Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance.

The mechanical properties of 15 elastomeric liner products used in limb prosthetics were evaluated under compressive, frictional, shear, and tensile loading conditions. All testing was conducted at load levels comparable to interface stress measurements reported on transtibial amputee subjects. For each test configuration, materials were classified into four groups based on the shapes of their response curves. For the 15 liners tested, there were 10 unique classification sets, indicating a wide range of unique materials. In general, silicone gel liners classified within the same groups thus were quite similar to each other. They were of lower compressive, shear, and tensile stiffness than the silicone elastomer products, consistent with their lightly cross-linked, high-fluid content structures. Silicone elastomer products better spanned the response groups than the gel liners, demonstrating a wide range of compressive, shear, and tensile stiffness values. Against a skin-like material, a urethane liner had the highest coefficient of friction of any liner tested, although coefficients of friction values for most of the materials were higher than interface shear:pressure ratios measured on amputee subjects using Pelite liners. The elastomeric liner material property data and response groupings provided here can potentially be useful to prosthetic fitting by providing quantitative information on similarities and differences among products.

Tissue engineering of perfused microvessels.

One major obstacle toward the creation and survival of larger, three-dimensional tissues is the lack of a vascular network that provides transport of oxygen, nutrients, and metabolic byproducts. Although attempts to create microvasculature in vitro have been described previously (Microcirculation 2 (1995), 377; Tissue Eng. 6 (2000), 105; Ann. NY Accd. Sci. 944 (2001), 443), these methods depend on vascularization of void spaces within the tissue-construct or on the utilization of empty capillary networks by host vessels. In the present study, we examined the possibility of creating perfused microvessels in vitro that can be included in an artificial tissue. First, strands of nylon line with their ends fit into microtubing were positioned within small perfusion chambers. Vascular smooth muscle cells (SMCs) were then seeded onto the nylon strands and tubing. The cells multiplied to form concentric layers. Layer thickness was approximately 100 microm after 21 days and 150 microm after 28 days of culture. The lines were then extracted and the chambers connected to a perfusion system. The vessels were continuously perfused with culture medium over 7 days without failure. Artificial microvessels may prove useful in tissue engineering and as models for vascular research.