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Updated: Dec 8, 2025
Quantification of Strain in a Porcine Model of Skin Expansion Using Multi-View Stereo and Isogeometric Kinematics
Published on: April 16, 2017
Modeling Tissue Expansion with Isogeometric Analysis: Skin Growth and Tissue Level Changes in the Porcine Model
Lindsay E Janes1, Joanna K Ledwon1, Elbert E Vaca1
1From Northwestern University Feinberg School of Medicine, Ann & Robert H. Lurie Children's Hospital of Chicago, Division of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute; and the School of Mechanical Engineering, Purdue University.
Background:
Tissue expansion relies on the ability of skin to grow in response to sustained mechanical strain. This study focuses on correlation of cellular and histologic changes with skin growth and deformation during tissue expansion.
Methods:
Tissue expanders were placed underneath the skin of five Yucatan minipigs and inflated with one fill of 60 cc of saline 1 hour, 24 hours, 3 days, and 7 days before the animals were killed, or two fills of either 30 cc or 60 cc at 10 and 3 days or 14 and 7 days before the animals were killed. Skin biopsy specimens and three-dimensional photographs were used to calculate skin growth and stretch according to the authors' novel finite element analysis model.
Results:
The mitotic index of keratinocytes in the basal layer increased 1 hour after stimulus was applied (4 percent) (p = 0.022), peaked at approximately day 3 (26 percent) (p < 0.0001), and tapered by day 7 (12.5 percent) (p = 0.012) after tissue expansion. The authors demonstrated that it is the volume per fill rather than the total volume in the expander that scales the magnitude of response. Lastly, the authors demonstrated that the ratio of deformation attributable to growth versus stretch (Fgrowth/Fstretch) after 60 cc of tissue expansion fill was 1.03 at 1 hour, 0.82 at 1 day, 0.85 at day 3, and 0.95 at 7 days.
Conclusions:
Peak cell proliferation occurred 3 days after tissue expansion fill and is scaled in response to stimulus magnitude. The growth component of deformation equilibrates to the stretch component at day 7, as cell proliferation has started to translate to skin growth.
