Novel Minimally Invasive Fractional / Microneedle Radiofrequency Device and Applications in Cosmetic Dermatology

Introduction:
The field of cosmetic dermatology in the treatment of tissue tightening and scar remodelling has developed very rapidly over the past several years, with many new devices appearing on the market that utilize radiofrequency (RF) energy to effectively tighten and rejuvenate the skin.^{( 1,2} What originally began with a single monopolar RF device has progressed into a world in which there are skin-tightening devices that utilize, besides monopolar RF energy, bipolar energy and tripolar energy, and newer machines that boast five and eight poles of RF energy.

Microneedle / Fractional RF is a newer technology used for skin rejuvenation, tightening, body sculpting, and scar remodeling. These technologies provide an alternative to ablative lasers, and are said to reduce the incidence of side effects and increase patient compliance. Microneedle / Fractional RF induce dermal neocollagenesis causing minimal or no epidermal disruption, thereby limiting adverse effects and very minimal down-time of few hours to 2-3 days

Mechanism of action of Radiofrequency based devices
RF energy is produced by an electric current rather than by a light source. Radiofrequency energy is conducted electrically to tissue, and heat is produced when the tissue's inherent resistance (impedance) converts the electrical current to thermal energy. This reaction is dictated by the following formula: energy (J) = I 2 x R x T (where I = current, R = tissue impedance, and T = time of application). ³ High-impedance tissues, such as subcutaneous fat, generate greater heat and account for the deeper thermal effects of RF devices.
Radiofrequency energy can be transferred from an electric field to charged particles in the target tissue via 3 mechanisms: the orientation of electric dipoles that already exist in the atoms and molecules in the tissue, polarization of atoms and molecules to produce dipole moments, or displacement of conduction electrons and ions in the tissue. In all 3 mechanisms, heat is generated by the movement of particles in response to an electric field respectively by the collisions between the transmission charges and immobile particles.⁽⁴⁾
Various considerations are required for there to be successful transfer of the RF energy into thermal energy, including the size and depth of the tissue being treated, as one needs to consider the tissue impedance of the skin being treated. Since RF energy produces an electrical current instead of a light source, tissue damage can be minimized, and epidermal melanin is not damaged either. Using this theory, RF energies can be used for patients of all skin types since does not act on any chromophores mainly melanin and allows for different depths of penetration based on what is to be treated, allowing for ultimate collagen contraction and production of new collagen. ⁽⁵⁾

Evolution of Radiofrequency devices:
The first device in this technology was a monopolar radiofrequency (RF) device that was US FDA approval for noninvasive treatment of the periorbital rhytids in 2002, and for the full face in 2004 using this proven mechanism of skin tightening. ^(6,7)Disadvantages of that 1st generation device included inconsistency of clinical results and significant discomfort during treatment. Newer bipolar and multipolar RF devices are constantly being developed to improve results and minimize discomfort.

Monopolar systems deliver current through a single contact point with an accompanying grounding pad kept at a different location in contact with the body that serves as a low resistance path for current flow to complete the electrical circuit. ³ Monopolar electrodes concentrate most of their energy near the point of contact, and energy rapidly diminishes as the current flows toward the grounding electrode.⁷ Bipolar devices pass electrical current only between two adjacently positioned electrodes applied to the skin. No grounding pad is necessary with these systems because no current flows throughout body to complete the circuit. ⁸

The tripolar / multipolar RF systems exclusively utilize the effects of combining unipolar RF and bipolar RF energies in one applicator to simultaneously heat deep and superficial tissue layers, while protecting the surface skin. ⁷ The tripolar RF technology uses sophisticated algorithms to control the treatment electrodes which change the current and polarity to achieve variable energy focus in different fat layers resulting in visible clinical results. This system is also used for the treatment of skin laxity and facial recontouring.

Newer devices have been introduced, like the Viora Reaction™ (Viora, NJ, USA) which also utilizes three poles of RF energies, but is distinguished from the other devices in that it emits its RF energies at different RF frequencies which is unique to this machine. Clinical trials with this device have not been published except individual case reports. Another new device, the Venus Freeze™ (Venus Concepts, AZ, USA) uses eight poles of RF energy and pulsed magnetic fields to have its effect on skin rejuvenation and body contouring. Clinical published studies with this device are also not yet available.

This article will focus on the Fractional Microneedle RF (FMRF) which is a very new technology which has been developed and upgraded in the last 2 years.

What is Sublative (Superficial) Fractional RF :
Fractional RF was developed to address the shortcomings of ablative and non-ablative device modalities performing ablation on small microscopic “ dots ” of skin allowing rapid healing with minimal pain and downtime. ^9,10
In Sublative Rejuvenation™ the treatment is delivered via a hand-held applicator that is fitted with a square disposable tip at its distal end. The tip consists of parallel rows of bipolar arranged electrode-pins, forming an array of positively and negatively charged electrodes for multiple delivery of 1 MHz of RF energy. ( Figure 1A) Energy up to 20 J can be delivered at a 5% or 10% coverage rate via 64 or 144 (according to the specific tip) equally spaced electrode-pins, each approximately 200 µm in diameter. Radiofrequency delivery via dry skin flows between each pair of positively and negatively charged electrode-pins such that part of the electrode-pinhead array forms a closed circuit of bipolar RF current that passes into the epidermis and deeper into the dermis. (Figure 1B) This results in heating of areas which are directly targeted by the electrode-pins to temperatures leading to ablation and resurfacing of the skin directly in contact with and below the array, leaving intact or slightly affected zones in between the targeted areas. In the short term, the preserved tissue helps to maintain skin integrity. In the long term, it serves as a pool of cells that promote wound healing.

Figure 1A. Showing the tip showing consists of parallel rows of bipolar arranged electrode-pins	Figure 2A. Showing the disposable tip which can detached after use
Figure 1B. RF current flows between the positive and negative mini-electrodes such that part of the electrode-pinhead array forms a closed circuit of bipolar RF current that passes into the epidermis and deeper into the dermis. Control of this current allows varying degrees of tissue impact. In the space of no current flow a healing reservoir of epidermis and dermis is obtained.

Figure 2B. Monofractional and Bifractional tips.

The radiofrequency modality in the bipolar electrode scheme applies the configured energy in a “pyramid” shape, which creates a predetermined controlled wound with a small epidermal component and larger volume in deeper tissue. (Figure 3B) Ablative technology commonly forms a conical or columnar injury zone. The term “sublative” is a derivative of “sub-ablative,” referring to the ability to generate heat energy well beneath the ablated zone below the epidermal surface and where the effect is largely caused by a large volume of heated tissue.>

Figure 3A. RF energy passed through epidermis in a fractional array.	Figure 3B. Heat generated as a “pyramid” shape, which creates a predetermined controlled wound with a small epidermal component and larger volume heating in deeper tissue.

Sublative rejuvenation causes limited epidermal disruption less than 5% of the surface is treated with one pass which translates to minimal downtime for patients and makes it an optimal choice for darker skin. The bulk of the effect is coagulative and occurs mainly in the mid-dermis, where it has the most effect on wrinkles and scars.

This unique technology provides the capability to combine epidermal fractional microablation and deep nonablative dermal heating allowing the optimal multilayer treatment needed for conditions which would benefit from dermal remodelling.

What is Microneedle / Fractional Microneedle RF :

Microneedle RF works by the same principle of dermal remodelling by Sublative RF but with the use of microneedles which are inserted into the skin to desired depth and RF current is passed. In microneedle RF the treatment is delivered through probe tip which consists of an array of microneedles over a minimum area of 10 mm2 that form an array of positively and negatively charged electrodes. The microneedles delivered bipolar radiofrequency energy in a fractional manner that can be inserted into the skin at a depth of 0.5 to 3.5 mm depending on level of treatment in the dermis.

Figure 4A. In the microneedle tip, the length of needles can be adjusted to pass RF energy through epidermis in a fractional array into the desired depth in dermis.	Figure 4B. In Sublative RF tip, the RF energy is passed from the epidermis into upper dermis.

The microneedles array can consists of needles as low as 25 needles per tip to 81 needles per tip. Some tips have higher number of needles for superficial dermal remodelling. The microneedles can be insulated except the tip or non-insulated. Non-insulated microneedles causes epidermal thermal injury which can produce epidermal resurfacing while insulted microneedles work in the dermal zone causing profound dermal remodelling.

The microneedles can also be blunt which will work as the same mechanism as Sublative RF working through the epidermis into deeper part of dermis. The sharp microneedles in contrast deliver the RF energy directly to the desired zone of the dermis creating better treatment outcome.

Figure 5A. In sharp insulated/uninsulated tip, the Rf current is passed directly into deep dermis for target dermal remodelling.

Figure 5B. In Blunt tip it works like the Sublative RF tip, RF energy is passed from the epidermis into upper dermis. This causes thermal injury to the lower epidermis and upper dermis	Figure 5B. In Blunt tip it works like the Sublative RF tip, RF energy is passed from the epidermis into upper dermis. This causes thermal injury to the lower epidermis and upper dermis.

More the distance between the needles, longer needles can be used and deeper the needles can be passed into the dermis with higher RF energy delivery. Different needles lengths are available are separate tips. Newer tips have manual and motorised adjustment of length of needles, this is very useful since the same tip can be used to deliver RF energy to different levels in the dermis. The RF energy is delivered to a deeper part of dermis then needle length is shortened and again the RF energy is placed above the previous heated zone. (Figure 6) This creates different zones of dermis heated at the same treatment improving the results with better dermal remodelling.

Parameters :
Parameters have individual variations depending on different equipment since each company has a different interface. Few basic parameters which are common to most of the Microneedle RF equipment are discussed below.

1. Continuous or Pulsed wave.
2. ON and OFF time.
3. Energy.
4. Depth adjustment of needles.
5. Manual Vs Automated needle insertion.
6. Number of Passes.

Continuous or Pulsed wave:
Continuous wave means when the RF energy is passed, it continuously delivers the energy till the foot switch or ON button is pressed. There is no ON or OFF time associated with it. Pulsed wave has an oscillating wave when the ON button or foot switch is pressed and it has an ON and OFF time. (Figure 7) When a continuous wave is used there is no cooling phase since there is no ON and OFF time which can be painful for the patients. The pulsed mode can be single or repeat. Single mode means only one wave of pulse is passed when the foot switch is pressed. Repeat mode means multiple waves of the pulse are delivered till the foot switch is ON.

Fig 7

ON and OFF time:
The ON and OFF time is set in seconds and it is used only when the pulsed wave mode is selected. Ideally as low as 0.5 seconds to 3 seconds is kept as ON time. The OFF time is the time given for the cooling of the treated area before the next wave passes, it reduces the discomfort to the patient. The OFF time can be equal to ON time or more than ON time, it all depends on the patients comfort.

Energy:
The energy is in watts or joules. Its set to a value depending on the depth of penetration and also the amount of heat needed to be delivered to the dermis. The energy E in joules (J) is equal to the power P in watts (W), times the time period t in seconds (s): E(J) = P(W)× t(s), joules = watts × seconds (J = W × s).
Example : What is the energy in joules when a power or 10 watts is used for time duration of 2 seconds? Using the formula it can be derived as E(J) = 10W × 2s = 20J. An Energy joules of 10 – 40J can be used depending on the condition and location of treatment area.

Figure 8. The basic parameters interface is shown with an ON time of 1.5secs and OFF time of 3.0secs and Power of 10 W which is calculated to 15 joules.	Figure 9 shows a rotating scale which has depth adjustment from 0.5mm to 3.5mm.

Manual Vs Automated needle insertion
Manual insertion of needles is done by the user but it can lead to difference in depth penetration. But in newer automated needle insertion, the handpiece pushes the needle to the same depth every time it inserts giving precision to the treatment.

Passes:
Passes means treating the area again after few minutes of completing the first pass treatment. The number of passes can be from 2 to 4 passes depending on the area being treated. Near the eye and forehead will need one to two passes, the cheek and chin two to four passes and for the neck two passes is sufficient.

Anaesthesia:
Topical anaesthetic under occlusion for 30 – 45 minutes is enough. Tumescent anaesthesia can be given if larger and deeper area are being treated for example in the treatment of axillary hyperhidrosis

Contraindications:

1. Patient who is on a pacemaker.
2. Pregnancy.
3. Skin infections like herpes simplex which can be treated accordingly.
4. Previous use of thread lifts in the area you have planned for FMRF.

Indications :

1. Improving superficial fine lines and wrinkles of the face, eyes, neck. ⁽¹¹⁾
2. Improving the elasticity of aged, striae and photodamaged skin. ^{(12,13,14,15,16)}
3. Treating scars of all types but particularly acne scars. ^{(17,18,19,20)} 
   It has a great advantage over laser for darker skin types.  Its effective because of deeper treatment levels and without the pigmentation risks.²¹
4. Tightening loose skin on all parts of the body including:  arms, chest, knees, abdomen.  There are no limitations as to where the skin can treated on the body.
5. New method of treatment for acne ^(22,23,24)and hyperhidrosis⁽²⁵⁾

Advantages :

1. No exclusion of patients based on skin type, safer on all skin types.
2. Downtime is limited to only about 2 days of sunburn like sensation and slight redness.
3. Minimally invasive.
4. Shorter procedure time and downtime compared to Co2 fractional laser. ⁽²⁴⁾
5. Lower risks such as post-inflammatory hyperpigmentation and scarring.⁽²⁶⁾
6. Can be combined with fractional lasers for better treatment outcome. ⁽²⁷⁾
7. Targetted dermal remodelling can be achieved. This remodeling involves heat-related collagen shrinkage and an initial inflammatory phase followed by increased levels of matrix metalloproteinases (MMPs) that degrade the fragmented collagen matrix followed by production of new collagen( Neocollagenesis).⁽²⁸⁾ Use of 0.5mm needle or non-insulated can cause thermal injury to epidermis causing epidermal remodelling. Thus, for effective resurfacing to occur, regeneration of the epidermis as well as portions of the dermis is required, thereby improving both the appearance and health of the aged skin.⁽²⁹⁾

Results :

Fig 10 A	Fig 10 B

Figure 10A. Closeup of Acne scar before Fractional microneedle RF
Figure 10B. Closeup After two treatments of Microneedle RF of 20-25 J, two passes in each sessions. 1.5-3.0mm depth of needle. Note the levelling of the boxcar scars with improvement in ice pick scars seen on the bottom right corner.

Fig 11 A	Fig 11 B

Figure 11A. Acne boxcar scar before Fractional microneedle RF
Figure 11B. After one of Microneedle RF of 20 J, two passes. 2.5-3.0mm depth of needle. Improvement seen after 6 weeks.

Post Treatment Care :
Mild redness and swelling may occur a few hours and up to 24 hours after treatment. Massage and excessive sun exposure should be avoided at this time. More aggressive treatments may result in skin flaking or scabbing as the new skin layer regenerates. Do not exfoliate by force. Apply enough sunblock. Avoid a sweaty exercise, spicy and strong tasting food. Avoid drinking alcoholic beverages. Avoid having a swim and taking a sauna for the time being. Use of antibiotics and antinflammatory can advocated. Moisturisers, broad spectrum sunscreens and avoiding direct ultraviolet exposure are highly recommended during this recovery phase. Use of epidermal growth factor can enhance healing and ensures faster recovery.

Conclusion:
Fractional ablation and resurfacing with fractional RF can achieve effective skin rejuvenation with effects on both the epidermis and dermis. This newer RF delivery system can be accurately optimized to treat a wide range of clinical conditions by modulating the energy level and coverage rate with good correlation with histological signs at the cellular level. Fractional RF treatment is safe, easily tolerated and effective in reducing wrinkles with an overall improvement in skin texture. Future developments will continue to keep RF technology at the forefront of the dermatologist’s armamentarium for skin tightening and rejuvenation.

References

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2. Gold MH. Tissue tightening – update 2010. Submitted for publication. J. Clin. Aesthet. Dermatol. 3(5), 36–41 (2010).
3. Fitzpatrick R, Geronemus R, Goldberg D, Kaminer M, Kilmer S, Ruiz-Esparza J. Multicenter study of noninvasive radiofrequency for periorbital tissue tightening. Lasers Surg Med 2003;33:232-42.
4. Stuchly M, Stuchly S. Electrical properties of biologi­cal substances. In: Gandhi OP, ed. Biological Effects and Medical Applications of Electromagnetic Energy. Upper Saddle River, NJ: Prentice Hall; 1990:76-112.
5. Michael H Gold. The Increasing Use of Nonablative Radiofrequency in the Rejuvenation of the Skin. Expert Rev Dermatol. 2011;6(2):139-143. 
6. Weiss RA, Weiss MA, Munavalli G, Beasley KL. Monopolar radiofrequency facial tightening: A retrospective analysis of efficacy and safety in over 600 treatments. J Drugs Dermatol 2006;5:707-12.
7. Zelickson BD, Kist D, Bernstein E, Brown DB, Ksenzenko S, Burns J, et al. Histological and ultrastructural evaluation of the effects of a radio-frequency- based non-ablative dermal remodeling device: A pilot study. Arch Dermatol 2004;140:204-9.
8. Sadick N, Alexiades-Armenakas M, Bitter P, Hruza G, Mulholland S. Enhanced full-face skin rejuvenation using synchronous intense pulsed optical and conducted, bipolar radiofrequency energy ELOS: Introducing selective radiophotothermolysis. J Drugs Dermatol 2005;4:181-6.
9. Hantash BM, Mahmood MB. Fractional photothermolysis: a novel aesthetic laser surgery modality. Dermatol Surg. 2007;33:525-534.
10. Jih MH, Kimyai-Asadi. Fractional photothermolysis: a review and update. Semin Cutan Med Surg. 2008;27:63-71.

More References are Available on Request