The latest issue of Plastic and Reconstructive Surgery Journal November 2018 was filled with articles in my wheelhouse. I love fat grafting, and many of the studies and articles were all about it. This one was good for technical aspects- does the size of the cannula affect how much fat survives?
This is not something you, the patient, has any clue about. When we harvest fat and inject it, we use cannulas. The cannula is a rod, with little holes at the end of it. Harvesting cannulas are used to collect the fat, injecting cannulas to inject the fat.
The question is does size matter?
The study is out of Pittsburgh, from Dr. Rubin, a longtime researcher on fat transfer. This study was, “The Architecture of Fat Grafting II: Impact of Cannula Diameter.”
How do we get more fat to survive? We know volume retention varies. Graft that is place more than 2mm from the recipient bed will die. So these researchers harvested fat by liposuction and stained it with blue dye. They then grafted the fat using different sized cannulas (12, 14 15, and 19 gauge cannulas) and different volumes (0.1, 0.5, and 1.0cc). They looked at the diameter of each deposit, and looking at how many of these deposits were larger than a radius of 2mm. Again, greater than 2mm radius = too big to get blood supply = fat dies.
Findings:
- When you inject with 0.1cc per injection, no fat deposits were too big, regardless of cannula size.
- If you did 0.5cc and the larger the cannula, more deposits were more than 2mm–with 6% too big using a 14 gauge cannula.
- Doing 1.0cc per injection had a much higher rate of fat which was too large– going up to 44% with a 12 gauge injection cannula.
Conclusion?
- Don’t use 14 gauge cannulas when doing 1.0cc per pass.
- Use smaller volumes and smaller cannula sizes.
What do I think?
Yay for me. When I am doing fat grafting to the face, I use a 19 or 20 gauge cannula, and I do multiple passes per 1.0cc, somewhere usually between 0.1 and 0.2 per droplet. In his project when you did small deposits and used a small cannula, the fat deposit size was good to avoid necrosis.