A histologic analysis of three-dimensional versus two-dimensional tissue expansion in the porcine model

Objective: Recently, a two-dimensional Silastic Dacron stretching skin devi ce has been developed for scalp reduction surgery. Attached subgaleally, th is device stretches skin over time, while avoiding the visible volumetric d istention that is typical of three-dimensional tissue expanders. Unlike thr ee-dimensional expanders, the histological changes observed with a two-dime nsional stretching device have not been described in the literature. The pr esent study compares the histological effects of two-dimensional and three- dimensional skin tissue expansion in the porcine model. Study Design: A uni versity Institutional Review Board-approved study in which 16 domestic pigl ets were used. The 16 piglets were divided evenly into four cohorts as foll ows: 1, 1-week control cohort; 2, 1-week experimental cohort; 3, 4-week con trol cohort; and 4, 4-week experimental cohort. Methods: Tissue expanders ( three-dimensional) and Dacron Silastic tissue stretchers (two-dimensional) were surgically inserted into the lateral skin of 16 domestic pigs. Animals were killed at either 1 or 4 weeks based on group assignment, Light micros copic ocular micrometry and stereological point counting were used to deter mine the depth of the epidermis, dermis, and subdermal adipose tissue layer ; width of the panniculus muscle; diameter of sweat gland follicles; percen tage ratio of dermal collagen, blood vessels, and tissue space; and epiderm al mitotic index in 100 specimens. One-way ANOVA was used to evaluate stati stical differences. Results: Both tissue expanders yielded increased values compared with control subjects, with respect to epidermal, dermal, and fat widths and blood vessel counts, whereas adnexal structures in the pannicul us muscle width were unaltered. Conclusions: Although statistically the two types of expansion produced histologically similar changes, the degree of change varied according to the type of expander that was used and the durat ion of tissue expansion. Most notably, three-dimensional expansion produced more tissue gain per unit area expanded at both the 1-week and the 4-week time intervals, and early (1-week) two-dimensional tissue expansion stimula ted a greater angiogenic response than three-dimensional expansion. These f indings will assist the surgeon in understanding the physical changes that occur with these two forms of tissue expansion, as well as the potential cl inical advantages and shortcomings of each method.