Terminology and Subtypes

Physical modalities is a broad term referring to a variety of instruments, machines, and tools traditionally used in physical therapy for musculoskeletal conditions, including chronic low back pain (CLBP). Two important categories of modalities are electrotherapeutic and physical agents.^1,2 Electrotherapeutic modalities involve the use of electricity and include therapies such as transcutaneous electrical nerve stimulation (TENS), electrical muscle stimulation (EMS), and interferential current (IFC).³ The term superficial TENS is also used to differentiate it from TENS administered through a spinal cord stimulator. Electroacupuncture is the application of electrical stimulation, typically with high frequency TENS, through acupuncture needles.

Physical agents are modalities that involve thermal, acoustic (produced by sound waves), or radiant energy, and include interventions such as therapeutic ultrasound (US), superficial heat (hot packs), and cryotherapy (cold packs or ice).³ US refers to acoustic energy above 20,000 hertz (Hz), and is used for both diagnostic and therapeutic purposes. Therapeutic US uses more energy than diagnostic US, which is also referred to as sonography.⁴ Phonophoresis is the use of therapeutic US to facilitate the absorption of topical products such as analgesic or anti-inflammatory creams.⁵ The term physical modality should be distinguished from physical therapy, which refers to an allied health profession rather than any specific treatment administered by this profession. This distinction is akin to that between medication and medicine. The term passive modalities is also sometimes used to describe physical modalities in which no active participation is required by the patient, and to distinguish these interventions from active rehabilitation such as supervised exercise therapy, which is also used by physical therapists.

Within electrotherapeutic modalities, common interventions include TENS, EMS, and IFC. TENS delivers an electrical current through superficial electrodes placed on the skin around the area of symptoms and causes a tingling sensation by stimulating sensory nerve fibers. EMS also delivers an electrical current through superficial electrodes placed on the skin, but uses a different type of electrical current than TENS to target motor nerve fibers. IFC is also administered through superficial electrodes and uses a much higher frequency than TENS, which is thought to allow for deeper penetration of the electrical current and is thought to cause less discomfort. There are several types of TENS, EMS, and IFC devices available, including larger units intended for use in clinical settings and smaller, battery-operated units that may be portable and worn under clothing for prolonged use throughout the day (Figure 14-1).

Figure 14-1 Typical stationary (A) and portable TENS machines (B).

(Courtesy of Dewey Neild. In Pagliarulo MA. Introduction to physical therapy, ed 3. St. Louis, Mosby, 2006.)

Common physical agents include US, superficial heat, and cryotherapy. US produces sound waves that are transmitted to the affected area through a hand-held, wand-shaped probe using conductive gel. Settings on the US machine may deliver pulsed or continuous waves. Hot packs are typically reusable, moldable bags of gel that are heated and wrapped in moist towels before being placed on the affected area to provide heat (Figure 14-2). Cold packs are typically reusable, moldable bags of gel that are frozen and wrapped in moist towels before being placed on the affected area to provide cold (Figure 14-3). Both hot and cold packs are available as disposable types that create a temporary heating or cooling effect through a chemical reaction initiated by crushing the packs by hand, or as reusable types that need to be placed in the microwave or freezer according to manufacturer recommendations (Figure 14-4). Other types of physical modalities used in the treatment of CLBP and not discussed in this chapter include various types of laser therapy, electromyography/biofeedback, electromagnetic fields, diathermy, and vapocoolant spray.

Figure 14-2 Typical moldable and reusable hot pack.

(From Salvo S: Massage therapy: principles & practice, ed 3. St. Louis, 2008, Saunders.)

Figure 14-3 Typical moldable and reusable cold pack.

(From Salvo S: Massage therapy: principles & practice, ed 3. St. Louis, 2008, Saunders.)

Figure 14-4 Typical disposable adhesive hot pack.

(© istockphoto.com/Marlin Allinger)

History and Frequency of Use

Electrotherapeutic modalities and physical agents have long been used in the management of musculoskeletal disorders, including CLBP, mostly by physical therapists.^1,2 Heat and cold have likely been used to relieve various types of pain symptoms for millennia. One of the earliest references to using electricity for medical purposes came from the scribe, Largus, who in Rome in 46 AD recommended placing live torpedo fish on painful areas to alleviate symptoms.⁶ The use of electrotherapeutic modalities grew following World War I, when injured veterans were treated for musculoskeletal injuries with therapeutic exercise, manual therapy, and electrical stimulation. IFC was developed in the 1930s, allowing for a more comfortable application of electrical stimulation than its precursors.⁶ The first TENS device was approved for use in pain management by the United States Food and Drug Administration (FDA) in the 1970s, and portable units were introduced shortly thereafter.⁷ Clinical research comparing various types of electrotherapeutic modalities began to appear in the 1970s. Although modern electrotherapeutic modalities incorporate more sophisticated displays and an increasing number of programmable settings, their internal components are mostly unchanged in recent decades.

Physical modalities, including heat, US, and EMS, are often administered in conjunction with spinal manipulation by chiropractors for the management of low back pain (LBP) where permitted by scope of practice.^8,9

A prospective study of health care utilization among 1342 patients with LBP who presented to general practitioners in Germany reported that 34% used local heat, 17% used electrotherapy, and 9% used TENS in the subsequent 1 year follow-up.¹⁰ Local heat was the most commonly reported service, electrotherapy was the fourth most common, and TENS was the seventh most common.

Practitioner, Setting, and Availability

Electrotherapeutic modalities and physical agents are typically administered by physical therapists working in various practice settings nationwide, including private practice, rehabilitation centers, specialty spine or sports medicine clinics, and hospitals. Other health professionals involved in the management of CLBP, such as physicians, occupational therapists, chiropractors, and athletic trainers, may also use these types of physical modalities. Additionally, some of these physical modalities can be purchased, borrowed, or rented by patients for use at home following some instruction from the clinician. Portable TENS units, superficial heat, and ice are commonly used in home settings. These interventions are widely available throughout the United States.

Procedure

There are numerous specific treatment protocols for each of the common electrotherapeutic modalities and physical agents, some of which are developed by therapists through anecdotal evidence. For electrotherapeutic modalities such as TENS, EMS, and IFC, the intervention often begins with the provider exposing the patient’s skin in the lumbosacral area and wiping it clean with an alcohol-based solution. Superficial skin electrodes are then placed over areas of pain (TENS, IFC) or on adjacent targeted muscle groups (EMS). To prevent accidental shocks or excessive currents, electrodes are usually placed on the skin while the machines are turned off and then connected to the device. Once the electrodes are in place, the provider will then gradually increase the intensity of the electrical current until a particular goal is achieved. For TENS and IFC, this goal will be a mild to moderate (but not unpleasant) tingling sensation. For EMS, the goal will be the attainment of a mild to moderate muscle contraction that is visible to the provider. The devices are then programmed by the provider to deliver current at constant or varying intensities over a period of 15 to 30 minutes, during which the provider will periodically inquire about the patient’s comfort and may increase current intensity to maintain a steady stimulus.

With US, the intervention begins by exposing and cleaning the skin in the lumbosacral area. Conductive gel is then applied to the hand-held US probe and spread over the treatment area. This gel is required to conduct US waves from the probe to the skin since acoustic energy will not travel to the intended target through air. The US device is then activated and a specific intensity of acoustic power (measured in watts/cm²), frequency (MHz), and cycle (pulsed or continuous) are selected based on target tissue thickness (lower frequency for deeper tissues) and treatment objective (pulsed for nonthermal effects, continuous for thermal effects). The provider then slowly moves the US probe in circular motions over the target area during a specific treatment time, usually 6 to 10 minutes. Unlike TENS, EMS, and IFC, patients may not directly perceive anything at all while the US is being applied using the pulsed setting; a slight warming sensation may be felt by some with the continuous setting. Hot or cold therapy involves the provider applying one or more layers of towels to the targeted area before applying the hot or cold pack. Packs are usually applied either for a specific period of time (e.g., 10-15 minutes) or until a desired effect is achieved (e.g., area feels numb to the touch after applying ice or feels less stiff to move after applying heat).

Regulatory Status

Electrotherapeutic and US equipment is generally regulated by the FDA as class II medical devices. Obtaining this approval mainly requires that the manufacturer submit evidence that the new device is substantially equivalent to a currently approved similar device.

Mechanism of Action

Each of these interventions has a general mechanism of action that is summarized in the following paragraphs; it is currently unknown whether these hypotheses also apply specifically to the use of physical modalities for CLBP.

Electrotherapeutic Modalities

TENS may use low or high frequencies. At lower frequencies (5-10 Hz), TENS is thought to produce muscle contractions and provide pain reduction for several hours. At higher frequencies (80-100 Hz), TENS is thought to temporarily reduce pain by acting as a counterirritant stimulus.¹¹ IFC is also thought to temporarily reduce pain by acting as a counterirritant stimulus. EMS provokes muscle contractions in the applied region, which is thought to act as a counterirritant stimulus, reduce muscle spasm, and increase muscle strength and endurance. A counterirritant stimulus is thought to provide pain relief through the gate control theory of pain (Figure 14-5). This theory proposes that input from sensory fibers other than pain (e.g., electrical stimulus) can override input from adjacent nociceptive fibers, thereby inhibiting perception of pain at the spinal cord level. EMS also delivers an electrical current through superficial electrodes placed on the skin, causing one or more adjacent muscles to contract, which is thought to promote blood supply and help strengthen the affected muscle.

Figure 14-5 Gate control theory of pain.

(Modified from Fritz S: Mosby’s fundamentals of therapeutic massage, ed. 4. St. Louis, 2009, Mosby.)

Indication

Electrotherapeutic modalities and physical agents are generally used for one of the following two main objectives: (1) to reduce pain, swelling, or tissue restriction; and (2) to increase strength, muscle activity, coordination, or rate of healing.³ These interventions are therefore indicated for nonspecific, mechanical CLBP.

Assessment

Before receiving electrotherapeutic modalities or physical agents, patients should first be assessed for LBP using an evidence-based and goal-oriented approach focused on the patient history and neurologic examination, as discussed in Chapter 3. Additional diagnostic imaging or specific diagnostic testing is generally not required before initiating these interventions for CLBP. The clinician should also inquire about general health to identify potential contraindications to this intervention.

Clinical Practice Guidelines

Systematic Reviews

Electrotherapeutic Modalities

Transcutaneous Electrical Nerve Stimulation

Cochrane Collaboration

An SR was conducted in 2007 by the Cochrane Collaboration on TENS versus placebo for CLBP.¹⁷ A total of four RCTs examining CLBP were identified; two allowed participants with prior back surgery to be included and one allowed patients with LBP with neurologic involvement to be included.^18–21 For pain relief, three RCTs observed statistically significant decreases among those receiving TENS after 2 and 4 weeks of follow-up but only one RCT found clinically meaningful differences.^18,19,21 None of the RCTs observed differences between TENS and placebo on the different types of functional outcomes, except for one RCT that found improved function on the Oswestry Disability Index for TENS but the difference was deemed clinically unimportant.^20,21 Regarding general health status, one RCT observed no statistically significant differences between TENS and placebo, while another RCT found statistically significant benefits for four of eight subsections of the short-form 36 (SF-36) for conventional TENS and the same relationship was observed for two of eight subsections of the SF-36 for acupuncture-like TENS.^19,21 This Cochrane review concluded that there was insufficient evidence supporting the routine use of TENS for CLBP.¹⁷ This SR also concluded that further research on TENS for LBP is warranted and that future RCTs should report baseline information, means and standard deviations for each treatment group, adverse events, and should also monitor use of analgesic medication, and examine long-term follow-up.

American Pain Society and American College of Physicians

An SR was conducted in 2006 by the American Pain Society and American College of Physicians CPG committee on nonpharmacologic therapies for acute and chronic LBP.²² That review identified one SR related to TENS for CLBP, which was the Cochrane Collaboration review mentioned above.¹⁷ Five SRs that compared other interventions to TENS were also included.^23–28

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

Management of Acute Low Back Pain Nucleoplasty Functional Restoration Trigger Point Injections Medicine-Assisted Manipulation Therapy Assessment of Low Back Pain

Stay updated, free articles. Join our Telegram channel

Join