Ultrasound therapy
Mechanical vibration at increasing frequencies is known as Sound Energy. The normal human sound range is from 16 Hz to 15-20,000 Hz. Mechanical vibrations beyond this upper limit is known as Ultrasound. The frequencies used in therapy are typically between 1.0 and 3.0 MHz.
Sound waves are longitudinal waves consisting of areas of compression and rarefaction. Particles of a material, when exposed to a sound wave will oscillate about a fixed point rather than move with the wave itself. As the energy within the sound wave is passed to the material, it will cause oscillation of the particles of that material.
Ultrasound therapy involves the application of Ultrasound waves above that of the range of human hearing in order to treat various types of injuries.
Benefits of therapeutic Ultrasound
Heating and relaxing of the muscles in order to alleviate the pain.
Increasing the blood to enhance the healing process.
Softening of any existing scar tissue.
A low-intensity Pulsed Ultrasound (LIPUS) is used for fracture repair.
Management of the Knee Osteoarthritis
How is Ultrasound transmitted through tissues?
All materials (tissues) will present an impedance to the passage of sound waves. The specific impedance of a tissue will be determined by its density and elasticity.
In order for the maximal transmission of energy from one medium to another, the impedance of the two media needs to be as similar as possible.
The greater the difference in impedance at a boundary, the greater the reflection that will occur, and therefore, the smaller the amount of energy will be transferred.
To minimize this difference, a suitable coupling medium has to be utilized.
The coupling medium should be fluid so as to fill all available spaces.
Even a small air gap between the transducer and the skin causes the proportion of US to be reflected, which means that there will be no effective transmission.
The coupling media used in this context include water, various oils, creams and gels. At the present time the gel based media appear to be preferable to the oils and creams.
Water is a good media and can be used as an alternative but clearly it fails to meet the above criteria in terms of its viscosity. There is no realistic (clinical) difference between the gels in common clinical use
Absorption and attenuation
In order for energy to have an effect it must be absorbed. More energy is absorbed in the superficial tissues than in the deep tissues.
As the US beam penetrates further into the tissues, a greater proportion of the energy will have been absorbed and therefore there is less energy available to achieve therapeutic effects. This shows the importance of half value depth.
Half Value Depth represents the depth in the tissues at which half the surface energy is available. These will be different for each tissue and also for different US frequencies.
As the penetration or transmission of US is not the same in each tissue type, it is clear that some tissues are capable of greater absorption of US than others.
Generally, tissues with high water content and low protein content absorb little of the US energy (e.g. blood and fat) whilst those with a lower water content and a higher protein content will absorb US far more efficiently.
Tissues can be ranked according to their relative tissue absorption and this is critical in terms of clinical decision making.
The best absorbing tissues in terms of clinical practice are those with high collagen content – LIGAMENT, TENDON, FASCIA, JOINT CAPSULE, SCAR TISSUE
The Therapeutic effects of US
THERMAL | NON THERMAL |
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The mechanical US therapy is attributed primarily to a combination of CAVITATION and ACOUSTIC STREAMING.
CAVITATION | ACOUSTIC STREAMING |
formation of gas filled voids within the tissues & body fluids | small scale eddying of fluids near a vibrating structure such as cell membranes and the surface of stable cavitation gas bubble. This phenomenon is known to affect diffusion rates & membrane permeability. |
The result of the combined effects of stable cavitation and acoustic streaming is that the cell membrane becomes ‘excited’ and increases the activity levels of the whole cell.
Therapeutic effects of US
US and Tissue healing- US accelerates the rate of healing and enhances the quality of repair.
US and Tissue repair.
US during Inflammatory phase
During the inflammatory phase, US has a stimulating effect on the mast cells, platelets, white cells with phagocytic roles and the macrophages.
??? By increasing the activity of these cells, isn’t the overall influence of therapeutic US pro-inflammatory rather than anti-inflammatory??? Then how does it help in repair and healing???
The chemically mediated inflammatory events are associated with stimulation of the next (proliferative) phase.
Thus it promotes the inflammatory phase and acts as a promoter of the proliferative phase.
US during Proliferative stages
During the proliferative stage, it does not change the normal proliferative phase, but maximises its efficiency by producing the required scar tissue in an optimal fashion.
Studies show that low dose pulsed ultrasound increases protein synthesis and several research groups have demonstrated enhanced fibroplasia and collagen synthesis. Myofibroblasts help in early wound contraction.
For tissues in which there is an inflammatory reaction, but in which there is no ‘repair’ to be achieved, the benefit of ultrasound is to promote the normal resolution of the inflammatory events, and hence resolve the ‘problem’ This will of course be most effectively achieved in the tissues that preferentially absorb ultrasound – i.e. the dense collagenous tissues.
US during Remodeling phase
During the Remodeling phase, the scar tissue adopts functional characteristics of the tissue that it is repairing.
A scar in ligament will not ‘become’ ligament, but will behave more like a ligamentous tissue. This is achieved by a number of processes, but mainly related to the orientation of the collagen fibres in the developing scar and also to the change in collagen type.
Therapeutic Us can enhance the appropriate orientation of the newly formed collagen fibers and also to the collagen profile change from mainly Type III to a more dominant Type I construction, thus increasing tensile strength and enhancing scar mobility.
Indications of therapeutic Ultrasound
To reduce pain and swelling
To reduce muscle spasm
Muscle injury
Ligament injury
Tendonitis
Osteoarthritis
Rheumatoid arthritis
Myofascial pain
Bursitis
Pressure sores
Epicondylitis
Therapeutic Us is of value because it has the capacity to stimulate or enhance these normal events and thus increase the efficiency of the repair phases.
The application of therapeutic ultrasound at an appropriate dose will enhance this activity.
Your Physical therapist is the right person who to decide on the exact dosage of Ultrasound, depending on your condition.
At Valley Healing Hands, Brownsville, Texas, we provide the best physical therapy treatment for pain, muscle and ligament injuries, tendonitis, myofascial and other injuries requiring Ultrasound therapy. Our patients are satisfied with our service. You may check out what they have to say about us here and connect with us as well. Our patients love us and you too will!