Evaluation and comparison of the efficacy and safety of cross-linked and non-cross-linked hyaluronic acid in combination with botulinum toxin type A in the treatment of atrophic acne scars: A double-blind randomized clinical trial.

[INTRODUCTION] Acne vulgaris is a common skin condition that affects a significant percentage of adolescents, with scarring being one of its permanent complications. This study aims to compare the efficacy and safety of using botulinum toxin type A (BTA) in combination with cross-linked and non-cross-linked hyaluronic acid (HA) for the treatment of atrophic acne scars.

[METHOD] Our study is a randomized, double-blind clinical trial conducted on 16 patients with atrophic acne scars. The patients were randomly assigned to one of two groups: one group received a single session of BTA and crossed link HA combination, while the other group received two sessions of BTA and non-crossed link HA, 1 month apart. The patients were followed up at 3 and 6 months after baseline to evaluate the number and area of fine and large pores and spots, scar grading, patient satisfaction, and complications.

[RESULTS] The mean age of individuals in both the cross-linked HA and non-cross-linked HA groups was 32.75 ± 4.26 and 31.50 ± 8.48 years, respectively (p = 0.71). In terms of gender, three (37.5%) and seven (87.5%) individuals in the cross-linked and non-cross-linked HA groups were female, respectively (p = 0.11). There were no significant differences in the count and area of fine and large pores and spots between the two groups at baseline and the first follow-up session. However, in the second follow-up session, the non-cross-linked HA group had significantly better results than the cross-linked HA group in terms of large pores count and area (p = 0.01). In terms of changes over time, the non-cross-linked HA group showed significantly better improvements in the count and area of large pores compared to the cross-linked HA group (p = 0.03). Additionally, both groups experienced a significant decrease in the count and area of fine pores over time (p = 0.001), but the amount of changes was not statistically significant between the two groups (p = 0.06). Concerning acne grade, initially, 62.5% and 12.5% of cases in the cross-linked HA and non-cross-linked HA groups, respectively, had severe grades. However, in the last session, these percentages significantly decreased to 0% for both groups (p = 0.002 and 0.005, respectively). In terms of treatment complications, none of the patients experienced any adverse effects.

[CONCLUSION] The study demonstrated that both cross-linked HA and non-cross-linked HA were effective in reducing acne severity and improving the appearance of pores and spots. The treatments had similar effects on fine pores, spots, and overall acne severity. However, non-cross-linked HA appeared to have a better result on large pores compared to cross-linked HA.