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October 2004


Ultrasound: Underused?

By Kathy Henderson, PT, CS, RAA; Mandy Burnett, PTA; and Beth Reigart, MPH, OTR/L, CHT

Your patient's shoulder has been throbbing for weeks and providing severely limited range of motion. Ice, hot packs, heat lamps, and soft tissue massage have all been tried without gaining much relief or healing. Could ultrasound be the treatment that gets her arm and shoulder back into action?

Therapeutic ultrasound has been used in the treatment of musculoskeletal injuries and conditions for years, primarily because it effectively promotes healing in the injured tissue and helps reduce pain. Its ability to penetrate deeper than other heat-based modalities facilitates a beneficial effect on deep muscle tissue. Unique capabilities that allow either thermal or nonthermal applications make it a valuable option as a therapeutic treatment for a wide range of acute and chronic conditions, such as tendonitis, muscle spasms, bursitis, fasciitis, edema, sprains, contractures, and adhesions. However, in spite of the beneficial healing effects, pain reduction, and the versatility of the process, ultrasound therapy continues to be underutilized by many rehabilitation professionals.

Underutilization tends to result from several factors. One is that therapists may not have enough information on the benefits of working with ultrasound, so there is less motivation to employ it. Second is the one-on-one nature of this modality versus other types of treatment that are also effective and require less hands-on work. Last, the technique for application is very specific and needs to be performed properly with carefully calibrated equipment to achieve optimum results. Often, the reluctance is due to disappointing outcomes experienced in past attempts, which, in fact, may have been the result of insufficient knowledge or training. With education and a better understanding of the process, these factors can be alleviated as rehabilitation professionals gain greater confidence in the capabilities of ultrasound and a better grasp of the proper techniques for achieving success.

CLINICAL FUNDAMENTALS
Ultrasound delivers sound waves to tissue at a frequency above the range of human hearing, providing a "micro-massage" via mechanical vibrations. Clinical ultrasound is delivered as either a thermal (continuous) or nonthermal (pulsed) application, generally at frequencies of 0.75 MHz to 3 MHz. A topical medium, such as water, gel, cream, lotion, or mineral oil, must be applied to the skin surface before treatment. Determination of frequency, duration, and whether to use pulsed or continuous application depends on the equipment being used, as well as the type of injury (eg, adhesion, muscle spasm, tendonitis, contracture, edema, etc).

To ensure correct application and the desired outcome, it is important for rehabilitation therapists to understand how ultrasound works. Combining knowledge of the physical agent, the pathology of the injury, and the correct technique for delivering it significantly increases the potential for success.

Ultrasound works by delivering acoustic vibrations via a transducer that utilizes a quartz crystal to convert electrical energy to ultrasonic waves, which can then be applied to human tissues for therapeutic purposes. Absorption of this energy takes place at the molecular level with the protein in the tissue acting as the absorbing agent. Muscle, fat, and hemoglobin all absorb ultrasound. Since numerous factors affect absorption and the benefits received, an understanding of the physiology, the delivery process, and any contraindications are key for ensuring that patients' results are maximized.

The basic benefits provided through this treatment include:
  • Increased elasticity of collagen in tendons, joint capsules, and scar tissue.
  • Increased motor and sensory nerve conduction velocities, which assists in reducing pain.
  • Altered contractile activity to skeletal muscle, which reduces muscle spasm.
  • Diminished muscle spindle activity, another factor in muscle spasm reduction.
  • Increased blood flow.
These factors make ultrasound the modality of choice for conditions involving muscle spasm, pain, scar tissue, and acute and chronic soft tissue inflammation. It can be delivered over smooth, even surfaces such as the lower back, as well as uneven joint surfaces such as the ankle and wrist. For example, for an elderly patient whose muscles are tightening up due to aging or for the shoulder injury discussed earlier, ultrasound's unique characteristics allow the tissue to be stretched more easily and with less trauma, resulting in better gains. Another example would be a case of edema, in which it can be challenging to initiate movement, but the ultrasound's mechanical process helps increase the mobility of the fluid, thus reducing the chances of increasing trauma or injuries to that area.

While there are numerous therapy options (eg, electromagnetic radiation, electrical stimulation, hot packs, cryotherapy, massage, and exercise) that can be considered for treatment of musculoskeletal injuries, ultimately the choice depends on an analysis of factors such as the type and location of injury, as well as the condition of the patient and any underlying issues. Once again, the key to determining the most effective method to use is in knowing as much as possible about the treatment options and the injury.

While all modalities have some overlapping qualities, it is important to know the distinctive qualities and contraindications of each option to determine the most appropriate choice. For instance, hot packs provide heat, but do not penetrate as deep as ultrasound. With electromagnetic radiation, the depth of penetration is slightly less compared to ultrasound, in addition to a loss of energy through the surface of the skin during sweating. Ultrasound, which is very deep, produces heat proportional to the heat absorbed in the tissues so there is no loss of energy from the skin, thus having maximal benefit of the diathermy modality.

The only real limitation for ultrasound is in the size of the area that can be treated, which is determined by the size of the transducer head, ie, an acute muscle spasm over a large part of the lower back would be difficult to treat and would tend to make electromagnetic radiation the better choice of diathermy for such cases. The treatment selected also depends on whether the injury being dealt with is acute or chronic. While ultrasound can work effectively for either one because of its thermal and nonthermal qualities, some of the other options do not possess that capability.

TECHNIQUES FOR OPTIMAL RESULTS
To ensure the best possible outcome, ultrasound is typically prescribed in combination with other modalities. For example, in acute injuries (eg, back or neck injury, or knee or ankle sprain), the therapist may use ice, compression, and gentle exercise, etc, depending on the severity and location of the injury and the specific symptoms. For chronic injury, treatment might include aggressive stretching and manual therapies in addition to ultrasound, which is useful for allowing muscle spasms to relax, reducing edema, and mobilizing adhered tissues. A combination of ultrasound and electrical stimulation is very effective in treating muscle spasms, controlling pain, and increasing range of motion.

Various pharmaceuticals, such as hydrocortisone creams, vitamin E, or a local anesthetic, also can be delivered to an injury site more effectively via ultrasound as it increases cell membrane permeability through the positive and negative forces, allowing the entire molecule to penetrate into the tissue.

To achieve desired outcomes, it is necessary to pay close attention to these aspects of the procedure:
  • Position patient so that the treatment area is easy to reach, and if needed, with enough room for a slight stretch of the target area.
  • Set machine to appropriate settings for intensity, duration, and pulsed or continuous application, based on injury type and location, patient condition, etc.
  • Explain procedure to patient and that he or she should not feel anything more than a slight vibration or warmth. Ask for feedback if it becomes hot or uncomfortable.
  • Keep the application area small.
  • Ensure that the skin surface is smooth and free of hair, oil, or lotions that might inhibit the sound waves.
  • Spread the topical ultrasound medium smoothly and evenly on the site. Ultrasound gel, which is highly aqueous, is generally considered the preferred medium.
  • Use a slow, sweeping, circular motion, slightly overlapping by half as the area is covered. Keep the ultrasound head in contact with and perpendicular to the skin and moving at all times.
When combining ultrasound with certain other forms of treatment such as stretching, it is important to provide the stretching component of the therapy immediately after to take advantage of the increased elasticity and reduced pain achieved in the therapy session.

One example of how proper application can produce desired results would be a typical frozen shoulder, a condition in which external rotation of the shoulder is difficult to achieve. We have had several patients insist that in their experience, ultrasound did not help their condition, yet we have achieved the desired outcome through careful positioning, proper technique, and application of the correct intensity and duration for the specific injury. Typically, the therapy includes providing a gentle stretch during the ultrasound procedure, and afterwards combining other effective therapeutic intervention, such as joint mobilization or specific deep tissue massage and myofascial work, with significantly positive results.

For larger areas, larger heads are available, or the treatment area can be divided into zones. For instance, the therapist can treat small areas of the distal section of a hamstring first, followed by more proximal sections of the thigh, etc, in 5-minute increments until all zones have been treated.

Some therapists find that underwater application can be effective for treating small bony areas such as ankles and wrists, although the technique does demand careful attention to maintain the perpendicular angle of the transducer head and a consistent one-inch distance from the injury site.

CONTRAINDICATIONS AND PRECAUTIONS
Certain medical conditions preclude the use of ultrasound therapy, including pregnancy, malignancy, circulatory insufficiency (eg, DVT or occlusive vascular disease), myositis ossificans, acute infection, or severe sepsis infection. In addition, the treatment site must be considered contraindicated if it would require application over the eyes, heart, spinal column, growing bones, testes, epiphyseal plates, carotid sinuses, cervical stellate ganglion, vagus nerve, or a demand pacemaker.

Other important precautions include:
  • Diminished or absent sensation to pain and temperature
  • Hypersensitivity to ultrasound
  • An area of tendon repair
  • An area of cemented prosthesis
  • Areas of reduced circulation such as a recent scar
In order to make the best clinical decision and achieve the maximum potential results from the treatment, it is critical to weigh the known physiological benefits along with any indications, contraindications, and precautions.

CONCLUSIONS
Essentially, the key to increased utilization of ultrasound-and the opportunity for more patients to take advantage of its many benefits-lies in rehabilitation professionals updating their knowledge and training. Having an understanding of the procedure, its benefits, effects, proper application, and potential outcomes provides a foundation for more effective application of the process. That is important in the health care industry now, because the number of therapy visits a patient is allowed is usually limited by insurance coverage. When determining a therapy plan, it is vital to know as much as possible at the outset about the patient's general condition, the injury to be treated, treatment goals, as well as any potential modalities that can offer an appropriate solution. Ultrasound may not be the answer for every patient; however, it does offer unique benefits that should be taken into consideration.

For RehabWorks, Kathy Henderson, PT, CS, RAA, is lead clinical specialist, Southeast Division in Birmingham, Ala; Mandy Burnett, PTA, is director of operations for the North Dallas Area; and Beth Reigart, MPH, OTR/L, CHT, is director of operations in Mount Pleasant, SC.

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