Therapeutic ultrasound
Therapeutic ultrasound refers generally to any type of ultrasonic procedure that uses ultrasound for therapeutic benefit. Physiotherapeutic ultrasound was introduced into clinical practice in the 1950s, with lithotripsy introduced in the 1980s. Others are at various stages in transitioning from research to clinical use: HIFU, targeted ultrasound drug delivery, trans-dermal ultrasound drug delivery, ultrasound hemostasis, cancer therapy, and ultrasound assisted thrombolysis[1][2] It may use focused ultrasound or unfocused ultrasound.
In the above applications, the ultrasound passes through human tissue where it is the main source of the observed biological effect (the oscillation of abrasive dental tools at ultrasonic frequencies therefore do not belong to this class). The ultrasound within tissue consists of very high frequency sound waves, between 800,000 Hz and 20,000,000 Hz, which cannot be heard by humans.
There is some evidence that ultrasound is more effective than placebo treatment for treating patients with arthritis pain,[3] a range of musculoskeletal injuries[4] and for promoting tissue healing.[5]
Relatively high power ultrasound can break up stony deposits or tissue, accelerate the effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, and can be used to sort cells or small particles for research.
There are three potential effects of ultrasound. The first is the increase in blood flow in the treated area. The second is the decrease in pain from the reduction of swelling and edema. The third is the gentle massage of muscle tendons and/ or ligaments in the treated area because no strain is added and any scar tissue is softened. These three benefits are achieved by two main effects of therapeutic ultrasound. The two types of effects are: thermal and non thermal effects. Thermal effects are due to the absorption of the sound waves. Non thermal effects are from cavitation, microstreaming and acoustic streaming.[1]
Cavitational effects result from the vibration of the tissue causing microscopic bubbles to form, which transmit the vibrations in a way that directly stimulates cell membranes. This physical stimulation appears to enhance the cell-repair effects of the inflammatory response.
History[edit]
The first large scale application of ultrasound was around World War II. Sonar systems were being built and used to navigate submarines. It was realized that the high intensity ultrasound waves that they were using were heating and killing fish.[8] This led to research in tissue heating and healing effects. Since the 1940s, ultrasound has been used by physical and occupational therapists for therapeutic effects.
Knee Oseteoarthritis[edit]
According to recent research, therapeutic ultrasound has not shown any significant improvement for chronic low back pain, chronic neck pain, and hip pain in combination with other physiotherapeutic techniques.[16][17] However, the most conclusive evidence to support therapeutic ultrasound use is seen with its use in patients with knee osteoarthritis. Knee osteoarthritis affects approximately 250 million people worldwide.[18] While there is no known cure, therapeutic regimens are often used to intervene with the diseases chronic symptoms.[18] In a systematic review of 15 studies, patients who received ultrasound treatments were compared to those who received a placebo treatment. The evidence demonstrated that therapeutic ultrasound significantly relieved pain, increases range of motion, and reduced WOMAC functional scores in patients with knee osteoarthritis when compared to the placebo group.[3] In a separate meta-analysis, it reinforced the use of therapeutic ultrasound by deeming it as a safe non-pharmalogical treatment option that may provide additional pain relief as well as functional improvement when used secondarily to therapy in patients with knee osteoarthritis.[18]