Skin tightening devices have become some of the most popular cosmetic procedures patients are currently asking cosmetic dermatologists to perform in their offices. These devices have been developed to augment many of the other noninvasive cosmetic procedures we are performing on a regular basis in our office settings. They have introduced new terms into our laser vocabulary, which now has to be expanded into the new field of energy-based systems. These energy-based systems utilize terms such as monopolar, unipolar, bipolar radiofrequency (RF), and tripolar. The RF devices that have been developed for skin tightening, as well as several other devices that rely on the absorption spectrum of water in the infrared range of light, allow sufficient deep dermal heating to produce the desired effects. All the skin tightening devices on the market work via the same basic premise: deep dermal heating, which causes collagen denaturation, followed by collagen repair and ultimate deposition of new collagen and, ultimately, skin tightening. The major skin-tightening devices available on the market at the time of this writing are shown in Table 54.1.

RF energy produces a thermal effect when its high-frequency electrical current moves through the skin. The amount of heat generated in the tissue of the skin can be described by the mathematical formula known as Joule's law: H = j2/σ, where j is the density of the electrical current and σ is the specific electrical conductivity. The tissue impedance, or resistance, is inversely proportional to the electrical conductivity.