Fractional CO₂ Laser Treatment vs Autologous Fat Transfer in the Treatment of Acne Scars: A Comparative Study

ing the fat immediately after an injection of local anesthetic could help in limiting exposure time and avoiding the adverse effects described above,⁸ and this is what was done in our study.

Another controversy over fat grafting is the processing of fat. Centrifugation was performed at 3,000 rpm for 7 minutes to produce the desirable separation of the aspirated content. (Centrifugation was introduced to the technique of fat graft at 3,000 rpm for 3 minutes as it will not destroy fat lobules.²⁰) Another study compared washed vs centrifuged fat graft both done on half of the face of the same patient in a double-blind study, showing symmetrical results on both sides of the face regardless of the fat-processing methods. One may conclude that the survival rate depends not on the processing, but on other factors such as the quantity of fat or recipient site and the fat’s anatomical and physiologic features.²¹ Some authors have suggested that the presence of blood cells might stimulate macrophage to remove fat cells.²² It was discovered that fat survival by centrifugation is no better than that by filtration.²³

Regarding texture improvement in both groups: in group A, 2 patients showed excellent improvement and 3 showed marked improvement, while in group B, 1 patient showed excellent improvement, 2 showed marked improvement, 0 showed moderate improvement, and 6 showed mild improvement. The difference in response may be attributed to the parameter settings of the laser device that needed adjustment according to the scar, and it has been suggested that aggressive treatment results in skin tightening. ⁵ Fractional CO₂ was used on 15 patients with skin laxity and 1 with acne scars. They received 15 W to 25 W, 2 passes, in 3 to 5 treatments of 3-week intervals with a dwell time of 500 μsec to 800 μsec with cooling. The results showed that 79% patients had good to excellent improvement in skin laxity, and 50% to 75% patients had good overall results in acne scars.²⁴ Other studies had similar results.²⁵

Histologic and immunohistologic studies demonstrate a large difference in results between fat grafting and fractional ablative CO₂ laser for the treatment of acne scars, and they favor fat grafting. Histologic and immunohistologic studies compared biopsies taken from nude mice before and after fat graft, and these showed an increased density of extracellular matrix surrounding the fatty tissue and between the fatty tissue and the dermis.¹⁶ In another study on mice, the skin changes with fat grafting were investigated in skin biopsies 8 weeks after the graft, which revealed that the fat graft caused increased collagen fibers neosynthesis at the recipient site and thickened the dermis. Regarding skin color and scar quality, marked improvement could be seen after fat graft.¹²

In group B, oozing and pinpoint bleeding occurred in 4 patients and resolved 4 days after the session. This was reported by another study despite use of higher energies.⁶ This adverse effect was explained as being the result of deep dermal penetration with insufficient coagulation to produce hemostasis.⁵ All patients in group B experienced a grainy crust that resolved after a maximum of 5 days, which increased the downtime postsession. In the present study, one patient was dropped from the study and replaced by another after refusing to continue after the first session due to the crusts and the weeklong downtime.

Postinflammatory hyperpigmentation occurred in 2 patients in group B and 1 patient in group A who reported not using sun protection. The hyperpigmentation was diffuse even in areas not subjected to treatment, which excludes any of the treatment methods as being the cause of the hyperpigmentation. Overall, though, the incidence of postinflammatory hyperpigmentation is low with fractional ablative laser treatment.⁵ Another study used 20 mJ on photodamaged patients, with 20% of the patients developing postinflammatory hyperpigmentation.²⁴ A study on Asians used 15 W fractional CO₂ laser on 12 patients with skin type IV, and 92% of the patients developed postinflammatory hyperpigmentation that cleared after 5 weeks with the use of 4% hydroquinone.⁴

Transient erythema occurred in 4 patients within group B and resolved within a week. Similar results were shown in another study.⁶ It was suggested that the duration of erythema and its intensity corresponds to the extent of inflammation.²⁷ Erythema occurred in one patient in group A (Figure 6 ).This is probably due to superficial injection. The apical layer of subcutaneous fat is rich in blood vessels and lymphatic channels, meaning that disruption of this layer leads to edema and erythema.²⁸

There were no incidents of infection in either group, and preventive antibiotics were not required.²⁹ However, in a large surface area, antibiotics should be given 1 day before and 5 days after the laser treatment.⁵ No patients had a history of herpes simplex infection, so there was no need for antiviral prophylaxis.