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Contact Low-frequency Ultrasound Used to Accelerate Granulation Tissue Proliferation and Rapid Removal of Nonviable Tissue in Colonized Wounds: A Case Study

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Contact Low-frequency Ultrasound Used to Accelerate Granulation Tissue Proliferation and Rapid Removal of Nonviable Tissue in Colonized Wounds: A Case Study


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Mr. Aviles is Clinical Director of Therapy Services and a Wound Specialist for a long-term acute care facility in Natchitoches, LA. Please address correspondence to:   Advanced wound care modalities are available for clinicians to promote chronic wound repair. Chronic wounds tend to contain high bioburden, senescent cells, and nonviable tissue,1 making wound bed preparation essential to attaining a vascularized stable wound bed while managing bacterial count and exudate. Low-frequency ultrasound not only provides the ability to prepare the wound bed by removing necrotic tissue and debris, but it also may help balance bacteria in wounds.2 In addition, ultrasound may increase angiogenesis in vitro.3  Ultrasound applications have been available since the 1930s and are used as diagnostic and therapeutic settings. In wound care, ultrasound is used to facilitate cavitation (expanding and contracting gas-filled bubbles within tissues that result in cell changes) and microstreaming (manipulating the movement of fluids around tissues in the body). Cavitation occurs because ultrasound can induce pressure changes in tissue fluids, increasing flow in the surrounding fluid.4 Microstreaming may alter cell membrane structure, function, and permeability.5 The effects of cavitation and microstreaming have been demonstrated in vitro and include stimulation of fibroblast repair and collagen synthesis,6 tissue regeneration,7 and bone healing.8   Ultrasound interacts with one or more components of the inflammatory process. In vitro ultrasound studies9 have demonstrated resolution of inflammation, fibrinolysis, stimulation of macrophage-derived fibroblast mitogenic factors, fibroblast recruitment, angiogenesis, matrix synthesis, dense collagen fibrils, and tissue tensile strength.   Various methods of preparing a wound bed for healing are available to clinicians. Surgical debridement, the most aggressive approach, is typically preferred and depends on physician experience and patient appropriateness. Sharp debridement can be performed by physicians as well as nonphysician healthcare personnel (eg, PTs, RNs, PAs); in some cases, this method may not be appropriate, especially if the patient is taking blood thinners or the wound has moist, stringy slough that cannot be easily handled with instruments. Contact low-frequency ultrasound provides another viable option that selectively removes necrotic tissue in complicated nonsurgical patients and on wounds where sharp debridement alone failed to achieve desired results. This option can be utilized by nonphysician healthcare personnel and used in conjunction with other forms of debridement.   The author works in a rural area LTAC facility where resources and specialty practices are limited. This case study is the result of a search for available advanced modalities to improve outcomes and achieve rapid removal of necrotic tissue. Various contact and noncontact ultrasound devices were trialed; Sonic One (Misonix, Inc., Farmingdale, NY) best met established facility goals and needs. According to clinician observations, the device was able to remove necrotic tissue faster than sharp debridement alone, helped establish a well-granulated wound bed, jumped-started “stalled” wounds, and helped save limbs slated for amputation. This device can deliver ultrasound energy to the wound bed while selectively debriding necrotic tissue, irrigating debris, and promoting angiogenesis especially on complicated patients.

Case Study

  History. Seventy-nine-year-old Mr. D was admitted to the author’s log-term acute care (LTAC) facility on June 24, 2009 of his own volition as a last measure before undergoing a recommended amputation of his right lower extremity. His history included diabetes, left below-knee amputation (April 2008), coronary artery disease, congestive heart failure, pacemaker, previous right toe amputations, and multiple debridements to his right foot. His lab test results indicated a white blood count within normal limits, albumin 1.6, prealbumin 3 (which increased to 5 by July 13, 2009), elevated glucose, sed rate >100 mm/hour), and elevated C-reactive protein (14.16 mg/dL). X-rays showed no bone destruction; a bone scan showed no abnormalities, Doppler was negative for thrombus, monophasic wave form was noted on posterior tibialis, and the clinician was unable to find the dorsalis pedis artery, which was confirmed by arterial test.   Wound assessment noted an extensive, odorous necrotic wound on Mr. D’s right lateral foot that had started as a blister and worsened while previous treatments failed to produce desirable results. The wound measured 16.9 cm x 6.5 cm, with depth at least 1.5 cm, yielding a surface area 109.85 cm2, volume 164.8 cm3. A fruity odor, moderate serosanguinous drainage with yellow stain on bandage that was 45% black, 35% yellow, and 10% pink tissue was noted, along with purulence (see Figure 1). No granulation tissue or induration was noted, light touch response was absent in the right lower extremity, and the clinician was unable to manually palpate pulses.   Diagnosis. The wound was designated a Wagner Scale 4 and diagnosed a nonhealing diabetic ulcer.   Management. At admission on June 24, 2009, Mr. D was scheduled for surgical debridment on June 26. On admission, vitamin C (500 mg), zinc (220 mg), Santyl (Healthpoint, Fort Worth, TX), and Prostat (Medical Nutrition, Englewood, NJ) were started; 1 day later, pentoxifylline (400 mg) and Juven® (Abbott Nutrition, Abbott Park, IL) were added to Mr. D’s care regimen. Dressing selection changed from Santyl to Mesalt (Mölnlycke Health Care, Norcross, GA) early during the stay. Offloading also was initiated by floating heel/foot with a pillow, followed by an offloading boot while in bed.   On June 26, Mr. D received his first contact ultrasound treatment. The first treatment lasted 10 minutes (due to the amount of necrotic tissue); a standard probe at a continuous setting and an ultrasonic output level of 5 (output level ranges from 0 to 5. The SonicOne probe oscillates at a frequency of 22.5 kHz) was used. Mr. D received a total of eight, 8- to 13-minute contact ultrasound treatments using the same output level of 5 and continuous pulse setting over 26 days (see Figures 2 through 7).   Meanwhile, bone exposure and clinical signs (ie, fruity odor with yellow residue on bandage) of Pseudomonas were noted. The wound culture was positive for Pseudomonas aeruginosa, Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus (MRSA). At day 16, Mr. D was started on levofloxacin for the Pseudomonas but the medication did not successfully treat the MRSA. Topical antiseptics (Dakins/acetic acid rinses) were started immediately along with contact low frequency ultrasound to combat Pseudomonas-type drainage/odor. Pentoxifylline was increased on June 30 to three times per day; Mr. D then received two ultrasound treatments 5 days apart (July 1 and July 6 – Figures 4 and 5). On July 8, he underwent minimal surgical debridement; the following day, he was provided antibiotics for the Pseudomonas that were MRSA-resistant. During this time, Mr. D’s wound continued to progress toward healing and granulate despite lack of antibiotics for MRSA and positive repeat culture for this organism on July 18 (see Figure 8).   Negative pressure wound therapy (NPWT) was initiated on July 10 after another ultrasound treatment. NPWT was applied for a period of 3½ weeks at a pressure of 80 mm Hg at a constant rate using a foam-based dressing and Vaseline® gauze (Chesebrough Ponds, Inc.) over the bony area changed every 2 to 3 days. Two successive ultrasound treatments (July 13 and July 16 – Figures 7 and 8) were provided. On July 18, the wound was re-cultured and found to be MRSA-positive; Mr. D received ultrasound treatment followed by NPWT. On July 21, Mr. D was provided Bactrim DS (Hoffman-LaRoche Ltd., Nutley, NJ) twice daily for 7 days for MRSA, along with ultrasound and NPWT therapy (see Figure 9).   On August 4, Mr. D’s foot wound measured 14.8 cm x 5 cm, 0.5 cm depth; surface area was 74 cm2 and volume 37 cm3. The wound exhibited no odor, minimal serosanguinous drainage (95% red, 5% yellow tissue), positive granulation tissue, and no induration, Mr. D was discharged to home health and NPWT on August 5.


  In 39 days, Mr. D’s right lateral foot wound had decreased in surface area by 37% and in volume by 88% (see Figure 10). Upon admission, Mr. D was aware of amputation recommendations and understood the seriousness of his condition. At this point, the primary goal was to assess/address existing soft tissue and/or bone infection, as well as his circulatory status; remove extensive amount of necrotic tissue; improve his nutritional status; offload the extremity while protecting it from further trauma; and prepare the wound for advanced modalities.   Mr. D was surgically debrided with limited removal of nonviable tissue. Ultrasound treatment achieved excellent necrotic tissue removal while promoting granulation growth. The literature indicates that ultrasound devices also may stimulate angiogenesis. In this case study, granulation in the wound bed and over the bone was noted after 3 to 6 days of using the low-frequency ultrasound device. This rapid granulation growth over bone had not been experienced in the author’s patients, especially in the diabetic population, before using this device. NPWT also played a role in Mr. D’s wound management by increasing granulation tissue formation, managing exudate, maintaining a moist wound bed while protecting the area, and stimulating circulation to the wound bed.   The author helps healthcare workers and facilities in rural areas with their wound care needs throughout the continuum of care. This approach has been effective in coordinating treatments after inpatient stays, improving the communication between agencies and physicians, establishing positive outcomes, and most importantly improving the care provided to patients by means of increasing knowledge/skills while emphasizing standard of care.


  Despite initial physician recommendations to amputate, Mr. D’s wound continued to progress with the use of advanced wound care modalities and coordination of his care throughout the continuum. By the end of week 3, total wound surface area was decreased 27.7 cm2 (28%) and overall volume decreased 90.84 cm3 (56%). Incidentally, the author also noticed that bacterial load was managed and wound healing progressed — a robust, red granulated wound bed was achieved without additional antibiotics for the organism cultured. Unlike with sharp debridement, necrotic tissue was removed effectively at the bedside using this contact low-frequency device.


  Contact low frequency ultrasound allowed for necrotic tissue removal while promoting granulation on a complicated patient. Mr. D and his family are pleased and thankful that he has regained leg function and his normal lifestyle. The author continues to use this device successfully with new and improved ultrasonic probes, achieving similar results on complicated patients and the wound continues to heal (see Figure 11).


1.Whitney J, Phillips L, Aslam R, et al. Guidelines for the treatment of pressure ulcers. Wound Repair Regen. 2006;14(6):663–679. 2. Conner-Kerr T. The effects of low-frequency ultrasound (35kHz) on methicillin-resistant Staphylococcus aureus (MRSA) in vitro. Ostomy Wound Management. 2010;56(5):32–42. 3. Young SR, Dyson M. The effect of therapeutic ultrasound on angiogenesis. Ultrasound Med Biol. 1990;16(3):261–269. 4. Josza L, Kannus P. Human Tendons. Anatomy, Physiology and Pathology. Champaign, IL: Human Kinetics;1997. 5. Williams AR. Production and transmission of ultrasound. Physiotherapy. 1987;73:113–116. 6. Webster DF, Harvey W, Dyson M, Pond JB. The role of ultrasound-induced cavitation in the in vitro stimulation of collagen synthesis in human fibroblasts. Ultrasonics. 1980;18:33-7. 7. Dyson M, Luke DA. Induction of mast cell degranulation in skin by ultrasound. IEEE Trans Ultrasonics Ferroelectrics Frequency Control. 1986;UFFC–33:194. 8. Pilla AA, Figueiredo M, Nasser P, et al. Non-invasive low intensity pulsed ultrasound: a potent accelerator of bone repair. Proceedings of the 36th Annual Meeting Orthopedics Research Society. New Orleans, LA. February 1990. 9. Speed CA. Therapeutic ultrasound in soft tissue lesions. Rheumatology. 2001;40(12):1331–1336. This article was not subject to the Ostomy Wound Management peer-review process.