The origin of expanded tissue.

Tissue expansion results in an increase in the total population of epidermal cells: a dividend. The dermis thins initially, but probably reconstitutes over time.

Complications in tissue expansion.

Appropriate patient selection, proper informed consent, and a calm and thoughtful approach to problems of implant deflation, infection, and exposure should prevent true "disasters" in tissue expansion.

Histopathology of human expanded tissue.

In this article the authors summarize statistical data from 19 patients obtained during quantitative analysis of the thickness of expanded skin and soft tissues utilizing silicone expander procedures. Histopathologic and ultrastructural changes that take place in individual levels of expanded tissues are also illustrated.

Tissue expansion: dividend or loan?

Epidermal mitotic activity during tissue expansion has been assessed in the guinea pig using tritiated thymidine and other confirmatory techniques. Implant inflation results in a threefold elevation of epidermal mitotic activity within 24 hours, followed by a gradual return to normal baseline over 2 to 5 days. Implant deflation, conversely, causes a transient decrease in epidermal mitotic activity. Neither of these phenomena has been previously described. It confirms previous animal studies which illustrate the highly responsive nature of the epidermis to physical stimuli and supports the view that tissue expansion is a highly useful manipulation of normal physiologic processes.

Intracellular collagen fibers in the capsule around silicone expanders in guinea pigs.

Ultrastructural studies of fibrous capsules surrounding silicone tissue expanders in guinea pigs revealed a number of fibroblasts containing collagen fibers inside cytoplasm with typical periodicity. These fibers were single or multiple, appeared straight, coiled, or bent, and lay in narrow, undulating membrane spaces. These intracellular collagen fibers were found in as many as 15% of the cells in capsules between 7 and 12 weeks of expansion. These observations suggest that during capsule development there is some imbalance between the synthesis of collagen fibers and their degradation. It is possible that increased synthesis of collagen fibers as well as their phagocytosis by fibroblasts may exist simultaneously.

Histomorphologic evaluation of guinea pig skin and soft tissue after controlled tissue expansion.

To evaluate the histologic changes attendant on tissue expansion in the guinea pig, self-inflating implants were placed in the dorsal subcutaneous space and the tissue response was sequentially studied at periods ranging from 1 to 18 weeks. Fixation artifacts have been minimized. The cellular response is relatively benign. The epidermis does not undergo thinning during expansion, although dermis and panniculus carnosus become significantly thinner. Atrophy of panniculus muscle is demonstrable. This study supports the hypothesis that tissue expansion results in a net gain of donor tissue.

A self-inflating tissue expander.

Tissue expansion is a means of mechanically creating an excess of soft tissue, contiguous to a defect, for use in reconstruction. To accomplish this, a self-inflating implant has been designed, tested, and used clinically. It offers potential advantages over similar percutaneously inflated devices, but has also presented new problems. Histologically, tissue expansion in the guinea pig is relatively innocuous, utilizing this implant; clinical results were similarly encouraging. Further clinical studies and applications await the identification of a more permeable membrane.

Electron microscopic evaluation of guinea pig skin and soft tissues "expanded" with a self-inflating silicone implant.

An electron microscopic study of guinea pig skin and soft tissue after expansion by self-inflating silicone implant for periods of 7 weeks to 8 months revealed definite ultrastructural changes. In the epidermis, the cells of the malpighian layer contained larger groups of tonofilaments forming tonofibrils. Intercellular spaces in all layers of expanded epidermis were much more reduced than in normal epidermis. The basal lamina and the laminar surfaces of the basal cells demonstrated more undulation than those of the controls. The expanded dermis contained large bundles of compacted collagen fibers, as well as thin collagen fibers, active fibroblasts, and a few myofibroblasts. The subcutaneous tissue contained a paucity of adipose tissue and thickened collagen fibers in the interlobular spaces. The skeletal muscle showed larger amounts of sarcoplasm in relation to myofibrils. An increased number and size of mitochondria were found with sarcomeres abnormally arranged. The capsule around the implant was composed of active, elongated, and flattened fibroblasts and bundles of collagen fibers with variable fiber width. Intracellular collagen fibers were found in the cytoplasm of the fibroblasts. Myofibroblasts in the capsule were observed more often in early expanded tissue. Small blood vessels in the capsule showed multiplication of the basal lamina or were surrounded by a very wide, homogenous material. Inflammatory cells were not found in the capsule. Such findings are important in developing and evaluating future skin-expansion research in humans and animals.

The tophus in calcium pyrophosphate deposition disease.

A 61-year-old man had a tophus on the third finger of his right hand. There was no history of arthritis, no laboratory abnormality, and no chondrocalcinosis. Crystalline material from the tophus was identified as calcium pyrophosphate dihydrate by x-ray diffraction.