Plastic Surgery Research Council
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PSRC 60th Annual Meeting
Program and Abstracts

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Method to the Madness: How To Optimize Fat Graft Quality and Retention During Placement
David A. Atashroo, MD, Taylor Wearda, BS, Jordan Raphel, MS, Kevin Paik, BS, Elizabeth R. Zielins, MD, Graham Walmsley, BA, Ruth Tevlin, MB BAO BCh, MRCSI, Michael S. Hu, MD, Dominik Duscher, MD, Zeshaan Maan, MBBS, MSc, MRCS, Christopher Duldulao, MS, Derrick C. Wan, MD, Geoffrey C. Gurtner, MD, Sarah Heilshorn, PhD, Michael T. Longaker, MD, MBA.
Stanford University, Palo Alto, CA, USA.

Purpose:
Owing to the unique availability and biocompatibility of fat, lipotransfer has become an attractive method for treating soft tissue deficits. However, it is limited by unpredictable graft survival and volume retention. Currently little is known about the viscoelastic properties of fat after injection using variable techniques. In this study, we use rheology, the study of material flow and deformation, to quantify the effects that cannula diameter, length, and shape, flow rate, and extensional flow have on the integrity of fat.
Methods:
Lipoaspirate was harvested from cosmetic surgery patients using suction assisted liposuction, and then prepared for grafting. A syringe pump was used to inject fat at a controlled flow rate through cannulas of various gauge, length, and shape. Lipoaspirate was then injected at various flow rates and with variable extensional flow. Processed samples were then tested in triplicate on a rheometer to measure their viscoelastic properties. Fat grafts representative from each group were then placed into the scalps of CD1 athymic nude mice. After 8 weeks, fat graft retention was measured using micro-CT and then grafts were explanted, weighed, and sectioned for histology and CD 31 staining.
Results:
Lipoaspirate injected through smaller, longer, and curved cannulas and at higher flow rates exhibited more shear thinning with diminished graft weight, volume retention, and quality. The storage modulus (G’) of fat processed with 18 gauge or 16 gauge cannulas was significantly lower than for fat processed with 14 gauge or larger cannulas (*p < .05). Similarly, the long cannula group had a significantly lower G’ than the short cannula (*p < .05). The optimal flow rate was .5ml sec, and this group had a significantly improved integrity compared to the 1 ml/sec and faster groups (*p < .05). Extensional flow negatively correlated with fat graft integrity.
Conclusions:
Discrete modifications in the equipment and method used for fat placement can have a significant impact on immediate graft integrity, and ultimately on graft survival and quality. Respecting these biomechanical influences during the placement phase of lipotransfer may allow surgeons to optimize outcomes.


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