Radiofrequency has been used in medicine for over 50 years and in aesthetics since the early 2000’s. It’s indications are for improving skin tone, laxity, and the appearance of scars, particularly acne scars. Unlike lasers, the energy delivered to the skin or deeper structures is not chromophore dependent and is reliant on the flow of energy between electrodes. While promoted as being safe for “all skin types”, darker skin types are more susceptible to complications, primarily PIH. The various complications associated with RF treatments will be discussed and precautionary measures needed to prevent them. Treatments for the complications are included as well.
12 Radiofrequency and Microneedle Radiofrequency
Radiofrequency (RF) use in minimally invasive facial rejuvenation dates to the first FDA-approved device for periorbital wrinkles in 2002. The indications were expanded to face and body in 2004 and 2006, respectively. Since then, there have been dozens of RF devices approved with various forms of delivery systems which have been proven to improve skin laxity/quality/tone, wrinkles, acne scars, acne, hyperhidrosis, pore size, and striae.
12.2 Science of RF
RF creates oscillating electrical current (millions of cycles per second), causing vibration and collisions between charged molecules, thus resulting in production of heat as described by Belenky et al. 1 Electrical energy is converted to thermal energy as resistance in the tissue is met. 2 Energy transfer is dictated by Ohm law: Energy (J) = I 2 × R × T (where I = current, R = tissue impedance and T = time of application). Impendence is dependent on skin hydration, electrolyte composition, collagen content, temperature and other variables. 3 Unlike lasers which use a photothermal energy (selective photothermolysis), RF energy is independent of pigmentation/skin type, and is strictly an electrothermal effect. The RF devices used in aesthetic procedures range from 0.3 to 10 MHz. Depth of penetration is inversely proportional to frequency used. 4
The heat generated by RF leads to immediate collagen contraction as the heat liable bonds within the triple helical collagen strands are broken. Temperatures below 65 °C lead to various degrees of collagen denaturing which is followed by an inflammatory cascade which includes heat shock proteins and new collagen formation. If temperatures exceed 65 °C, coagulation of the dermal tissues is possible and what follows is a more robust response leading to replacement of the RF thermal zone (RTZ) with collagen, elastin, hyaluronic acid, and other extracellular matrix.
RF is not dependent on a chromophore as lasers are, so theoretically, RF is “safe for all skin types.” Where lasers have difficulty when there are competing pigmentary targets in darker skin types, RF can transmit its energy to the dermal tissues based solely on the impedance (not skin type), current, and time variables as per Ohm law. However, darker skin types will be more susceptible to complications from RF such as postinflammatory hyperpigmentation (PIH).
12.4 Methods of RF Delivery
There are two methods of delivering RF energy through the skin—monopolar and bipolar.
Monopolar RF: The energy flows from an active electrode within the operator’s handpiece to a grounding pad (passive electrode) placed distally on the patient’s body. Early RF devices used monopolar RF, and it is still a popular technology in current devices. Its advantage is energy can be deposited rather deeply from a surface electrode—deep dermis and fibroseptal network.
Bipolar RF: The energy flows between two adjacent electrodes, all contained within the operator’s handpiece. The depth of penetration (for the transepidermal devices) is postulated to approximate ½ the distance between the electrodes although this is not universally accepted. Higher energies can be delivered with bipolar than monopolar, but the depths are less (Table 12.1).
12.5 Safety Measures
The threshold for epidermal burn is 44 to 45 °C and it is also time dependent. The conundrum is that optimal collagen stimulation with the dermis is at temperatures of 65 to 70 °C. 5 Impendence of the epidermis and subcutaneous fat is intrinsically higher than the dermis, so the energy naturally travels to the area of least resistance. However, extraordinary measures are needed to protect the epidermis from heating. These include:
Cooling—most common method utilized (cryogen, cooling footplate, air chiller).
Motion—by moving heat source, you can create a field effect and less likely to have hot spots.
Temperature/Impedance feedback—limits/controls RF delivered when critical limits are reached to give safer pulses.
Infrared (IR) camera—monitors skin temperature.
Topicals—steroids, growth factors, platelet rich plasma (PRP), antibiotics, occlusive serums can expedite healing and reduce downtime.
Low-level laser therapy (LLLT)—proven to improve downtime—swelling, erythema, and probably reduces burn risk.
Insulatedneedles (RF microneedling)—helps protect epidermis from heating.
Settings—giving lower energies with more passes gave similar results with less risks and discomfort. Also, in darker skin types, less energy is recommended to avoid PIH risks.
12.6 Patient Selection
Preprocedure counseling is key for patient satisfaction, particularly important when online reviews are so ubiquitous. The definition of downtime varies among patients, and it’s imperative to explain that there will be swelling, and erythema (bruising in invasive RF) in almost all RF cases. In addition, optimal results can take a series of treatments and take up to 3 months to see the final result. Complete understanding of expected outcomes with the possibility of minimal or no result must be explained. The provider mustn’t overly promote a particular RF technology without also mentioning alternatives such as lasers, peels, and surgery. RF skin tightening has its limitations and a surgical candidate will most likely not appreciate the changes RF has to offer. The best patients are using RF as a preventative measure (“prejuvenation”) or those that aren’t quite ready for surgery and desire a mild tightening.
RF outcomes are the direct result of how one’s body reacts to the heat generated from the treatment. This requires an immune response for healing and production of collagen and elastin. Patients with the following conditions should be treated with caution:
Impaired immune function.
Extreme solar damaged skin.
Areas of prior radiation therapy.
Negative metabolic state.
The complications of RF are generally rare and have been reported to be 2.7% in one large study of a monopolar device. 6
12.7.1 Prolonged Swelling, Erythema, Discomfort
Swelling, erythema, and discomfort can be considered universal to most RF procedures. Depending on the technology used, this can last from a day to up to 7 days or longer. Patients have different perceptions of downtime and tolerances to these side effects. If patients are counseled upfront, usually they will understand postprocedure. To expedite swelling resolution, sleeping upright for at least 2 days is helpful. LLLT has been shown to expedite the healing process and has no negative side effects. 7 Erythema can be improved with topicals (calming gels or steroids). If prolonged, a vascular laser can expedite resolution. It is imperative to quell any prolonged skin inflammation in a darker skin individual to minimize the PIH risk and aggressive measures including steroids, and/or Nd:YAG laser might be required. Discomfort needs to be assessed for other complications such as infection but can usually be controlled with acetaminophen. The inflammatory response is required for RF results so refrain from NSAIDs and minimize steroid use if possible.