How much does facial movement contribute to facial ageing? Researchers are using a ‘real-time dynamic three-dimensional imaging’ technique to study the strains placed on the soft tissues by facial expressions, reports a study in Plastic and Reconstructive Surgery—Global Open®, the official open-access medical journal of the American Society of Plastic Surgeons (ASPS).
In a pilot study, ASPS Member Surgeon, Vivian M. Hsu of University of Pennsylvania and colleagues used a technique called ‘speckle tracking photogrammetry’ to evaluate and measure strain on the facial soft tissues produced by facial movements. ‘The technology of three-dimensional optical imaging can be used to advance our understanding of facial soft tissue dynamics and the effects of animation on facial strain over time,’ the researchers write.
3D imaging to show facial soft tissue strain
The study used a specialised 3D optical imaging system to measure the strain on soft tissues associated with facial movement. The study included 13 adult volunteers between age 18 and 70. The procedure began by spraying a ‘speckle’ pattern onto the subjects’ faces.
After a digital image was made in a ‘neutral’ facial expression, the subjects were photographed making different facial expressions, such as smiling, laughing, and grimacing; surprised and angry expressions; and whistling (pursed lips). Using the speckle pattern, the imaging system software was able to demonstrate and quantify the strain on facial soft tissues caused by these facial movements.
The 3D imaging technique—used by engineers to measure strain on various materials—has recently been applied to measuring the mechanical properties of biological organs and tissues. The system generated a ‘heat map’ colour scale, with red indicating the area of greatest strain and blue showing areas of lesser strain.
Facial strain is greater in older subjects
For all six expressions, the heat map showed the areas of greatest strain were located in the midface and lower face. For subjects older than 40 years, strain was greater in the perioral region (around the mouth): about 58%, compared to 34% for those younger than 40.
The age-related increase in strain with lip-pursing was even greater in the nasolabial folds (the lines running from the nose to the corners of the mouth)—about 62% in subjects over 40 versus 33% in younger subjects. Older subjects also showed greater asymmetry of strain in the nasolabial fold: 18% versus 5%.
Overall stretch in the lower face during lip-pursing was greater in women than men. For smiling and other facial expressions, measurements of strain were similar for older and younger subjects.
The results may lend new insights into the ‘intricate and multifactorial process’ of facial ageing. Facial movement is clearly affected by facial ageing, but “the relationship between dynamic and static aging remains to be understood,’ Dr Hsu and coauthors write.
Three-dimensional dynamic imaging techniques may help researchers to better understand ‘the multidimensional attributes of the aging face.’ The pilot study confirm what plastic surgeons know from experience: that movement of the perioral tissues is an important contributor to facial ageing.
‘We hope these data will serve as a first step for improving our ability to understand and develop more effective treatments for the lower face and beyond,’ Dr Hsu and coauthors write. They believe that soft tissue strain analysis could also have ‘broad and functional implications’ for various types of reconstructive surgery procedures, such as abdominal wall reconstruction, facial reanimation surgery, and facial reconstruction after trauma.