Ratio Analysis Evaluation of Dermal Collagen and Elastic Fiber Contents: A Comparison of the Horizontal and Vertical Directions of Skin Tissues

Background: Stretching force on the skin leads to the widening of scars and/or hypertrophy. The uneven distribution profile of collagen and elastic fibers in the human dermis (evaluated based on their topographic areas) might determine the direction of incision for a more pleasing aesthetic result. Materials and methods: Full-thickness skin samples were collected in the horizontal and vertical directions from 15 areas of 32 human cadavers. The histological preparation of the skin samples was performed using special Verhoeff-van Gieson staining. Image analysis in the TissueQuant software was performed using photomicrographs. Quantitative fraction measures for collagen and elastic fibers were completed. From the data obtained, various ratios between collagen in the horizontal (CH) and vertical (CV) directions and elastic fibers in the horizontal (EH) and vertical (EV) directions were established and expressed as CH:CV and EH:EV. Results: In the areas where CV:CH was less than 1 (low ratio of significance), the collagen content was significantly higher in the horizontal direction than the vertical direction (CH>CV). However, this finding is reversed (CV>CH) in areas where CV:CH is greater than 1 (high ratio of significance). Similarly, in areas where EV:EH is less than 1 (low ratio of significance), the elastic fiber content was significantly higher in the horizontal direction than the vertical direction (EH>EV), whereas such is reversed (EV>EH) where EV:EH is greater than 1 (high ratio of significance). Conclusion: The evaluation of ratios of dermal collagen and elastic fibers in different directions together with the data of asymmetric distribution provide a useful guideline for aesthetic surgeons looking to place elective incisions in the direction that will ensure an improved aesthetically pleasing result.