Ultrasound

Description of Intervention

Therapeutic ultrasound is a physical modality commonly used by Occupational Therapists and Physical Therapists to relieve pain and promote tissue healing. It involves the application of longitudinal sound waves generated by a transducer head to a target area. These sound waves penetrate soft tissues and causes vibrations that induce both thermal and nonthermal physical changes within the target tissues. Therefore, although ultrasound may be classified as either thermal (continuous mode) or nonthermal (pulsed mode), its therapeutic effects include a combination of both phenomena.^1,2 The physiological effects of thermal ultrasound include increased tissue temperature, increased local blood flow, increased tissue extensibility, and reduced viscosity of fluid elements in the tissue, while its primary nonthermal (mechanical) effect is the acceleration of tissue metabolism by promoting cellular permeability and ion transport.²

The intended use of ultrasound varies depending on parameters like frequency, duty cycle, wavelength, energy, power, and intensity, which determine how the sound waves are transmitted, attenuated, and reflected through the tissue. Reflected sound waves are typically used for diagnostic imaging, while attenuated and transmitted waves are typically used for therapeutic purposes. High-intensity ultrasound is primarily utilized for cancer and surgical applications, while low-intensity ultrasound (20–1,000 mW/cm²) produces relatively little heat over time and is intended for painful musculoskeletal conditions.³ The frequency of therapeutic ultrasound generally ranges from 0.5–3.0 MHz, with the higher end selected when treating superficial tissues and the lower end utilized when treating deeper tissues.^2,4

Indications for Intervention

Ultrasound is indicated for any soft-tissue musculoskeletal injury that leads to acute or chronic pain in the hand, wrist, or elbow. Patients recovering from surgery in these regions may also be candidates for ultrasound.

Diagnosis

1. Ask the patient to describe their medical history, including any recent injuries to the hand/fingers, wrist, or elbow, or any recent surgeries performed.
2. Ask if the patient has any comorbidities, including smoking, diabetes, or osteopenia.
3. Perform a physical examination of the area of interest. If range of motion (ROM) is impaired, measure the active and passive ROM of any involved joint(s) and compare these measurements to the contralateral side.
4. Ask the patient to rate their pain on the visual analogue scale (VAS) or a similar outcome measure.
5. Consider using the DASH (Disabilities of the Arm, Shoulder, and Hand) questionnaire to evaluate the patient’s subjective impairment of the upper extremity.
6. If the patient presents with pain anywhere in the upper extremity, consider utilizing TENS therapy.

Intervention Options^1,4,5

In most cases, therapeutic ultrasound should be integrated into a comprehensive, individualized treatment program designed by a physical therapist or hand therapist. Depending on the patient’s diagnosis, the program may also include strengthening exercises, stretching exercises, manual therapy, functional training, and/or other therapeutic modalities to alleviate symptoms and increase physical function.

Prior to initiating ultrasound, ask the patient to remove any clothing to expose the skin of the target area and inspect the skin for any infections, burns, or active wounds. If the skin is clear, apply a small amount of hypoallergenic gel or cream to the skin, which will help conduct the sound waves to the soft tissues. The subsequent treatment steps of therapeutic ultrasound are listed below:

• Set the ultrasound unit to the appropriate parameters, including frequency, power, wavelength, and intensity
  • Use a higher frequency (eg, 3.0 MHz) for superficial tissues and a lower frequency (eg, 0.5 or 1.0 MHz) for deeper tissues
  • Select an intensity that will produce the desired heating of soft tissues
    • For example, an intensity of 500 mW/cm² will lead to a heating rate increase of 0.04°C/min at 1 MHz and 0.3°C/min at 3 MHz, while an intensity of 1,500 mW/cm2 will lead to a heating rate increase of 0.3°C/min at 1 MHz and 0.9°C/min at 3 MHz
• Apply the transducer of the ultrasound unit to the skin in a slow, circular motion continuously for 5–10 minutes; in some cases, a longer duration may be needed
• After completing treatment, wipe the gel or cream off the target area

Therapeutic ultrasound may be used in a clinic several times per week, but usually only once per day. Be sure to regulate the patient’s comfort level during treatment and adjust the parameters if necessary.