AAPS Main SiteTargeted Strain Reduction: A Novel Dynamic 3-D Imaging Technique for Precise Quantification of Botulinum Toxin Efficacy
Anthony J. Wilson, MD, Vivian M. Hsu, MD, Bianca Chin, MD, Ivona Percec, MD, PhD..
Hospital of the University of Pennsylvania, Philadelphia, PA, USA.
Targeted Strain Reduction: A Novel Dynamic 3-D Imaging Technique for Precise Quantification of Botulinum Toxin Efficacy
Goals/Purpose: Neuromodulation is a well-established treatment for dynamic rhytids. Neurotoxin treatment outcomes, despite their accepted efficacy, have been poorly quantified, thereby limiting advances in anatomically-based, personalized treatment regimens. We have previously validated the use of dynamic 3-D imaging for facial strain quantification. The purpose of this study is to apply this innovative technology for the precise quantification of botulinum toxin efficacy in specific anatomic regions.
Methods/Technique: Fourteen female subjects (mean age = 44) were evaluated using a dual camera system and 3-D optical analysis (ARAMIS, Trilion Quality Systems, PA). Points of maximal excursion were identified on the forehead and glabella and measured in a resting and dynamic motion over a 36 frame period during brow elevation and furrowing. Measurements for each patient were conducted at two time points: prior to and two weeks after the injection of 20 units of onabotulinumtoxinA (Allergan, Irvine, CA) into the glabella and forehead by a single trained injector. Unregistered frames were excluded resulting in a total of 446 pre-injection and 516 post-injection frames for analysis. Average and maximum strain in treated areas were measured and analyzed across all available frames. Using STATA (Statacorp, Texas) a Wilcoxon signed-rank test was employed to calculate differences before and after injection.
Results/Complications: After neurotoxin injection, average strain of the frontalis during brow elevation decreased from 4.3% to 1.8% (p = 0.03), maximum strain decreased from 40.4% to 23.1% (p = 0.03). The average strain in the glabella decreased from 10.7 % to 5.0 % (p = 0.03) while maximum strain decreased from 57.4% to 34.2% (p = 0.04). After neurotoxin injection, average strain of the frontalis during brow furrowing decreased from 9.12% to 1.7% (p= 0.009), maximum strain decreased from 41.9% to 15.5% (p= 0.04). Average strain in the glabella declined from 2.8% to 1.0% (p = 0.001), maximum strain decreased from 36.11% to 24.41 % (p= 0.03). 
Figure 1: Patient prior to injection of neurotoxin during brow furrowing. Blue, green, yellow and red demonstrate increasing local strain. 
Figure 2: Patient following injection of neurotoxin during brow furrowing. Blue, green, yellow and red demonstrate increasing local strain.
Conclusion: We validate a novel technique for objectively quantifying the effects of botulinum toxin using dynamic 3-D imaging and demonstrate that neuromodulation has a precise, statistically significant effect on upper facial strain. The application of this technology pre- and post-injection will advance our understanding of neurotoxin effects on specific anatomic sites and thereby have significant implications for the development of personalized, anatomically-based treatment regimens, for minimizing associated complications, and for maximizing the education of a new generation of plastic surgeons.
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