9.2 Therapeutic Ultrasound in Wound Care
Key Takeaways
- Wound ultrasound is divided by frequency: low-frequency ultrasound in the kilohertz range (about 20 to 40 kHz) for contact ultrasonic debridement and noncontact mist therapy, and high-frequency ultrasound in the megahertz range (about 1 to 3 MHz) for traditional therapeutic ultrasound.
- Nonthermal effects such as cavitation, acoustic streaming, and microstreaming change cell membrane permeability, stimulate growth factor release and angiogenesis, and disrupt bacteria and biofilm; thermal effects dominate with continuous megahertz ultrasound.
- Contact low-frequency ultrasonic debridement is reported with CPT codes based on the tissue removed (selective debridement 97597/97598 or surgical debridement 11042–11047), while noncontact, nonthermal low-frequency ultrasound therapy is reported with CPT 97610.
- Evidence for low-frequency ultrasound suggests benefit for some chronic wounds, but trials are small and heterogeneous, and payer coverage for noncontact ultrasound varies.
- Avoid therapeutic ultrasound over malignancy, a pregnant uterus, the eyes, reproductive organs, pacemakers and other implanted electronic devices, areas of active bleeding or thrombosis, and, for thermal ultrasound, ischemic or insensate tissue.
9.2 Therapeutic Ultrasound in Wound Care
Core Clinical Principle: "Ultrasound" in wound care covers very different tools. Low-frequency (kilohertz) ultrasound is used to debride tissue and disrupt biofilm, either through a contact probe with saline irrigation or as a noncontact saline mist, while high-frequency (megahertz) therapeutic ultrasound delivers heat or nonthermal energy to deeper tissue. Choosing correctly depends on the goal, the wound, and safety limits.
The CWSP outline lists ultrasound under biophysical technologies in Patient Management, and the treatment tasks name both contact and noncontact ultrasound. Diagnostic imaging uses of ultrasound, such as duplex scanning, are covered in the vascular and imaging sections.
Frequency Determines Use
| Feature | Low-Frequency Ultrasound (kHz) | High-Frequency Therapeutic Ultrasound (MHz) |
|---|---|---|
| Typical frequency | About 20 to 40 kHz | About 1 to 3 MHz |
| Delivery | Contact probe with saline irrigation, or noncontact saline mist | Transducer moved over coupling gel on intact periwound skin or through a sterile coupling medium |
| Main effects | Nonthermal: cavitation, streaming, mechanical debridement, biofilm disruption | Thermal (continuous mode) or nonthermal (pulsed mode); 1 MHz reaches deeper tissue, 3 MHz is more superficial |
| Wound uses | Debridement of slough, necrotic tissue, and biofilm; stimulation of stalled wounds | Historically used to stimulate healing; evidence for chronic wounds is weak |
How Ultrasound Affects Tissue
- Cavitation: Pressure waves make microbubbles form and oscillate. Stable cavitation creates gentle fluid movement that alters membrane permeability and signaling, while transient (inertial) cavitation makes bubbles collapse violently, fragmenting necrotic tissue and bacteria.
- Acoustic streaming and microstreaming: One-directional fluid movement around cells and bubbles that increases calcium influx, mast cell degranulation, and release of growth factors from macrophages and platelets.
- Angiogenesis and fibroblast activity: Experimental work shows increased nitric oxide, VEGF expression, fibroblast proliferation, and collagen deposition.
- Antibacterial and antibiofilm effects: Mechanical disruption of biofilm matrix and increased susceptibility of bacteria to antimicrobials.
- Heat: Continuous megahertz ultrasound raises tissue temperature, increasing blood flow and collagen extensibility, but also risks burns in insensate or ischemic tissue.
Contact Low-Frequency Ultrasonic Debridement
A handheld probe vibrating at about 22 to 35 kHz is applied with continuous saline irrigation. Cavitation separates devitalized tissue from viable tissue while sparing much of the healthy bed, so it can be less painful than sharp debridement and is useful for irregular wounds, tunnels, and exposed tendon or bone.
- Anesthesia: Topical or local anesthesia is often needed for deeper debridement.
- Aerosol precautions: Like pulsed lavage, the device generates contaminated spray. Use gowns, gloves, masks with eye protection or face shields, an enclosed treatment space when possible, and cleaning of nearby surfaces.
- Coding: The procedure is reported by the deepest tissue removed and the surface area, not by the device: 97597/97598 for selective debridement of epidermis, dermis, and nonviable tissue, or 11042–11047 when subcutaneous tissue, muscle, or bone is excised.
Noncontact Low-Frequency Ultrasound Therapy
Noncontact devices operating at about 40 kHz deliver energy through a saline mist from a transducer held about 0.5 to 1.5 cm from the wound, usually for a few minutes depending on wound size, several times a week. The therapy does not touch the wound, so it is often well tolerated in painful or fragile wounds.
- Evidence: Randomized and comparative studies in diabetic foot ulcers, venous leg ulcers, and ischemic wounds have reported faster healing or pain reduction, but trials are small, some benefits appear only in per-protocol analyses, and systematic reviews rate the certainty of evidence as low.
- Coding: CPT 97610 describes low-frequency, noncontact, nonthermal ultrasound, including topical applications when performed, wound assessment, and instructions for ongoing care, per day.
- Coverage: Payer policies vary; several commercial payers and some Medicare contractors have considered it investigational or not reasonable and necessary, so check local coverage before treatment.
High-Frequency Therapeutic Ultrasound
Megahertz ultrasound was studied for venous leg ulcers and pressure injuries, usually delivered in pulsed mode on the periwound skin. Cochrane reviews have found no clear evidence that it improves healing of venous leg ulcers or pressure injuries, so it plays little role today apart from musculoskeletal rehabilitation.
Contraindications and Precautions
| Area or Condition | Concern |
|---|---|
| Malignancy in the treatment area | Possible stimulation of tumor growth or spread |
| Pregnant uterus, eyes, reproductive organs | Heat and cavitation injury |
| Pacemakers and implanted electronic devices | Device interference |
| Active bleeding, bleeding disorders, recent thrombosis | Increased bleeding or embolization |
| Ischemic or insensate tissue (thermal ultrasound) | Burns because heat cannot be dissipated or felt |
| Growth plates in children, laminectomy sites, plastic or cemented implants (thermal ultrasound) | Heat injury |
| Acute infection with systemic signs | Treat the infection; ultrasonic debridement is a local adjunct |
Clinical Traps
Trap 1: Coding the Device Instead of the Tissue
Contact ultrasonic debridement has no device-specific CPT code; the depth of tissue removed and the area decide between 97597 and 11042–11047. CPT 97610 applies only to noncontact, nonthermal treatment.
Trap 2: Skipping Splash Precautions
Ultrasonic debridement aerosolizes bacteria. Protect staff and nearby patients with personal protective equipment and room cleaning, just as with pulsed lavage.
A wound clinic adds a device that delivers 40-kHz ultrasound through a saline mist held about 1 cm from the wound without touching it, and the clinician documents wound assessment and home care instructions. Which description and CPT code best fit this treatment?
A physician uses a 25-kHz contact ultrasonic probe with saline irrigation to remove devitalized subcutaneous tissue from a 12 cm² diabetic foot ulcer, leaving a bleeding subcutaneous base. How should the debridement be reported?
A clinician is considering continuous 1-MHz therapeutic ultrasound over the lower leg of a patient with a nonhealing ulcer. Which finding makes thermal ultrasound inappropriate over this area?