Cryolipolysis and its mechanism of action
Cryolipolysis is a completely different modality from the techniques discussed so far. The principle behind this technology exploits the premise that adipocytes are more susceptible to cooling than other skin cells.
Precise application of cold temperatures triggers the death of adipocytes that are subsequently engulfed and digested by macrophages.12,13 No changes in subcutaneous fat are noticeable immediately after treatment. An inflammatory process stimulated by apoptosis of adipocytes, as reflected by an influx of inflammatory cells, can be seen within 3 days after treatment and peaks at approximately 14 days thereafter as the adipocytes become surrounded by histiocytes, neutrophils, lymphocytes, and other mononuclear cells. At 14–30 days after treatment, macrophages and other phagocytes surround, envelope, and digest the lipid cells as part of the body’s natural response to injury. Four weeks after treatment, the inflammation lessens and the adipocyte volume is decreased. Two to 3 months after treatment, the interlobular septa are distinctly thickened and the inflammatory process further decreases. By this time, the fat volume in the treated area is apparently decreased and the septae account for the majority of the tissue volume.14,15
In 2010, the FDA cleared a cryolipolytic device (CoolSculpting®; ZELTIQ Aesthetics, Inc., Pleasanton, CA, USA) for reduction of flank and abdominal fat. In April 2014, the FDA also cleared this system for the treatment of subcutaneous fat in the thighs (Figure 1).16 One part of the device is a cup-shaped applicator with two cooling panels that is applied to the treatment area. The tissue is drawn into the handpiece under moderate vacuum and the selected temperature is modulated by thermoelectric elements and controlled by sensors that monitor the heat flux out of the tissue. Each area is treated for approximately 45 minutes and should be massaged for 2 minutes upon completion to improve the clinical outcome. The patient is then discharged home and is free to resume normal activities immediately after treatment.17 The number of treatment cycles needed depends on the treatment area. While good results at the flanks can usually be achieved with only one treatment, the back and the inner and outer thighs often require more than two treatments.18 Repeated treatment sessions should be spaced 8 weeks apart to allow the inflammatory process to resolve.15