Efficacy and adverse reactions of fractional CO 2 laser for atrophic acne scars and related clinical factors: A retrospective study on 121 patients.

Objective: This study was performed to analyze the efficacy, adverse reactions of fractional CO ₂  laser for atrophic acne scars, and related clinical factors.
Methods: The clinical data of 121 patients with atrophic acne scars treated with ultra-pulsed fractional CO ₂  laser in the Cosmetic Dermatology from August 2014 to March 2020 were retrospectively analyzed. The efficacy and adverse reactions of atrophic acne scar after fractional CO ₂  laser therapy were statistically analyzed. The clinical factors related to efficacy and adverse reactions after the first therapy session were analyzed by multivariate logistic regression.
Results: A total of 121 patients received 206 sessions of fractional CO ₂  laser therapy, with an average of 1.7 sessions. Moderate to excellent improvement rate reached 50.4% after the first session. Multivariate logistic regression analysis indicated that rolling scars responded better to fractional CO ₂  laser treatment than icepick scars (OR = 7.3, 95% CI [1.2, 43.4], p = 0.029), and scar improvement was more significant in the high-energy laser group than in the low-energy laser group (OR = 10.9, 95% CI [1.1, 106.8], p = 0.041). The main adverse reactions after fractional laser surgery were pigmentation, skin sensitivity, persistent erythema, and acneiform eruption. Multivariate logistic analysis revealed that the longer the scar duration, the higher incidence of postoperative adverse reactions (OR = 1.3, 95% CI [1.1, 1.5], p = 0.008). Compared with icepick scars, rolling scars (OR = 10.4, 95% CI [2.3, 47.7], p = 0.003) and boxcar scars (OR = 12.0, 95% CI [3.3, 44.0], p < 0.001) had higher risk of developing adverse reactions. The incidence of postoperative adverse reactions was also higher in the combined mode group (DeepFX mode + ActiveFX mode) than in the single-mode group (OR = 7.8, 95% CI [2.4, 25.5], p < 0.001).
Conclusion: Fractional CO ₂ laser was effective in the treatment of atrophic acne scars, without serious adverse reactions. Scar type and laser energy were independent clinical factors affecting its efficacy. Scar course, scar type, and fractional laser mode were independent clinical factors affecting its adverse reactions.
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