High-Intensity Focused Ultrasound Thermotherapy for Scar Treatment

SUMMARY

The formation of pathological scars is a common medical and aesthetic problem worldwide. Surgical interventions, burns and injuries are the most common cause. Treating these scars is a challenge for any surgeon. The Clinic of Plastic-Reconstructive and Aesthetic Surgery with Thermal Trauma and Imaging Diagnostics applied an innovative method of thermotherapy with high-intensity, focused ultrasound in 20 patients with hypertrophic scars and keloids of different age, etiology and parameters. After a series of procedures, we got excellent results, reducing scar size, pigmentation, pain and itching. This type of thermotherapy is successfully applied to pathological scars. In this way, a change in scar density is achieved by converting hard collagen into a gelatin-like mass.As a subsequent procedure, moderately compressive massages are applied for faster resorption of the pathological collection. Our results show that high-intensity focused ultrasound thermotherapy of pathological scars is a non-invasive method of treatment with reasonably good results as regards both aesthetic and functional aspects.

Introduction

Pathological scars and keloids can be formed as a result of burns, surgical interventions, injuries and other. Rough scars can cause both functional and psycho-emotional disorders. In an experimental study conducted in 2011, Brawer et al.¹ attempted to treat scars with high-intensity focused ultrasound (HIFU). Ultrasound waves penetrate to a specific tissue depth and generate a significant amount of heat energy. The effect of this procedure has both diagnostic and therapeutic purposes. For the first time in Bulgaria, our team treated hyperpigmented scars with whitening medications, applied intradermally in combination with HIFU - thermotherapy. This study aims to determine the effect of HIFU thermotherapy treatment on hypertrophic scars and keloids.

The procedures were performed on an outpatient basis. The initial photography and ultrasound measurements of the parameters of the scar were performed. We applied gel for ultrasound and anti cicatricial medications (urbazon, contractubex, scarex gel, dermatics, sodermix, dermacol whitening, cica-care) between therapies. Depending on the thickness of the scar, five types of transducers were used with different characteristics: from 1.5 mm to 13 mm for depth penetration, frequency 4MHz - 7MHz, wavelength 25 mm, and output power 0.2J-2.0JAC 110-240V.A temperature above 56°C was reached. 15-30 pulses were applied to each zone for one procedure. Every day the patient performed at-home massage procedures with moisturizing products in the area of the scar.

Material and methods

The study included 20 patients over eight months with pathological signs of various etiology, location and age. A multidisciplinary team of specialists selected the patients in the Plastic and Reconstructive and Aesthetic Surgery and Imaging Departments. Inclusion criteria were patients with mature hypertrophic scars and keloids. Exclusion criteria were severe acute and chronic diseases, pregnancy and mental illness. No intralesional preparations were used during treatment. To date, no patient has received such treatments.

According to a protocol prepared by us, patients were divided by age, sex, type and size of the scar, the number of procedures performed, and the effect of the applied therapy (Table I). The interval between two procedures was on average 50 days. All patients filled in informed consent for the performed procedure.

Table I.

Patient distribution on sex, age, type of scars and number of procedures

Sex	Hypertrophic scars	Keloids	Two procedures	Three procedures	Four procedures
Male	4	1	3	1	1
Female	24	3	20	4	3
Boys	5	1	5	1	0
Girls	13	2	13	1	1

Results

As a result of the treatment, all patients showed a decrease in the volume of pathological tissue, a decrease in scar density, and a reorientation of the collagen fibers. The difference in normal skin and scar tissue is demonstrated in Figs. 1 and 2.

Fig. 1.

Normal skin with epidermis - 0.3 mm, dermis - 0.6 mm, subdermal layer - 0.9 mm

Fig. 2.

Pathological scar with epidermis - 0.8 mm, dermis - 6.80 mm, subdermal layer - 1.7 mm

Patients reported a significant reduction in itching and pain, as well as the lightening of pigment spots. Ultrasound images of before and after the procedure are demonstrated in Fig. 3. We did not observe any side effects related to the HIFU procedure.

Fig. 3.

Change in the parameters of the skin layers before (A) and after (B) thermotherapy with HIFU

The significant difference in the thickness of the skin layers in normal and pathological skin, mainly at the expense of the dermal layer, is impressive. This is where the focal point of thermotherapy is fixed. Pathological tissue is demonstrated in Fig. 4.

Fig. 4.

Histological changes from hypertrophic scars (A) and keloids (B)

We found a significant difference in the thickness of the skin layers before and after thermotherapy, reducing the dermal layer after each subsequent procedure. We present several clinical cases with a different number of HIFU applications in combination with and without other non-invasive scar management modalities. There is a significant reduction in the scar area, thickness, and hyperemia (Figs. 5, 6, 7 and 8).

Fig. 5.

Thermotherapy with HIFU before (A) and after 3 procedures (B) of hypertrophic scars

Fig. 6.

Thermotherapy with HIFU on the thigh and back before (A,B) and after 4 procedures (C,D) of hypertrophic scars

Fig. 7.

Thermotherapy with HIFU in combination with anti-scarring and whitening agents before (A) and after 4 procedures (B) of hypertrophic scars

Fig. 8.

The evolution of keloids of the thorax after 4 thermotherapy procedures (A,B,C,D) with HIFU and cica-care silicon sheet

Discussion

The functions of the skin are numerous. It participates in thermoregulation, maintaining water-electrolyte balance, and protecting the body from physical, chemical and biological agents.

In the case of violation of the skin and subsequent recovery, a process of scarring is observed. With normal tissue healing, a normotrophic scar is formed, equal to the surrounding skin and of the same color. In the case of imbalance in the phases of tissue healing, pathological scars are formed. They are hypo- and hypertrophic scars and keloids. Pathological scarring is due to disturbances in microcirculation during scar formation. Hypoxia stimulates collagen formation.² Hypertrophic scars are located above the surrounding healthy skin, but only within the primary scar. They have a dense-elastic consistency and are often hyperemic. Keloids are also located above the surrounding healthy skin but extend beyond the original scar. In most cases, they have cartilage density and cause pain, itching and discomfort. The most common locations for keloids are the earlobes, anterior chest wall, shoulders, and upper back. They are not known to spontaneously regress and have high recurrence rates with most therapies. A complete resolution of a keloid scar is rare.³

In contrast to keloid scars, hypertrophic scars do not extend beyond the original cutaneous injury’s boundaries. They tend to be raised above the surrounding cutaneous topography and firm in consistency.

The chaotic position of the collagen fibers in the dermis makes scar tissue dense and irregular in shape. Those changes result in compression of both the epidermis and the underlying subdermal layer. After thermotherapy, the expressed compression is reduced. Respectively the ischemia in the epidermis is reduced, and as a consequence, it restores its normal thickness.⁴ In addition to reducing the physical parameters of the scar, thermotherapy achieves the arrangement of collagen fibers in the mesoderm. In combination with depigmenting products, both the existing melanin in the defect is reduced, and the production of the new one is activated.⁵

The treatment of scars begins with actions that prevent their pathological growth. These are daily hydration, anti cicatrizants, and protection from direct sunlight. Extensive scars require mechanical compression of the scar with elastic compressive bandages and clothing for at least two months.⁶ The maturation of the scar lasts about 1-2 years, after which the reverse development of hypertrophic scars begins. Keloids are not reversible.⁷

In the presence of a functional deficit in the volume of a joint movement, microstomy, ectropion, even immature scars are surgically treated.⁸ The treatment should begin during the maturation of scars and keloids.⁹ When there are no functional disorders of the body, conservative treatment is applied. In addition to moisturizing and healing preparations and elastic compression, heat and light therapy can be applied. These physical agents also influence the processes of scar formation.

The mechanism of action of HIFU is focusing of the sound waves. A concentrated beam of ultrasound is directed to a specific focal point. Upon reaching the focal zone, the energy density increases significantly. Depending on the strength and duration of treatment, local temperature rise can lead to complete coagulation necrosis and cell death.¹⁰

High-intensity ultrasound usually refers to ultrasound with an intensity greater than 5 W/cm2, causing coagulation necrosis of tissues, and is most commonly used for HIFU ablation. In contrast, low-intensity ultrasound of 0.125–3 W/cm2 results in non-necrotic treatment and is in the range used for physiotherapy.¹¹ HIFU has been studied for its therapeutic use in the selective destruction of deep-seated tissues without damaging proper layers and anatomical structures.

Coagulation necrosis usually occurs at 56°C with a duration of exposure of 1 second. Hyperthermic temperatures of approximately 40 to 45°C for 1 hour may make the tissue more susceptible to drug treatment.¹² In this way, preparations that suppress scarring are impregnated. If a pathological scar is already present, its reverse development is affected.¹³

Many HIFU applications are found today. As a safe and non-invasive therapeutic method, its use in treating solid tumors, acne treatment, and in aesthetic dermatology improves skin properties.¹⁴ Elevated subdermal temperature leads to tissue hyperemia, good oxygenation, with subsequent production of collagen and elastin.¹⁵ In-depth, heat on surface fat deposits leads to a reduction in the volume of fat cells. In this way, non-invasive contouring of the body can be achieved.¹⁶ High-intensity focused ultrasound was a commercial success in the beauty industry, where various low-cost body contouring devices appeared. In these treatments, operating at 3-10 MHz, the focal points of HIFU are usually located in the subcutaneous adipose tissue, and the treatment aims at thermal lipolysis and reduction of fat in the treated field, improving the contour of the body.¹⁷ Gadsten describes HIFU treatment in a patient before abdominoplasty. The histopathology reports disruption of adipocytes within the targeted superficial adipocyte layer.¹⁸

HIFU may represent a safe means for performing noninvasive body sculpting,¹⁹ though its clinical efficacy and significance of body sculpturing that may be achieved remains highly debatable.²⁰

Conclusion

Thermotherapy of pathological scars with HIFU gives reasonably good functional and aesthetic results. It reduces the volume of scars, contributes to their softening, and reduces the feeling of itching in the treated patients.