The depth of arterial supply of forehead: a meta-analysis.

Summary

Pooling 5 studies (201 SOA, 282 STA), the meta-analysis shows STA becomes more superficial distally while SOA depth is consistent. Practical guidance emerges: inject ≤2.5 mm in the medial forehead and up to 3.5 mm laterally, with pre-procedure high-resolution ultrasound mapping to avoid arterial injury.

Key Findings

• SOA depth: 5.68 mm at glabella and 5.53 mm above eyebrow; STA depth: 4.45 mm at glabella and 3.53 mm above eyebrow.
• STA becomes more superficial along its course; SOA maintains consistent depth across levels.
• Recommended injection depths: ≤2.5 mm medially and ≤3.5 mm laterally; pre-injection high-resolution ultrasound advised.

Clinical Implications

Adopt ultrasound mapping of STA and SOA before forehead filler injections and adhere to conservative depths (≤2.5 mm medial; ≤3.5 mm lateral) or inject laterally to the arterial paths to reduce vascular events.

Limitations

• Only five source studies with potential heterogeneity in measurement methods (cadaver vs. in vivo).
• Population differences (age, sex, ethnicity) and dynamic tissue changes were not uniformly controlled.

Future Directions

Prospective ultrasound-based mapping studies across diverse populations; correlate injection depth adherence with complication rates to validate safety thresholds.