Therapeutic ultrasound is a physical modality in which nonionizing radiation, in the form of sound, is transferred to the body's tissues and absorbed as heat. It is applied at frequencies of 1.0 MHz and 3.0 MHz and is the most commonly used deep-heating modality, capable of reaching depths of five centimeters and more below body surface. Ultrasound, like short-wave diathermy, may be applied in the continuous format or in pulsed waves to apply therapeutic heat and nonthermal effects.
One intended use of ultrasound is to achieve the benefits of deep heating. As with other methods of therapeutic heat, the use of ultrasound in this capacity is thought to increase collagen extensibility, circulation, pain threshold, enzymatic activity, cell membrane permeability, and nerve conduction velocity. Conversely, use of ultrasound in the pulsed mode has been proposed to have the nonthermal effects of acoustic streaming, cavitation, and micromassage caused by the mechanical vibration of the sound waves. Nonthermal benefits are reported to increase cellular activity and protein synthesis and to decrease edema. Until recently, ultrasound was applied clinically in hopes of gaining the above benefits, based on a limited theoretical basis. However, in a recent review published by Baker et al. in Physical Therapy, the authors concluded that there is currently "insufficient biophysical evidence to provide a scientific foundation for the clinical use of therapeutic ultrasound for the treatment of people with pain and soft tissue injury."
In hemophilia, the use of therapeutic heat to deep structures is contraindicated because the increased blood flow from induced vasodilitation would increase the tendency to bleed. In addition, because a hemorrhage is a high-fluid area, the undesirable effect of cavitation (the vibrational effect of ultrasound on gas bubbles present in blood or tissue fluids) can occur at clinical settings of 1-2 w/cm2, causing tissue damage. Although the intensity and duty cycle of ultrasound may be set at high versus low settings, Baker et al. also note that the biophysical effects of pulsed versus continuous ultrasound cannot be viewed as separate occurrences and that some heating does occur even using a pulsed mode.
In addition to the lack of proven biophysical benefits, there is also little evidence to support clinical effectiveness of ultrasound, as shown by Robertson and Baker in Physical Therapy. They reviewed thirty-five randomized controlled trials using ultrasound, spanning the years 1975 to 1999, to treat pain, musculoskeletal injuries and soft tissue lesions. Their review showed that there is little evidence that ultrasound is clinically effective for those problems.
In light of the poor theoretical foundation and lack of proven clinical effectiveness of ultrasound, along with the potential danger of deep heat and cavitation effects, MASAC does not recommend its use in the hemophilia population for the resorption of blood. MASAC will review emerging data as they become available and will modify this recommendation if new data warrant a change.
Baker KG, Robertson VJ, Duck FA. A review of therapeutic ultrasound: biophysical effects. Physical Therapy 2001; 81:1351-1358.
Lehmann JF. Therapeutic heat and cold. Baltimore, MD: Williams and Wilkins; 1990, pp. 504-561.
Lehmann JF, DeLateur BJ. Diathermy and superficial heat and cold therapy. In: Kottke FJ, Stillwell GK, Lehmann JF, editors. Krusen's handbook of physical medicine and rehabilitation. Philadelphia, PA: WB Saunders; 1982, pp. 304-322.
Robertson VJ, Baker KG. A review of therapeutic ultrasound: effectiveness studies. Physical Therapy 2001; 81:1339-1350.
Ziskin M, McDiarmid T, Michlovitz S. Therapeutic ultrasound. In: Michlovitz SL, editor. Thermal agents in rehabilitation. Philadelphia, PA: F.A. Davis; 1990, pp. 134-169.
This material is provided for your general information only. NHF does not give medical advice or engage in the practice of medicine. NHF under no circumstances recommends particular treatment for specific individuals and in all cases recommends that you consult your physician or local treatment center before pursuing any course of treatment.