Lameness

High-Quality Data to Power High-Powered Lasers

By Paul Basilio

High-power laser therapy is often used to treat soft-tissue injuries in humans and horses, but there are few controlled studies looking at its safety and efficacy. Anecdotal data seem promising, but will lasers hold up to rigorous study?

“A lot of therapy modalities are used before they are actually tested in a standardized, controlled study,” admitted Mathilde Pluim, DVM, MSc, of Tierklinik Luesche, Germany, and Ghent University in Belgium.

In 2018, Dr. Pluim and her colleagues published a single-center retrospective study in Veterinary Science that included 150 horses with lesions in the superficial deep digital flexor tendon, the suspensory ligament, and the suspensory branches.

The horses received high-power (15 W) laser therapy for 2 consecutive weeks, and data were logged pre-treatment, directly after treatment, and at 4 weeks post-treatment. Long-term results were also obtained up to 2 years later.

“We found significant improvement directly after laser therapy,” she explained during a virtual presentation for the 66th Annual AAEP Convention. “Reinjury rate after 2 years was pretty low at 18%. The horses started controlled exercise—trotting under saddle—after 4 to 7 weeks, and they were back at their previous performance level between 4.7 and 6.1 months later. This is quite fast.”

There was no sign of improved outcomes among horses that also received plateletrich plasma (PRP) or stem cells in addition to the laser therapy over those treated with laser therapy alone. However, horses with acute injuries tended to have better prognoses than horses with chronic injuries.

The results of this retrospective study also showed a much sooner return-to-work when compared with other studies on equine tendon and ligament injuries. But there was one caveat.

“That study had flaws because there was no control group,” Dr. Pluim said. “There was also a diverse group of horses with diverse lesions.”

As a result, Dr. Pluim and her team set out to perform a study using a standardized lesion induction model.

There was significant improvement directly after laser treatment.

The Controlled Study

Twelve Warmblood horses (5 geldings and 7 mares) were included in the study. Six were evaluated for 4 weeks, and 6 had extended follow-up at 6 months. Lesions were induced in the lateral suspensory branch of all 4 limbs, and laser therapy was performed in 2 limbs. Healing was evaluated through medical imaging, monitoring for lameness, and histopathologic examination.

Laser therapy was performed daily for 4 weeks with a class-4 laser that emits 4 different wavelengths simultaneously. The laser penetrates up to 7.2 cm.

“There were preset treatment protocols available with the device,” she added. “Depending on the depth of penetration and the effect you want to achieve [i.e., biostimulation, anti-inflammatory or analgesic], you can pick a preset protocol suited to the type of lesions and the lesion site.

One day after inducing the lesions, no heat, swelling, pain, or lameness were noted. Analgesics were initiated. The team began to walk and trot the horses for 10 minutes a day, slowly increasing to 30 minutes after 1 week.

“After 1 week, we did see clear signs of [equine suspensory] desmitis,” Dr. Pluim said. “The horses in the long-term group were handwalked up to 3 months, and after that trotting and cantering exercise were slowly increased up to a full workload after 6 months.”

Results

Dr. Pluim found enlargement of the lesions in the treated and control limbs through the first 4 weeks. However, the lesion was not as clear on imaging in the treated limbs, and tissue began filling in already after 4 weeks in the treated limb.

“On ultrasound, enlargement was significantly lower in the laser-treated lesions in both circumference and surface area,” she explained. The Doppler signal on ultrasonography was significantly higher in the treatment group for the first 4 weeks.

Overall on MRI, the surface area of the treated lesions was significantly lower than that of the control limbs.

“The mean MRI signal was also significantly lower in the treatment group,” Dr. Pluim added. “After 6 months, the signal was significantly lower in both groups when compared with 4 weeks. However, the signal was significantly lower in both the short- and long-term laser treated lesions.”

Dr. Pluim and her team are now hard at work studying histopathological findings of these types of treated lesions, to analyze the quality of the healing tissue.

For more information:

Pluim M, Martens A, Vanderperren K, et al. Short- and long-term follow-up of 150 sports horses diagnosed with tendinopathy or desmopathy by ultrasonographic examination and treated with high-power laser therapy. Vet Sci. 2018;119(8):232-238. https://www.sciencedirect.com/science/article/abs/pii/S0034528818302455?via%3Dihub

Pluim M, Martens A, Vanderperren L, et al. High-power laser therapy improves healing of the equine suspensory branch in a standardized lesion model. Front Vet Sci. 2020 Sept 3. doi.org/10.3389/fvets.2020.00600. https://www.frontiersin.org/articles/10.3389/fvets.2020.00600/full