INTRODUCTION
As the facial aging process includes changes in skin, bone structure, fat and muscle,1 a wide range of fillers, toxins and energy-based technologies have been developed to combat the aging process and achieve a more natural, youthful appearance. Among energy-based technologies, microfocused ultrasound with visualization (MFU-V) has become a key foundation for aesthetic treatment and the gold standard for nonsurgical lifting and skin tightening in aesthetic medicine (Ultherapy® System + DeepSEE®; Merz North America, Inc., Raleigh, NC).2-6 Several available MFU transducers permit the delivery of ultrasound energy to depths of 1.5 to 4.5 mm where subcutaneous tissue heating occurs to ~65°C7,8 creating small (<1 mm3) thermal lesions or coagulation zones form within the dermal and subdermal layers of the skin. The heated collagen immediately contracts,8 followed by neocollagenesis and collagen remodeling to tightening and lift lax skin.9,10 The use of ultrasound imaging prior to treatment ensures the device is properly coupled to the skin for safe energy delivery and avoids non-target tissues. The efficacy,11,12 safety13,14 and patient satisfaction15,16 associated with the MFU-V procedure have been well-documented.
Another aesthetic technique which has not been addressed in recent MFU-V treatment guidelines is its combined use with suspension threads. This procedure involves the use of absorbable and nonabsorbable sutures which are anchored in the dermis, subcutis, and superficial musculoaponeurotic system areas to lift lax skin.17-19 As MFU-V is designed to penetrate tissue to a depth of 4.5 mm, and subcutaneous tissue may thin with age,20 clinicians have anecdotally expressed concerned about the safety of combining the use of suspension threads with MFU-V for fear of changing the structure and integrity of suspension threads or stimulating an inflammatory response and foreign body reaction. Therefore, the object of this research was to assess the safety and clinical effectiveness of combining MFU-V and suspension threads for treating lax skin on the face and neck.
Another aesthetic technique which has not been addressed in recent MFU-V treatment guidelines is its combined use with suspension threads. This procedure involves the use of absorbable and nonabsorbable sutures which are anchored in the dermis, subcutis, and superficial musculoaponeurotic system areas to lift lax skin.17-19 As MFU-V is designed to penetrate tissue to a depth of 4.5 mm, and subcutaneous tissue may thin with age,20 clinicians have anecdotally expressed concerned about the safety of combining the use of suspension threads with MFU-V for fear of changing the structure and integrity of suspension threads or stimulating an inflammatory response and foreign body reaction. Therefore, the object of this research was to assess the safety and clinical effectiveness of combining MFU-V and suspension threads for treating lax skin on the face and neck.
METHODS
Ex Vivo Animal Study
Initially, the effect of MFU-V on suspension threads was assessed using an ex vivo animal model. Using 5 cm x 10 cm sections of fresh pig skin, threads made of poly-L-lactic acid (absorbable), polyethylene (nonabsorbable), and polyamide thread (nonabsorbable) were passed through the skin parallel to the dermis at depths of 1 to 5 mm. Each section of skin was immediately treated with 60 lines with each of three MFU-V transducers (4 MHz/4.5 mm, 7 MHz/3.0 mm and 10 MHz/1.5 mm). Transverse biopsies were obtained across the inserted threads and treated with hematoxylin and eosin (H&E) stain and examined by a pathologist.
In Vitro Heat Testing
A hot water bath was used to assess the behavior of suspension threads at different temperatures. Poly-L-lactic acid, polyethylene, and polyamide suspension threads was submerged at temperatures of 45ºC (113ºF), 65ºC (149ºF) and 100ºC (212ºF) for periods of 1, 2, and 3 minutes and then examined microscopidoi:
Initially, the effect of MFU-V on suspension threads was assessed using an ex vivo animal model. Using 5 cm x 10 cm sections of fresh pig skin, threads made of poly-L-lactic acid (absorbable), polyethylene (nonabsorbable), and polyamide thread (nonabsorbable) were passed through the skin parallel to the dermis at depths of 1 to 5 mm. Each section of skin was immediately treated with 60 lines with each of three MFU-V transducers (4 MHz/4.5 mm, 7 MHz/3.0 mm and 10 MHz/1.5 mm). Transverse biopsies were obtained across the inserted threads and treated with hematoxylin and eosin (H&E) stain and examined by a pathologist.
In Vitro Heat Testing
A hot water bath was used to assess the behavior of suspension threads at different temperatures. Poly-L-lactic acid, polyethylene, and polyamide suspension threads was submerged at temperatures of 45ºC (113ºF), 65ºC (149ºF) and 100ºC (212ºF) for periods of 1, 2, and 3 minutes and then examined microscopidoi:
