Chronic venous leg ulcers (VLUs) impact negatively on patients' quality of life. Standard treatment in the UK for patients with VLUs is compression bandaging or stockings. The MIST ultrasound system is a noncontact device which delivers low frequency ultrasound through a gentle saline mist directed at a patient's wound. This study aims to determine whether the use of the MIST device used in combination with standard treatments can improve healing of VLUs compared to UK standard practice. This will be assessed by measuring any reduction in wound size in the two groups after receiving 8 weeks of either Standard Care once a week or MIST combined with Standard Care three times a week.

Venous leg ulcers (VLUs) are wounds which are often chronic and difficult to heal. VLUs affect between 1 and 3.2 people per 1000; they cause pain, reduced mobility and impact negatively on patients' quality of life (QoL). Standard treatment for patients with VLUs is the application of strong, sustained compression with bandages or stockings. This pragmatically-designed study aims to determine whether the use of a device called MIST used in combination with standard treatments can improve healing of VLUs compared to UK standard practice. It will also show whether the MIST regimen improves participants' QoL and reduces the incidence of infection.

The MIST ultrasound system is a non-contact device which delivers low-frequency ultrasound through a gentle saline mist directed at a patient's wound. Patients (over 18 years old) will be invited to take part in this study if they have had a VLU for 6 weeks or more, which measures between 5 and 100 cm^2, and is not infected. Participants with diabetes must show good blood glucose control, and those with underlying chronic disorders which may affect wound healing will be excluded.

All study participants will receive four weeks of standard treatment once a week at a single clinic at the Wound Healing Research Unit (WHRU), University Hospital of Wales. Patients whose wounds reduce by more than 40% during this time will be withdrawn from the study. Remaining patients will be randomly allocated to either the active group or the control group to receive a further eight weeks of treatment. Participants in the active group will receive treatment with the MIST device three times a week, as well as standard care (change of compression bandage and dressings) three times a week. The control group will receive UK standard care (which is dressing and compression bandage change at least once a week). The participants' ulcers will be measured and photographed once a week, and the wound characteristics will be assessed. Changes in participants' health related QoL will be assessed using a questionnaire at the beginning and end of the trial. Wound recurrence rates 90 days after the end of the treatment will be assessed by telephoning patients.

Inclusion Criteria:

• Venous leg ulcers (as diagnosed by the clinician)
• Ankle Brachial Pressure Index (ABPI) >0.8
• If multiple ulcers are present treat largest ulcer only (index ulcer) with minimum distance of 1 cm between index ulcer and any other ulcer
• 18 years or older
• Ulcer size of 5 cm^2 - 100 cm^2 (with no longest length being greater than 10 cm) at randomisation point (week 5)
• Mobile enough to attend clinic
• Index ulcer between 6 weeks and 5 years duration prior to screening date

Exclusion Criteria:

• Uncontrolled diabetes (Hba1c ≥12%) as tested within the past 3 months
• Index ulcer has active infection on day of inclusion requiring use or oral or IV antibiotics
• Renal failure
• Index ulcer has exposed tendons, ligaments, muscle, or bone
• Osteomyelitis or cellulitis or gangrene in study limb
• Subjects with amputation above a trans metatarsal amputation (TMA) in the study limb
• Subjects with active malignancy on the study limb
• Index ulcer that is of arterial disease aetiology
• Females of child bearing potential who are not willing to use a method of highly effective contraception during the entire study
• Planned vascular surgery, angioplasty, or thrombolysis procedures within the study period, or 6 weeks post-operatively
• Planned surgical procedure during the study period for the index wound
• Prior skin replacement, negative pressure therapy, ultrasound therapy applied to the index wound 2 weeks before screening
• Oral or IV antibiotics within 48 hours of baseline measurements
• Growth factor therapy within previous 14 days of screening date
• Currently receiving or has received radiation or chemotherapy within 3 months of randomisation
• Pregnant or breast feeding women
• Subject is currently enrolled or has been enrolled in the last 30 days in another investigational device or drug trial
• Subject's wound would require ultrasound near an electronic implant or prosthesis
• Subjects lacking capacity to provide informed consent.

Study period of 13 weeks

Any undesirable clinical occurrence in a subject whether it is thought to be related to the NLFU or not. All subjects experiencing AEs were monitored until symptoms subside or until there is a satisfactory explanation for the changes observed. The nature of venous leg ulcers meant that AEs were common in both the SOC and NLFU groups

Difference in treatment frequency between the groups which could potentially bias results.

Standard deviation proved to be larger than estimated from the available literature which resulted in the study having reduced statistical power.