Advancing the Evidence on Glabellar Contraction Patterns—A Prospective Multicenter Study on Its Clinical Relevance for Glabellar Neuromodulator Injections

BACKGROUND: Glabellar neuromodulator injections are frequently guided by skin surface contraction patterns, assuming that visible rhytids reflect underlying muscular anatomy. However, emerging anatomical and imaging evidence has questioned the clinical relevance of pattern-based treatment adaptations. OBJECTIVE: To prospectively evaluate whether different glabellar contraction patterns influence clinical and patient-reported outcomes when a standardized, anatomy-based, FDA-approved 5-point injection algorithm is applied. METHODS: This prospective, multicenter clinical study enrolled 125 patients treated across five independent centers. Patients were classified into five previously described glabellar contraction patterns (V-shape, U-shape, converging arrows, omega, and inverted omega) based on standardized photographs during maximal frowning. All patients received neuromodulator injections following the same standardized 5-point technique using either onabotulinumtoxinA or abobotulinumtoxinA with dose equivalence. Clinical outcomes were assessed using the Glabellar Line Severity Scale (GLSS) at baseline, 15 days, and 90 days, while patient-reported outcomes were evaluated with the Global Aesthetic Improvement Scale (GAIS) at 90 days. Statistical analyses included non-parametric group comparisons and multivariate ordinal logistic regression. RESULTS: A total of 119 patients completed the study. A significant improvement in GLSS was observed at 15 days (p < 0.001), followed by partial regression at 90 days (p < 0.001 vs. baseline). No statistically significant differences in GLSS or GAIS were identified between contraction pattern groups at any time point (all p > 0.05). Multivariate analysis demonstrated that age and body mass index significantly influenced treatment outcomes, whereas glabellar contraction patterns and Fitzpatrick skin type did not. Mild, transient local adverse events were observed and resolved spontaneously. CONCLUSION: Glabellar contraction patterns do not significantly affect clinical or patient-reported outcomes when neuromodulator injections are performed using a standardized, anatomy-based 5-point technique. These findings support prioritizing muscular anatomy and patient-specific biological factors over surface rhytid patterns in glabellar neuromodulation.