| | Introduction | Ultrasound | Electrical stimulation | Iontophoresis | Photon therapy | Magnetic therapy | Manual therapies | References | About the Author
Introduction
Equine therapy has been an undervalued area of equine health care. This has been due to the lack of veterinary education in this area and because no educational courses were available for the equine therapy specialist. In recent years the use of physical agents on horses has increased and their value in equine health care has been recognized.
Physical agents are various forms of energy, such as heat, cold, water, sound, electrical currents, light, magnetic fields, exercise, and manual pressure. These agents are often called modalities and their use forms the basis of the practice of equine therapy. Human medicine holds the use of these agents as standard care, not as alternatives to accepted medical practice. For the horse, the use of equine therapy tools and techniques are a valuable aid to rehabilitation, making it more comfortable, enabling the horse to be more functional throughout recovery, and shortening the duration of recovery. An equine therapist should be skilled in goal-oriented treatment processes and knowledgeable in all therapeutic modalities.
The techniques of the equine therapist are applied to reduce tissue inflammation, to relieve pain, to reduce tissue congestion, to alter circulatory flow, to increase collagen extensibility, to maintain muscle tone, and to increase the patient's sense of well being. They are applied as preparation for controlled exercise and used to make rehabilitative exercise more comfortable. Equine therapy is applied post-surgically or after an injury to shorten the recovery time. The techniques of the equine therapist are useful as part of the daily training regimen of the athletic horse to minimize post-exercise muscle soreness and the wear and tear effects of sports training and competition. In this manner, equine therapy techniques can be used preventatively, reducing the cumulative effects of over-use injuries.
Until recently there has been little research using horses as subjects to validate the claims made for the effects of therapeutic modalities. This is changing rapidly, as veterinary interest in these tools and techniques grows. Not only is the body of research using horses growing, the research on new modalities such as photon and laser energy and magnetic fields has increased.
Midway College, near Lexington, Kentucky is meeting the need for skilled equine therapists. Midway College, located in Midway, Kentucky, in the heart of Bluegrass horse country, recently added the only bachelor's degree program in equine therapy in the United States to its curriculum. This degree program offers students the opportunity to acquire the skills and certification needed to work in this rapidly growing field.
The Equine Therapy curriculum, which is open to women, is a professional degree program. Students must complete 65 college credit hours of pre-equine therapy courses before making formal application into the professional phase of the program. The professional courses will stress practical application and include clinical experience under the supervision of practicing therapists and veterinarians. Students will acquire skills in equine therapy, rehabilitation, and injury prevention. Upon completion of the course work, students will take a certification examination administered by the college.
An increasing number of veterinary clinics are hiring equine therapists to extend their practice into secondary care. As graduates of this program become available, the concept of equine therapy will leave the ranks of alternative medicine and find its place in standard veterinary practice. A graduate from the equine therapy program at Midway College will have an understanding of diagnostic techniques, but will not be responsible for diagnosis. The trained equine therapist will have an understanding of pharmacology, but will not prescribe medications. The professional parameters of equine therapy include the ability to assess the horse's state of health, extent and location of injury, and follow a complete veterinary diagnosis with the application of physical agents and therapeutic care.
Scientific literature documents the effects of physical agents on blood and lymph vascular tissue, on cellular activity, on the inflammatory process, in pain reduction, and on healing of both bone and soft tissues. Thousands of studies could be used to justify the use of therapeutic agents on injury conditions in horses. Deciding which study to use to represent the effects of each modality is more of a challenge than finding a study that validates its use. In this report, I have selected an example from the scientific literature to validate the use of each of the agents of the equine therapist.
Ultrasound
Ultrasound is high frequency sound waves that transmit energy by compressing and rarefying material in its path. Ultrasound waves have a frequency of greater than 20,000 Hz, or cycles per second. This is based on the limits of normal human hearing of 16 to 20,000 Hz. Therapeutic ultrasound units have frequencies of between .7 and 3.3 MHz, frequencies that are absorbed by soft tissue to a depth of 2-5 cm.
Recently, a 45 kHz ultrasound unit has been introduced. This lower frequency unit, called long wave ultrasound, dissipates sonic energy over a wider area.
A study by Morcos and Aswad, Histological Studies of the Effects of Ultrasonic Therapy on Surgically Split Flexor Tendons (1), was published in the Equine Veterinary Journal in 1978. The researchers describe a favorable clinical response in horses with injured superficial flexor tendons, to ultrasound therapy. The histological picture of the repair process in surgically split tendons is described following 10 minutes of treatment 6 times/week, for 2 weeks. One month after surgery the treated tendons showed an absence of the inflammatory reaction and the degenerative areas that were observed in the control tendons. A network of newly branching blood vessels was seen crossing the incision line and passing into the tissue. The authors reported that this vascular network was associated with massive invasion of young fibroblasts migrating to the incision gap from the surrounding tissue. Six weeks after surgery, collagen fibrils were seen to join with the cut tendon surfaces. The ultrasound treated tendons healed with little scar.
Electrical Stimulation
Electric current is the flow of charged particles. In the body, electrical current stimulates the movement of ions across cell membranes. Electrodes applied to the skin deliver low-voltage stimulation to the surface nerves in the skin. For the horse, electricity provides a comfortable modality with a broad range of applications. Horses tolerate the use of therapeutic electrical currents well, often going into a state of deep relaxation during treatment. I consider this deep relaxation an important aspect of equine therapy.
In 1986, Vasco reported on 8 cases of laminitis that were successfully treated using electrical stimulation (2). A low voltage alternating current was applied within 2 hours of the onset of laminitis symptoms. Relief was immediate and persisted for hours after treatment. Twice daily treatments resulted in 50% reduction in the symptoms of pain and lameness. It was concluded that electrotherapy abbreviated the acute inflammatory process and reduced pain. Based on the lack of recurrence of clinical signs and the resolution of sub-solar abscesses, it appeared that electrotherapy promoted the healing process and was a useful therapeutic aid to laminitis.
Iontophoresis
Iontophoresis is also called ion transfer, and uses direct current to drive water-soluble medications into subcutaneous tissue. It is non-invasive and requires minimal ionic concentrations. Iontophoresis uses quite low levels of electric current, so indications and contraindications pertain to the ion selected, rather than to the use of electricity. A direct electrical current provides the electromotive force to move the ionized particle of the drug past the barrier of the skin and into the deeper tissues. Using an electrode of the same polarity as the charge of the ion, the drug's active ingredient, the ion is electrostatically moved through the skin. The route of entry is through the pores, sweat glands, and hair follicles. Additionally, the skin acts as a reservoir for the drug, extending its release into the deeper layers after the iontophoresis device is removed.
Elements of low atomic weight, less than 8000 Daltons, migrate much faster than those of high atomic weight. Such drugs include:
- local anesthetics such as Lidocaine
- antibiotics such as Gentamicin and Naxcel
- corticosteroids such as Dexamethasone
- nonsteroidal anti-inflammatories such as Phenylbutazone
A study reported at the 1999 AAEP conference, found no dexamethasone in the tibiotarsal joint fluid or blood from the saphenous vein proximal to the joint. This study is in contrast to other reports.
Looking at the results of dexamethasone iontophoresis for the treatment of rheumatoid arthritic knees, pain relief was seen at rest and on movement in a study using human subjects. Joint fluid and blood levels were not assessed. (3)
An unpublished trial using horses found the presence of betamethasone in the tibiotarsal joints of 2 of the 3 horses used in this trial (4). Thermographic images revealed increased heat following iontophoresis indicative of increased blood flow in the area of treatment. The researchers attribute the lack of drug presence in one sample to be due to difficulty in establishing sufficient electrode contact. The quality of interface between the electrodes and the skin is one limiting factor to successful drug delivery in iontophoresis.
Photon Therapy
Photon therapy is often called "laser" therapy in the equine industry and "cold laser" in human therapy. In the US the FDA has not approved the use of cold lasers for therapeutic application because it considers the animal and cell culture studies to be inconclusive. Studies on the effects of photon energy yield mixed results. The devices emit light in the infrared or in the visible range of the electromagnetic spectrum. The difference between lased light and light emissions used for photon therapy is that laser is monochromatic (or one frequency), coherent (waves are in phase), and non-divergent (minimal spread of beam). Light emitted by the units popularly used on horses does not have all of these characteristics and there is debate about the therapeutic importance of coherency. Many studies indicate that light at around 50 mW/cm2 power density with an energy density of less than 35 J/cm2 is biostimulative and facilitates healing.
Equi-Light of Denver, Colorado has devoted considerable time and money to the study of how photon energy works in the body. Their research has revealed effects on serum nitric oxide levels in both humans and horses. In a study using human subjects, Horwitz, Burke, and Carnegie observed the results of 890 nm monochromatic infrared energy on recalcitrant dermal lesions, including venous ulcers, diabetic ulcers, and a wound related to scleroderma (5). The rate and quality of healing of these previously refractory wounds was thought to be related to local increases in nitric oxide concentration.
In an unpublished blinded placebo controlled trial, serum nitric oxide was measured after diode pads were placed on the equine jugular vein for 45 minutes resulting in an energy delivery of 30 Joules/cm2. Equi-Light's photo energy delivery caused dissociation of nitric oxide from hemoglobin within the red blood cells of skin capillaries and small vessels directly under the diode pads.
Magnetic Therapy
At the Center for Biomedical Engineering at the University of Kentucky in Lexington, a research team is looking at the effects of static magnetic fields on cultured neurons. Preparations of dorsal root ganglia were exposed to magnetic fields at amplitudes of 900 g, 450 g and 225 g for 1 hr per day for 2 days (6). In all experiments Nerve Growth Factor was included since it is essential for normal growth and differentiation of sensory neurons. Under the influence of the 900 g magnet, neurite area increased 39.5% over the control. The weaker magnetic fields did not show significant growth, indicating that relatively high magnetic fields are required to produce a significant effect.
Magnetic fields penetrate the tissue inducing small local electrical currents that stimulate nerves. A common complaint is that therapeutic magnets exert a field that is very weak, but weak electromagnetic forces are the means by which inter and intra cellular communication takes place. A well-known example is the "current of injury" which appears while a wound or bone is healing.
Manual Therapies
Research on manual techniques has not reached the level of sophistication to indicate what the effects are on the cellular level, but it is known that kinetic movement produces a weak electrical field in tissues. The effect of manual therapy on neurotransmitter activity is obvious in the deep relaxation evident in a horse following skilled application of these techniques. Although there is a lack of data to "prove" the degree of effectiveness, it is evident that horses, which receive these treatments, and those described above, are more comfortable, recover from injury more quickly, and are able to perform to their potential.
Equine therapy has much to offer the horse at any phase of his life. The therapists of Equine Therapy, Inc, in Lexington, Kentucky, have successfully intervened in cases of flexural deformity in foals, wounds from superficial lacerations to fractures in yearlings, and racing injuries such as tendonitis, bursitis, muscle trauma, EIPH, and foot pain in the athletic horse. Retired horses have been aided in their transition from an athletic career to a breeding career and successfully treated for chronic racing injuries and laminitis. We rely on a complete veterinary diagnosis and continued consultation with the referring veterinarian throughout the course of treatment. Equine therapy is a continuation of complete health care for the horse.
References
| 1. | Morcos, MB and A Aswad. Histological Studies of the Effects of Ultrasonic Therapy on Surgically split Flexor Tendons. Equine Vet J. 10 (4). 267-269. 1978. |
| 2. | Vasko, KA, A Spauchus, and M Lowry. Laminitis Treatment With Electrotherapy. Equine Practice. 8 (4). 28-31. 1986. |
| 3. | Li, LC etal. The Efficacy of Dexamethasone Iontophoresis for the Treatment of Rheumatoid Arthritic Knees. Arthritis Care and Res. 9 (2). 126-132. 1966. |
| 4. | Dorian, R. Clinical Investigation of Iontophoresis of Betamethasone in the Horse Hock Joint. Unpublished. Edna Valley Veterinary Clinic. San Luis Obispo, CA. |
| 5. | Horwitz, LR, TJ Burke and D Carnegie. Augmentation of Wound Healing Using Monochromatic Infrared Energy. Advances in Wound Care. Jan/Feb. 1999. |
| 6. | Sisken, B etal. Effects of Static Magnetic Fields on Neurite Outgrowth of Dorsal Root Ganglia Neurons In Vitro. Unpublished. Center for Biomedical Engineering and Department of Anatomy and Neurobiology. University of Ky. |
About the Author
Mimi Porter has a Masters degree in physical education and is a certified and licensed athletic trainer. A long association with horses led her to apply her therapeutic skills to the horse. She has a successful equine therapy business and is responsible for developing the first college curriculum on equine therapy at the Midway College in Kentucky.
This information was presented at, and appears in the Proceedings of, the 2001 Alberta Horse Breeders and Owners Conference.
This information is maintained by of the Horse Industry Section of Alberta Agriculture in conjunction with Sylvia Schneider at Pondside Web Productions.
Mimi Porter
Equine Therapy, Inc.
Lexington, Kentucky |
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