The Architecture of Fat Grafting II: Impact of Cannula Diameter.

BACKGROUND: Fat grafting has emerged as the treatment of choice for soft-tissue augmentation and reconstruction. Variability of volume retention remains the greatest challenge for this technique, often requiring multiple operations to achieve the desired volume. Graft that is placed greater than 2 mm from the recipient bed will undergo necrosis. Improved understanding of the architecture of fat within the recipient bed is paramount to improving outcomes. The impact of cannula diameter on graft architecture is unknown. METHODS: Fat was harvested by liposuction and stained with methylene blue. Stained fat was grafted into 4 × 2 × 1-cm sections of excised abdominal tissue with 12-, 14-, 16-, and 19-gauge Coleman cannulas at three different volumes: 0.1, 0.5, and 1.0 cc. Each tissue block was sectioned for stained graft visualization. The diameter of each deposit and percentage with a radius greater than 2 mm were recorded. RESULTS: With an injection volume of 0.1 cc, no fat deposits had a radius greater than 2 mm, regardless of cannula size. A graft volume of 0.5 cc created globules greater than 2 mm with larger cannulas (0 percent with 19-gauge, 2.9 percent with 16-gauge, 6.1 percent with 14-gauge, and 4.3 percent with 12-gauge). Injecting 1.0 cc resulted in a significant increase in the percentage of fat parcels expected to undergo central necrosis (16 percent with 19-gauge, 21 percent with 16-gauge, 26 percent with 14-gauge, and 44 percent with 12-gauge). CONCLUSIONS: Injection cannulas of 14-gauge or larger are more likely to create deposits with dimensions that may be susceptible to central necrosis when injecting 1.0 cc per pass. Smaller cannula sizes or lower volumes per pass should be considered. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

The Architecture of Fat Grafting: What Lies beneath the Surface.

BACKGROUND: Fat grafting is a powerful procedure limited by unpredictable volume loss. Grafted tissue survives via plasmatic imbibition until neovascularization occurs; therefore, fat that is deposited more than 0.2 cm from capillaries will undergo central necrosis. This study aims to determine the architecture of fat deposits within the recipient bed following fat grafting. METHODS: Fat was harvested by liposuction and stained with methylene blue. Stained fat was grafted into 4 × 4 × 2-cm sections of pannus tissue at graft-to-recipient volume ratios ranging from 1:10 to 1:1. Each tissue block was sectioned for stained graft visualization. The diameter of each deposit and the percentage with a radius greater than 0.2 cm were recorded. RESULTS: Average tunnel diameter was 0.20 ± 0.01 cm at a graft-to-recipient ratio of 1:10, 0.25 ± 0.01 cm at 1:8, 0.26 ± 0.01 cm at 1:6, 0.31 ± 0.01 cm at 1:4, 0.40 ± 0.01 cm at 1:2, and 0.57 ± 0.02 cm at 1:1. All comparisons reached statistical significance (p ≤ 0.05) except 1:8 versus 1:6 (p = 0.96). The percentage of fat parcels with a radius greater than 0.2 cm was 3.0 percent at 1:10, 5.3 percent at 1:8, 9.5 percent at 1:6, 20.9 percent at 1:4, 42.0 percent at 1:2, and 68.3 percent at 1:1. All percentage comparisons were significant except 1:10 versus 1:8 (p = 0.15). CONCLUSION: As the total volume transferred increases, grafted deposits coalesce to form larger globules, particularly at ratios beyond 1:4, likely contributing to central necrosis and subsequent volume loss. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.