Radiofrequency Delivery: Monopolar, Bipolar RF Delivery, and Combination Systems
There are 2 major electrode configurations available in current RF devices: monopolar and bipolar. Monopolar devices deliver current using one active electrode that transmits the electromagnetic current toward a grounding pad. In some cases, a cooling spray is used to protect the epidermis from the volumetric dermal heating. The energy can be delivered by conductive or capacitative coupling. Conductive coupling is based on energy concentrated at the distal portion of the electrode being delivered to the target tissue. This leads to heat production at the skin surface in contact with the electrode, which can produce epidermal injury. Capacitive coupling disperses energy across a surface to create a uniform zone of heat.
Monopolar RF energy has been successfully used to accomplish noninvasive skin tightening of the face, periorbita, abdomen, and extremities. The first monopolar RF device was the ThermaCool device (Thermage, Inc.), which was introduced in 2001 and approved by FDA for the noninvasive treatment of periorbital rhytids and wrinkles in 2002, for full face treatment in 2004, and for body contouring in 2006.[25,26] Among the largest studies of monopolar RF in aesthetic applications was by Bassichis et al, who conducted a blinded, multicenter trial where 86 patients received a single treatment in lateral canthal and forehead areas. A total of 83% of patients had improvement by at least one point on the Fitzpatrick Wrinkle Classification System, and 50% were satisfied with the improvement in periorbital wrinkling. Eyebrow lift of ≥0.5 mm was noted in approximately 62% of patients. Overall complication rates were low, with an incidence of 0.36% secondary burns. This is consistent with the study by Bassichis et al who also evaluated ThermaCool for rejuvenation of the upper third of the face by assessing changes in brow position. They found that treatment led to statistically significant brow elevation of 0.5 mm in 87.5% of patients. Despite this, 64% of patients did not perceive a cosmetic benefit and no complications were recorded. Nahm et al also studied the use of monopolar RF for brow elevation in 10 patients. This study treated one side of the face with a single pass using the ThermaCool device. By 3 months posttreatment, there was a statistically significant average elevation of 4.3 mm of the mid-brow and 2.4 mm of the lateral brow with a 1.9 mm increase at the level of the palpebral crease. Jacobson et al treated 24 patients with the ThermaCool device for lower face and neck laxity. They showed notable improvement of neck, nasolabial folds, marionette lines, and jawline up to 3 months following treatment. Alster and Tanzi showed similar findings, with improvement in moderate cheek laxity and nasolabial folds. El-Domyati et al used a different monopolar RF device (Biorad, Guangdong, China) to treat patients for 3 months at 2-week intervals. All 6 patient had notable improvements in skin tightening of the periorbital and forehead regions that continued 3 months after treatment. Skin tightening improved from 35% to 40% at the end of treatment to 70% to 75% at 3 months following treatment. Javate et al and Taub et al independently evaluated a 4-MHz monopolar system (Pelleve; Ellman International, Inc., Oceanside, N.Y.), showing favorable results. Javate et al evaluated patients 1, 3, and 6 months after treatment, and statistically significant changes were noted clinically and according to electron microscopy evaluation. Similarly, Taub et al used the device to reach a target surface temperature of 40°C–42°C, noting an overall 25%–30% improvement 2 weeks after the first treatment, with an average improvement of 46% 6 months after final treatment.
Monopolar devices typically have mild and self-limited adverse effects mainly limited to transient erythema and edema. Weiss et al published a thorough review of adverse effects following ThermaCool consistent with mild side effects. There were rare cases of superficial crusting, slight contour deformities, subcutaneous erythematous papules, and neck tenderness. The overall rate of adverse side effects was 2.7%, but none of these side effects were experienced when using a lower energy multiple-pass treatment algorithm.
Bipolar devices differ from monopolar because they pass electrical current only between 2 positioned electrodes. The tissue to be heated and tightened is between these 2 electrodes, and the depth of penetration is approximately half the distance between the electrodes. Thus, bipolar radiofrequency devices offer a shallower depth of penetration when compared with monopolar. However, this configuration does provide more controlled or localized distribution of energy and less discomfort. No grounding pad is necessary with these systems because current does not flow through the rest of the body. Although this heat is targeted between the 2 electrodes, monopolar devices are believed to lead to a more uniform volumetric heating. Theodorou et al reported outcomes on 40 patients undergoing bipolar RF-assisted liposuction (Bodytite; InMode, Lake Forest, Calif.) without any major complications and 2 minor complications, including a superficial burn and a seroma that resolved with aspiration. Patient satisfaction was high at 6 months, with >90% of patients satisfied to extremely satisfied. Three independent plastic surgeons evaluated pre- and postoperative photographs and indicated that the improvement in arm contouring was good to excellent 80% of the time. Dayan et al reported similar findings with bipolar radiofrequency (InMode, Lake Forest, Calif.) in a variety of body areas, including arms, supraumbilical regions, thighs, and axillary rolls (Figures 1, 2). The clinical skin contraction obtained was reported at 40% improved. Minor complications included erythema, prolonged swelling past 2 months, and subdermal banding. Dayan et al further published the largest study to date using a combination bipolar radiofrequency protocol (Morpheus8 and Facetite; InMode, Lake Forest, Calif.). In 247 patients with lower face and neck laxity, the pretest mean Baker Face Neck Score was 2.66 (SD, 0.72) and the posttest mean value was 1.86 (SD, 0.64). This mean difference (μ = 0.81; SD, 0.46) was statistically significant [t(237) = 27.34; P < 0.001], and the effect size was large (D = 1.76).
Photographs showing pre- (A) and post-radiofrequency–assisted liposuction (B) of the arms.
Plast Reconstr Surg Glob Open. 2020;8(8):e2861 © 2020 Lippincott Williams & Wilkins