IN-DEPTH: LAMENESS REHABILITATION
commercial compression splint with circulating coolant. This indicated that topical application of cold can reduce core SDF tendon temperature in standing horses and that the temperatures achieved during treatment were not detrimental to the viability of the cells. Cold immersion of the distal limbs has also been shown to be effective in reducing the severity of laminitis by decreasing the activity of laminar metallomatrix proteinases MMP and causing laminar vasoconstriction.19,20
Heat
The benefits of heat include increased circulation, muscle relaxation, and increased tissue pliability.21 When tissue blood flow is increased, metabolites are mobilized, oxygen levels are increased, and the met- abolic rate of cells and enzyme systems are in- creased. The metabolic rate increases two to three times for an increase of 10°C. Increases in blood flow and vascular permeability can promote tissue edema resorption. Heat can also decrease pain via similar mechanisms to cold therapy. Tissues are more effectively stretched after warming. Heat therapy can be used to increase joint and tendon mobility. Heat is usually applied after the acute inflammatory period has ended. Heat is commonly applied using hot packs. Deep
heat may be applied using therapeutic ultrasound. Most of the physiologic effects of heat occur when tissue temperatures are raised to between 40 and 45°C.21 Tissue temperatures above 45°C may re- sult in tissue damage.21 To achieve heating of deeper tissues to the therapeutic range, constant heat must be applied for 15–30 minutes. Kaneps21 found that tissue temperature changes due to warm water hose therapy ranged from 3.7 to 10.8°C. Temperature elevation is short lasting and depends on the distance to the surface, with limited effect on tissues deeper than 1.5–2 cm below the skin surface.21 Using therapeutic ultrasound, Montgomery et al22
found that the SDF tendon and deep digital flexor tendon (DDFT) are heated to a therapeutic temper- ature using a frequency of 3.3 MHz and intensity of 1.0 W/cm2. However, the epaxial muscles are not heated to a therapeutic temperature using a fre- quency of 3.3 MHz and an intensity of 1.5 W/cm2.22
9. Low-Level Laser Therapy
The low-level laser uses an intense beam of light to stimulate the body’s processes. It is reported to activate waste removal, increase repair activity, re- lieve swelling, heal skin wounds, and stimulate the blood and lymphatic systems.23 It has been re- ported to increase serotonin.23–25 It has been re- ported to have biostimulating effects such as acceleration of cell division, increase in leucocytic phagocytosis, stimulation of fibroblastic activity, and enhancing regeneration of lymph and blood ves- sels.23–25 Studies have shown it can cause vasodi- latation.23–25 All of these effects can assist healing
248 2016 Vol. 62 AAEP PROCEEDINGS
and provide some relief of chronic pain when prop- erly applied. Lasers are divided into safety classifications in the
United States by the American National Standard Institute. Class 1, 2, and 3a have low power output and are not used for therapeutic purposes. These will not be presented. Class 3b lasers cannot emit an average radiant
power greater than 0.5Wfor an exposure time equal to or greater than 0.25 seconds or 0.125 J for an exposure time less than 0.25 seconds for wave- lengths between 0.18 and 0.4 m, or between 1.4 and 1 mm. In addition, lasers between 0.4 and 1.4 m exceeding the Class 3a accessible emission limit (AEL) cannot emit an average radiant power greater than 0.5 W for exposures equal to or greater than 0.25 seconds, or a radiant energy greater than 0.03 J per pulse. Class 4 lasers and laser systems exceed the Class 3b AEL. There is little research on the use of low-level laser therapy (LLLT) in the equine. Berg et al,26 found superficial morphological changes in equine epider-
mis after treatment with 91 J/cm2 of defocused CO2 laser and severe changes with a homogeneous eosin- ophilic acellular zone of underlying dermis and a significantly thinner epidermis, when irradiation doses of 450 J/cm2 were applied. Berg et al27 also
found that irradiation with defocused CO2 laser causes a moderate-to-vigorous heating effect in su- perficial tissue and a marked increase in blood flow. This increase in temperature could increase the risk of thermal injuries to the skin.27 The results also
suggest that treatment with defocused CO2 laser is not statistically better than placebo at reducing the grade of lameness in horses with traumatic arthritis of the fetlock joint.27 Ryan et al28 found that laser- light transmission was not affected by individual horse, coat color, or leg. However, it was associated with leg condition. Tendons clipped dry and cleaned with alcohol were both associated with greater transmission of light than the unprepared limbs. The use of alcohol without clipping did not associate increase laser light transmission. They recommended that the area treated should be clipped and cleaned beforehand. The wavelengths of light used for LLLT fall into
an “optical window” at red and near-infrared (NIR) wavelengths (600–1070 nm).29 Wavelengths in the range 600–700 nm are used to treat superficial tis- sue, and longer wavelengths in the range 780–950 nm, which penetrate farther, are used to treat deep- er-seated tissues.29 Wavelengths in the range 700–770 nm have been found to have limited bio- chemical activity and are therefore not used.29 The most common method of determining laser therapy dosage is to measure the density of energy applied to the surface. This is typically expressed in J/cm2. Variation in clinical effects can be ob- served at very high (50 W) or very low (1W) power settings using the same J/cm2 dose. The dose required for a particular condition is dependent
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