Physiologic therapeutics make use of the therapeutic effects of mechanotherapy, hydrotherapy, electrotherapy, light, heat, cold, air, soft-tissue manipulation, and massage. The rational application of these natural forces requires a knowledge of the actions and effects on pathophysiologic processes.

The use of physiotherapy to facilitate basic chiropractic care has been popular within the profession since the turn of the century. However, any therapeutic agent possesses a potential for effectiveness and a potential for danger. Each modality has its Indications and contraindications, and certain precautions must be observed if the modality is to be applied safely and effectively in line with the biophysics and physiologic responses involved.

When properly applied, benefits are gained in normalizing function, preventing and minimizing pain and deformities, and maintaining what has been gained in treatment. The physician-operator must be well acquainted with the physics involved and the underlying application fundamentals to properly prescribe or utilize an appropriate modality, as well as be skilled with the technique of application, its intensity and duration, and to effectively analyze the anticipated effects.


Effects of Common Physical Agents

Each of the common physical agents utilized has more or less specific primary effects and secondary effects. Heat from any source, for example, has a primary thermal effect with secondary effects in hyperemia, sedation, and attenuation of microorganisms. Cold from any source offers a hypothermal primary effect with secondary effects of decongestion, ischemia, and sedation.

Photochemical and electrochemical effects are seen with some physical agents. For example, sunlight, heated metals, and carbon or mercury-vapor arcs present primary photochemical effects and secondary effects of erythema, pigmentation, and activation of ergosterol. Galvanic current offers a primary electrochemical effect and secondary polarization and vasomotor effects.

Kinetic and electrokinetic effects are seen with other physical agents. For example, vibration, massage, traction, and therapeutic exercise offer primary kinetic effects with secondary actions of muscle stimulation, increased venous and lymph flow, stretching of tissue, and reflex stimulation. Electric currents (eg, low-frequency, alternating, interrupted, sinusoidal) present primary electrokinetic effects with secondary effects of muscle stimulation, increased venous and lymph flow, tissue stretching, and reflex stimulation.

Ultrasound therapy is unique in that it offers primary mechanothermochemical effects with secondary effects of intracellular massage and thermal sedation.


Reflex Considerations

The efficiency of physical therapy in the treatment of injury and disease depends to a great deal on (1) the direct reflex effects of the stimulating agent employed and (2) the influence of these agents exerted through the autonomic centers.

The relief of visceral pain by means of any stimulating agent applied to the skin which elicits localized peripheral vasodilation probably depends mainly upon the associated visceral hyperemia. Traumatic and visceral pains are not uncommonly associated with ischemia of the organ or tissues involved. The pain receptors involved are stimulated by a chemical substance which accumulates in the tissues because the circulation is insufficient to remove it. The function of the vasomotor nerve consequently plays a major role both in the cause of pain and its alleviation.


Procedure Applications Relative to Pathogenesis

As disease is a dynamic process rather than a static entity, the primary intent of chiropractic physiotherapeutics is to assist the body in adapting to and/or normalizing the aberrant processes within an abnormal state. The abnormal process existing at the time of therapy determines the particular type of therapy applicable. Any injury or disease state comprises a number of abnormal physiologic reactions depending upon its state of healing or adaptation. Thus, therapy must be varied according to the process at hand to assist the body in normalizing or adapting to the condition. The therapeutic goal is often to stop or reverse a noxious reaction which is preventing or delaying normal healing processes.

Brandstetter points out that whether a tissue becomes primarily injured through frank trauma or microtrauma, or is undergoing a change such as a secondary reaction to a neuropathic process initiated elsewhere, four stages usually occur. See Table 14.1. While these stages and their processes usually exist in varying degrees within tissues simultaneously, one process usually dominates. Treatment should be directed primarily at the dominant process and altered as the dominant feature changes. In this regard, as Brandstetter states, the presence of a coexisting neuropathy must be realized and the area of therapy should be considered as not only at the site of local symptoms, but also at the neuromere or spinal segment directly or indirectly involved.

In any particular stage of physiologic activity, a misapplied or too vigorous application may be an insult to the lesion as well as to healthy tissue causing a return to active inflammation. Any overtreatment, whether it be of time or intensity, may counteract the beneficial effects desired.

I.   Stage of Hyperemia or Active Congestion

• Ice packs:   vasoconstrictive effects.
  
  
• Positive galvanism:   vasoconstrictive, hardening of tissues effects.
  
  
• Ultrasound:   dispersing effects; increased membrane permeability effects.
  
  
• Rest, with possible support:   prevents irritation and further injury.

II.   Stage of Passive Congestion

• Alternating hot and cold applications, preferably in 3:1 ratio every few hours: revulsive effects.
  
  
• Light massage, particularly effleurage: revulsive effects.
  
  
• Passive manipulation: effects of revulsion, maintenance of muscle tone, freeing of coagulate and possibly early adhesions.
  
  
• Mild range of motion exercise: effects same as 3.
  
  
• Sinusoidal stimulation, of a surging nature: effects same as 3.
  
  
• Ultrasound: increase in gaseous exchange, dispersion of fluids, liquefaction of gels, and increased membrane permeability effects.

III.   Stage of Consolidation and/or Formation of Fibrinous Coagulant

• Local moderate heat, preferably of a moist nature: mild vasodilation, increased membrane permeability effect.
  
  
• Moderate active exercise: revulsive effects, freeing of coagulant and early adhesions, maintenance of tone, and ligamentous and muscular integrity effects.
  
  
• Motorized alternating traction: effects same as 2.
  
  
• Moderate range of motion manipulation: effects same as 2.
  
  
• Ultrasound: hyperemia, liquefaction of gels, dispersion of gases and fluids, increased membrane permeability, and tissue-softening effects.
  
  
• Sinusoidal current, surging or pulsating: effects same as 2.

IV.   Stage of Fibroblastic Activity and Fibrosis

• Deep heat, prolonged (eg, diathermy): prolonged vasodilation, increased membrane permeability, increased chemical activity effects.
  
  
• Deep massage (eg, petrissage or other soft-tissue manipulation: tends to break down fibrotic tissue and create more elasticity.
  
  
• Vigorous active exercise, preferably with slight traction or at least without weight bearing: maintains muscle and ligamentous integrity, stretches fibrotic tissues, breaks adhesions, and creates greater elasticity.
  
  
• Motorized alternating traction: effects same as 3.
  
  
• Negative galvanism, partic?ularly with an antisclerotic (eg, potassium iodine): vasodilation, softenting, liquefaction, and antisclerotic activity effects.
  
  
• Ultrasound: effects causing softening of tissues as previously mentioned.
  
  
• Active joint manipulation: reduction of muscular spasm, breaking of adhesions and fibrotic tissue, and restoration of physiologic motion effects.

Heat is applied in a number of fashions such as hot water, whirlpools, steam baths, sauna-like hot air, sand and mud, paraffin dips, hydrocollator packs, hot moist packs, electric pads, ultrasound, shortwave diathermy, microwave, radiant heaters, sunlight, infrared rays, and incandescent lamps. Regardless of the mechanism used, the surface effects of heat on tissues are essentially the same, but deeper effects vary according to intensity, concentration of application, duration, wave-length, and the vascularity of the area.


Physiologic Effects of Heat

The rule of thumb is that heat should never be applied to a body part until 48 hours after injury, or even longer if recurrent bleeding is a danger. When tissue is injured, the body establishes a defensive inflammatory mechanism that temporarily blocks circulation and white and red cells hasten to the affected part. After the acute stage has passed, fresh blood must be brought to the injured part to carry on the battle to enhance healing processes. Because lesion waste products are difficult to move through the small venous vessels, heat is an aid.

It takes time for heat to penetrate. For example, when hot-water bags whose water temperature is 133°F are continually placed on an extremity, the outside of the towel covering the bag will be about 122°F. It takes about 30 min for the skin temperature to rise from 90°F to 110°F, about 40 min for subcutaneous tissue to rise from 91.2°F to 105.5°F, and about 50 min for intramuscular temperature to rise from 94.2°F to 99.6°F.

As with cold, the exact physiologic mechanisms by which heat achieves its effects are not completely understood. For example, paradoxical decreases in intra-articular temperatures have been recorded, and increases have been recorded with surface cold.


Indications and Contraindications

Local heat relieves muscle spasm, dilates superficial blood and lymph vessels, increases phagocytosis and perspiration, and sedates the nervous system.

It also reflexly dilates blood and lymph vessels in deeper tissues in various degrees depending upon the application site.

General heat applied to the body increases circulation, heart rate, perspiration, respiration, and urine formation. The blood tends to become more alkaline while the tissues become more acidic.

Some authorities have shown that variations of temperature applications to various parts of the body will produce vascular shifts and also have a toning effect upon the blood vessels, thus explaining the benefits of alternate hot and cold applications.

Local heat is contraindicated in acute inflammations, suppuration, hemorrhagic tendencies, impaired or hypersensitive thermal sense, or over encapsulated swellings where vasodilation may result in rupture or dispersion. Heat should never be applied to an acute injury where extravasated blood and fluids occur as great damage can be done by increasing localized edema and bleeding from ruptured capillaries. Great care must be used in applying local heat to the diabetic.


Physiologic Effects of Shortwave Diathermy

Different wave lengths have different effects; ie, the shorter the wave length, the deeper the penetration. As the name implies, this modality utilizes high-frequency alternated currents of short wave lengths.

Shortwave diathermy produces local hyperlymphemia and sedation. Histamine production is increased, which causes vasodilation. Enlargement of the venous capillary system hastens resorption and removal of bacteria and waste products at the site of the lesion. Because defensive mechanisms (phagocytosis) are assisted by the effect on serum and leukocytes, a bactericidal effect is present. Both locally and generally, phagocytosis and leukocytosis are increased through increased circulation rate. Osmosis of serum proteins is reestablished from increased capillary pressure, and metabolism is influenced from the increased oxidation rate of blood. There is a general rise in body temperature, associated with increased heart, BMR, perspiration, and respiratory rates.

      Indications and Contraindications

The deep heat from diathermy relieves muscle cramps, spasms and associated pain, and increases glanduar secretions. Because of a lowered concentration of pain-producing substances below the irritation level of nerve receptors, a general sedative effect and relief of pain occurs.

Shortwave diathermy uses high-frequency current (27 megacycles) to heat body tissues, the result of tissue resistance to the current. It is probably the most common modality used when deep heat is desired. Subacute and chronic strains, sprains, tenosynovitis, and myositis respond well. It should be kept in mind, however, that the deeper tissues affected by diathermy do not have the heat sensitivity enjoyed by the superficial tissues. Thus, thermal devitalization can occur in deep tissues without pain or other warning signs. For this reason, it is best to apply deep heat cautiously.

The common contraindications seen in athletics are acute injury and inflammations, deficient thermal sensation, menstruation, large or inflammed varicosities, over epiphyses, through the brain, or whenever systemic fever would be contraindicated. As seen in general practice, states of tuberculosis, malignancy, pregnancy, cardiovascular or renal disease, metallic inplants, ulcerative disorders, advanced osteoporosis, and severe weakness are certainly contraindications. Even in the healthy, only one-half of the normal rate should be applied over encapsulated organs.

Physiologic Effects of Ultrasonic Diathermy

Ultrasound therapy is produced by a frequency about 1 million cycles/sec, far above that perceptible to the human ear. The depth of penetration is 4 cm or more, and its primary effect is the result of the vibrations passing into tissue causing an internal friction which results in heat. Unlike light, ultrasound passes through all tissue liquids and solids which inhibit the passage of light.

Mechanical, thermal, chemical, and neural effects are seen with the use of ultrasound. Mechanically, there is a dispersion of fluids, an increase in molecular movement (cellular micromassage), and increased membrane permeability. Thermally, hyperemia (thus increased leukocytosis and alkalosis) and increased glandular activity are produced. Chemically, ionization through membranes, chemical oxidation, and gaseous exchange are increased. Thixotrophic gels may be converted into liquid forms.

Phonophoresis is presently being investigated, wherein certain substances are incorporated into the coupling medium to enhance the therapeutic effect. Adequate data on this noninvasive innovation are not as yet available.

      PATHOPHYSIOLOGIC NEURAL EFFECTS

Whether they be mechanical, chemical, or psychic, irritations cause the nervous system to alter its normal physiologic response, and it is such altered responses that are exhibited as signs and symptoms of a given disorder. A paper by the ACA Council on Physiotherapy brings out that, "This neurotrophic response may also be sensitized and result in an aberration of normal irritability with the subsequent maintenance, facilitation, and/or production of disease processes occurring as the nervous system responds to the average extrinsic and intrinsic stresses of normal life processes. Ultrasound affects the nervous system in such a way as to reduce its conductivity and, therefore, tends to abort the maintenance of a neural pattern of disease."

Because of this latter effect, ultrasound is wisely applied to several areas which parallel the pathogenic process. For example: (1) The local area, to scatter or dissolve the pathologic process before neuropathy is firmly established and to provide symptomatic relief. (2) Known areas of referred or reflex activity, to halt or dissolve areas of neuropathy. And (3) over the synaptic areas of specific neuromeres when "sensitization" of the neurotrophic process may have occurred.

Therapy over a neurologic area (eg, nerve root) should be conducted at half duration and a lower intensity as compared to that utilized over the primary site. Ultrasound can also be used as a diagnostic probe in locating paraverte- bral and peripheral trigger points and deep-seated areas of sensitivity.

      CONTRAINDICATIONS

Ultrasound is generally contraindicated over sites of potential hemorrhage, the stellate ganglion, gonads, eyes, growing or unfused epiphyses, implants, infections, and bony protuberances. In general practice, advanced heart disease, malignancies, pregnancy, pulmonary tuberculosis, and sensory paralysis are also contraindications.

Ever since Guillaume Duchenne published Physiologic des Mouvements in 1867, galvanism has been used in the treatment of injuries and disease. Galvanic current is the only current which is applied in regard to polarity. Its physiologic effects are those of heat, chemical processes, and as a cellular excitant. The chemical effect is derived from the dislocation of sodium from tissue salt.

Most galvanic current is of a direct current of low voltage usually not exceeding 100 volts and of low amperage usually not greater than 50 milliamperes. The current is unidirectional, consisting of a stream of ions which flow at low tension. No muscle contraction results unless the current is interrupted.


Polar Effects of Galvanism

The negative pole tends to attract alkalies and repel acids, to increase circulation via vasodilation thus relieving chronic pain, to decrease nerve sensitivity at high intensities, to increase irritability at low intensities, and to soften tissue. The positive pole tends to attract acids and repel alkalies, to decongest tissues via vasoconstriction thus relieving acute pain, to inhibit nerve irritability, and to toughen tissue.

      CONTRAINDICATIONS

High-intensity current should never be applied through the heart or brain, or on an individual with impaired sensory response. Galvanism is contraindicated in any condition where its effects would be inadvisable for the state of a disorder at the time or in any disease process where stimulation might produce harmful results (eg, possible tumor).

Iontophoresis

Iontophoresis consists of transferring ions into the body by an electromotive force. The greatest concentration is moved into the skin where the skin is broken, or along sweat glands and hair follicles. Because the depth is minimal, the ions transferred into the skin are taken up by the circulation and do not proceed through the tissues to the other electrode.

The caustic ions of heavy metals such as copper and zinc have been found useful in the management of septic surfaces and in chronic infections of cavities (eg, sinuses). Copper salts (2%), for example, are 12 times more microbicidal when taken into tissues through iontophoresis. Iodine and chlorine ions are often used for softening fibrotic tissue and loosening adhesions and superficial scars after joint injuries.


Higher-Voltage Modalities

During the past few years, relatively high-voltage, low-amperage galvanism has been employed with oustanding results. The physiologic effects apparently are produced by the increased capability to move bound and unbound tissue fluids.

Kaesberg, who has studied various models, lists the primary advantages as circulation stimulation, elimination of muscle spasms in minutes, immediate pain control, and the ability to locate and break trigger points in seconds. This rapid removal of pain fills a long need within chiropractic in highly acute disorders. Another interesting point is that following shortwave or ultrasonic diathermy, high-voltage therapy greatly reduces the adverse and hidden deeptissue edematous effects created by deep heat without interfering with the therapeutic value of these modalities.

High-volt units are neither galvanic in action, nor are they similar in most ways to low voltage units. High-volt units generate an electromotive force of up to 500 volts. They use a unidirectional, monophasic, interrupted (noncontinuous) current that consists of twin spikes. The total pulses per second (pps) can be manually varied by the operator. In comparison to pulsed low-volt units, the pulses of high-volt units are on for an extremely short time and this interval may be controlled to some extent in some units. High-volt units have a relative- ly low current amperage, averaging between 1.0 and 1.5 ma.

Jaskoviak points out that high-volt stimulators have a distinct advantage over low-volt units in that the former have the ability to reach much higher wave peaks. The ability to achieve this without burning the patient is possible in high-volt units because the pulse duration is extremely short; ie, a low average current is produced. In other words, high-volt units generate a relati=- vely high-peak wave with a low--average current amperage.


Physiologic Effects

High-volt therapy generally affects body tissues in certain ways to modulate pain, muscle spasm, inflammation, tissue healing and repair, based on the way that the control settings on the unit are adjusted. The major effects may be summarized as:

(1) pain reduction,
(2) muscle spasm reduction,
(3) muscular exercise and reeducation,
(4) circulation enhancement,
(5) edema reduction, and
(6) insignificant chemical changes without appreciable iontophoresis.

      CONTRAINDICATIONS

High-volt modalities are one of the safest electrotherapies in use today. The worst effects possible appear to be caused by increasing the intensity too fast, thereby pushing the current at such a rapid rate that tissue accommodation cannot occur. If this happens, considerable discomfort is suffered by the patient even though a burn does not occur.

The three standard contraindications to applying high-volt therapy are:

(1) applications over the low back or abdomen during pregnancy,
(2) applications over neoplastic areas, and
(3) using the therapy on patients wearing a pacemaker. It should also be noted that extreme caution must be used if use is made near the heart or carotid sinus, and any possible clinical value of applying high-volt transcerebrally is highly questionable.

      MUSCLE STIMULATORS

To be effective, a muscle stimulus must have a certain intensity and duration. In addition, its final intensity must rise with adequate speed.

Any procedure used to stimulate muscle tissue by electricity falls under the general category of electrical muscle stimulation. Various types of modalities, frequencies, and wave forms can be utilized to stimulate muscle fibers electrically. Common objectives of electrical muscle stimulation include the reduction of spasticity, the exercise of weak muscles, and diagnostic evaluations to determine the state of a possible degree of degeneration. The therapy may be applied to normally innervated muscles or to muscles that are abnormally innervated or denervated.

Muscle stimulators are typically low frequency modalities. Low frequency currents are those electrical currents that can stimulate a patient at a frequency of under 1000 pulses per second. Such currents are primarily used to exercise muscles after injury, develop muscular strength and tone, trigger chemical changes, alleviate pain, and break muscle spasm. The primary reasons for applying electrical stimulation to muscle tissue are weakness of innervated muscle, muscle spasm, and dysfunction of denervated muscle.

The basic effect on the body is muscle contraction if an alternating current of 1 Hz is applied to normal innervated muscle; ie, a single twitch-like contraction will occur. As the pulse rate is gradually increased, the rate of twitching correspondingly increases. As the frequency nears 20 Hz, the contractions merge until a tetanic contracture (persistent tonic spasm) results.

      TENS UNITS

The acronym TENS refers to transcutaneous electrical nerve stimulation, a procedure where an electric current is passed across the skin. In its broadest sense, TENS refers to many types of therapeutic devices, including high-volt modalities. However, the term is generally reserved for those small portable electrical units that the patient wears to control pain.

TENS units are designed to provide sensory and not motor stimulation. This fact is important because motor stimulation will produce contractions in many cases of severe pain that result in aggravation of the patient's complaint.

Application

TENS is intended for the symptomatic relief of a large number of painful syndromes until the cause can be found, the relief of chronic intractable pain syndromes, or cases where analgesic drugs would be contraindicated. The pain modulation usually lasts only while the current is turned on; ie, it has no residual posttherapy effects.

Many excellent types of stimulators are available for home and professional use, and the following features are common to most pain control TENS devices:

1. Because afferent nerve fibers differ greatly from efferent nerve fibers in

   (a) length of refractory period,
   (b) accommodation to stimuli,
   (c) threshold of firing, and
   (d) response to different wave forms, TENS wave form widths are 40–500 ms or less (usually under 130 ms), while pulse widths for triggering motor responses are 500 ms or better, and frequencies can usually be set in the 70–150 pps range for effective pain control.

2. The wave forms are usually spiked; ie, they are not smooth symmetrical waves. Most units have a wave that alternates and is a variation on the faradic or square wave.

3. Electrode placement should be on the same dermatome(s) as is the patient's perception of pain, preferably over or proximal to the site of pain. In radiating pain, electrodes may additionally be placed over the major nerve pathways (eg, in sciatica). In cases of nerve damage, electrodes should be placed proximal (never distal) to the site of pain. If the site of pain is so sensitive that the slightest stimulation is excruciating, the stimulation of the contra- lateral area will initially provide partial relief that tends to become more effective after a few days. Acupuncture points far distant from the site of pain have also proved to be successful sites of stimulation. In fact, some authori- ties have suggested that TENS and acupuncture have a similar mode of action.

A great deal has been written about TENS, and there are many fine charts available as a guide for the placement of electrodes. Some examples are shown in Figure 13.8. Studies have shown that TENS provides significant short-term relief for 65–80% of patients and long-term relief for 30–35%.

      CONTRAINDICATIONS

Electrical stimulation of any type should obviously be used with caution in undiagnosed pain syndromes where the etiology has not been firmly established. The only contraindication known, when used with a physician's prescription, is in patient's using a demand-type pacemaker. However, stimulation over the carotid sinus, the heart in patients with known arrhythmias or myocardial disease, the pregnant uterus, open wounds, or the pharyngeal/laryngeal muscles would undoubtedly be hazardous.

      INTERFERENTIAL CURRENT

Interferential current is totally different from the other modalities that have been described. It consists of two medium frequency currents that cross deep within a body part, and, in so doing, trigger the formation of a third current that radiates from the inside to the outside of a body part, thus creating an endogenous physiotherapeutic approach.

The Physiological Basis

To fully appreciate this type of therapy, it should be remembered that one of the major effects of high frequency stimulation is that the frequency or rapidity with which the stimulus bombards the skin is so rapid that skin resistance is immediately overcome, allowing for deep penetration of the therapy. Low frequency currents, in contrast, have frequencies of under 1,000 Hz and do not produce such deep penetration, but they do have a profound effect on electroexcitable tissues (eg, muscles, nerves).

The medium frequencies that are applied with interferential current are generally 4,000 cps sine wave currents that are crossed simultaneously (triggered by two generators). However, they cross at slightly different frequencies. One of the sine waves has a fixed frequency (generally, 4000 Hz), and the frequency of the other current can be set at a variable amount that is usually be- tween 4000 and 4250 Hz.

The linear superimposition of the second wave on the first wave is called interference. In Figure 13.9, it can be seen that the placement of four electrodes on the skin, as shown, will establish the specific location where current intersection takes place. By placing the two currents close to one another, the depth of penetration is kept superficial, while placing the electrodes farther apart will increase the depth of penetration. The density of the body tissues involved will also alter the depth of penetration and the locale of intersection. At the area of intersection, a low frequency endogenous current will be generated. This endogenous current, for all practical purposes, has a frequency that is the difference of the two frequencies which were originally applied.

Because interference current therapy is a by-product of a superimposition of two alternating sine wave currents, there will be no direct current effects within the involved tissues. Chemical alterations and polar changes do not occur as they do with direct current. Because of this factor, an operator need not be especially concerned about burning the patient with interferential therapy. As explained, the placement of electrodes predetermines the exact site and degree of interference.

Application

The following points are considered to be some of the major advantages of interferential therapy:

(1) endogenous stimulation,
(2) slight or no danger of burns from therapy,
(3) it can be used over areas with nonelectronic metallic implants,
(4) there is great depth of penetration,
(5) resistance of the skin is minimal between 3000 and 4000 Hz, thus higher intensities can be provided without patient discomfort, and
(6) hypesthesia is not a contraindication.

      CONTRAINDICATIONS AND SPECIAL PRECAUTIONS

The following special concerns and contraindications should always be taken into account prior to treatment with interferential current:

(1) metastatic carcinoma,
(2) implanted pacemaker,
(3) pregnant uterus,
(4) over carotid sinus,
(5) transcerebrally, and
(6) through the chest or over the heart.

Special care and consideration should likewise be given before interferential therapy is administered in the following cases:

(1) localized inflammatory processes;
(2) thrombosis, decreased vascularity, poor circulation, varicosities;
(3) tendency to hemorrhage;
(4) tuberculosis;
(5) over pelvic organs during menstruation; and
(6) hyperpyrexia.

Interferential vs High-Volt Therapy

Interferential current has its effect by an intersection (superimposition) that occurs within the tissues, the depth of which is determined by where the electrodes are applied. Although intersection may occur in muscles, tendons, and ligaments, its effect is not dramatic. High-volt therapy is preferred when a dramatic effect would be desirable. On the other hand, high-volt currents do not penetrate as deeply. Thus, interferential is preferred in the treatment of deep joints such as the shoulder, hip, knee, or spine.

The general rules to apply are:

(1) if it's a deep or large joint problem, interferential is the modality of choice;

(2) if it's a soft-tissue injury of muscles, tendons, ligaments, and/or other pariarticular tissues, then high-volt therapy is the preferred modality.

Inasmuch as human skin sensitivity varies within a wide normal range due to variations in skin thickness and pigmentation, a "minimal erythema dose" must be conducted on each patient prior to therapy to determine an "average" dose. Application is generally utilized in acne, psoriasis, indolent ulcers, and certain fungal disorders.


Physiologic Effects

The physiologic effects of ultraviolet light include local erythema, pigmentation, metabolic effects, bactericidal effects, and counterirritation effects.

      DEGREES OF ERYTHEMA

First Degree:   slight reddening appears in a few hours and disappears in 1-2 days.

Second Degree:   visible reddening followed by slight desquamation and pigmentation such as seen is common sunburn.

Third Degree:   intense redness, slight edema, marked desquamation and pigmentation. This degree is often called the counterirritant dose.

Fourth Degree:   increased third-degree signs with painful blistering. Often called the destructive or bactericidal dose.

      METABOLIC EFFECTS

Several metabolic effects are noted from ultraviolet rays. Skin sterols are activated to Vitamin D, thus aiding in calcium absorption and calcium-phosphorus metabolism (ie, an antirachitic effect). Ultraviolet improves skin tone, elasticity, and secretory functions, and increases both red blood cells and reticulocytes. It also raises the BMR and general physiologic activity of the body.

      BACTERICIDAL AND COUNTER-IRRITATION EFFECTS

Ultraviolet has a lethal effect on some bacteria, viruses, fungi, and other pathognomonic organisms if exposed to the proper spectrum. The counterirritation effects are produced by absorption of destroyed albumin of the irradiated area and the reflex stimulation of the irradiated zone.

Contraindications

Few contraindications are seen in sports such as seen in general practice in cases of diabetes mellitus, severe weakness, advanced cardiovascular or renal disease, hyperthyroidism, tuberculosis, hemorrhagic tendencies, suppurative dermatitis, and skin cancer.

      HYDROTHERAPY

Water is an excellent medium for therapy because of its high specific heat. This property allows for

(1) slow absorption of heat by the body through the process of conduction and

(2) slow cooling of the body or any of its exposed parts. Water is quite versatile to use because it permits full or partial immersion of a part or it can be specifically directed by spraying onto an isolated area of the skin.

The most common technique for hydrotherapy involves the use of the small whirlpool tank, which permits immersion within agitated water of one or more extremities or the patient may sit in the tub. Larger therapy units (eg, a Hubbard tank), incorporating larger whirlpools, can accommodate both a patient and a therapist. This latter type of therapy is beneficial when passive exercise is indicated during the treatment.

Several different types of hydrotherapy are in common use. Examples are whirlpools, sitz baths, hot and cold sprays and douches, and colonic irrigation. Some authorities include several other modalities of care under the general classification of hydrotherapy, including applications of ice; hot or cold moist packs, compresses, and dressings; and paraffin.


The Physiologic Basis

Water as a therapeutic agent allows for several remarkable possibilities. There are many reasons why water can be utilized successfully as a method of therapy for a patient in distress. The major properties that serve as the basis for intelligent application are water's buoyancy, the cohesion and viscosity factor, hydrostatic pressure, mechanical stimulation, conductivity, versatility, temperature, and the chemical effects involved. The application of heat or cold in any form to one area of the body has an effect on circulation in other areas.

Several factors determine the extent of the effects of water as a therapeutic agent that should be taken into consideration prior to the use of water as a modality:

(1) the degree of temperature change desired;
(2) the water temperature itself;
(3) the suddenness with which the water therapy is applied;
(4) the duration and pressure of application;
(5) the extent of body surface treated;
(6) the frequency of application; and
(7) the age, weight, and general condition of the patient.

Indications

The major physiologic effects of hydrotherapy and the corresponding indications for care may be summarized as follows:

(1) thermal or hypothermal effects;
(2) increase in circulation;
(3) increase in mobility, especially when exercise is performed underwater;
(4) relaxation;
(5) analgesia or sedation, especially during cold water therapy;
(6) debridement (eg, open wounds);
(7) promotion of tissue healing and repair; and
(8) relief of muscle spasm. Water also has variable cleansing, diaphoretic, and hypnotic effects.

Traction is the act of drawing or pulling a body part or parts by any means. It was crudely practiced therapeutically even prior to Hippocrates for the reduction of structural compression, alterations, and deformity. Skin traction is both a definitive treatment method as well as a first-aid measure. The traction force applied to the skin is transmitted to bone by way of underlying fascia and muscle.


Physiologic Effects of Moderate Continuous Traction

Traction encourages length, alignment, and functional stability. Mild structural compression results in ischemia and pain sited either locally and/or distally, resulting in muscle spasm producing functional contraction. The associated nerve irritation, which may be sensory or motor or both, may exhibit signs of pain, flaccidity, and diminished reflexes.

Continuous moderate traction tends to immobilize and "splint" strained musculoskeletal tissue, to relieve spasms by placing them in "physiologic rest," and to stimulate proprioceptive reflexes, thus relieveing associated pain and tenderness. It stretches fibrotic tissues and adhesions (anticontracture factor) and relives compression effects on articular tissues (eg, cartilage, discs) due to muscular spasm, gravity, or other compression forces (commonmly seen in chronic subluxations) to restore connective tissue resiliency and contour. Traction can reduce edema in an extremity if the traction unit elevates the affected part above the heart.

In the spine, traction reduces the circumference of the intervertebral disc, thus helping to restore its normal positioning (eg, suction, molding, axial pull) and relieves compression effects of formainal distortion and/or narrowing; ie, increases the intervertebral foramen's diameter. A byproduct of these effects is the dissipation of congestion, stasis, edema, and dural-sleeve adhesions in associated tissues.


Physiologic Effects of Intermittent Traction

Intermittent or alternating traction effects include increased vascular and lymphatic flow (suction aspiration effect) which tends to reduce stasis, edema, and coagulates in chronic congestions. It tends to stretch and free periarticular and articular adhesions and fibrotic infiltrations, and is an efficient supplement to manual adjustments. Traction stimulates proprioceptive reflexes and helps to tone muscles which tends to reduce fatigue and restore elasticity and resiliency. In the spine, it encourages the expansion and contraction of disc tissues, thus improving their nutrition.


Indications and Contraindications of Traction

Traction is indicated whenever the physiologic effects are desired and structure is in such a state as to withstand the stress. It has been found helpful in brachial neuritis, occipital neuralgia, osteoarthritis, scalenus anticus syndrome, spinal curvatures, vertebral disc thinning, spinal neuralgia, Steinbrocker's syndrome, and subacute torticollis, vertebral subluxation, and whiplash syndrome.

Traction is contraindicated in localized vascular disease, acute trauma syndromes, hemorrhagic states, and in healing fractures and dislocations. Few other contraindications are seen in sports as are seen in clinical practice in cases of bone disease, spinal cord afflictions, severe cardiovascular disease, pregnancy, and hypertensive disorders. In addition to these factors, intermittent or alternating traction is contraindicated in inflammtory joint conditions, severe muscle spasms, chronic musculoskeletal inflammations (eg, bursitis, tendinitis), and an acute intervertebral disc syndrome. Excessive traction will easily result in skin damage, thus careful monitoring must be done on proper padding, strapping, and angulation.

      STRETCHING

Therapeutic stretching may involve any manual or mechanical force that is designed to lengthen abnormally shortened soft tissues to produce an increase in joint range of motion. It may or may not involve pure traction forces. The tissues affected may be skin, fascia, ligaments, and/or muscles and tendons, and the cause of the exhibited tissue shortening may be

(1) trauma,
(2) any infection or degenerative pathology that results in fibrosis, adhesions, or contractures,
(3) a connective-tissue disorder, or
(4) restricted mobility of physiologic (eg, spasticity), postural, neuromyogenic (eg, scoliosis), or disuse (eg, immobilization) etiologies.

General Considerations

The physiologic effects of stretching therapy are similar to those of soft- tissue traction. Besides manual application, various devices are available for this purpose. See Figures 13.14 and 13.15.

Stretching therapy may be applied

(1) passively with or without mechanical advantage such as a pulley or lever apparatus,
(2) actively by the patient (with or without mechanical assistance), or
(3) actively assisted. The therapy is invariably indicated in such situations as profound weakness or paralysis.

Mechanical supports include such items as strapping, taping, braces, casts, corsets, canes, collars, crutches, slings, shoelifts, and certain bandages.


Physiologic Effects

Most mechanical supports are designed to relieve weight bearing or motion stress on bones and joints, and to immobilize structures in a sustained position to assist healing. A byproduct of these features is to relieve muscle spasm and pain. Shoelifts and some other supports allow for contracture and/or stretching of musculoskeletal tissues to encourage structural change. In acquired or congenital malformations, such supports help to relieve poorly compensated structural and functional inadequacies.


Indications and Contraindications

The use of supportive appliances is a matter of clinical judgment. When used wisely with a thorough knowledge of the biomechanics involved and corrective chiropractic care, recovery can be greatly enhanced. Mechanical support is usually indicated in situations of pain, weakness, deformity, function assistance, or paralysis of a part of the body.

Mechanical supports are contraindicated whenever immobilization tends to promote muscular atrophy and weakness or when immobilization tends to promote the organization of inflammatory coagulant and consequent adhesions and/or fibrotic infiltration, depending upon the nature and stage of the condition. Support is also contraindicated whenever immobilization may produce congestion, ischemia, or vascular stasis, or when immobilization or a fixed position may induce unsatisfactory stretching and/or contracture changes. These contraindications depend greatly upon the nature and stage of the condition.


Adhesive Strapping

Adhesive taping or strapping is used in athletics for both injury prevention and treatment to limit joint motion, to secure protective devices and padding, to support and stabilize a part, and to hold dressings secure. Tape should be stored on end, never on its side, in a cool dry location.

The rule of thumb is: the larger the part, the wider the tape; eg, 2or 3-inch tape is best for thighs or shoulders, and half-inch tape for fingers and toes. In athletics, heavy backed (85 longitudinal fibers per square inch) with a rubber-base adhesive is usually preferred for greater backing strength and superior adhesion as opposed to the acrylic adhesives and lighter backing used in surgery. Before tape is positioned, clean and dry the skin, treat cuts, shave hair, and apply a nonallergenic skin adherent.

Strips of adhesive tape are used, rather than one continuous winding, to avoid constriction. After one turn of the tape, the tape is torn. Further strips are overlapped 1 inch at the ends and at least a half inch above or below. Tape must be carefully smoothed and molded to fit the natural contour of the part as it is laid on the skin with equal tension.

Most irritation is seen in the mechanical irritation caused by tape removal, but the reddened area disappears quickly. Allergic reactions are rarely seen and are characterized by erythema, papules, vesicles, and edema. A patch test will indicate a positive reaction within 48 hours if a sensitivity exists. The irritative effects of inhibited sweating beneath tape may be relieved by using a porous nonocclusive-type tape.


Extremity Pressure Supports

Enhanced circulation in any musculoskeletal injury is almost always a benefit, and this is especially true if immobilization is required. The use of hot packs, ultrasound, massage, and sometimes whirlpools have been of some, but not excellent, benefit in this regard. There also has been a problem obtaining lightweight but strong supports that restrict motion in some ranges but still allow some type of activity (eg, locomotion). Some technical advances, as described below, appears to have solved some of these problems.

      THE AIRCAST/AIRSTIRRUP SYSTEM

Aircasts and Airstirrups have proved themselves excellent innovations in the treatment of extremity injuries and have overcome many of the disadvantages of conventional plaster casting or adhesive strapping. An Aircast consists of two plastic half shells that are connected by Velcro straps, and two or more self-inflated/self-sealing air bags are attached to the inner surface of the shells. See Figure 13.20. AirStirrups are similar U-shaped appliances for the lower extremity.

An athlete with a mildly sprained ankle, for example, can continue running almost immediately in many instances when the appliance has been applied. Such appliances also allow normal, gradual recuperative functions to take place, prevent recurrence of injury during rehabilitation, and eliminate motion pain while still allowing motion in nonpainful directions. They appear to efficiently bridge the gap between immovable plaster casts and inefficient flexible supports.

      HYDROPULSE AND PRESSION UNITS

To meet the need for immobilization and support without some venous and lymphatic circulatory deficit, new approaches have been introduced in recent years that pulsate warm water or air within specially designed cuffs. Two examples are the Hydropulse and Pression units. Such appliances, which optimally offer a unidirectional action towards the heart, are efficient in treating sprains, strains, spasticity, cramps, decreased circulation, local edema, and other types of pain or discomfort arising from a degree of anoxia and/or circulatory stasis.


Mobilization After Support

To minimize strength loss, improve nutrition of the part, and reduce atrophy, exercise of adjacent joints should be advised when support is provided as well as thereafter. Both progressive passive manipulation and active exercise are the keys to fast recovery. However, joint movement should not be made whenever it increases pain, muscle spasm, or involuntary splinting.

Postinjury edema soon becomes filled with fibroblasts (joint glue), and excessive collagen formation produces stiffness, especially when collateral ligaments are immobilized in a position shorter than that for the functional position. However, a normal joint can tolerate a long session of immobilization without ill effects, such as that seen in fracture healing. Degenerative changes, intra-articular adhesions, and periarticular stiffness are more of a concern in the elderly patient in short-term immobilization than the young athlete in longterm immobilization. It is not abnormal to have some swelling after removal of a lower-extremity support, but this may be minimized by elastic stockings and contrast baths followed by elevation.


      TREATMENT FREQUENCY

Athletes typically demand immediate relief of pain; however, this should be no excuse for overutilization. The specific modality used; the patient's age, sex, and physical condition; and the severity and duration of each complaint -- all should play a part in determining the number and frequency of treatments that will be required.

General Guidelines

The following general guidelines for musculoskeletal complaints were developed by Jaskoviak. They may be used in developing a treatment program for a patient. However, each practitioner must remain responsible for basing every therapeutic program on an individual patient's current physical condition.

      PHASES OF THERAPY

1. Acute stage.   Following an acute musculoskeletal injury, especially during the first 24–48 hours, it may be necessary to treat the patient once or several times each day until the pain subsides. In some patients with severe IVD injuries, multiple treatments or concentrated care combined with bed rest is often the regimen of choice.

2. Postacute healing stage.   Treatments for musculoskeletal complaints after the acute pain has subsided need not be spaced as close together as during the acute stage. Treatment is usually administered on a daily basis, then every other day, and eventually to about once per week. If pain persists after 10–15 visits, it is probably advisable to completely re-examine the patient and reevaluate the initial diagnosis, seek consultation, or refer the patient for further specialized evaluation before therapy is continued.

3. Strengthening stage.   As healing becomes more complete, treatment should be directed to developing strength and tone in the injured muscles, tendons, and ligaments. Therapy during this stage is frequently scheduled once (possibly twice) a week and is usually combined with a specific exercise program that is given to the patient (by demonstration/explanation and writing) to apply at home.

Pain reflects the body's alarm system. It is helpful, immobilizing, yet agonizing. When prolonged, it can lead to anxiety, depression, anorexia, dyspnea, fatigue, insomnia, and countless other adverse signs and symptoms.

Pain can be controlled through either drug or nondrug means. The use of opium as an analgesic was known to the Egyptians as early as the 16th century B.C. It was also known that repeated applications of chili pepper, oil of cloves, and ginger cause sensory nerves to become numb. But one of the most effective means to relieve acute pain without the use of drugs has been the use of counterirritation. The age-old practices of acupuncture, cupping, deep massage, heat, ice rubs, manipulation, moxa, plasters, and poultices are well known. In more recent times, articular adjustments, needle sprays, percussion, trigger-point therapy, deep heat, galvanism, TENS, ultrasound, and other forms of electrotherapy undoubtedly have a counterirritative effect.

While the exact mechanisms of how counterirritation relieves pain is not fully explained, its effects are readily demonstrable. Rubbing an injured area, for example, is almost an instinctive reaction. It has only been during the last 2 decades, however, that several theories have been advanced that have improved the professional management of painful syndromes.


Receptor-Pathway Mechanisms

Hirschy describes five types of sensory receptors: (1) mechanoreceptors, which detect mechanical deformation of the receptors or cells adjacent to the receptors; (2) chemoreceptors, which detect tastes, odors, arterial oxygen levels, osmolarity of body fluids, CO425 concentrations, and other factors that make up body chemistry; (3) thermoreceptors, which detect changes in temperature, with some receptors detecting cold and others warmth; (4) electromagnetic receptors, which detect light on the retina; and last but not least, the (5) nociceptors, which detect damage in the tissues, whether it be of a physical or chemical nature. These sensory receptors initiate impulses from their sites to the spinal cord via Type A, B, and C afferent fibers.

Pain signals are essentially transmitted centrally by Type A fibers at velocities between 3 and 10 meters/second and by Type C fibers at velocities between 0.5 and 2 meters/second. Guyton states that these latter fibers constitute over two-thirds of all fibers within the peripheral nervous system.

Upon entering the spinal cord at the dorsal roots, pain and temperature impulses enter the tract of Lissauer where they are transmitted up or down 1–3 segments and then terminate with second-order neurons in the gray matter of the posterior horns of the cord. From here, fibers pass through the anterior commisure to the opposite side of the cord where they form the lateral spinothalamic tract, whose impulses eventually terminates in the intralaminar nuclei of the thalamus, medulla, pons, and mescencephalon. Communication with the cerebral cortex is made via third-order neurons from the thalamus and intralaminar nuclei.

      SPECIFICITY THEORIES

Von Frey proposed the most famous specificity theory. It suggested that there are specific receptors or fibers that respond to different stimuli and transmit specific signals of pain, pressure, temperature, and position to higher centers in the brain. This theory, which serves as the anatomical basis of surgical intervention and "nerve blocks" to control intractable pain, has brought attention to the fact that there are extremely specific subcutaneous receptors and pathways.

      PATTERN THEORIES

Livingston's "summation" theory is the most famous pattern theory. It proposes that abnormal volleys of patterned nerve impulses are conveyed to the brain via the dorsal horns where the neurons undergo intense stimulation. Once these circuits are established, a chain of self-exciting neuronal circuits are believed to be produced to create a continuous self-generating mechanism that is unrelated to the initial trauma -- thus explaining the phantom limb pain of an amputated limb. Other pattern theories include those of (1) Noordenbos, whose "sensory interaction" theory proposed that the large afferent fibers had an inhibitory effect upon on central transmission, while the small afferents had an excitatory effect; and (2) Goldscheider, who suggested that stimulus intensity and central summation are the two critical determinants of pain. However, as Siegele points out, it has been Melzack and Wall's "Gate" theory that has encouraged the most practical applications in the field of pain management. Yet even this theory does not answer all the questions posed.

      THE GATE CONTROL THEORY OF PAIN

The original gate theory suggested a mutual presynaptic inhibition between receptors that register pain (nociceptors) and those that do not (eg, mechanoreceptors). See Figure 13.21. The nociceptor path is comprised principally of unmyelinated Type C and small Type A fibers, and the mechanoreceptor path represents the Type A fibers that mediate sensations of touch and pressure. Once these fibers have entered the dorsal gray horn of the spinal cord (probably within the substantia gelatinosa of Rolando), both the mechanoreceptor and nociceptor fibers send projections to second-order neurons. These second-order neurons synapse with what is called a trigger cell (T cell), which has access to the higher somesthetic centers involved in the perception of pain via the paleospinothalamic tract. A higher central decoding mechanism located somewhere in the brain is hypothesized, which subsequently monitors spinothalamic activity and exerts descending control on the system. Prior to communicating with the T cell, however, the mechanoreceptor and nociceptor fibers give off collateral axons that terminate with interneurons in the dorsal horn. Impulses of the mechnoreceptor collateral axons impose presynaptic inhibition, which produces primary afferent depolarization of the mechanoreceptor and nociceptor terminals ending on the T cell and, thus, inhibit the mechanoreceptor and nociceptors impulses reaching the T cell. In contrast to the mechanoreceptor collateral, the collateral circuit from the nociceptor has a second interneuron interposed in its pathway. This is an inhibitory interneuron that silences the presynaptic inhibitory interneuron whenever the nociceptor is stimulated. The effect of this is to remove the presynaptic inhibitory effect from the system. Thus, according to the gate theory, mechanoreceptor stimulation (eg, counterirritation) tends to "close" the gate, inhibiting mechanoreceptor and nociceptor input to the T cell; while nociceptor stimulation tends to "open" the gate, allowing both mechanoreceptor and nociceptor input to reach the T cell.

The original gate theory, however, did not support further findings. For example, several studies have shown that (1) nociceptor stimulation does not appear to open the gate and (2) the hypothetical T cell has never been found. Nevertheless, most authorities agree that there is presynaptic inhibition in both the mechanoreceptor and nociceptor pathways. In recent years, a revised concept has been proposed that is based on the fact that "like impulses presynaptically inhibit like impulses." For example, nociceptors presynaptically inhibit other tonic nociceptors, phasic mechanoreceptors presynaptically inhibit other phasic mechanoreceptors, and tonic mechanoreceptors presynaptically inhibit other tonic mechanoreceptors.

See Figure 13.22. The dotted lines joining the interneurons communicating with the mechanoreceptor and nociceptor collaterals represent some spillover from one receptor type to the other, but the dominant presynaptic effect is reflected back upon the input involved. Thus, there must be a functional spill- over of the presynaptic inhibitory effect from mechanoreceptor to nociceptor, or vice versa, to induce the gating phenomenon.

Neither the original nor the revised gate theory have been firmly established anatomically and physiologically. Other factors must be involved because even the revised gate theory does not adequately account for the various nonsegmental, psychologic, social, and cultural factors that influence an individual's pain threshold and/or perception. However, even if the gate phenomenon is not exact as described, many of its clinical predictions have proven useful empirically (eg, TENS). Fortunately, some answers have been found in studies involving the production of endogenous opiate-like substances.


Selective Neural Mechanisms

It has been known for several years that central stimulation can produce pain, but only within the last decade or so has it been found that the stimulation of specific intracranial sites is capable of inhibiting pain.

      ANALGESIA FROM CENTRAL STIMULATION

Mayer and Price have shown that intracranial stimulation-produced analgesia is an extremely specific antinociceptive effect, rather than a generalized sensory, motor, or psychologic deficit (ie, subjects will respond to mild temperature and light touch stimuli within the area of analgesia). At times, this stimulation-produced analgesia may last for many minutes or hours following stimulation, but the key to purposefully prolonging this effect has yet to be found. It appears that such stimulation does not result from a temporary disruption of pain afferents but exerts its effects caudally through active, selective inhibition of afferent volleys elsewhere in the nervous system such as in the spinal cord or the nucleus of the 5th cranial nerve.

The sites, mechanisms, and effects of intracranial stimulation-produced analgesia are closely parallel with those of morphine. These extremely specific sites are broadly and unevenly distributed throughout the brain. Optimal sites appear to be located in the periaqueductal gray matter of the midbrain.

      THE OPIATE RECEPTORS

Opiates such as morphine, which have extreme chemical specificity, appear to produce their effects by interacting with specific postsynaptic receptors. This fact suggests that if morphine can effect the CNS, there must be an anatomical receptor site or sites present to elicit its effects. As it is doubtful that the body would evolve receptors just for the extracts of poppy seeds, it was theorized that the nervous system must produce some substances that are similar or equivalent to morphine. Some of these substances have recently been isolated, and they are collectively called endorphins -- naturally occurring endogenous substances whose analgesic effect can be 200 times stronger than that of morphine.

It has been found that naloxone, a specific narcotic antagonist, blocks morphine analgesia, simulation analgesia, and acupuncture analgesia -- thus all three must involve an opiate-like receptor. Such receptors have been found in the marginal cell zone and substantia gelatinosa of the dorsal horn of the spinal cord, the trigeminal nucleus, various components of the vagal system, and the area postrema.

      THE ENDORPHINS

To date, many endogenous substances that possess opioid properties pharmacologically have been found. The first two endorphins to be isolated turned out to be pentapeptides, and they were called enkephalins. Endorphins and enkephalins are the body's own natural opiates, and they are produced in certain tissues (eg, pituitary gland) in response to pain, high stress, acupuncture, electrical stimulation, and other stimuli, either centrally or peripherally. Hundreds of types have been discovered, and each affects pain in a different region or regions of the body.

Stimulating the Production of Endorphins. Stimulations of the skin with a needle or an electric impulse triggers the brainstem to increase endorphin levels in the blood stream, cerebrospinal fluid, and the gastrointestinal tract. The levels build up within 30 seconds; however, clinical results are often not appreciated by the patient until 12–24 hours later. It should be carefully noted that the site of stimulation determines the type of endorphin that is released and the area of the body that it will affect. Thus, endorphins are site-specific in their effect. Since an active endorphin is a circulating hormone, the side of the body (when bilateral points exist) stimulated makes little or no difference (other than psychological). When electrotherapy is utilized, a small diameter electrode, no larger than a dime, should be used. Most research indicates that from 1 to 10 pulses per second (Hertz) for the frequency of stimulation is appropriate. However, recent evidence seems to indicate that the best results occur at 4–6 Hz.

Stimulating the Production of Enkephalins. Stimulating the production of en- kephalins clinically is primarily by means of electrical stimulation to the skin. Dampened sponge electrodes, 3 or 4 square inches in size, are commonly used. Firm skin contact is essential. Stiff electrodes that do not readily conform to the shape of the surface make poor conductors and greatly limit the depth of impulse penetration. Research appears to indicate that pulse rates of 70–130 Hz when using high-volt modalities and 90–100 Hz when using interferential units are most valuable. Some studies with interferential therapy tend to indicate that modulation of frequency is valuable because it limits accommoda- tion. Although almost all modalities produce some analgesic properties, low frequency spiked-wave therapies (eg, TENS) are preferred. Note that careful placement at the segmental level of involvement is essential. With patients in acute pain (eg, an IVD syndrome), it should be made certain that the intensity of the stimulation is just to the level where the patient barely perceives the current. In this manner, the physician is able to achieve effective sensory stimulation without aggravating the patient's complaint by producing muscle contractions.

      CLOSING REMARKS

Adjustive therapy, electrotherapy, cryotherapy, acupuncture, TENS, hypnosis, autosuggestion, biofeedback, certain drugs, and neurosurgery have all earned respectable places in the arsenal of pain control. As the understanding of pain pathways and mechanisms improve, researchers have great hopes of discovering even better methods of analgesia. The search is on for better methods of producing nonaddictive endogenous analgesics.