OK, forget about the popularized depictions of lasers as light sabres and alien death rays. In the therapeutic context, a laser is simply a source of electromagnetic energy that is monochromatic – providing a consistent wavelength that travels in the same direction.
Until recently, most medical lasers have been thermal or ‘hot’, in that they are capable of deeply penetrating and heating body tissue -- thus cutting, cauterizing or destroying it. Thermal lasers, such as those used in surgery, typically operate at power levels in excess of 25,000 mW.
Non-thermal, or “cold” lasers, are also capable of penetrating into human tissue, but do not heat the tissue sufficiently to cause damage. Non-thermal lasers, such as those indicated for Low Level Laser Therapy (LLLT) typically operate at power levels between 10 mW and 500 mW and are totally painless. They are a delivery mechanism for electromagnetic energy (at a specific wavelength within the infrared range of the electromagnetic spectrum) which triggers the cellular metabolic cascade discussed later.
A HISTORY OF LOW LEVEL LASER THERAPY (LLLT)
In the late 1960's, scientists in Europe began to research the use of very low powered lasers (less than 5 mW) to produce non-thermal effects, or ‘biostimulation,’ in human tissue. The first experimental applications of LLLT were reported in 1968, when researchers used ruby and argon lasers on non-healing or slow-to-heal ulcers. Later research substantiated the efficacy of LLLT to accelerate the healing of wounds, attenuate pain, and reduce tissue inflammation in both humans and animals. During the 1980’s, the use of more highly-powered lasers was investigated, though power levels were still very low by today’s standards. Power levels in LLLT devices today range from 50 mW (very low power) up to 500 mW (high power).
In the past ten years, LLLT technology has advanced significantly for three key reasons:
Extensive research has been conducted at leading academic and medical institutions around the world concerning the basic underlying science of how LLLT affects mammalian tissue. For example: At the annual meeting of the American Society for Laser Medicine and Surgery in April, 2003, teams from the U.S., Canada, England, Ireland, Russia, China, Italy, Iran and Egypt presented papers on topics ranging from the effect of laser light on fibroblasts and the rheological properties of red blood cells, to the effects of LLLT on pressure ulcers, tibia fractures and snake bites. Even the U.S. Department of Defense has funded research at the Uniformed Services University in Maryland into the use of LLLT to treat wounded soldiers.
The number of sophisticated (i.e., prospective, double-blind, randomized, placebo-controlled) clinical trials for LLLT has increased substantially. Clinical trials over the last several years have ranged from the study of LLLT to treat pain associated with carpal tunnel syndrome and soft tissue injuries to dermatological and dental applications. The quality of data collected from these clinical trials has significantly improved.
In January, 2002, the FDA changed the device classification on LLLT devices to be classified as a “non-significant risk”, greatly streamlining the FDA clearance process. As a result, the number of LLLT devices cleared for the treatment of various medical conditions has increased dramatically.
HOW LLLT WORKS
The effects of exposing human and animal tissue to low level laser light in the infrared range appear to be photochemical, in that it initiates a chain of chemical reactions similar to photosynthesis in plant cells. In LLLT, light energy is received within the cell mitochondria and at the cell membrane by specific chromophore receptors, initiating the conversion of light energy into metabolic cellular energy through a process called photobiostimulation.
In mammal tissue, photobiostimulation results in an apparent increase in the cellular metabolic rate and stimulation of the immune, lymphatic and vascular systems -- all of which expedite cell repair. The net result, as observed in clinical trials to date, is a reduction in pain, inflammation, edema and an overall reduction in healing time. The sooner LLLT is applied to the affected area, the faster results appear to be achieved. Also, the effects of LLLT have been proven to be greater in compromised or damaged cells. Exactly how LLLT effects mammal tissue is still a subject of considerable investigation within the scientific community. But with an ever-increasing number of peer-reviewed papers published, the basic metabolic pathways and mechanism of action of LLLT are becoming well understood. In laboratory research and clinical applications, LLLT has produced the following physiological effects:
Intracellular chromophores (including endogenous porphyrins, mitochondrial and membranal cytochromes, and flavoproteins – which are all photosensitizers) absorb electromagnetic radiation in the IR range and transfer it to nearby oxygen molecules, thus producing reactive oxygen species (ROS) and antioxidants. At very low concentrations, ROS have strong stimulatory effects on cellular metabolic pathways.
· Stimulates ATP production within mitochondria, elevating overall cellular metabolism.
· Increases RNA and DNA synthesis, which promotes cell proliferation. This helps damaged cells be replaced more promptly, which reduces healing time.
· Stimulates Superoxide Dysmutase (“SOD”) production. SOD is an enzyme that breaks down free radicals, which can be a cause of muscle pain.
· Increases vascularity by increasing the formation of new capillaries and repairing damaged ones. The resulting increase in blood circulation promotes localized healing.
· Stimulates cell proliferation and motility (ability to move under their own power).
· Stimulates fibroblast formation. Fibroblasts are present in connective tissue and give rise to precursor cells, which form the fibrous, binding and supporting tissues like collagen and glycoprotein.
· Stimulates the production of collagen, which is the most common protein found in the body. It is essential for the repair of damaged tissue and for replacing old tissue. Collagen is the substance that holds cells together, in particular the fibres of tendons, ligaments and the fascia. Also, by increasing collagen production less scar tissue is formed at the damaged site.
· Stimulates tissue granulation and connective tissue projects, which are part of the healing process of wounds, ulcers or inflamed tissue.
· Stimulates leukocyte production. Leukocytes, or white blood cells, are involved in defending the body against infective organisms and foreign substances.
· Stimulates macrophages and phagocytosis. Macrophages are large white blood cells that engulf and destroy (phagocytosis) microorganisms, cellular debris and other foreign matter. Macrophages are involved in cell-mediated immune responses. They are drawn to inflamed areas and are particularly important in the body’s defense against infection.
· Stimulates the release of endorphins, enkephalins, and dynorphins - which are the body’s natural pain fighting chemicals.
· Reduces the excitability of nervous tissue, thus reducing the sensory transmission of pain.
· Accelerates lymphatic system activity. Edema, which is the swelling process of the body, has two basic components. The first component is liquid, which can be evacuated by the cardiovascular system. The second is comprised of proteins, which have to be evacuated by the lymphatic system. Research has shown that the lymph vessel diameter and the flow of the lymph system can be doubled with the use of low-level laser therapy. The venous diameter and the arterial diameters can also be increased. This means that both edema components (liquid and protein) can be evacuated at a much faster rate - to relieve inflammation.
· Inhibits prostaglandins’ physiological effects on tissue, which effects vasodilation, edema, and stimulated intestinal and bronchial smooth muscle.
· Stimulates serotonin release. Serotonin is an endorphin precursor, and is also associated with the relief and resolution of inflammation. The net result of properly administered LLLT can be significant reductions in pain and inflammation accompanied by accelerated healing times.
LLLT EXAMPLE: ACUTE SOFT TISSUE TRAUMA
An injury of this type consists of damage to muscular, neural, lymphatic and vascular tissue. The body's natural reaction to acute soft tissue trauma is to "splint" the injury with edema, an accumulation of thin or watery fluid in tissue spaces or cell interstices, which causes swelling. This swelling prevents excessive movement of the damaged tissue and results in trauma pain from the injured tissue, as well as secondary pain from the swelling itself. In such instances, LLLT has been shown to improve the efficiency of the lymphatic system, thereby correcting the fluid balance in the body and reducing edema and improving range of movement. LLLT has also been shown to decrease the transmission of pain by C-fiber nerves, and increase overall cellular metabolism, so cells replicate and heal at a much faster rate.
LLLT can be used in conjunction with the majority of traditional medicines, including narcotics, opiates, anticonvulsants and antidepressants; however, cortisone steroids may negate LLLT’s immune enhancement. LLLT can also be used in conjunction with other forms of energy therapy such as ultrasound, TENS therapy and electrical stimulation.
LLLT EXAMPLE: TREATMENT OF CHRONIC PAIN
Chronic pain is typically defined as pain that continues for a month or more beyond the usual recovery period for an illness or injury, or pain that occurs for months or years due to a chronic medical condition. Examples include pain resulting from cancer or cancer therapy, pre-operative pain (pain induced by invasive surgical procedures) and pain associated with arthritis and fibromyalgia.
Traditional methods for pain management include over-the-counter and prescription medications, physical therapy, TENS therapy (the application of electrical impulses to the skin), psychological therapy and nerve blocking (injections that provide temporary relief). More aggressive options include neuromodulation (the implantation of devices that utilize electrical impulses to control chronic pain), implantable drug pumps and alternative therapies such as acupuncture. LLLT has the potential to replace many of these therapies for the treatment of pain, particularly chronic and acute spine and joint pain, for several reasons:
Safety - Many current therapies for the treatment of chronic pain have a number of significant drawbacks. For example, the negative impact of long-term non-steroidal anti-inflammatory, narcotics and opiate use on the gastrointestinal and nervous systems has been highly documented. The implantation of pain management devices such as neuromodulators and drug pumps is accompanied by even greater risks, including infection, bleeding and an adverse reaction to anaesthesia. LLLT technology, on the other hand, can be safely applied to most regions of the body, including directly over the spinal vertebrae and over orthopaedic hardware or stimulators that have been surgically implanted. Ultrasound and high-level electrical stimulation, in comparison, are contraindicated for clinical applications directly over the spine. Ultrasound is also contraindicated for use over orthopaedic hardware. In fact, the primary adverse effects associated with LLLT are minor, and include redness and skin irritation.
Comfort – LLLT is a non-invasive procedure, and minimal pain has been documented from its use. This is not the case with more aggressive options such as TENS therapy, nerve blocking injections, and the implantation of drug pumps and neuromodulators.
Efficacy – LLLT has been shown to improve chronic pain to a statistically significant degree in just twelve sessions lasting 10 to 30 minutes each. In an early IRB-sponsored study performed by Therapeutic Laser Associates on 20 patients who had undergone spinal fusion using bone harvested from the iliac crest, the mean improvement in donor site pain for patients undergoing at least eight sessions of LLLT was 50.1%. The mean improvement in donor site pain during the last 24 hours of LLLT treatment was 47.0%, some improvement in donor site pain was noted in 80.0% of patients, and 65% of patients had pain reduction of 50% or more. Equally as important as pain relief, however, is the ability of LLLT to enable critical medical intervention in high-risk situations. For example, many skeletal injuries result in massive edema that can hinder a surgeon’s ability to repair the fracture. In certain situations, delaying surgery can result in severe loss of limb function, and may even result in a medical condition that requires amputation. In these instances, LLLT has been demonstrated to reduce edema sufficiently so that corrective surgery can occur in a timely manner.
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