Efficacy of Collagen Biostimulator Injections for Facial Aesthetics: A Systematic Review and Meta-analysis Based on Global Aesthetic Improvement Scale (GAIS) Outcomes

Abstract

This systematic review and meta-analysis evaluated the efficacy of injectable collagen biostimulators for facial aesthetic enhancement. The primary outcome was the Global Aesthetic Improvement Scale (GAIS), with adverse events assessed as a secondary outcome. A comprehensive literature search was conducted across five databases (PubMed, Embase, Scopus, Web of Science, and Cochrane CENTRAL) following the PRISMA 2020 guidelines. Eligible studies included healthy adults receiving facial injections of poly-L-lactic acid (PLLA), polydioxanone (PDO), calcium hydroxylapatite (CaHA), polycaprolactone (PCL), or poly-D,L-lactic acid (PDLLA); however, no eligible PDLLA studies were identified. The included studies consisted of randomized controlled trials and observational studies. Data were synthesized using a random-effects meta-analysis model, and the risk of bias was evaluated using the RoB 2 and ROBINS-I tools. Twenty-four studies were included in the quantitative synthesis. The pooled mean GAIS score was 3.88 (95% CI: 3.63–4.14), indicating moderate to marked aesthetic improvement. Subgroup analysis revealed the highest GAIS scores with PDO (4.20), followed by PLLA (4.13, single study), PCL (4.00), and CaHA (3.33). Reported adverse events were mostly mild and transient, including erythema, swelling, and tenderness. Based on the GRADE assessment, the overall certainty of evidence was low for efficacy and very low for adverse events. Collagen biostimulators demonstrated favorable efficacy profiles for facial rejuvenation. Although all four agents were effective, outcomes varied by product type, suggesting the importance of personalized treatment selection. These findings provide evidence-based support for clinical application and highlight the need for future comparative studies with standardized outcome reporting.