A comparative study of the pain-relieving effect of laser treatment and acupuncture

A Review of Low-Power Laser Pain-Relieving Controlled Clinical Trials

The use of low-power “soft” lasers for the relief of pain has become popular among physiotherapists and acupuncturists, mainly on the strength of uncontrolled anecdotal reports of their efficacy. This review of the available controlled clinical trials suggests that, except in certain specific areas, the role of lasers in the relief of pain is merely that of a powerful placebo.

Laser Acupuncture Analgesia: An Overview

In recent years, low power laser therapy has become a popular treatment modality. While its use as an alternative to needles in acupuncture is contentious, the studies reviewed above demonstrate the possibility of analgesic effects with such treatments. However, the majority of the trials conducted to date can be criticised on a number of points. This has contributed to the criticism surrounding the technique. Furthermore, the clinical significance of such treatment parameters as wavelength, energy density and pulsing frequency are poorly understood. Further research is therefore necessary on a number of levels: clinically to validate the claims made on behalf of lasers, and experimentally to identify optimum values for treatment parameters. Hopefully, as research in this field progresses, clinicians will benefit from firm treatment guidelines.

While in the final analysis lasers will probably never be able to replace needles, the potential advantages in their use in HLTVor hepatitis patients are obvious. Squeamish or very young patients may also react more favourably to laser rather than needle acupuncture. To this end, laser acupuncture represents a challenging and interesting field for future research.

Laser acupuncture: past, present, and future

Laser acupuncture is defined as the stimulation of traditional acupuncture points with low-intensity, nonthermal laser irradiation. Although the therapeutic use of laser acupuncture is rapidly gaining in popularity, objective evaluation of its efficacy in published studies is difficult because treatment parameters such as wavelength, irradiance, and beam profile are seldom fully described. The depth of laser energy transmission, likely an important determinant of efficacy, is governed not only by these parameters, but also by skin properties such as thickness, age, and pigmentation-factors which have also received little consideration in laser acupuncture. Despite the frequently equivocal nature of the published laser studies, recent evidence of visual cortex activation by laser acupuncture of foot points, together with the known ability of laser irradiation to induce cellular effects at subthermal thresholds, provides impetus for further research.

Double-blind, placebo-controlled investigation of the effect of combined phototherapy/low intensity laser therapy upon experimental ischaemic pain in humans

BACKGROUND AND OBJECTIVE

This study assessed the putative analgesic effect of combined monochromatic light/laser irradiation at low intensity (660-950 nm; 31.9 J/cm2; pulsed at 16 or 73 Hz).

STUDY DESIGN/MATERIALS AND METHODS

The investigation was completed under double-blind conditions using a standardised form of the submaximal effort tourniquet technique. Healthy male volunteers naive to the experimental conditions (n = 45) attended on two occasions for the purposes of pain induction, the first during which baseline data were obtained and on a second occasion during which they were randomly allocated to one of two treatments or a placebo condition. For the treatment conditions, irradiation was applied to the ipsilateral Erb's point at the parameters stated; for the placebo condition, sham "irradiation" was delivered using a dummy unit. Pain was measured using computerised visual analogue scales and McGill Pain Questionnaires (MPQ) to assess "current pain intensity" and "worst pain experienced," respectively.

RESULTS

Analysis of variance and appropriate post hoc tests demonstrated only a weak (but significant) hypoalgesic effect compared to placebo (P < 0.05) in the treatment group irradiated at 16Hz for the sensory component of the MPQ; other comparisons were found to be nonsignificant.

CONCLUSIONS

These results do not provide convincing evidence for the hypoalgesic potential of combined monochromatic light/laser irradiation, at least at the parameters used here, and thus indicate the necessity of additional work to investigate this modality further in order to assess the potential benefit, if any, of such treatment in the clinical setting.

Evidence for the existence of low-energy laser bioeffects on the nervous system

The reported effects of low-energy laser irradiation on the nervous system are manifested in alterations in cellular and extracellular biochemical constituents and reactions, as well as in changes in cell division rates. These bioeffects were observed in both in vivo and in vitro experiments. Other observed phenomena relate to the function of the nervous system and consist mainly of induced alteration in electrical conduction, stimulation thresholds, and behavioral effects. Clinical aspects of low-energy laser bioeffects relate mainly to pain mitigation and postponement of the posttraumatic neural degeneration processes. Many of the reported observations were obtained by experiments apparently conducted according to less than rigorous scientific criteria, and some could not be duplicated. On the whole, however, there is little doubt that low-energy laser irradiation exerts some effects on the nervous system under specific conditions of irradiation and tissue exposure via a mechanism which is probably photochemical in nature.

Is low-energy laser treatment effective in lateral epicondylalgia?

The aim of this double-blind study was to explore the pain-alleviating effect of low energy laser in lateral epicondylalgia. Forty-nine patients were consecutively assigned at random to two groups, laser or placebo. The Mid 1500 Irradia laser was used with the following parameters: wavelength 904 nm; average power output 12 mW; peak value 8.3 W; frequency 70 Hz (pulse train 8000 Hz). The laser (Ga-As) was locally applied to 6 sites on and around the epicondyle. Each point was treated for 30 sec, resulting in a dose of 0.36 J/point and an area of treatment of 0.2 mm2. Patients were treated 2-3 times weekly, for a total of 10 treatments. Follow-ups were done after three and 12 mo. The statistical analysis showed that the laser treated group had a significant improvement in some objective outcomes after the treatment period and at the 3 mo follow-up, but there were no significant differences in the subjective outcomes between the groups. Irradia laser treatment may be a valuable therapy in lateral epicondylalgia, if carried out as described in this study. However, further studies are necessary before low energy laser can be employed as a pain-relieving method.

Interactions between chemical and thermal cutaneous stimuli: inhibition (counterirritation) and integration

Methyl salicylate, a commonly used chemical counterirritant, was applied topically to the forearm to determine whether a nonpainful chemical irritation could inhibit the perception of another (weaker) chemical irritation. In the first experiment, sensations of irritation (burning and stinging) produced by a 10% solution of methyl salicylate were significantly attenuated when a 15% solution of the same chemical was applied to the opposite forearm. In the second experiment, neither the perception of warmth nor the heat pain threshold was affected by application of 10% or 15% methyl salicylate to a site 10 cm from the thermal stimulus. Inhibition did, however, occur in the opposite direction: Chemical irritation was reduced after the thermal stimulus reached a painful level. In the third experiment, a 15% solution of methyl salicylate was applied immediately adjacent to the thermal stimulus, with the result that ratings of warmth intensity increased rather than decreased, and perceived irritation was again attenuated following a painful heat stimulus. Overall, the results indicate that (1) chemical counterirritation can occur at nonpainful levels; (2) the resulting inhibition is confined to the nociceptive system; and (3) when the nociceptive and warmth system are activated together, the tendency is toward integration rather than inhibition.

Hypalgesic efficacy of acupuncture on experimental pain in man. Comparison of laser acupuncture and needle acupuncture

The analgesic effect of acupuncture on cutaneous heat stimuli of 43 degrees C has been evaluated in a controlled experimental study with healthy, informed volunteers. Laser acupuncture was administered to 39 probationers using a helium-neon laser under double-blind conditions. The point Hegu (L.I.4) and Jianqian (Extra.) on both sides were each irradiated for 1 min. Forty probationers were needled with stainless steel needles in the point Hegu (L.I.4) on both sides under single-blind conditions. Pain threshold was measured in terms of the time (in msec) that the probationers needed to perceive the cutaneous heat stimulus of 43 degrees C. The painful stimulus was generated by a computer-controlled standardized procedure. The Wilcoxon test was used for the statistical evaluation. Laser acupuncture did not change the pain threshold. Needle acupuncture did, however, increase the pain threshold compared with the initial value (alpha = 0.1%). The difference compared with the control group, where a placebo point was needled, was also significant (alpha = 5%). This controlled experimental study proves the analgesic effect of needle acupuncture on painful heat stimuli. Laser acupuncture had no effect on pain threshold in this study.