Integration of Thermal Imaging With Subsurface Radiofrequency Thermistor Heating for the Purpose of Skin Tightening and Contour Improvement: A Retrospective Review of Clinical Efficacy

December 2014 | Volume 13 | Issue 12 | Original Article | 1485 | Copyright © December 2014


Douglas J. Key MD

Key Laser Institute, the Center for Regenerative Cosmetic Medicine, Portland, OR

Abstract
INTRODUCTION: Radiofrequency has remained a staple procedure for the treatment of skin laxity as therapeutic heat thresholds effectively promote collagen remodeling. Nevertheless, comprehensive skin tightening involves both dermal and hypodermal collagen remodeling. However, transcutaneous radiofrequency is unable to deliver consistent and measurable temperatures to the hypodermal layers. Herein, we evaluated a newly emerging approach that provides precise and controlled subdermal heating is thermistor-controlled subdermal skin tightening (ThermiTight) using a percutaneous radiofrequency treatment probe.
METHODS: A retrospective analysis of 35 patients was completed on patients having undergone ThermiTight for submental skin tightening. Treated sites included under-chin and under-chin and jowls. The ThermiTight probe temperature was set between 50 to 60oC and was maintained using the thermistor integrated electrode. The probe was guided at a deliberate pace, treating a surface area of 3.0 cm2 every two minutes. The clinical endpoint was an epidermal temperature of 42oC. Two blinded reviewers assessed photographs taken at baseline and 30 days post-procedure. They were randomly presented with a photograph and asked to rate the photograph using a 4.0 skin laxity scale.
RESULTS: The combined mean change comparing baseline and post-procedure skin laxity scores was -0.78, which was statistically significant (Table 2; P<0.0001). Each blinded reviewer correctly categorized photographs as either being “baseline” or “post-procedure” 89% of the time. No adverse events were reported.
DISCUSSION: These data demonstrate the safety and efficacy of the ThermiTIght procedure for the treatment of skin laxity.

J Drugs Dermatol. 2014;13(12):1485-1489.

INTRODUCTION

A burgeoning non-invasive treatment for skin laxity is transcutaneous thermogenesis – achieved using ultrasound, radiofrequency, or light. These approaches use heat to promote neocollagenesis, denaturation of collagen cross-links, activation of wound healing pathways, contraction of collagen, and increase in collagen fibril size.1-3 However, for transcutaneous treatments, their effect is limited to dermal collagenous tissue.4 This is a critical limitation as the dermis and the deeper hypodermis combine to create an interwoven network of collagenous tissue that involves the papillary and reticular layers of the dermis, fibrous septum with fat, and the underlying structure of fascia layers.4,5 For example, the fibrous septum reinforces skin elasticity by anchoring the dermis to deep fascia.5 Dermal and subdermal tissues, together, contribute to the skin’s quality and durability. Accordingly, improvement in the overall quality of lax skin would require concurrent remodeling of both dermal and deeper hypodermal collagenous tissue.
Heat-induced collagen remodeling requires disruption of intraand inter-molecular forces, which occurs within a well-defined temperature range. Therefore, maintaining a temperature within this range requires accurate temperature monitoring and regulation. The inability to monitor subdermal temperatures represents another chief limitation of transcutaneous therapy. The only measureable temperature value is the epidermis. Accordingly, epidermal temperatures approaching the burn threshold generally designate the treatment endpoint. However, the temperature threshold for burns in the epidermis is lower than the temperature threshold required for collagen remodeling. Therefore, stopping treatment because epidermal temperature thresholds were reached may imprudently shorten the treatment and prevent subdermal temperatures from reaching therapeutic temperatures. Without a means to monitor or regulate subdermal temperatures during a transcutaneous treatment, there is much uncertainty concerning treatment optimization.
A newly emerging approach that provides precise and controlled subdermal heating is thermistor-controlled subdermal skin tightening (ThermiTight). This approach uses a percutaneous treatment probe to administer radiofrequency directly to dermal and subdermal tissue. Subdermal temperatures are
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