects on patients with pain of musculoskeletal origin. All patients indicate they were completely or partially relieved by the low power laser treatment. Many of the pains arising from these musculoskeletal strain and sprain conditions are the result of soft tissue injuries. In the human body, muscles, tendons, ligaments, fascia and periosteum are soft tissues which can be injured following falls, sports injuries, auto accidents, and birth traumas. Routine and repetitive movements can perpetuate these injuries. Tendons and ligaments are composed of collagen fibers and penetrate as Sharpey fibers into the periosteum and cortical plate of the bone. These fibers at the periosteum are vulnerable to repetitive stress and sudden tears from trauma or any acceleration-deceleration injury. These injuries are commonly seen along the tips of the spinous processes of the lower cervical and upper thoracic vertebra 11. They may also be found along the attachment sites of tendons and ligaments of the shoulders as well. The arms, elbows, wrists, hands, and fingers may become involved with severe pain, tingling and numbness, but such pain is frequently due to one or more primary sites of injury in the cervical area and shoulder. It is well known that when injury occurs in the lower cervical spine, pain can be referred into the arms, forearms, wrists, hands and fingers 12,13.
Following soft tissue injury, noxious chemicals such as bradykinins, prostaglandins, histamines, and others are released and stimulate the free pain nerve endings 14. The pain stimulus travels by way of A-delta and C fibers to the posterior horn of the spinal cord and then up the spinal cord to the brain where pain is perceived. Some pain impulses are transmitted to the anterior horn of the spinal cord by way of the interneuronal connections and to local and remote muscles causing muscle tension, splinting, spasms, contractures, and resulting in muscle ischemia. Muscle contractures can result in entrapment of blood vessels. As a result, the soft tissue peripheral to the entrapment may develop signs and symptoms of inflammation. Soft tissue lesions occurring along the superior and inferior tips of the cervical spinous processes result in the release of pain chemicals which stimulate paravertebral muscles to contract causing compression of the intervertebral disc and irritation to the nerve root, resulting in paresthesias, numbness and other autonomic responses in one or both upper extremities.
Sites of soft tissue lesion or injury locations are determined by palpation, usually at periosteal-osseous sites at insertions or origins of muscles as well as ligamentous bony attachments. In the cervical vertebrae, the interspinous ligaments at C5-7 are found to be prone to tear following neck injuries 15,16. The interspinous ligaments are relatively slack when the posture of the head and neck is in the upright or balanced position.
During hyperextension of the head (>25 degrees from the vertical), the ligaments are more slack and tips of the spinous process may touch one another, however, in hyperflexion (>10 degrees from the vertical), the cervical interspinous ligaments are extended to their maximum physiologic range and the interspinous ligaments are most vulnerable to tears usually at the inferior and superior aspects of the cervical tips of the spinous processes. The tips of the spinous processes are blended and intertwine with the ligamentum nuchae, which is attached to the occipital protuberance. The ligamentum nuchae also blends with the trapezius muscle, and the occipital protuberance blends with the nuchal line. Thus, cervical soft tissue injuries, depending on its extent and severity, may not only produce symptoms in the arms, wrists and hands, but also pain and tightness of the head and shoulder muscles.
Laser is the acronym for Light Amplification by Stimulated Emission of Radiation; its unique light is coherent, monochromatic and collimated. Unlike the high power laser which has been used as a surgical tool to cut and coagulate tissue, the low power laser uses a much lower level of intensity that is approximately 100 mW. This therapy, by definition, is restricted to low energy levels sufficient to produce biological effects with minimal or no heating (it cannot cut or coagulate tissue). With the exception of eye precautions, there is virtually no damage to tissue and no major adverse effects with low power laser therapy. The availability of low power diode lasers has made the instrument small, lightweight, portable, easy to use, and safe.
Research studies in small animals have demonstrated that low power laser light can effect the dilation of small blood and lymphatic vessels 17,18. By this method large molecules of pain chemicals accumulated in the interstitial spaces can be mobilized and eliminated, and more blood cells can be brought into the target area. When pain chemicals are removed, the pain stimulus is reduced and the heightened sympathetic activity and vasoconstriction are lessened. Consequently, the involved contracted and spastic muscles relax, and muscle ischemia gradually disappears 19-21. |
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