Therapeutic ultrasound uses sound waves with frequencies above the range of human hearing to accelerate soft tissue healing. This non-invasive treatment delivers energy directly to the affected tissue, stimulating the body’s natural repair processes. It is often used as an adjunct therapy, complementing standard wound care to improve outcomes for patients with persistent wounds.
How Ultrasound Promotes Healing
The therapeutic action of ultrasound on wounds results from both mechanical and thermal effects. The sound waves cause vibrations in the tissue’s molecules, and this mechanical energy is a primary driver of the healing response, creating biochemical reactions within the cells.
One mechanical effect is acoustic streaming, which is the movement of fluids in response to the ultrasound waves. This agitation stimulates cells involved in wound repair, such as fibroblasts, which produce collagen to structure new tissue. It also activates macrophages, which clean the wound area by removing debris and dead tissue.
Another mechanical process, stable cavitation, also contributes to healing. This involves the formation and oscillation of microscopic gas bubbles in tissue fluids. The vibration of these bubbles helps to gently break down devitalized tissue in a process called debridement and can reduce the bacterial load in the wound, further encouraging cells to begin the repair process.
Beyond these mechanical actions, ultrasound produces a mild thermal effect. The energy from the sound waves creates a gentle, deep heat within the tissues. This warmth increases local blood flow, and the improved circulation delivers more oxygen and nutrients to the wound site while helping to carry away waste products.
Types of Therapeutic Ultrasound
Therapeutic ultrasound technologies are categorized by their frequency, which determines their use in wound care. The two main types are low-frequency ultrasound (LFU) and high-frequency ultrasound (HFU), each with distinct applications.
Low-Frequency Ultrasound
Low-frequency ultrasound (LFU) operates in the 20-40 kilohertz (kHz) range. Its primary application is for wound debridement, which is the removal of dead tissue, and cleansing the wound bed. LFU is effective at breaking down biofilms, which are communities of bacteria that can impede healing. It is often delivered using non-contact methods, such as a saline mist, where the ultrasound energy is transmitted through a fine spray to avoid direct contact with a sensitive wound.
High-Frequency Ultrasound
High-frequency ultrasound (HFU) uses a much higher frequency, between 1 and 3 megahertz (MHz). Unlike LFU, which targets the surface, HFU is designed to penetrate deeper into the underlying soft tissues. Its main purpose is to stimulate cellular repair processes beneath the skin, making it suitable for treating injuries to muscles and ligaments. HFU is a contact therapy, requiring a transducer head to be applied directly to the skin with a coupling gel to ensure efficient transmission of sound waves.
Wounds Treated with Ultrasound Therapy
Ultrasound therapy is useful for treating chronic wounds, which are wounds that fail to heal in a timely manner. These types of wounds often persist for weeks or months and are common in patients with underlying health conditions.
A primary application is managing diabetic foot ulcers. Patients with diabetes often have compromised circulation and reduced sensation in their feet, making them susceptible to ulcers that heal slowly. Ultrasound can create a better environment for healing.
Venous leg ulcers are another common type of chronic wound treated with ultrasound. These ulcers are caused by poor blood circulation in the veins of the legs, which leads to pressure buildup and skin breakdown. Ultrasound can help accelerate the healing of these persistent wounds.
Pressure ulcers, often called bedsores, are also candidates for this therapy. These wounds develop from prolonged pressure on the skin that restricts blood flow and causes tissue damage. Ultrasound can be beneficial by stimulating the healing process in deep tissues.
The Patient Experience During Treatment
The process for ultrasound therapy is straightforward and well-tolerated. A clinician cleans the wound area and, depending on the type of ultrasound, applies either a coupling gel or a saline mist to transmit the sound waves. The clinician then moves a small, handheld device called a transducer over or near the wound.
The treatment is painless, though some patients report a slight warming or tingling sensation in the treated area. The duration of each session is relatively short, lasting between five and twenty minutes, depending on the size and condition of the wound.
Ultrasound therapy is not a one-time solution and requires a series of sessions to achieve the desired healing outcomes. A treatment plan may involve multiple sessions per week over several weeks. The frequency and duration of the treatment are determined by a healthcare provider based on the wound’s severity and response to the therapy. After each session, a fresh dressing is applied, and patients can resume their normal activities.