Lu GN, et al. - Using a New England white rabbit model, researchers investigated the ideal ratio of skin to cartilage and the importance of the perichondrial attachment for graft survival. The results provide preliminary evidence that changing the skin to cartilage ratio resulted in a negative association with survival when the size of the cartilage was larger than the skin. A significant decrease in composite graft survival was noted when skin and cartilage were separated before transfer.

Methods

• This study was performed at the Laboratory for Animal Research at University of Kansas Medical Center from January 25 to March 18, 2016.
• Researchers transplanted four varying designs of chondrocutaneous auricular grafts to dorsal back defects, with a total of 10 grafts per treatment arm completed.
• They designed four chondrocutaneous circular grafts: group A, 1.5-cm diameter graft of equal skin to cartilage ratio; group B, 2.0-cm diameter skin and 1.5-cm diameter cartilage; group C, 1.5-cm diameter skin and 2.0-cm diameter cartilage; and group D, 1.5-cm diameter skin and cartilage separated and placed back together in a layered fashion.
• They observed grafts until postoperative day 21, harvested, and evaluated them with visual observation as well as histopathologic assessment.
• Two blinded academic facial plastic surgeons marked the visually graded areas of survival and calculated these for approximate survival.
• Evaluation of hematoxylin-eosin–stained, paraffin-embedded 5-μm slides was performed for overall survival rate, rate of cartilage necrosis, and mean vessel density per high-power field.
• Observers were blinded in both cases as in the study group.

Results

• The five female rabbits underwent visual assessments indicating significant agreement between surgeons and consistency, with a Spearman coefficient of 0.84 and an intraclass correlation of 0.98.
• Visual grading displayed significantly decreased mean survival (45.4%; 95% CI, 23.3%-67.4%) in Group D (skin and cartilage separation) compared to group A (mean survival, 97.4%; 95% CI, 94.8%-99.9%; P < .001), group B (mean survival, 87.6%; 95% CI, 69.9%-100%; P=.004), and group C (mean survival, 82.1%; 95% CI, 66.0%-98.1%; P=.008).
• On histopathologic assessment, group D again displayed significantly inferior overall survival, increased cartilage necrosis, and decreased mean vessel density vs group A.
• In addition, Group C displayed markedly reduced cartilage survival vs group A (65% vs 0%; P < .001) and group B (65% vs 35%; P=.02).