Introduction

The appearance of rhytides and skin laxity are near certainties during the aging process. A number of modalities have been used to reduce the appearance of rhytides and skin laxity, including laser, mechanical, and surgical techniques. Over a decade ago, ablative resurfacing lasers were deemed the gold standard for facial skin tightening. Despite substantial clinical benefits, the technology was beset with significant downtime and an increased risk of side effects such as erythema, permanent pigmentary changes, infection, and scarring. Patients are now more accustomed to procedures with both reduced downtime and sufficient clinical improvement. This has led to a burgeoning number of non-ablative technologies with little to no recovery time and a more favorable risk–reward profile. Unlike ablative lasers, non-ablative technologies induce thermal injury to the dermis or subcutaneous tissues without epidermal vaporization. Epidermal protection is customarily achieved through the use of adjunctive surface cooling.

In terms of skin laxity specifically, the gold standard of treatment remains rhytidectomy or surgical redraping. The goal of this chapter is to review the major types of minimally invasive, non-ablative tissue tightening techniques, including radiofrequency-, light-, and ultrasound-based devices (Table 9.1). These devices are not a replacement for surgical procedures and appropriate patient selection remains key to overall satisfaction.

Table 9.1 Major types of skin-tightening technologies

Thermal collagen remodeling

All skin-tightening devices work by delivering heat in the form of energy to the skin or underlying structures. This creates mechanical and biochemical effects that lead to both immediate contraction of collagen fibers and delayed remodeling and neocollagenesis via a wound-healing response (Box 9.1).

Collagen fibers are composed of a triple helix of protein chains linked with interchain bonds into a crystalline structure. When collagen fibers are heated to specific temperatures, they contract due to breakage of intramolecular hydrogen bonds. Contraction causes the crystalline triple helix structure to fold, creating thicker and shorter collagen fibers. This is thought to be the mechanism of action of immediate tissue tightening seen after skin-tightening procedures. Studies have also found selective contraction of fibrous septae in the subcutaneous fat, which is thought to be responsible for the inward (Z-dimension) tightening (Fig. 9.1).

Figure 9.1 Human skin (A) before and (B) 4 months after treatment with the ThermaCool^® TC, showing epidermal thickening and increased dermal density.

Photographs courtesy of Solta.

Problems can arise if too much heat is delivered as the collagen fibrils will denature completely above a critical heat threshold. This can lead to cell death, denaturation, and scar formation. If too little heat is delivered, there will be no tissue response, although it appears that mild thermal injury gives rise to new dermal ground substance and tissue remodeling of photodamaged skin over time. The optimal shrinkage temperature of collagen has been cited as 57–61°C; however, contraction is in actuality determined by a combination of temperature and exposure time. For every 5°C decrease in temperature, a tenfold increase in exposure time is needed to achieve an equivalent amount of collagen contraction. Studies show that for exposure times in the millisecond domain the shrinkage temperature is greater than 85°C, whereas for exposure times over several seconds the shrinkage temperature is at a lower range of 60–65°C.

The other main mechanism in skin rejuvenation is a secondary wound-healing response that produces dermal remodeling over time. The wound-healing response entails activation of fibroblasts to increase deposition of type I collagen and encouraging collagen reorganization into parallel arrays of compact fibrils.

Radiofrequency devices

Radiofrequency devices have been used for hemostasis, electrocoagulation, and endovenous closure in medical dermatology. In the aesthetic arena, the technology has been used for skin resurfacing and non-invasive tissue tightening.

Radiofrequency energy is energy in the electromagnetic spectrum ranging from 300 MHz to 3 kHz. Unlike most lasers, which target specific absorption bands of chromophores, heat is generated from the natural resistance of tissue to the movement of electrons within the radiofrequency field as governed by Ohm’s law (Box 9.2). This resistance, called impedance, generates heat relative to the amount of current and time by converting electrical current to thermal energy. Consequently, energy is dispersed to three-dimensional volumes of tissue at controlled depths.

The configuration of electrodes in a radiofrequency device can be monopolar or bipolar, and both have been used for cutaneous applications. The main difference between the two is the configuration of electrodes and type of electromagnetic field that is generated. In a monopolar system, the electrical current passes through a single electrode in the handpiece to a grounding pad (Box 9.3). This type of electrode configuration is common in surgical radiofrequency devices because there is a high density of power close to the electrode’s surface with the potential for deep penetration of tissue heating. In tissue-tightening applications, surface cooling is used to protect the outer layers of the skin and heat only deeper targets. In a bipolar system, the electrical current passes between two electrodes at a fixed distance (Box 9.4). This type of electrode configuration has a more controlled current distribution; however, the depth of penetration is limited to approximately one-half the distance between the electrodes.

With radiofrequency technologies, the depth of energy penetration depends upon not only the configuration of the electrodes (i.e. either monopolar or bipolar), but also the type of tissue serving as the conduction medium (i.e. fat, blood, skin), temperature, and the frequency of the electrical current applied (Box 9.5). Tissue is made up of multiple layers, including dermis, fat, muscle, and fibrous tissue, all of which have different resistances to the movement of radiofrequency energy (Table 9.2). Structures with higher impedance are more susceptible to heating. In general, fat, bone, and dry skin tend to have low conductivities such that current tends to flow around these structures rather than through them. Wet skin has a higher electrical conductivity allowing greater penetration of current. This is why, in certain radiofrequency procedures, improved results can be seen with generous amounts of coupling fluid and increased hydration of skin. The structure of each individual’s tissue (dermal thickness, fat thickness, fibrous septae, number and size of adnexal structures) all play a role in determining impedance, heat perception, and total deposited energy despite otherwise equal parameters.

Table 9.2 Dielectric properties for human tissue at 1 MHz and room temperature

Temperature also influences tissue conductivity and the distribution of electrical current. Generally, every 1°C increase in temperature lowers the skin impedance by 2%. Surface cooling will increase resistance to the electrical field near the epidermis, driving the radiofrequency current into the tissue and increasing the penetration depth. Conversely, target structures that have been pre-warmed with optical energy will, in theory, have greater conductivity, less resistance, and greater selective heating by the radiofrequency current. This is the theoretical advantage touted by hybrid skin-tightening devices that use a combined approach of light and radiofrequency energy together giving synergistic results.

Monopolar radiofrequency

The first monopolar tissue-tightening device on the market was the ThermaCool^® device (Solta Medical, Hayward, CA), introduced in 2001. It remains the most exhaustively studied and published apparatus. The ThermaCool^® device uses a capacitive coupled electrode at a single contact point and a high-frequency current at a frequency of 6 MHz. A disposable membrane tip is used to deliver the energy into the skin, with an accompanying adhesive grounding pad serving as a low-resistance path for current flow to complete the circuit. The use of capacitive rather than conductive coupling is important because it allows the energy to be dispersed across a surface to create a zone of tissue heating. With conductive coupling, the energy is concentrated at the tip of the electrode, resulting in increased heating at the contact surface and an increased risk of epidermal injury (Fig. 9.2).

Figure 9.2 (A) Thermage ThermaCool^® device; (B) capacitively coupled electrode treatment tip.

Photographs courtesy of Solta.

In the early clinical experience, one of the main drawbacks to the ThermaCool^® procedure was a high degree of discomfort during the procedure, requiring heavy sedation or frank anesthesia. The protocol at that time was to perform 1–2 passes at higher energies. The treatments were quite painful, results tended to be inconsistent from patient to patient, and some adverse events such as fat necrosis and atrophic scarring were noted. Over the years, treatment protocols have evolved to a paradigm utilizing lower energies, multiple passes, and patient feedback on heat sensation as the end point of therapy. This has all but eliminated the risk of unacceptable side effects and has greatly reduced the pain involved such that most procedures can be performed without any anesthesia. Monopolar radiofrequency energy is now commonly used to accomplish skin tightening of the face, eyelids (Case study 1), abdomen (Fig. 9.3), and extremities.

Figure 9.3 Tightening of abdominal skin with the ThermaCool^® TC: (A) before, and (B) 1 year after one pass at 15.5 J.

Case Study 1

A 47-year-old woman presents for a consult regarding excess skin on her upper eyelids. She states she has noticed a gradual increase in drooping over the last several years and she is finding it difficult to wear eye shadow. She has her thirtieth high school reunion in 4 months and states she wants improvement by then. She tells you she is not trying to look 18 again, but just wants to look as good as she feels. On examination, the patient has mild to moderate excess skin laxity on the upper eyelids with minimal bulging of the fat pads. Her brows are in a normal position without significant ptosis. This patient would be a candidate for either radiofrequency skin tightening or a surgical blepharoplasty. She may be a better candidate for non-surgical tightening because of her mild to moderate skin laxity without underlying structural deficits. She also has realistic expectations about results and has several months post-procedure for the skin tightening to take effect before her goal event. Most of the skin-tightening technologies can be used over multiple areas of the body; however, there are a few locations that favor some devices over others. The ThermaCool^® device is an excellent choice for skin tightening of eyelid skin because it has a small 0.25 cm² tip, high eye safety profile and lack of significant discomfort during treatment. When the eyelids are being treated, plastic corneoscleral lenses must be put in place. These should be gently inserted and removed so as not to cause erosions of the corneal surface. In addition, the operator should be careful not to deliver too much pressure on the globe, as this can result in vasovagal stimulation and bradycardia. Practitioners should never use ThermaCool^® tips larger than the 0.25 cm² eyelid tip owing to the depth of penetration.

The clinical results of non-ablative radiofrequency skin tightening were first reported by Fitzpatrick and colleagues for the periorbital area in 2003. At least some degree of clinical improvement was reported in 80% of subjects (Figs 9.4–9.6) In 2006, Dover and colleagues compared the original single-pass, high-energy technique with the updated low-energy, multiple-pass technique using immediate tissue tightening as a real-time end point. With the original treatment algorithm, 26% of patients saw immediate tightening, 54% observed skin tightening at 6 months, and 45% found the procedure overly painful. With the updated protocol, 87% had immediate tissue tightening, 92% had some degree of tightening at 6 months, only 5% found the procedure overly painful, and 94% stated the procedure matched their expectations (Figs 9.7, 9.8). The low-energy, multiple-pass protocol has also been reported to be significantly safer, lowering the incidence of adverse events to less than 0.05%.

Figure 9.4 Eyebrow lift following Thermage^® treatment: (A) baseline, and (B) 4 weeks post-treatment with a mean lift of 3.42 mm (right brow) and 3.41 mm (left brow).

Photographs courtesy of Solta.

Figure 9.5 Periorbital rejuvenation following Thermage^® treatment: (A) baseline, (B) 2 months post treatment, and (C) 4 months post-treatment.

Photographs courtesy of Solta.

Figure 9.6 Periorbital rejuvenation following Thermage^® treatment: (A) baseline, and (B) 4 months post-treatment.

Photographs courtesy of Solta Medical Aesthetic Center.

Figure 9.7 Lower-face skin tightening following Thermage^® treatment: (A) baseline, and (B) 3 months post-treatment.

Photographs courtesy of Dr Ivan Rosales.

Figure 9.8 Facial skin tightening following Thermage^® treatment: (A) baseline, and (B) 4 months post-treatment.

Photographs courtesy of Solta Medical Aesthetic Center.

Bipolar radiofrequency

A device using bipolar radiofrequency alone is the ePrime^® (Candela-Syneron, Wayland, MA). The ePrime^® device is different from other applications on the market in that it uses a microneedle electrode array to deliver bipolar radiofrequency energy into the reticular dermis while bypassing the epidermis and papillary dermis. Single-use treatment cartridges are utilized that contain five independently controlled, 32-gauge, bipolar microneedle pairs. The 250 µm needles are spaced 1.25 mm apart and each needle pair is independently powered by the generator. The needles are 6 mm long, with the top 3 mm insulated to protect the superficial portion of the skin during treatment, and the bottom 3 mm exposed to allow electrical current flow. The needles are inserted at a 20° angle to the epidermis so that the tip of the needle is 2 mm from the epidermis. Insertion is done by spring-loaded injection. Because current flows between the two needles in each pair, the radiofrequency energy creates five damage zones (one between each pair). If heat is applied long enough, temperature conduction expands the damage zone in all directions. Epidermal cooling is achieved via an integrated thermokinetic cooling bar on the applicator. This approach creates zones of thermal injury with real-time temperature monitoring to help maintain a target temperature of approximately 70°C regardless of varying skin conditions and possibly improve consistency between patients.

Alexiades-Armenakas and colleagues compared baseline and 3–6-month follow-up photographs of 15 patients who underwent skin tightening using a microneedle radiofrequency device with those of 6 patients who had undergone rhytidectomy. The radiofrequency device patients were judged to have a 16% improvement from baseline and the surgical patients were judged to have a 49% improvement from baseline. The authors concluded from this that the mean laxity improvement from a single microneedle radiofrequency treatment was 37% that of a surgical facelift.

Combined electrical and optical energy

Another type of skin-tightening device combines radiofrequency energy with optical energy from laser or light sources. The currently available combined electrical and optical energy devices utilize bipolar electrodes and include the Galaxy^®, Aurora^®, Polaris^®, and ReFirme^® systems (Syneron Medical Ltd, Yokneam, Israel). The hypothetical advantage to these devices is that the two forms of energy may act synergistically to generate heat. Target structures that have been pre-warmed with optical energy will, in theory, have greater conductivity, less resistance, and greater selective heating by the radiofrequency current. No grounding pad is required as the current flows between the electrodes rather than throughout the remainder of the body as with monopolar systems. One major adverse event noted with these devices is known as tissue arcing, which can result in tissue burns and possible scar formation. Proper technique will help avoid the issue as arcing has been associated with the handpiece not being properly placed in contact with the skin.

The technology has been used in hair removal, wrinkle reduction, skin tightening, and the treatment of both pigment and vascular disorders (Case study 2). The premise is that less radiofrequency energy is ultimately needed for proper collagen denaturation and remodeling. The major disadvantage to these devices is that bipolar radiofrequency energy does not penetrate very deep into the skin. There is also some criticism that bipolar radiofrequency is unable to produce a uniform, volumetric heating response comparable to monopolar radiofrequency. Furthermore, because the bipolar radiofrequency devices are often combined with other light-based technologies, it is difficult to assess exactly how large a role bipolar radiofrequency plays in the clinical outcomes of such treatments.

Case Study 2

A 54-year-old male presents to your office and states that he has been recently divorced and wants to improve his appearance so that he feels more comfortable re-entering the dating scene. He states he is against injectable treatments such as botulinum toxin or fillers because he does not want to put what he calls ‘foreign substances’ in his body and he does not want to have to come into the office for repeated maintenance. On examination, he has fair skin with scattered lentigines on the cheeks and forehead and fine telangiectasias over the cheeks and nose creating a blush-type erythema. He has early changes consistent with skin laxity predominantly in the mid-face region, brow, and jawline. Combined electrical and optical energy may be the best option for patients who wish to treat their skin laxity in combination with other signs of photodamage such as lentigines or telangiectasias. A 2002 study by Bitter evaluating a series of 3–5 combined intense pulsed light and radiofrequency energy treatments on photoaged skin revealed a 70% improvement in erythema and telangiectasia, a 78% improvement in lentigines, and a 60% improvement in skin texture as determined by subject satisfaction levels. Because these devices can also be used for hair removal, caution should be used in treating the lower face and neck in a male patient so as not to thin or remove the beard. This patient is fair skinned; however, prudence should also be used when treating darker skin types or tanned skin with devices utilizing an optical component absorbed by pigment. As a general guideline, optical fluences should be lowered by a minimum of 20% when treating darkly pigmented lesions or dense pigment irregularity, even in light-skinned patients, to avoid side effects such as burns, crusting or pigmentary alteration.

Vacuum-assisted bipolar radiofrequency

Bipolar radiofrequency has been combined with an accompanying vacuum apparatus in an attempt to take advantage of several benefits of vacuum technology. The first device to do this was the Aluma^® (Lumenis, Santa Clara, CA) using what has been termed FACES (functional aspiration controlled electrothermal stimulation) technology. The vacuum apparatus suctions a fold of skin in alignment between two electrodes. Non-target structures such as muscle, fascia, and bone are avoided. The theory is that this may help to overcome the depth limitations inherent in bipolar radiofrequency technology by bringing the target tissue closer to the electrodes. Less overall energy may also be required for an effective treatment. It has also been hypothesized that increased blood flow and mechanical stress of fibroblasts from the vacuum suction may lead to increased collagen formation. Vacuum technology has the added benefit of helping to reduce procedure discomfort.

In a pilot study of 46 adults undergoing eight facial treatments with vacuum-assisted bipolar radiofrequency, Gold found significant improvements in skin texture. The mean elastosis score of study participants went from 4.5 pre-treatment to 2.5 by 6 months post-treatment, indicating a shift from moderate to mild elastosis. The authors noted a short-term tightening effect due to collagen contraction followed by a gradual, long-term improvement due to the wound-healing response and neocollagenesis. Although subjects were generally pleased with the treatment outcome, their satisfaction levels declined somewhat during the follow-up period. This can be a common finding in radiofrequency skin treatments owing to delayed neocollagenesis and long-term wound-healing response. Subjects may have difficulty accurately remembering the exact condition of their skin pre-treatment, particularly when 6 or more months have passed.

Hybrid monopolar and bipolar radiofrequency

The first system to combine monopolar and bipolar radiofrequency in one device was the Accent^® (Alma Lasers, Buffalo Grove, IL). The theory behind using both types of radiofrequency is to deliver different depths of current to the skin. The bipolar electrode handpiece allows for more superficial, localized (non-volumetric) heating based on tissue resistance to the radiofrequency conductive current. The monopolar electrode handpiece targets deeper, volumetric heating via the rotational movement of water molecules in the alternating current of the electromagnetic field. The monopolar handpiece delivers a higher amount of energy since it theoretically is heating a greater tissue volume than the bipolar handpiece. Typically the monopolar handpiece is used to treat the forehead, cheeks, jawline, and neck (Fig. 9.11). The bipolar handpiece is used to treat the glabella, lateral periorbital area (Fig. 9.12), upper lip and chin, and leg (Fig. 9.13). Despite the use of monopolar radiofrequency, this particular system uses a closed system where no grounding plate is required (Case study 3).

Figure 9.11 Skin tightening of the neck and jawline region: (A) before, and (B) immediately following a single treatment with the Accent^® treatment.

Photographs courtesy of Dr Alexiades-Armenakas.

Figure 9.12 Periorbital rejuvenation: (A) before, and (B) 3 months after four treatments with the Accent^® treatment.

Photographs courtesy of Dr Alexiades-Armenakas.

Figure 9.13 Cellulite treatment on the right leg following five treatments with the Accent^® and the left leg serving as an untreated control.

Photograph courtesy of Dr Alexiades-Armenakas.

Case Study 3

A 42-year-old woman comes into your office with the complaint of skin laxity in the upper arm area. She states she is no longer comfortable wearing sleeveless clothing because she feels like her arms look like what she calls ‘cottage cheese’. She states she has always maintained a relatively normal weight. On examination, she is of a normal weight for her height and build. She has a mild to moderate skin laxity predominantly in the posterior portion of her upper arm and dimpling in the texture of both the anterior and posterior surface of the arms. In this case the patient has two main options for improvement including upper arm liposuction and non-surgical skin tightening. She may be a better candidate for non-surgical skin tightening because the textural abnormality in her upper arms extends around the full circumference. Liposuction would predominantly improve the skin in the ‘bat wing’ area on the posterior portion of the arm. She would not be a candidate for surgical brachioplasty due to her young age, milder degree of laxity, and desire to wear sleeveless clothing. In this case, the hybrid Accent^® device would be a good choice for tissue tightening with the added benefit of possible volume reduction. One case report compared treating skin laxity on one arm with the ThermaCool^® device and the opposite arm with the Accent^® device. The ThermaCool^® arm was treated with a single treatment at settings of 351.5–354 with a minimum of six passes on the inner arm and three passes on the outer arm (1200 pulses total). The Accent^® arm was treated with a series of nine treatments at 2-week intervals using the monopolar handpiece at an epidermal temperature of 42.5°C with three therapeutic phase passes. Although skin texture improved with both treatments, the Accent^®-treated arm was reported to be tighter and firmer after just two treatments, with a looser-fitting clothing sleeve. Because the ThermaCool^®-treated arm did not have a looser fitting clothing sleeve until the physician had gone back at the end of the study and performed two Accent^® treatments, the author suggested that the Accent^® radiofrequency energy penetrates deeper and may be the device of choice when patients require both tissue tightening and volume reduction.

Infrared light devices

Broadband infrared light in the range of 800 to 1800 nm, depending on the device, has been utilized for non-ablative tissue tightening. The infrared rays are selectively filtered to achieve gradual heating of the dermis, with pre, parallel, and post-cooling to assure epidermal protection. The first such light-based system on the market was the Titan^® (Cutera, Brisbane, CA). It utilizes light energy in the range of 1100 to 1800 nm to target water as a chromophore, causing collagen denaturation and ultimately collagen remodeling and tissue tightening. The StarLux IR^® (Palomar Medical Technologies, Burlington, MA) delivers fractionated energy through the handpiece of the device at a wavelength range of 850 to 1350 nm, which also targets water as the principal chromophore. Multiple treatments are required for optimal results. The SkinTyte^® device (Sciton, Palo Alto, CA) utilizes light at a wavelength range of 800 to 1400 nm.

In 2006, Ruiz-Esparza performed one to three treatments on 25 patients utilizing broadband infrared light from 1100 to 1800 nm. Most patients showed improvement ranging from minimal to excellent with immediate skin tightening visible in 22 of the 25 patients. Three patients showed no improvement. The best results were achieved when using a combination of lower fluences and a high number of pulses. Patients treated at 30 J/cm² expressed no pain during the procedure and had a high degree of satisfaction immediately post-procedure. The same year, Zelickson and colleagues looked at ultrastructural changes in cadaver and human skin post-treatment. Collagen fibril alteration was found to be highest with greater fluences and depths of 1–2 mm. Marginal results were observed at shallower depths and lower fluences, which were possibly due to the effect of contact cooling. Comparison of the two studies emphasizes that clinical skin tightening does not always correlate with immediate positive histological findings. This is explained by the fact that full clinical effect may take weeks or months to be demonstrated owing to a secondary wound healing response.

In 2006, a multi-center study reported longer-term (12–18-month) results using the 1100–1800 nm infrared device at 34–36 J/cm². Results were both immediate and delayed up to 6 months. Clinical outcomes ranged from mild to moderate in most patients. The authors concluded that using a lower fluence range of 30–40 J/cm², 2–3 treatments, 1–2 passes, and extra passes on areas that need immediate contraction or along vector lines yielded best results.

Complications were limited to minor erythema, but a few blisters were observed in areas that were overtreated. In 2007, Goldberg and colleagues noted positive results in 11 of 12 patients receiving two treatments with the same device (30–36 J/cm²). The best results were observed in patients who had loose draping skin, with less significant results in sagging skin that was firmly associated with the subcutaneous tissue. No improvement was noted in the jowl region.

Other laser wavelengths that have been used for tissue tightening include the 1064 nm and 1320 nm wavelengths. The chromophores for the 1064 nm wavelength, in decreasing order, are melanin, hemoglobin and water, and the primary chromophore for the 1320 nm wavelength is water. A 2005 study by Taylor & Prokopenko compared a single treatment using a monopolar radiofrequency system (73.5 J/cm²) with a single treatment using the 1064 nm neodymium : yttrium-aluminum-garnet (Nd : YAG) laser (50 J/cm²). The 1064 nm laser side was deemed to have better overall results in terms of improvement in wrinkles and skin laxity, although only modest improvements was noted in both modalities. Another study in 2007 by Key compared a single facial treatment with a monopolar radiofrequency system (40 J/cm²) to the 1064 nm Nd : YAG laser (73–79 J/cm²). The 1064 nm laser resulted in greater improvement on the lower face, while improvement on the upper face was equivalent with both modalities. In 2001, Trelles and colleagues treated 10 patients with a series of eight treatments using a 1320 nm laser system (30–35 J/cm²). Clinical improvement was subtle, with only two patients reporting satisfaction with the procedure. The authors suggested combining laser treatment with parallel epidermal treatment may yield better results and achieve higher patient satisfaction.

Ultrasound devices

High-intensity focused ultrasound (HIFU) is the most recent player to enter the skin-tightening technology realm. When an intense ultrasound field vibrates tissue, friction is created between molecules causing them to absorb mechanical energy and leading to secondary generation of heat. Thus, the primary mechanism responsible for tissue necrosis with focused ultrasound treatment is heating of the tissue due to the absorption of acoustic energy. Ideally, this leads to immediate tissue contraction and delayed collagen remodeling with the coagulative change limited to the focal region of the ultrasound field. In reality, the spectrum of cellular changes depends on the rise in temperature and the exposure duration and can range from total necrosis to subtler ultrastructural cell damage with modulation of cellular cytokine expression.

Intense focused ultrasound for skin-tightening applications uses short, millisecond pulses with a frequency in the megahertz (MHz) domain, rather than kilohertz (kHz) as is used in traditional HIFU, to avoid cavitational processes. Intense focused ultrasound also uses significantly lower energies than traditional HIFU, 0.5–10 J versus 100 J, which allows thermal tissue changes without gross necrosis. The main advantage to focused ultrasound is the potential for greater depth of skin changes than other technologies with the added benefit of precisely controlled, focal tissue injury. Ultrasound energy is able to target deeper structures in a select, focused fashion without secondary scatter and absorption in the dermis and epidermis. Early research on human cadaveric tissue showed intense ultrasound energy was able to target the facial superficial musculo-aponeurotic system (SMAS) to produce discrete zones of thermal injury while sparing non-targeted adjacent structures.

The first intense focused ultrasound device on the market is the Ulthera^® system (Ulthera Inc., Mesa, AZ). The system incorporates ultrasound imaging capability for visualizing the skin and deep tissue in combination with a therapeutic ultrasound module that creates small, approximately 1 mm³, wedge-shaped zones of thermal coagulation. The thermally induced zones result from selective absorption of ultrasound energy in the area of geometric focus of the beam. The depth and volume of the thermal lesions are determined by the preset focus depth and frequency of the probe in combination with the intrinsic characteristics of the tissue being treated. The source energy is an adjustable parameter. Higher-frequency probes are associated with more superficial tissue effect whereas lower-frequency probes are associated with a deeper tissue effect. Typically, higher-frequency probes are used to treat areas of thinner skin such as that of the neck, whereas the lower-frequency probes are used to treat areas of thicker skin such as that of the cheeks.

Current protocols aim for a geometric focal depth of therapy in the mid to deep dermis. One of the first clinical trials by Alam and colleagues in 2010 assessed the safety and efficacy of intense focused ultrasound on skin tightening. Significant improvement was seen in brow elevation in more than 83% of treated patients with an average increase in brow elevation of 1.7–1.9 mm (Fig. 9.14). Results developed over a 90-day period following treatment and were still noticeable at 10-month follow-up. The authors found lower face tightening more difficult to assess due to a lack of fixed anatomical landmarks. In 2011, Suh and colleagues treated 22 Asian patients with facial skin laxity with intense focused ultrasound; 77% of patients reported much improvement in the nasolabial folds, and 73% reported much improvement in the jaw line. Histological evaluation of skin samples showed greater dermal collagen with thickening of the dermis and straightening of elastic fibers in the reticular dermis after treatment (Figs 9.15 and 9.16).

Figure 9.14 Periorbital rejuvenation and brow lift following Ultherapy^® treatment: (A) baseline, and (B) post single-depth treatment using the 3.0 mm transducer or 4.5 mm transducer depth based on the periorbital region.

Photographs courtesy of Dr Jeff Dover.

Figure 9.15 Lower-face skin tightening following Ultherapy^® treatment: (A) baseline, and (B) post dual-depth treatment at 3.0 mm and 4.5 mm depths.

Photographs courtesy of Ulthera Inc.

Figure 9.16 Lower-face skin tightening following Ultherapy^® treatment: (A) baseline, and (B) post dual-depth treatment at 3.0 mm and 4.5 mm depths.

Photographs courtesy of Ulthera Inc.

Due to the relatively recent development of the device, large-scale trials are lacking and optimal treatment protocols are still being developed. Temporary nerve side effects can occur. Future advances may fine tune even deeper delivery of energy with the goal of producing focused thermal collagen denaturation in the SMAS.

Tips for maximizing patient satisfaction

Patient selection is of utmost importance in ultimate satisfaction with non-surgical skin-tightening technologies. Patients must be counseled that maximum results are slow and occur over a period of 3–6 months. In terms of expectations, these technologies should not be thought of as an equivalent technology to surgical lifting, but as an alternative option for a certain subset of patients. Despite a number of clinical studies reporting significant improvement in the appearance of lax skin, most patients show only mild improvement. It appears that patients who are younger with a lesser degree of skin laxity may yield the most promising clinical outcomes; skin laxity without a significant muscular attachment also appears to yield better results (Case study 4). Very elderly patients with severe sagging and wrinkles are, in general, suboptimal candidates for the degree of improvement expected with non-invasive tightening devices (Case study 5).

Case Study 4

A 78-year-old woman presents for a consult regarding general photoaging. She has avoided sun exposure her whole life and is a devoted wearer of sunscreen. She tells you she has been going to an esthetician for the past 15 years who gives her light glycolic peels every few months. She has also used a prescription tretinoin cream given to her by her general dermatologist for the past 25 years. She is otherwise healthy and would like to improve her appearance, but she would like to get your advice on what she needs. She has never had surgery before and tells you she would like to avoid having a facelift if possible. On examination she has remarkably preserved skin quality with very few deep lines and no major pigmentary issues owing to her diligent sun protection and long-term use of topical rejuvenation therapies. She does have some loss of definition along the jawline, with mild to moderate jowling, deepening of the nasolabial folds, descent of the eyebrow, and volume-related changes in the mid-face region. She also has prominent platysmal banding visible in the neck region. This patient would be an ideal candidate for almost any of the non-invasive skin-tightening approaches in combination with other therapies such as neurotoxins and fillers to augment her results. Although studies have shown that younger patients tend to have better results than older patients after tissue tightening procedures, this patient has extremely good skin quality and can be expected to have at least some degree of improvement. Because the skin-tightening procedure will not address her underlying changes in facial volume and musculature, performing adjunctive therapies such as botulinum toxin to the superior-lateral orbicularis oculi and platysma muscles would help her lift the brow, decrease banding on the neck, and achieve a more defined jawline. Filler to her mid-face region, nasolabial folds, pre-jowl region, and jawline would also be of use to restore underlying structure, increase the lifting effect, and give a more youthful shape to the face. A 2006 study by Shumaker and colleagues showed monopolar radiofrequency skin tightening to be safe when performed over multiple soft tissue fillers and indicated it may even have some synergistic effects in terms of long-term collagen growth. The patient has proven she is not averse to maintenance therapies and she will achieve a better overall result with global rejuvenation.

Conclusion

The quest for non-surgical skin tightening has led to a burgeoning number of devices on the market. Although dermal remodeling may occur with radiofrequency-, optical-, and ultrasound-based devices, patients and physicians should not expect results to be similar to those seen after surgical or possibly even ablative techniques. The techniques appear best suited for younger patients with mild to moderate skin laxity without a significant degree of underlying structural ptosis. Physicians must appreciate the indications, complications, benefits, and limitations of each device. The key to success remains rooted in patient selection and management of expectations. It is still uncertain as to how many treatments are ideal for the majority of these medical devices and how long the effects will be maintained. Future research and clinical trials will continue to refine techniques and delivery systems for optimal results.