Radiofrequency Treatment: Skin Tightening

Introduction

Skin laxity may result from chronological aging, photoaging, and changes in body dimensions during pregnancy or weight loss. Over the past decade, there has been increasing demand for safe and effective ways to decrease redundant or lax skin and smooth irregular body contours. Patients desire procedures with reduced recovery time, reduced risk and adequate clinical improvement. This has led to exponential growth in noninvasive body contouring and minimally invasive, nonablative tissue-tightening techniques, including laser, radiofrequency and ultrasound-based devices. The goal of this chapter is to review the use of radiofrequency devices in skin tightening specifically on the body.

Proposed mechanism(s) of action

Radiofrequency energy was the first modality specifically marketed for noninvasive skin tightening. Radiofrequency devices work by producing an alternating current that creates an electric field throughout the skin. The electric field shifts polarity millions of times per second, causing a change in the orientation of charged particles within the electric field. Heat is generated via tissue resistance to the movement of oscillating electrons within the radiofrequency field as governed by Ohm's law:

The process does not follow the principles of selective photothermolysis as heat is generated by the skin's resistance to the flow of current within an electric field, rather than chromophore-based photon absorption as with a laser. This makes radiofrequency technologies well suited for deep dermal heating as opposed to light-based technologies which have a suboptimal depth potential due to energy being scattered or absorbed in the upper layers of the skin. The depth of energy delivered by a radiofrequency device depends on several factors, including the arrangement of radiofrequency electrodes (monopolar or bipolar), the type of tissue serving as the conduction medium (fat, skin), temperature, and the frequency of the electrical current applied.

Radiofrequency energy is thought to induce skin tightening of the body by several mechanisms. The first is the immediate contraction of collagen fibers and fibrous septa in the subcutaneous fat due to direct thermal heating. Studies on samples of human abdominal skin have shown that when collagen fibers are heated to specific temperatures with radiofrequency energy, they contract due to breakage of intramolecular hydrogen bonds linking protein chains in the triple helix structure (denaturation). Contraction causes the helix to fold, leading to shorter, thicker, more ‘compact’ collagen fibers. Secondary wound healing also plays a role in tissue tightening with delayed remodeling and neocollagenesis over time ( Fig. 3.1 ). It has been postulated that thermal heating by radiofrequency energy results in a microinflammatory stimulation of fibroblasts which induces new collagen and elastin as well as encouraging collagen reorganization into parallel arrays of compact fibrils. Thus, radiofrequency effects are based on mild heating of the collagen and elastin fibers which can lead to collagen shrinkage and dermal thickening with a resulting improvement in firmness and elasticity of the skin. The degree of tissue tightening is dependent upon several factors, including the maximum temperature reached, the heat exposure time, tissue hydration, and tissue age.