Interstitial laser and internal aesthetic fiberlaser-assisted surgery

The history of interstitial (subcutaneous) laser treatment, including laser lipolysis, is a relatively brief one and has been summarized well by Dibernardo, who notes Apfelberg as being credited for describing the laser-fat interaction in subcutaneous laser treatment in 1992. Publications by Blugerman, Schavelzon and colleagues, and Goldman and colleagues followed, each demonstrating their experience with lasers on subcutaneous tissue including lipocytes. Badin and colleagues also highlighted the important tissue retraction noted with their subcutaneous laser techniques. Ichikawa and colleagues reported on the histologic evaluation of tissue treated with subcutaneous laser, showing the destructive changes of heat-coagulated collagen fibers and degenerated fat cell membranes with dispersion of lipid after laser irradiation of human specimens. These histologic changes correlate with clinical changes seen by both physicians and patients. Furthermore, the hemostatic properties of the 1064-nm wavelength have been well documented.

The thermal effect produced by the Nd:YAG laser (1064 nm) in the subcutaneous tissue promotes better hemostasis, resulting in less surgical trauma and wound healing with fewer adverse sequelae. In addition to the histologic evidence, clinical evaluation shows improved postoperative recovery, resulting in a more rapid return to daily activities with an excellent aesthetic result. The application of subcutaneous lasers to facial and neck rejuvenation in conjunction with advanced facial rejuvenation techniques, termed smartlifting, was introduced by Gentile in 2007. The initial procedures were performed with the Smartlipo 1064-nm laser (CynoSure, Westford, MA, USA), but on introduction of the Smartlipo MPX the 1064/1320-nm Multiplex laser was used. The use of internal aesthetic lasers represents a technical innovation in facial and skin rejuvenation, the benefits of which are listed in Box 1 .

The introduction of the internal laser for aesthetic facial and neck rejuvenation

The CynoSure Smartlipo laser was the first laser to be approved by the Food and Drug Administration (FDA) for laser lipolysis and subcutaneous use. The introduction of Smartlipo in the United States followed many years of use in Europe where the laser was introduced by Deka (Florence, Italy). In addition to the laser lipolysis indication the laser is approved for the surgical incision, excision, vaporization, ablation, and coagulation of soft tissue.

Since the introduction in 2006 of subcutaneous laser–based lipolysis techniques, other laser companies have introduced similar devices and many have introduced different wavelengths for the specific indication of laser lipolysis, including 980 nm, 1440 nm, and 1444 nm.

The introduction of the internal laser for aesthetic facial and neck rejuvenation

The CynoSure Smartlipo laser was the first laser to be approved by the Food and Drug Administration (FDA) for laser lipolysis and subcutaneous use. The introduction of Smartlipo in the United States followed many years of use in Europe where the laser was introduced by Deka (Florence, Italy). In addition to the laser lipolysis indication the laser is approved for the surgical incision, excision, vaporization, ablation, and coagulation of soft tissue.

Since the introduction in 2006 of subcutaneous laser–based lipolysis techniques, other laser companies have introduced similar devices and many have introduced different wavelengths for the specific indication of laser lipolysis, including 980 nm, 1440 nm, and 1444 nm.

Early clinical studies and observations of laser procedures

The original Smartlipo laser ( Fig. 1 ) delivered 1064 nm optical energy though a 300-μm fiber at 6 W ( Fig. 2 A ). All subsequent Smartlipo and Smartlipo MPX lasers use a 600-μm fiber ( Fig. 2 B), and now the 1000-μm fiber ( Fig. 2 C) for high-power laser lipolysis. The 600-μm optical fiber is introduced into a 1-mm diameter stainless-steel microcannula of variable length, and is used for facial laser-assisted procedures. The laser is fired through the distal end of the fiber, which protrudes 2 mm beyond the tip of the cannula. The distal end of the fiber interacts with the soft tissue of the face and neck. For visualization purposes, an aiming laser source is provided in the beam path, providing the precise location of the fiber tip and indicating where the laser is working.

Small-footprint Smartlipo 1064-nm Nd:YAG laser. The Smartlipo laser was initially approved at 6 W and underwent power upgrades to 18 W before advancing to the MPX and now TriPlex versions.

( A ) Original 300-μm fiber used for lipolysis and tissue coagulation, ( B ) 600-μm fiber, and ( C ) 1000-μm fiber. The laserfibers have progressed from the very small 300-μm fiber to the present 1000-μm fiber.

For most facial and neck anatomic regions, a 6- to 12-W, 100-microsecond pulsed laser at 40 Hz and 150 mJ has been used. The Smartlipo MPX laser, which is capable of blending both the 1064-nm and 1320-nm wavelengths, has been used in more recent studies.

The Nd:YAG laser produces photomechanical and thermal effects, which dissect the tissue quickly. In addition, the Nd:YAG laser’s hemostatic properties allowed for the coagulation of small blood vessels in the subcutaneous tissues. Multiplexing the 1064-nm and 1320-nm wavelengths provides some unique advantages ( Fig. 3 ), allowing individual as well as sequential emission of 1064-nm and 1320-nm wavelengths. The combination of these wavelengths increases the efficiency of laser lipolysis and offers a more evenly distributed laser energy profile.

Smartlipo MPX. The MPX or Multiplex permits laser use in either the 1064-nm or 1320-nm mode or in Multiplex mode, which consists of sequential emission of 1064 nm and 1320 nm in 3 blends.

These 2 wavelengths emitted sequentially also offer efficient vascular coagulation with the conversion of hemoglobin to methemoglobin. The 1320-nm wavelength heats the blood, converting hemoglobin to methemoglobin. The 1064-nm wavelength has a 3- to 5-fold greater affinity for methemoglobin than for hemoglobin, thereby increasing absorption and resulting in more efficient coagulation.

Smartlifting permits easier flap separation in areas that are typically difficult to reach, such as the nasal labial folds (NLF), the corner of the mouth, and infracommissural NLF, also known as marionette lines. The wavelength characteristics and thermodynamic photospectrum of the 1064-nm and 1064-/1320-nm multiplexed lasers and comparative thermal volumes are shown in Fig. 4 .

( A ) Wavelength (1064 nm) characteristics and photothermal footprint. ( B ) Wavelength (1320 nm) characteristics and photothermal footprint. ( C ) Multiplexed wavelength (1064/1320 nm) characteristics and photothermal footprint. ( D ) Relative thermal volume of laser pulse.

Surgical technique

Until late 2007 most in-office procedures that included interstitial laser techniques were completed by using the laser for laser lipolysis, with facial liposculpting or lipocontouring. Often these procedures did not monitor tissue temperature. Thermal end points were introduced so that the skin temperature could be more safely elevated without inducing skin necrosis. These end points are associated with a greater degree of tissue contraction. These studies were first completed by DiBernardo and Reyes, who demonstrated that epidermal necrosis was associated with external skin temperatures approaching 48° to 52°C. Their results showed the degree of skin tightening available with subcutaneous laser irradiation with thermal end points not exceeding 42°C.