The physiologic effects, indications, techniques, and precautions of various physical agent modalities, including cold, heat, ultrasound, electromagnetic waves, electricity, and mechanical force, are summarized in this chapter and eSlides.
Cryotherapy (eSlides 17.1 and 17.2)
Physiology
The major physiologic effects of cryotherapy (treatment involving lowering of local tissue temperature) include decreasing the nerve conduction velocity of pain fibers, reducing muscle spasm, and causing vasoconstriction, which may be followed by vasodilation.
Indications and Contraindications
Indications for cryotherapy include acute injury, acute swelling, hemorrhage and edema, acute contusion, acute muscle strain, acute ligament sprain, bursitis, tenosynovitis, tendinitis, muscle spasm or guarding, chronic pain, and myofascial trigger points. Contraindications include impaired circulation (e.g., Raynaud phenomenon, peripheral vascular disease), hypersensitivity to cold, skin anesthesia, open wounds or skin disorders (those that need cold whirlpools and contrast baths), and local infection.
Applications of Cryotherapy
Types of cryotherapy include ice packs, ice massage, cold whirlpools, chemical cold spray, and contrast baths. The primary action of cold spray is to stimulate Aβ nerve fibers to reduce the painful arc and muscle spasm. It can be used in the field to reduce pain and muscle spasm associated with an acute sports injury. Cold spray, in the technique of “spray-and-stretch,” is also commonly used to relieve muscle spasms of myofascial pain syndrome. Contrast baths are used to treat subacute swelling. They produce alternating vasoconstriction and vasodilation, which reduce local edema.
Superficial Heat (eSlides 17.3, 17.4, and 17.5)
Physiology
Thermotherapy, which can be divided into superficial heat and deep heat (diathermy), is used to increase tissue temperature. Superficial heating agents increase the temperature within the skin and subcutaneous fat. Deeper tissue heating is limited by vasodilation and the insulating properties of fat. Because of poor penetration (less than 1 cm), superficial heat generally only affects cutaneous blood flow and cutaneous nerve receptors. In addition to increasing local blood flow by applying heat, the higher cutaneous temperature also has an analgesic effect. Heat has the effect of relaxing skeletal muscle by simultaneously decreasing the stimulus threshold of muscle spindles and decreasing the gamma efferent firing rate.
Indications and Contraindications
Indications for thermal therapy include nonacute (longer than 6 weeks) inflammatory conditions, nonacute pain, subacute (6-12 weeks) muscle strain, subacute contusions, subacute ligament sprains, muscle guarding or spasm, decreased range of movement of a joint, and myofascial trigger points. Contraindications include acute musculoskeletal conditions, impaired circulation, peripheral vascular disease, skin anesthesia, open wounds, and infection.
Types of Devices and Techniques
Hydrocollator Pack
The most commonly used superficial heat method is the commercial hydrocollator pack.
Paraffin Bath
A paraffin bath (paraffin and mineral oil mixture) is a simple and efficient method for applying superficial heat, especially to small joints of the body such as the interphalangeal joints. It is most commonly used for rheumatoid arthritis and osteoarthritis. The combination of paraffin and mineral oil has a low specific heat, which enhances the patient’s ability to tolerate heat from paraffin (compared with water at the same temperature) ( ).
Infrared
Infrared is a superficial, dry heat modality, which tends to elevate superficial temperatures more than moist heat, but it may have a smaller depth of penetration. The advantage of an infrared lamp over other superficial heat modalities is that it can increase the temperature without touching the patient, making it the only superficial heating method appropriate for patients with skin defects.
Hydrotherapy
Hydrotherapy treats the patient through the medium of water. Water can provide warmth and coldness, moisten the soft tissues, and support the tissues. In addition to the thermal benefits of reducing pain, edema, and muscle spasm, a quick jet stream or stroking motion during whirlpool therapy has a local massage effect, which might cause further muscle relaxation and increase local circulation. When using a whirlpool, the patient can move the treated part easily in the whirlpool, which produces the additional benefit of exercise. A warm whirlpool is an excellent treatment for rheumatoid arthritis and osteoarthritis as it increases systemic blood flow and mobilization of the affected body part without exerting too much pressure on the joints.
Spinal Traction (eSlides 17.6 and 17.7)
Physiology
Spinal traction moves the spine overall and at each individual spinal segment. The amount of movement varies according to the position of spine, the amount of force, and the duration of traction. The major physiologic effects of spinal traction are derived from distraction of the spine, which may stretch ligaments, muscles, and facet joints; reduce disc pressure; facilitate return of the disc to its original position; decrease central pressure in the disc space and facilitate movement of the disc nucleus back to the central position; separate the joint surfaces, which releases the impingement of meniscal structures, synovial fringes, and osteochondral fragments between joint spaces; stretch specific paraspinal muscle groups, allowing better muscular blood flow; and activate muscle proprioceptors.
Indications and Contraindications
Spinal traction is indicated in patients with nerve impingement from disc herniation, spondylolisthesis, narrowed intervertebral foramen, spur formation, degenerative facet joints, joint hypomobility, discogenic pain, muscle spasm, and spinal ligament or connective tissue contractures. Contraindications include acute sprain or strain, acute inflammation, vertebral fracture or joint instability, pregnancy, tumors, bone disease, severe osteoporosis, and infection in bones or joints.
Techniques
When considering mechanical traction, several important parameters need to be set, including traction equipment, body position, force used, traction pattern (intermittent vs. sustained traction), and duration of traction. The effects of intermittent or sustained traction have been reported. In general, sustained traction is favored for treating intervertebral disc herniation because it produces a longer period of disc decompression, causing disc nuclear material to move centripetally and reducing the pressure of herniated disc on nearby nerve structures. However, intermittent traction is usually more comfortable than sustained traction with the same force, especially at higher forces.
Deep Heat (Diathermy)
Ultrasound (eSlides 17.8, 17.9, and 17.10)
Physiology and Mechanism of Action
The mechanism of heat transfer of ultrasound is conversion, which refers to the transformation of energy (e.g., sound or electromagnetic) into heat. Heat is produced when acoustic energy is absorbed, especially at or near the surfaces of structures with high attenuation coefficients, such as bone. The localized heating by ultrasound near bony surfaces (i.e., at soft tissue–bone interfaces) produces preferential hyperemia and increased extensibility of ligaments, tendons, and joint capsules. Ultrasound of higher frequency penetrates less into the tissues. Nonthermal effects of ultrasound include cavitation, media motion (acoustic streaming and microstreaming), and standing waves.
Sonophoresis
It has long been known that application of ultrasound to the skin increases its permeability and enables the delivery of various substances (most frequently, corticosteroid) into and through the skin via a process called sonophoresis or phonophoresis. Transdermal drug delivery offers several important advantages over traditional oral delivery or injections, including minimizing gastric irritation, first-pass effect, and injection pain.
Contraindications and Precautions
Using the stroking technique for ultrasound allows a more even energy distribution over the site being treated. The stationary technique should be generally avoided because of the potential for standing waves and hot spots. Heat should be generally avoided in areas of impaired sensation or in patients with cognitive impairment. Heat can exacerbate acute inflammation, and thus ultrasound should be avoided in the management of acute tendinitis, arthritis, or ligament sprain. Applying ultrasound near structures that are vulnerable to thermal injury, such as nerves, the brain, eyes, reproductive organs, growing bone (with open epiphyses), and laminectomy sites, should be avoided. Heat may theoretically increase the rate of tumor growth or hematogenous spread; therefore ultrasound diathermy should be avoided in areas of known malignancy. Applying ultrasound near a pacemaker is generally contraindicated because ultrasound may cause it to malfunction. Ultrasound should be avoided near implants that contain plastic materials such as artificial hip joints with polyethylene liner or breast implants. In contrast to shortwave diathermy or microwave diathermy (MWD), ultrasound is believed to be the only type of diathermy that can be used in areas with surgical metallic implants.
Shortwave (eSlides 17.11 and 17.12)
Physics
Shortwave diathermy (SWD) is a modality that produces heat by converting electromagnetic energy into thermal energy.
Indications and Evidence Basis
Continuous SWD is the technique of choice when uniform elevation of temperature is required in deep tissues and inside joints. Subacute or chronic conditions respond well to continuous SWD, whereas acute lesions are better treated with pulsed SWD.Continuous SWD, when applied properly, is believed to have the ability to relieve pain and muscle spasm, resolve inflammation, reduce swelling, promote vasodilation, and increase soft tissue extensibility and joint range of movement.
Contraindications and Precautions
In general, the common contraindications and precautions of SWD are similar to those for other methods of heating. Because of good bone penetration, SWD-induced heating of the epiphyseal plates in the long bones of children may affect growth; therefore injudicious application of SWD to a child may lead to long-term side effects. SWD is contraindicated in areas with metal implants and in patients with pacemakers or implanted deep brain stimulators.
Electromagnetic waves may selectively heat water; therefore, areas with excessive fluid accumulation, such as edematous tissue, moist skin, eyes, fluid-filled cavities, and a pregnant or menstruating uterus, should be avoided for both SWD and microwave treatment. Towels are usually necessary to be placed between the SWD applicator and treatment area to absorb moisture and avoid focal hot spots on body surfaces. A rule of “no water and no metal” is generally recommended when using both SWD and MWD.
Microwave
Physics
Microwaves have a shorter wavelength than SWD. They generate heat by oscillating a high-frequency electrical field with a lesser extent of magnetic field to induce internal vibration of molecules with a high polarity.
Indications and Contraindications
Microwaves are absorbed to a large extent by water, so they are theoretically able to selectively heat muscle. Because of its limited penetration, microwaves are preferred for heating superficial muscles and shallow joints. It is typically used in patients with chronic neck pain, back pain, or arthritis.
MWD treatment should be avoided in areas close to epiphyses, reproductive organs, nervous system tissues, and fluid-filled cavities. MWD should not be used on or near a patient with a cardiac pacemaker or lead electrodes.
Extracorporeal Shock Wave Therapy (eSlide 17.13)
Physics
The shock waves used in medicine for extracorporeal shock wave therapy (ESWT) are high-intensity pulsed mechanical waves with a relatively low repetition frequency. Unlike therapeutic ultrasound, the temperature increase in the focal area is negligible for intensities used in therapeutic applications.
Indications and Mechanisms of Action
The most widely accepted indications for ESWT are the treatment of plantar fasciitis, lateral epicondylitis, and rotator cuff calcified tendinopathy. The biological mechanisms are believed to involve the destruction of sensory unmyelinated nerve fibers and promotion of neovascularization. ESWT can stimulate bone remodeling; thus, it may be used as an alternative to surgical treatment for fractures, bony nonunion, and delayed union: settings in which it may yield better short-term clinical outcomes.
Contraindications and Precautions
Contraindications to ESWT include bleeding disorders and pregnancy. Complications may include soft tissue swelling, ecchymosis or hematoma, skin redness or erosion, transient bone edema, nerve lesions, and increased pain.
Electrotherapy
Physiology and Mechanism of Action
The mechanisms of action of electrotherapy devices in pain management can be broadly summarized as follows: (a) segmental inhibition of pain signals to the brain and the dorsal horn of the spinal cord (Melzack and Wall’s gate control theory) and (b) activation of descending inhibitory pathways and stimulation of the release of endogenous opioids and other neurotransmitters, such as serotonin, gamma-aminobutyric acid, noradrenaline, and acetylcholine.
Transcutaneous Electrical Nerve Stimulation
Commonly used transcutaneous electrical nerve stimulation (TENS) units provide either conventional TENS (which produces a tingling sensation) or low-frequency TENS (which produces a burning, needling sensation). In painful diabetic peripheral polyneuropathy and myofascial trigger points, TENS units have been found to be effective for up to 3 months.
Interferential Current (eSlide 17.14)
Interferential current therapy (IFC) employs alternating medium-frequency electrical current signals of slightly different frequencies, which penetrate tissues more easily and are less prone to neuronal adaptation than TENS. IFC therapy has been successfully used in a variety of musculoskeletal and neurologic conditions, as well as in the management of urinary incontinence for up to 3 months.
Iontophoresis
Iontophoresis is the technique of using the charges of ions and particles to drive them across tissues and membranes under the influence of an imposed electrical field. It can be useful for local or systemic drug delivery because it avoids first-pass hepatic metabolism and drawbacks associated with oral or intravenous routes, such as gastric irritation and variability of serum concentrations.
Precautions and Complications
Electrotherapy devices should not be used near implanted or temporary stimulators because of the potential for interference with the function of these devices. Abnormal vascular responses may develop when electrotherapy is used near sympathetic ganglia or the carotid sinus. IFC should not be used near open incisions or abrasions because of the potential for concentration of the electrical current at these sites. Electrotherapy devices should not be used near the gravid uterus because of potential adverse effects on fetal development or the possibility for stimulating uterine contractions. A deep venous thrombosis may be dislodged and propagated (resulting in an embolus) if electrotherapy induces stimulation of vascular smooth muscle in the area. Other precautions include insensate skin and patients with cognitive impairment.
Low-Level Laser Therapy (eSlide 17.15)
Physics and Bioeffects
Low-level laser therapy (LLLT) involves the use of relatively low light energy (less than 100-200 mW). The potential physiologic benefits of LLLT appear to be nonthermal; it can have a stimulating effect on target tissues. LLLT is used to decrease pain and inflammation, stimulate collagen metabolism and wound healing, and promote fracture healing.
Indications and Evidence Basis
LLLT may have a role in wound care, especially for diabetic foot ulcers. Following LLLT, pain is immediately reduced in patients with acute neck pain and over a period of 1–5 months in those with chronic neck pain. LLLT also reduces pain in the wrists, fingers, knees, and temporomandibular joints, as well as the pain associated with lateral epicondylitis.
Contraindications and Precautions
Precautions should be taken to ensure that the LLLT beam does not hit the eye directly or after reflection off a shiny surface. LLLT should not be used in areas with cancerous tissue.
Summary
Physical agent modalities are commonly used in the daily practice of physiatrists to relieve patient discomfort. Future research may focus on defining the best parameters of modality settings such as treatment dosage, duration, and frequency. Exploring the mechanism of treatment effects on tissues may also broaden our knowledge and aid in selecting the most appropriate modalities for various pathologies.
- 1.
Cryotherapy is generally used to treat acute injury, whereas thermotherapy is primarily used for subacute and chronic conditions. Heating produces modest increases in nerve conduction velocity, whereas cooling produces dramatic decreases in conduction velocity.
- 2.
Depth of penetration is arbitrarily divided into deep and superficial. Superficial heat therapy includes hot packs, paraffin baths, infrared therapy, and hydrotherapy. Deep therapy includes ultrasound diathermy, shortwave diathermy, and microwave diathermy.
- 3.
In Hubbard tanks, when only a portion of the body is immersed, more extreme temperatures can be used. For whole body immersion, neutral temperatures (34°C-36°C or 93°F-97°F) should be used to prevent core temperature fluctuations.
- 4.
Ultrasound diathermy should be avoided near nerves, brain, eyes, reproductive organs, and growing bones (with open epiphyses), but it may be the only diathermy that can be used in areas with surgical metallic implants.
- 5.
“No water and no metal” is recommended when considering the use of shortwave diathermy or microwave diathermy.
- 6.
The lower frequencies used in shortwave diathermy and microwave diathermy have the advantage of increased depth of penetration but the disadvantages of greater beam dispersion and the need for larger applicators.
- 7.
The potential physiologic effects of low-level laser therapy appear to be nonthermal.
Bibliography
1. Abramson D.I., Tuck S., Chu L.S., Agustin C.: Effect of paraffin bath and hot fomentations on local tissue temperatures. Arch Phys Med Rehabil 1964; 45: pp. 87-94.
2. Abramson D.I., Tuck S., Lee S.W., et. al.: Vascular basis for pain due to cold. Arch Phys Med Rehabil 1966; 47: pp. 300-305.
3. Ahmad E.T.: High-voltage pulsed galvanic stimulation: effect of treatment duration on healing of chronic pressure ulcers. Ann Burns Fire Disasters 2008; 21: pp. 124-128.
4. Ahn A.C., Bennani T., Freeman R., et. al.: Two styles of acupuncture for treating painful diabetic neuropathy—a pilot randomised control trial. Acupunct Med 2007; 25: pp. 11-17.
5. Aimbire F., Ligeiro de Oliveira A.P., Albertini R., et. al.: Low level laser therapy (LLLT) decreases pulmonary microvascular leakage, neutrophil influx and IL-1beta levels in airway and lung from rat subjected to LPS-induced inflammation. Inflammation 2008; 31: pp. 189-197.
6. Ainsworth R., Dziedzic K., Hiller L., et. al.: A prospective double blind placebo-controlled randomized trial of ultrasound in the physiotherapy treatment of shoulder pain. Rheumatology 2007; 46: pp. 815-820.
7. Akil H., Richardson D.E., Hughes J., Barchas J.D.: Enkephalin-like material elevated in ventricular cerebrospinal fluid of pain patients after analgetic focal stimulation. Science 1978; 201: pp. 463-465.
8. Akyol Y., Durmus D., Alayli G., et. al.: Does short-wave diathermy increase the effectiveness of isokinetic exercise on pain, function, knee muscle strength, quality of life, and depression in the patients with knee osteoarthritis? A randomized controlled clinical study. Eur J Phys Rehabil Med 2010; 46: pp. 325-336.
9. Alexander L.D., Gilman D.R., Brown D.R., et. al.: Exposure to low amounts of ultrasound energy does not improve soft tissue shoulder pathology: a systematic review. Phys Ther 2010; 90: pp. 14-25.
10. Alon G.: Interferential current news. Phys Ther 1987; 67: pp. 280-281.
11. Andrade Ortega J.A., Ceron Fernandez E., Garcia Llorent R., et. al.: Microwave diathermy for treating nonspecific chronic neck pain: a randomized controlled trial. Spine J 2014; 14: pp. 1712-1721.
12. Annaswamy T.M., De Luigi A.J., O’Neill B.J., et. al.: Emerging concepts in the treatment of myofascial pain: a review of medications, modalities, and needle-based interventions. PM&R 2011; 3: pp. 940-961.
13. Annaswamy T.M., Morchower A.H.: Effect of lidocaine iontophoresis on pain during needle electromyography. Am J Phys Med Rehabil 2011; 90: pp. 961-968.
14. Annette P.N.H.: The effectiveness of cervical traction. Phys Ther 2005; 10: pp. 217-229.
15. Aqil A., Siddiqui M.R., Solan M., et. al.: Extracorporeal shock wave therapy is effective in treating chronic plantar fasciitis: a meta-analysis of RCTs. Clin Orthop Relat Res 2013; 471: pp. 3645-3652.
16. Atamaz F.C., Durmaz B., Baydar M., et. al.: Comparison of the efficacy of transcutaneous electrical nerve stimulation, interferential currents, and shortwave diathermy in knee osteoarthritis: a double-blind, randomized, controlled, multicenter study. Arch Phys Med Rehabil 2012; 93: pp. 748-756.
17. Bakhtiary A.H., Fatemi E., Emami M., Malek M.: Phonophoresis of dexamethasone sodium phosphate may manage pain and symptoms of patients with carpal tunnel syndrome. Clin J Pain 2013; 29: pp. 348-353.
18. Balogun J.A., Okonofua F.E.: Management of chronic pelvic inflammatory disease with shortwave diathermy—a case-report. Phys Ther 1988; 68: pp. 1541-1545.
19. Barnes P.M., Bloom B., Nahin R.L.: Complementary and alternative medicine use among adults and children: United States, 2007. Natl Health Stat Rep 2008; 12: pp. 1-23.Related posts:
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