Pillared-surface microstructure and soft-tissue implants: Effect of implant site and fixation

Abstract

Previous work with subcutaneous implants in a rat animal model has shown that pillarlike surface microstructure will reduce fibrosis and enhance blood vessel approximation to the implant surface when compared with nontextured controls. This study was designed to determine the effect of microtissue anatomy and implant site on the observed response, as well as the effect of implant fixation. The lateral posterior sites were found to contain a fat pad which produced a dramatically reduced fibrosis for the micro-structured implants compared with smooth controls. Although significant differences between pillar-micro-structured implants and controls were found for most sites, neither fascia nor muscle reduces the level of cellular response to the same degree as fat. Suture fixation of the implants did not produce a significantly different response in these tests. The occupation of the interpillar spaces by fat and moderation of interfacial shear forces is proposed as a mechanism to explain these results.

Biomechanics of the Sensor-Tissue Interface—Effects of Motion, Pressure, and Design on Sensor Performance and the Foreign Body Response—Part I: Theoretical Framework

“…Numerous others have also reported that surface-textured implants (e.g., pillars, porous surfaces) exhibit a significantly thinner and less dense fibrous capsule. [56][57][58][59][60] The greatly increased surface area of these porous and pillared materials serves to reduce interfacial stresses at the tissue-implant interface by allowing the stresses to distribute over a much greater surface area. 58 Therefore, it is hypothesized that the body does not attempt to provide as much mechanical stabilization when forces are distributed, so capsules are thinner and less dense.…”

“…Surface microarchitecture (including microtopography, pillars, and porous coatings) is an area of abundant biomaterial research 14,58,60,102,103 and has been applied to glucose sensors. 4,19,20,43,50,104 It is known that materials of the exact same chemical composition can exhibit vastly different FBR depending on the surface microarchitecture.…”

“…Picha and Drake found that surface pillars reduced interfacial shear by improving tissue integration and resulted in reduced fibrosis, improved vascularity, and improved overall tissue response (Figure 3). 58 Similarly, porous coatings have been shown to improve tissue integration and FBR. 14,17,102 One caveat to the use of porous coatings for PerQ soft-tissue sensors is that some researchers suggest that the tissue integration could actually be detrimental, as external forces on the sensor are transmitted to the region occupied by the coating and beyond, a phenomenon that has been described as tearing the device from its implantation bed.…”

“…To minimize biomechanical forces due to modulus mismatch, sensors intended for SubQ implantation need to be much softer than those injected into the stiffer epidermis layers. 88,146 Even without a perfect modulus match, implantation studies in adiposerich tissues have exhibited a more benign FBR, 58,147 likely due to stress absorptive properties of fat. Of course, size constraints of the desire tissue compartment are important, that is to say, it would be difficult to place a 3-mm-thick sensor in a 1-mm-thick dermal layer.…”

Tissue reactions evoked by porous and plane surfaces made out of silicon and titanium

“…The surface topography seems to be the predominant factor for the induced tissue response when altering both material and topography [30], [31]. Textured, especially porous surfaces are preferable when compared with plane ones [32]- [34]. In vitro studies on cell culturing have shown that cell adherence and viability increased using porous silicon compared with planar silicon [35].…”