Many physical modalities used in human physical therapy are now being used routinely in canine rehabilitation. Electrotherapy, electromagnetic fields, light, hot and cold therapies and ultrasound can all improve outcomes for your patients. But these modalities alone will not guarantee good results. Proper training is essential. In fact, certified rehabilitation professionals complete many hours of coursework and hands-on learning to fine-tune their diagnostic techniques and the manual skills needed to use these physical modalities correctly.

Electrotherapy

Electrotherapy can be used for wound healing, pain control/relief, reduction of inflammation, muscle re-education, reversal of atrophy and strengthening. This modality works at many levels and can affect both the sensory and motor nerves. At the cellular level, electrotherapy causes excitation of nerve cells and changes in cell membrane permeability. It stimulates protein synthesis, osteosynthesis and fibroblast formation. At the tissue level, electrotherapy causes skeletal muscle and smooth muscle contraction. At the segmental level, it facilitates muscle-pumping action resulting in improved joint mobility, and circulatory and lymphatic drainage.

Transcutaneous Electrical Nerve Stimulation

Transcutaneous electrical nerve stimulation (TENS) is used primarily to manage pain. A small, battery-operated TENS unit delivers an electrical current though electrodes that are placed directly on the skin. The pulse rate, width and intensity can be adjusted according to treatment objectives. TENS works by stimulating faster sensory nerves with an electrical impulse causing an overload of interneurons. This limits the ability of sensory nerves to transmit pain signals to the brain, creating analgesia for the patient. The effect of this modality is short-lived, however, generally not lasting more than 1 hour. In veterinary rehabilitation, TENS is used immediately postoperatively and during therapy to help a patient work through a painful treatment.

Neuromuscular Electrical Stimulation

Neuromuscular electrical stimulation (NMES) is used to rehabilitate muscles. This modality involves stimulation to the motor nerve that causes the muscles to contract. It is delivered to the patient via leads and flexible, low-resistance electrodes that conform to the skin. NMES can be used to help prevent muscle atrophy, increase local blood circulation and maintain or increase joint mobility. It is particularly useful in patients with oedema, delayed wound healing, or in those unable to perform voluntary movement.

The NMES unit features a number of adjustable variables: intensity, pulse duration, current, frequency, on-off times, ramp duration and treatment duration. Ramp duration - the amount of time from the onset of the current until the full strength is delivered - is particularly important in veterinary rehabilitation. In human physical therapy, the therapist can explain how the current and contraction will feel. We do not have this luxury with our canine patients and must provide a slow, gradual onset of contraction strength. A NMES treatment generally lasts 15–20 minutes and achieves best results when used two or three times per week. Contraindications for electrotherapy include treatment over areas of electrical current, such as pacemakers, the carotid sinus, the cervical ganglia and the heart. This modality should be avoided (or at least used with caution) in pregnant patients or over a malignancy.

Light Therapy

LASER treatment is used for pain management, control of inflammation and tissue healing. The physiological effects include accelerated cell division via mitochondrial stimulation, increased leucocyte phagocytosis, stimulation of fibroblast production, enhanced synthesis of adenosine triphosphate (ATP) and angiogenesis. LASERs are divided into four classes based on their power. The majority of therapeutic or 'cold' LASERs are in class 3 with power ranging from 1–500 milliwatts. The 'hot' LASERs commonly used in surgery are in class 4 with more than 500 milliwatts of power. LASER therapy is measured in Joules - the energy delivered by 1 W of LASER energy in 1 second. Most therapeutic regimens call for 1–8 J of energy. The depth of penetration is determined by the wavelength of the LASER. Higher power simply delivers this energy to the same depth at a faster rate.

Hot and Cold Therapies

Thermotherapy or Heat Therapy

This is generally used to reduce pain from arthritis, trigger points and muscle spasms, and to prepare tissues for exercise or stretching. Heat can be applied by hot packs, infrared light, hydrotherapy and by therapeutic ultrasound. Thermotherapy can result in vasodilation with secondary increased local circulation, a decrease in pain, relaxed muscle tone, reduced muscle spasm and an increase in tissue extensibility, cellular metabolism and local tissue oxygenation. Heat therapy should not be used in patients with impaired thermal sensation, recent haemorrhage, malignancy or acute inflammation.

Cryotherapy or Cold Therapy

This is commonly used in the acute period after injury or surgery. It can be applied via ice bath, ice massage, ice pack, vapocoolant gel or circulating ice compression units. The beneficial effects of cryotherapy include vasoconstriction, reduced cellular metabolism, decreased nerve conduction velocity leading to analgesia, reduction of oedema and decreased muscle spasm. Caution should be taken in applying cold therapy to patients with decreased sensation, cold hypersensitivity, or the potential for reflex vasodilation - the 'hunting reflex', a profound vasodilation caused by extended exposure to cold.

Therapeutic Ultrasound

Therapeutic ultrasound involves the application of sound waves directly to the skin to produce a vibration in the underlying tissue. The intensity can be adjusted from 1–3 MHz depending on the desired effects, which could include deep local heating, an increase in blood flow and breakdown of scar tissue. This modality can be used in veterinary rehabilitation to treat a number of conditions including joint swelling, muscle spasms, strain lesions and bicipital tenosynovitis.

Similar to a diagnostic ultrasound, the therapeutic ultrasound converts electricity to sound waves by a piezoelectric effect in the transducer head. The tissues they pass through attenuate ultrasound waves. Bone attenuates the waves the most, followed by cartilage, tendon, skin, blood vessel, muscle, fat and finally blood. This variation must be taken into account when determining the treatment intensity for a tissue or lesion that sits deep in any of these tissues. There are many variables that can be applied to therapeutic ultrasound including duty cycle, frequency, intensity and treatment duration. Generally, treatment time will be about 5 minutes for a space that is twice the size of the transducer head.

Conclusion

There are many physical modalities and therapeutic exercise options available to the veterinary rehabilitation therapist that can add tremendous benefit to the patient. Simply purchasing the best equipment doesn't guarantee great results. Meticulous diagnostic techniques, excellent manual techniques and creative problem-solving are required. These skills require training and hands-on experience.

References

1.  Canapp DA. Select modalities. Clinical Techniques in Small Animal Practice. 2007;22(4):160–5.

2.  Calis HT, Berberoglu N, Calis M. Are ultrasound, laser and exercise superior to each other in the treatment of subacromial impingement syndrome? A randomized clinical trial. European Journal of Physical Rehabilitation Medicine. 2011;47(3):375–80.