10.1 Radiofrequency Technology

Liposuction has increasingly become the most sought after body contouring procedure internationally. However, the goal of achieving concomitant skin tightening in liposuction has been elusive at best. The need for a device that can accomplish tissue heating in a safe and reproducible way leading to skin contraction without lengthy incisions can have immeasurable benefits to patients. The use of RF was initially reported in the literature as a noninvasive device. It has led to the use of RF as an energy-based platform for body contouring with FDA approval in 2016.

The elusive goal of achieving skin tightening in liposuction has been attempted with laser assisted liposuction (LAL). ¹ Paul et al introduced RFAL technology in 2009 and showed linear contraction at 12 months of up to 47%. ^{2 , 3} Unlike laser liposuction the focus of the energy is not directed at the dermis per say but at a deeper level. The ability to heat and treat large volumes of tissue, due to RF’s ability to be utilized in the subcutaneous and deep adipose tissue without compromising skin safety, has been the mainstay of RFAL technology. This process of thermal enhanced remodeling of the soft tissue leading to skin tightening has led to the use of RFAL in patients who would otherwise be marginal or poor candidates for traditional liposuction techniques.

10.2 RFAL: Mechanism of Action

RF thermal-induced contraction has been described in medicine in various applications such as vein ablation, orthopedics, and ophthalmology.

Contraction of the collagen fibers occurs at different temperatures depending on the type of collagen. The optimal temperature for collagen contracture has been reported to be 60–80°C. ⁴ This contraction does not necessarily cause connective tissue damage but instead induces a restructuring effect of the collagen fiber framework. Once the tissue reaches the threshold temperature it immediately undergoes contraction in a dramatic fashion. This effect has been described in studies of the cornea, cartilage, and vascular tissue in the past. RF energy is applied internally directly to the deep adipose and subcutaneous tissue with lower heat levels applied to the dermis. This results in tissue contraction that occurs mainly due to the contribution of deeper adipo-fascial layers. Specifically, heating of the Fibro-Septal Network (FSN) leads to dermal contraction (▶Fig. 10.1).

The target temperature at which soft tissue matrix contracture optimally occurs is 38–42°C. ⁵ The internal measured temperature can range from 55–70°C however this is only relevant as it relates to the external temperature reading. In other words, the endpoint of 38–42°C measured externally should be reached in order to achieve the desired result of dermal tightening.

10.3 RF Device

The RFAL device Bodytite (Inmode, Ltd, Toronto, Canada) consists of a handpiece with two electrodes attached to an RF power source (▶Fig. 10.2). The internal electrode is coated with a Teflon tip in order to avoid end hit injuries. It has a conductive tip that emits RF energy that flows between the internal electrode and the external electrode which in turn overlies the surface of the skin. An energy field is thus created between the two electrodes that translates into a thermal effect on the interposed tissues. Once the area to be treated is tumesced the internal probe is inserted and is passed back and forth in smooth liposuction-like strokes. At the same time the external probe glides in tandem along the surface of the skin. The skin has been prepped with sterile ultrasound gel in order to minimize interference and facilitate movement of the external electrode.

The subcutaneous tissue between the two probes is heated accordingly. The treated tissue tends to be hotter at the tip of the probe and recedes in temperature as it approaches the handle.

The depth of the internal probe is controlled by a wheel on the device that increases or decreases the distance between the two electrodes giving it a caliper-like appearance. The larger the distance between the two electrodes the larger amount of tissue is “sandwiched” between them resulting in a larger area heated.

The process of heating the tissues begins deep just like in liposuction. The difference being though, that instead of “debulking” the operator is heating. The movement of the probe is identical to the stroke of a liposuction cannula. In other words, deliberate and methodical with care not to spend too much time in one area. As heating progresses and the operator begins to treat the more superficial tissue he or she will be adjusting the wheel to close the distance between the two probes. As the surgeon approaches the dermis the distance between the electrodes is shortened even more in order to address the more superficial layers of the treated area. At no point does the internal probe come into contact with the under surface of the dermis or the subdermal plexus of nerves and vessels.

In conclusion the RF handpiece coagulates the adipose and connective tissue as well as the deep vasculature via the internal probe. The heating of the dermis occurs internally just below the external probe. The heating of the treated tissue block is homogenous and uniform (▶Fig. 10.3). Once the target temperature of 38–42°C is achieved the operator maintains the heat in that area for 1–3 min for optimal results.

The operator can then switch to a standard suction-assisted lipectomy (SAL) or power-assisted liposuction device (MicroAire, Charlottesville, VA, USA) to address the contouring aspect of the operation and bring the case to conclusion.