Description:
Low-frequency ultrasound in the kilohertz range may improve wound healing. Several noncontact low-frequency ultrasound (NLFU) devices have received regulatory approval for wound treatment.

For individuals who have any wound type (acute or nonhealing) who receive noncontact ultrasound therapy, the evidence includes randomized controlled trials (RCTs) and systematic reviews. Relevant outcomes are symptoms, change in disease status, morbid events, quality of life, and treatment-related morbidity. The single double-blinded, sham-controlled randomized trial, which included patients with nonhealing diabetic foot ulcers, had substantial methodologic flaws (e.g., high dropout rate, baseline differences between groups) that limit the validity of the findings. In the remaining studies comprising the evidence base, all but 1 RCT comparing NLFU with standard wound care had improved (statistically significant) results on the primary outcome with NLFU. However, these studies also had several methodologic limitations. In terms of outcome assessment, complete healing is generally considered the most clinically relevant outcome; a 50% reduction in wound area over time and time to heal are also considered acceptable outcomes. A majority of trials included patients with venous leg ulcers. None of the RCTs evaluating venous leg ulcers reported complete healing or another acceptable outcome as its primary outcome measure, and none had blinded outcome assessment. Only 1 RCT, which addressed split-thickness graft donor sites, reported on the proportion of patients with complete healing and had blinded outcome assessment. Another limitation of the body of evidence is that some standard of care interventions involved fewer visits than the NLFU intervention, and the differences in intensity of care resulting from this differential in face-to-face contact could partially explain the difference in findings between intervention and control groups. The evidence is insufficient to determine the effects of the technology on health outcomes.

Background 
Ultrasound (US) delivers mechanical vibration above the upper threshold of human hearing (> 20 kHz). US in the megahertz range (1 – 3 MHz) has been used to treat musculoskeletal disorders, often by physical therapists. Although the exact mechanism underlying its clinical effects is not known, therapeutic US has been shown to have a variety of effects at a cellular level, including angiogenesis, leukocyte adhesion, growth factor, collagen production, and increases in macrophage responsiveness, fibrinolysis, and nitric oxide levels. The therapeutic effects of US energy in the kilohertz range have also been examined. Although the precise effects are not known, the low-frequency US in this range may improve wound healing via the production, vibration, and movement of micron-sized bubbles in the coupling medium and tissue.

The mechanical energy from the US is typically transmitted to the tissue through a coupling gel. Several high-intensity US devices with contact probes are currently available for wound débridement. Low- intensity US devices have been developed that do not require coupling gel or other direct contact. The MIST Therapy System delivers a saline mist to the wound with low-frequency US (40 KHz). A second device, the Qoustic Wound Therapy System, also uses sterile saline to deliver US energy (35 KHz) for wound débridement and irrigation.

US is intended as an adjunct to standard wound care. Therefore, the evidence is needed that demonstrates US plus standard wound care provides superior wound closure outcomes compared with standard wound care alone.

The primary end points of interest for trials of wound closure are as follows, consistent with 2006 guidance from the U.S. Food and Drug Administration for the industry in developing products for the treatment of chronic cutaneous ulcer and burn wounds1:

1. Incidence of complete wound closure.
2. Time to complete wound closure (reflecting accelerated wound closure).
3. Incidence of complete wound closure following surgical wound closure.
4. Pain control.

Regulatory Status
In 2005, the MIST Therapy^® device (Celleration) was cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process "to promote wound healing through wound cleansing and maintenance débridement by the removal of yellow slough, fibrin, tissue exudates and bacteria."² In February 2015, Celleration was acquired by Alliqua Biomedical (Langhorne, PA).

In 2007, the AR1000 Ultrasonic Wound Therapy System (Arobella Medical, Minnetonka, MN) was cleared for marketing by FDA through the 510(k) process, listing the MIST Therapy^® system and several other ultrasonic wound débridement and hydrosurgery systems as predicate devices. The AR1000 system probe uses "contact or noncontact techniques to achieve intended wound therapy modalities to promote wound healing."³ Indications in the 510(k) summary are listed as "Selective and non-selective dissection and fragmentation of soft and or hard tissue" and "Surgical, excisional or sharp-edge wound debridement (acute and chronic wounds, bums) for the removal of nonviable tissue including but not limited to diseased tissue, necrotic tissue, slough and eschar, fibrin, tissue exudates, bacteria and other matter."³ This device is now known as the Qoustic Wound Therapy System™.

Several other devices have been approved as being substantially equivalent to the earlier devices. FDA product code: NRB.

Related Policies
10116 Negative Pressure Wound Therapy
20157 Electrostimulation and Electromagnetic Therapy for the Treatment of Chronic Wounds

Policy:
Non-contact ultrasound treatment for wounds is investigational and/or unproven and is therefore considered NOT MEDICALLY NECESSARY.

Policy Guidelines
Please see the Codes table for details.

Benefit Application
BlueCard/National Account Issues
State or federal mandates (e.g., FEP) may dictate that all devices approved by the U.S. Food and Drug Administration (FDA) may not be considered investigational, and, thus, these devices may be assessed only on the basis of their medical necessity.

Rationale
Evidence reviews assess the clinical evidence to determine whether the use of technology improves the net health outcome. Broadly defined, health outcomes are the length of life, quality of life, and ability to function¾including benefits and harms. Every clinical condition has specific outcomes that are important to patients and managing the course of that condition. Validated outcome measures are necessary to ascertain whether a condition improves or worsens; and whether the magnitude of that change is clinically significant. The net health outcome is a balance of benefits and harms.

To assess whether the evidence is sufficient to draw conclusions about the net health outcome of technology, two domains are examined: the relevance, and quality and credibility. To be relevant, studies must represent one or more intended clinical use of the technology in the intended population and compare an effective and appropriate alternative at a comparable intensity. For some conditions, the alternative will be supportive care or surveillance. The quality and credibility of the evidence depend on study design and conduct, minimizing bias and confounding that can generate incorrect findings. The randomized controlled trial (RCT) is preferred to assess efficacy; however, in some circumstances, nonrandomized studies may be adequate. RCTs are rarely large enough or long enough to capture less common adverse events and long-term effects. Other types of studies can be used for these purposes and to assess generalizability to broader clinical populations and settings of clinical practice.

This literature review focuses on evidence evaluating whether the addition of noncontact low-frequency ultrasound (NLFU) improves wound healing compared with standard treatment alone. Observational studies may be considered if they provide additional information on adverse events or durability.

Noncontact Low-Frequency Ultrasound
Clinical Context and Therapy Purpose
The purpose of noncontact low-frequency ultrasound therapy in patients who have any wound type (acute or nonhealing) is to improve wound healing.

The question addressed in this evidence review is: Does the use of noncontact low-frequency ultrasound therapy improve the net health outcome in patients with any wound type (acute or nonhealing)?

The following PICO was used to select literature to inform this review.

Populations
The relevant population(s) of interest are individuals with any wound type (acute or nonhealing).

Interventions
The therapy being considered is noncontact low-frequency ultrasound therapy.

Comparators
The following therapies/tools/rules/practices are currently being used to make decisions about wound care: Standard wound care.

Outcomes
The general outcomes of interest are symptoms, change in disease status, morbid events, quality of life, and treatment-related morbidity.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

• To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
• In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
• To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
• Consistent with a 'best available evidence approach,' within each category of study design, studies with larger sample sizes and longer durations were sought.
• Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Systematic Reviews
Tricco et al. (2015) published an overview of systematic reviews on treatments for complex wounds, which reviewed multiple therapies including ultrasound.⁴ The review by Voigt et al. (2011) was included. Conclusions related to ultrasound therapy are summarized in Table 1.

Table 1. Overview and Summary Conclusions of Systematic Reviews

Adapted from Trico et al. (2015).⁴
HFUS: high-frequency ultrasound; LFUS: low-frequency ultrasound; MA: meta-analysis; QOE: quality of evidence; SR: systematic review; US: ultrasound; w/o: without.

Tables 2 and 3 summarize systematic reviews that compare results from NLFU with standard care. The Voigt et al. (2011) systematic review only included RCTs; studies used contact or noncontact ultrasound for treating chronic lower-limb wounds.⁵ Five RCTs on NLFU were identified, 1 of which was unpublished. A pooled analysis of 2 sham-controlled trials found a significantly smaller proportion of nonhealed wounds at 3 months in the NLFU group than in the control group (relative risk, 0.74; 95% confidence interval, 0.58 to 0.95; p = 0.02). The 2 NLFU studies were those by Ennis et al. (2005), described in the following section,⁶ and by Peschen et al. (1997),⁷ which delivered ultrasound therapy with a dated device during foot bathing. A systematic review by Chang et al. (2017)⁸ included all study types; however, only 2 of the RCTs (Ennis et al. [2005]⁶ and Kavros et al. [2007]⁹) were included. Chang et al. (2017) did not include meta-analyses, and the narrative synthesis did not provide complete information on the range of comparative effects; therefore, it is not included in the tables below.

Table 2. Systematic Review Characteristics

RCT: randomized controlled trial.

Table 3. Systematic Review Results

     
CI: confidence interval; NR: not reported; RR, relative risk.

Randomized Controlled Trials
One double-blind, multicenter, sham-controlled trial and a number of unblinded RCTs comparing NLFU with standard wound care alone have been performed. Trials including at least 25 patients are described in the Tables 4 – 7 and the following text. All RCTs used MIST therapy and, other than Beheshti et al. (2014)¹⁰ and Olyaie et al. (2013),¹¹ which did not report funding sources, all were industry-funded. One study addressed diabetic foot ulcers. Four RCTs included patients with venous leg ulcers and another evaluated treatment of split-thickness graft donor sites. All studies except that on split-thickness graft donor sites included patients with nonhealing wounds; eligibility criteria included wounds that had not healed after at least 4 weeks. Standard care interventions varied, but generally consisted of wound cleaning, noncontact dressings, compression and, if deemed necessary by providers, débridement. In 2 studies (White et al. [2016]¹², Gibbons et al. [2015]¹³), authors mentioned following national guidelines for the standard of care intervention. Prather et al. (2015)¹⁴ did not describe the standard care intervention and Beheshti et al. (2014) reported only that compression was used.

Table 4. Summary of RCT Characteristicsa

NLFU: noncontact low-frequency ultrasound; NR: not reported; RCT: randomized controlled trial; SOC: standard of care.
a Includes trials with ≥ 25 participants.

Table 5. Summary of RCT Results^a

CI: confidence interval; Diff: difference; HFUS: high-frequency ultrasound; HR: hazard ratio; NLFU: noncontact low-frequency ultrasound; NR: not reported; RCT: randomized controlled trial; SOC: standard of care; TE: treatment effect; VAS: visual analog scale.
a Includes trials with ≥25 participants.
b The comparison for this p-value is unclear.
c Per-protocol analysis.

Limitations in the body of evidence are summarized in Tables 6 and 7 and the following paragraphs. Ennis et al. (2005) published findings of a double-blind, multicenter, sham-controlled trial of MIST therapy for recalcitrant diabetic foot ulcers in 133 patients.⁶ Patients with were treated with active or sham MIST therapy 3 times per week, with débridement as needed and a weekly evaluation by an independent investigator. Twenty-four patients were lost to follow-up, and data from 54 patients were excluded from analysis due to protocol violations (5 centers inverted the treatment distances for the active and sham devices), leaving 55 (41%) patients for the per-protocol analysis. Investigators reported significant improvement in the active treatment group (11/27 [41%] patients) compared with the control group (4/28 [14%] patients) in the proportion of wounds healed (defined as complete epithelialization without drainage). However, intention-to-treat analysis showed no difference in wound healing between the active (n = 70 [26%]) and control (n = 63 [22%]) groups. In addition to the 59% loss to follow-up, there was a difference in the ulcer area at baseline (1.7 cm2 vs 4.4 cm2, respectively) and chronicity of wounds (35 weeks vs 67 weeks, respectively) that favored MIST therapy in the per-protocol groups. Due to the serious limitations of this trial, these results are considered inconclusive.

In the White et al. (2016),¹² Gibbons et al. (2015),¹³ and Prather et al. (2015)¹⁴ studies, patients and providers were not blinded, but outcome assessment was blinded. The other studies did not mention blinding. All but 1 RCT reported improved (statistically significant) results for the primary outcome with NLFU than with standard of care. However, these studies had methodologic limitations. Regarding outcome assessment, complete healing is considered the most clinically relevant outcome.¹⁵ Complete healing was reported in a subset of the studies, and most were not powered for this outcome or the outcome used to power the study was unclear. Only Prather et al. (2015)¹⁴ and Ennis et al. (2005)⁶ conducted blinded outcome assessments and reported complete healing. Another limitation of the body of evidence is that some of the standard care interventions involved different visit schedules than the NLFU intervention, and the effects of this differential in face-to-face contact could partially explain the difference in findings between intervention and control groups.

Table 6. Study Relevance Limitations in RCTs

NLFU: noncontact low-frequency ultrasound; SOC: standard of care
The study limitations stated in this table are those notable in the current review; this is not a comprehensive gaps assessment.
a Population key: 1. Intended use population unclear; 2. Clinical context is unclear; 3. Study population is unclear; 4. Study population not representative of intended use.
b Intervention key: 1. Not clearly defined; 2. Version used unclear; 3. Delivery not similar intensity as comparator; 4.Not the intervention of interest.
c Comparator key: 1. Not clearly defined; 2. Not standard or optimal; 3. Delivery not similar intensity as intervention; 4. Not delivered effectively.
d Outcomes key: 1. Key health outcomes not addressed; 2. Physiologic measures, not validated surrogates; 3. No CONSORT reporting of harms; 4. Not establish and validated measurements; 5. Clinical significant difference not prespecified; 6. Clinical significant difference not supported.
e Follow-Up key: 1. Not sufficient duration for benefit; 2. Not sufficient duration for harms.

Table 7. Study Design and Conduct Limitations in RCTs

RCT: randomized controlled trials.
The study limitations stated in this table are those notable in the current review; this is not a comprehensive gaps assessment.
a Allocation key: 1. Participants not randomly allocated; 2. Allocation not concealed; 3. Allocation concealment unclear; 4. Inadequate control for selection bias.
b Blinding key: 1. Not blinded to treatment assignment; 2. Not blinded outcome assessment; 3. Outcome assessed by treating physician.
c Selective Reporting key: 1. Not registered; 2. Evidence of selective reporting; 3. Evidence of selective publication.
d Data Completeness key: 1. High loss to follow-up or missing data; 2. Inadequate handling of missing data; 3. High number of crossovers; 4. Inadequate handling of crossovers; 5. Inappropriate exclusions; 6. Not intent to treat analysis (per protocol for noninferiority trials).
e Power key: 1. Power calculations not reported; 2. Power not calculated for primary outcome; 3. Power not based on clinically important difference.
f Statistical key: 1. Analysis is not appropriate for outcome type: (a) continuous; (b) binary; (c) time to event; 2. Analysis is not appropriate for multiple observations per patient; 3. Confidence intervals and/or p values not reported; 4.Comparative treatment effects not calculated.

Summary of Evidence
For individuals who have any wound type (acute or nonhealing) who receive noncontact ultrasound therapy plus standard wound care, the evidence includes randomized controlled trials (RCTs) and systematic reviews. Relevant outcomes are symptoms, change in disease status, morbid events, quality of life, and treatment-related morbidity. The single, double-blinded, sham-controlled randomized trial, which included patients with nonhealing diabetic foot ulcers, had substantial methodologic flaws (eg, high dropout rate, baseline differences between groups) that limit the validity of the findings. In the remaining studies comprising the evidence base, all but 1 RCT comparing NLFU with standard wound care reported improved (statistically significant) results on the primary outcome with NLFU. However, these studies also had several methodologic limitations. Complete healing is the most clinically relevant outcome. None of the RCTs evaluating venous leg ulcers reported complete healing as its primary outcome measure, and none had blinded outcome assessment. Only 1 RCT, which addressed split-thickness graft donor sites, reported on the proportion of patients with complete healing and had blinded outcome assessment. Another limitation of the body of evidence is that some standard of care interventions involved fewer visits than the NLFU intervention, and the differences in intensity of care resulting from this differential in face-to-face contact could partially explain the difference in findings between intervention and control groups. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

The purpose of the remaining sections in Supplemental Information is to provide reference material regarding existing practice guidelines and position statements, U.S. Preventive Services Task Force Recommendations and Medicare National Coverage Decisions and registered, ongoing clinical trials. Inclusion in the Supplemental Information does not imply endorsement and information may not necessarily be used in formulating the evidence review conclusions.

Practice Guidelines and Position Statements
Guidelines or position statements will be considered for inclusion in Supplemental Information if they were issued by, or jointly by, a U.S. professional society, an international society with U.S. representation, or National Institute for Health and Care Excellence (NICE). Priority will be given to guidelines that are informed by a systematic review, include strength of evidence ratings, and include a description of management of conflict of interest.

Association for the Advancement of Wound Care
In 2014, the Association for the Advancement of Wound Care (AAWC) published guidelines on the care of pressure ulcers.¹⁶ Noncontact low-frequency ultrasound therapy was included as a potential second-line intervention if first-line treatments did not result in wound healing.

The AAWC guidelines on the treatment of venous ulcers, updated in 2015, stated that low-frequency ultrasound treatment requires additional evidence before it can be considered an appropriate treatment.¹⁷

Society for Vascular Surgery, American Venous Forum, American Podiatric Medical Association
In 2014, the Society for Vascular Surgery in collaboration with the American Venous Forum published joint guidelines on the management of venous leg ulcers.¹⁸ The guidelines recommended adjuvant wound therapy options for venous leg ulcers that fail to demonstrate improvement after 4 to 6 weeks of standard wound therapy (strength of recommendation: grade 1; quality of evidence: level B), but recommended against routine ultrasound therapy for venous leg ulcers (strength of recommendation: grade 2; quality of evidence: level B).

In 2016, the Society for Vascular Surgery in collaboration with the American Podiatric Medical Association published joint guidelines on the management of diabetic foot ulcers.¹⁹ The guidelines recommended adjuvant therapy for diabetic foot ulcers that fail to demonstrate more than 50% wound area reduction after 4 weeks of standard wound therapy. The adjunctive wound therapy options listed in the guidelines included negative pressure therapy, biologics (platelet-derived growth factor, living cellular therapy, extracellular matrix products, amniotic membrane products), and hyperbaric oxygen therapy. Ultrasound therapy was not mentioned as a recommended adjuvant option.

U.S. Preventive Services Task Force Recommendations
Not applicable

Ongoing and Unpublished Clinical Trials
A search of ClinicalTrials.gov in December 2021 did not identify any ongoing or unpublished trials that would likely influence this review.

References: 

1. Center for Drug Evaluation and Research, Center for Biologics Evaluation and Research, Center for Devices and Radiological Health. Guidance for Industry: Chronic Cutaneous Ulcer and Burn Wounds -- Developing Products for Treatment. Rockville, MD: Food and Drug Administration; 2006 June.
2. Food and Drug Administration. MIST[TM] Therapy System: 510(k) Premarket Notification: K050129. https://www.accessdata.fda.gov/cdrh_docs/pdf5/K050129.pdf. Accessed November 1, 2019.
3. Food and Drug Administration. 510(k) Summary: 510(k) -AR1000 Series K131096, Arobella Medical, LLC. 2014; https://www.accessdata.fda.gov/cdrh_docs/pdf13/K131096.pdf. Accessed November 1, 2019.
4. Tricco AC, Antony J, Vafaei A, et al. Seeking effective interventions to treat complex wounds: an overview of systematic reviews. BMC Med. Apr 22 2015;13:89. PMID 25899006
5. Voigt J, Wendelken M, Driver V, et al. Low-frequency ultrasound (20-40 kHz) as an adjunctive therapy for chronic wound healing: a systematic review of the literature and meta-analysis of eight randomized controlled trials. Int J Low Extrem Wounds. Dec 2011;10(4):190-199. PMID 22184750
6. Ennis WJ, Foremann P, Mozen N, et al. Ultrasound therapy for recalcitrant diabetic foot ulcers: results of a randomized, double-blind, controlled, multicenter study. Ostomy Wound Manage. Aug 2005;51(8):24-39. PMID 16234574
7. Peschen M, Weichenthal M, Schopf E, et al. Low-frequency ultrasound treatment of chronic venous leg ulcers in an outpatient therapy. Acta Derm Venereol. Jul 1997;77(4):311-314. PMID 9228227
8. Chang YR, Perry J, Cross K. Low-frequency ultrasound debridement in chronic wound healing: a systematic review of current evidence. Plast Surg (Oakv). Feb 2017;25(1):21-26. PMID 29026808
9. Kavros SJ, Miller JL, Hanna SW. Treatment of ischemic wounds with noncontact, low-frequency ultrasound: the Mayo clinic experience, 2004-2006. Adv Skin Wound Care. Apr 2007;20(4):221-226. PMID 17415030
10. Beheshti A, Shafigh Y, Parsa H, et al. Comparison of high-frequency and MIST ultrasound therapy for the healing of venous leg ulcers. Adv Clin Exp Med. Nov-Dec 2014;23(6):969-975. PMID 25618125
11. Olyaie M, Rad FS, Elahifar MA, et al. High-frequency and noncontact low-frequency ultrasound therapy for venous leg ulcer treatment: a randomized, controlled study. Ostomy Wound Manage. Aug 2013;59(8):14-20. PMID 23934374
12. White J, Ivins N, Wilkes A, et al. Non-contact low-frequency ultrasound therapy compared with UK standard of care for venous leg ulcers: a single-centre, assessor-blinded, randomised controlled trial. Int Wound J. Oct 2016;13(5):833-842. PMID 25619411
13. Gibbons GW, Orgill DP, Serena TE, et al. A prospective, randomized, controlled trial comparing the effects of noncontact, low-frequency ultrasound to standard care in healing venous leg ulcers. Ostomy Wound Manage. Jan 2015;61(1):16-29. PMID 25581604
14. Prather JL, Tummel EK, Patel AB, et al. Prospective randomized controlled trial comparing the effects of noncontact low-frequency ultrasound with standard care in healing split-thickness donor sites. J Am Coll Surg. Aug 2015;221(2):309-318. PMID 25868409
15. Gottrup F, Apelqvist J, Price P, et al. Outcomes in controlled and comparative studies on non-healing wounds: recommendations to improve the quality of evidence in wound management. J Wound Care. Jun 2010;19(6):237-268. PMID 20551864
16. Association for the Advancement of Wound Care (AAWC). Guideline of Pressure Ulcer Guidelines. 2010; https://s3.amazonaws.com/aawc-new/memberclicks/AAWCPressureUlcerGuidelineofGuidelinesAug11.pdf. Accessed November 1, 2019.
17. Association for the Advancement of Wound Care (AAWC). International Consolidated Venous Ulcer Guideline (ICVUG) 2015 (Update of AAWC Venous Ulcer Guideline, 2005 and 2010). 2015; https://aawconline.memberclicks.net/assets/appendix%20c%20guideline%20icvug-textformatrecommendations- final%20v42%20changessaved18aug17.pdf. Accessed November 2, 2019.
18. O'Donnell TF, Jr., Passman MA, Marston WA, et al. Management of venous leg ulcers: clinical practice guidelines of the Society for Vascular Surgery (R) and the American Venous Forum. J Vasc Surg. Aug 2014;60(2 Suppl):3s-59s. PMID 24974070
19. Hingorani A, LaMuraglia GM, Henke P, et al. The management of diabetic foot: A clinical practice guideline by the Society for Vascular Surgery in collaboration with the American Podiatric Medical Association and the Society for Vascular Medicine. J Vasc Surg. Feb 2016;63(2 Suppl):3s-21s. PMID 26804367

Coding Section 

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other nonaffiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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