A hot topic in veterinary medicine these days is cold laser therapy. I’ve been reviewing the theory and research evidence for this treatment regularly from my first review in 2010 to my most recent look at the evidence in 2016. Overall, my conclusions have largely remained the same:
Lasers have significant measurable effects on living tissues in laboratory experiments, so it is plausible that they might have clinical benefits. The extensive research done in humans, however, has so far only found limited evidence to support the use of lasers in a few conditions, and high-quality controlled studies often contradict the positive findings of initial, small and poorly controlled trials.
The experimental evidence in veterinary species is mixed and low quality, and there are no high-quality published clinical trials validating laser therapy for specific indications. It is possible that high-quality research may one day validate some of the claimed benefits for laser therapy. However, at present the best that can be said about this intervention is that it appears promising for some conditions, such as wounds and musculoskeletal pain.
The growing popularity of lasers is based largely on anecdotal evidence and economic factors. Laser units are being aggressively marketed to veterinarians, often using unsubstantiated claims of clinical benefits. Laser therapy represents a potential source of income for practitioners and, of course, for laser device manufacturers. It appears likely that this profit potential contributes to an enthusiasm for laser therapy not matched by the quality of scientific evidence for its benefits to patients.
Veterinary therapies often lack robust high-quality clinical trial evidence to support their use, and this is not itself a reason to avoid these therapies. However, when employing interventions that have not yet been rigorously demonstrated to be safe and effective, we have a duty to acknowledge the limitations of the evidence. Clients should be fully informed about the uncertainties concerning the effectiveness of laser therapy and the potential for unforeseen effects. Established therapies with stronger evidence identifying their risks and benefits should take precedence over promising but unproven therapies like laser treatment. And those interested in promoting low-level laser, particularly those marketing laser equipment and training, should proportion their claims to the available evidence and assume some responsibility for developing the evidence base further so that practitioners and animal owners can make better-informed decisions about this practice.
Today I came across a new study looking at the use of cold laser in dogs having back surgery for intervertebral disk disease (IVDD). I have previously reviewed two other studies of laser for this purpose, one of which appeared to show some benefit and the other showed no effect. The new study is very similar in terms of the small sample size and the methodology, though it is generally stronger than the other two in terms of mechanisms that control for various types of bias and error.
Bennaim M, Porato M, Jarleton A, et al. Preliminary evaluation of the effects of photobiomodulation therapy and physical rehabilitation on early postoperative recovery of dogs undergoing hemilaminectomy for treatment of thoracolumbar intervertebral disk disease. AJVR 2017;78(2):195-206.
Briefly, the study classified dogs with severe neurologic symptoms caused by IVDD into groups based on the level of dysfunction. All dogs had surgical and standard medical treatment. Some also had laser therapy, some had physical therapy and fake laser treatment, and some had only standard care and fake laser treatment. The time to reach various stages of functional recovery and the amount of post-surgical intravenous pain medication each dog required were measured and compared between the groups. There were no differences in any of these measures between any of the groups. This indicates that neither laser treatment nor physical therapy added to surgery appeared to have any benefits above standard care.
The authors list a number of reasons why this negative result might have occurred even if laser therapy does actually have some benefit. The most plausible of these was the small sample size. A very large improvement due to laser could be seen even when evaluating only a relatively small number of patients, as in this study. However, if laser has some benefit and it is fairly small, it might not be possible to detect it in such a small study. Of course, the most likely explanation for the failure to find any benefit is simply that there is none.
Overall, these three studies do not provide much encouragement for using laser in dogs with IVDD. Only one of the three appeared to show any benefits, and that study lacked most standard controls for bias. The negative findings of the other two studies, especially the current study, which was the strongest of the three in terms of methodology, strengthens the view that laser therapy is not helpful for dogs having surgery for IVDD.
Of course, it is always possible that different laser treatment (different doses, duration of treatment, equipment, etc.) could be helpful, or that laser is useful for other conditions. We can, as always, only make provisional conclusions based on existing and imperfect evidence. With the evidence we have now, however, it seems likely that laser will not be helpful for dogs with IVDD that are severely affected enough to need surgery.