Simultaneous Versus Sequential Fractional CO2 Laser and Subcision Combination for Post-acne Atrophic Scars: A Split-face Comparative Study.

Acne vulgaris, a disease of the pilosebaceous unit, is estimated to afflict 9.4% of the global population, making it the eighth most prevalent and third most significant disease according to the global burden of disease. Post-acne atrophic scars may develop in 95% of acne patients due to aberrant wound healing that affects the pilosebaceous unit and surrounding tissue. Scars are cosmetically unattractive, contributing to the severe psychosocial discomfort observed in acne vulgaris patients. Several approaches exist for the treatment of post-acne atrophic scars, depending on various factors such as the individual's condition, the types of scars present, and the associated expenses. However, treating atrophic acne scars remains challenging for physicians because there is no gold-standard treatment. Thus, combinations of interventions are typically necessary. Fractional CO2 laser and subcision are therapeutic methods proven to be effective in treating post-acne atrophic scars. By creating hundreds of thousands of micro-heat treatment zones (MTZs), fractional CO2 lasers emitting small focal spots (50-80 m) via high-focusing mirrors can efficiently treat acne scars. These thermal damage columns accelerate the healing process of collagen synthesis. Subcision, which can be safely paired with other operations, should be the initial step in treating acne scars since it separates scars from underlying structures. Although several studies proposed that the combination of fractional CO2 laser and subcision was more efficacious than a single therapeutic modality, no study has to date compared the efficacy and safety of simultaneous versus sequential combination of these two methods in the treatment of post-acne atrophic scars. There is a critical need for basic research on the effectiveness and adverse events of combining modalities sequentially as compared to simultaneously due to the high expense of traveling and the downtime needed to recover after each treatment, especiall