Percutaneous device

In-Vivo Percutaneous Implant Experiment. The principle of percutaneous attachment has extensive application in many biomedical areas, including the attachment of dental and orthopedic prostheses directly to skeletal structures, external attachment for cardiac pacer leads, neuromuscular electrodes, energy transmission to artificial heart and for hemodialysis. Several attempts to solve the problem of fixation and stabilization of percutaneous implants(19) have been made. Failures were also attributed to the inability of the soft tissue interface to form an anatomic seal and a barrier to bacteria. In the current studies, the effect of pore size on soft tissue ingrowth and attachment to porous polyurethane (PU) surface and the effect of the flange to stem ratio and biomechanical compliance on the fixation and stabilization of the percutaneous devices have been investigated.(20)... 

A series of percutaneous implant devices with three stem/flange ratios (1 1, 1 2 and 1 4) was fabricated from three materials (Dacron velour - silicone, porous PU and porous metal). The implants were totally porous (coarse, 150-250 ym) with 1.5 mm diameter holes drilled throughout the device. Figure 6 shows the mold and the polyurethane percutaneous devices with three stem/ flange ratios and 1.5 mm diameter drilled holes. 

From these in-vivo implant studies, we learn that the following factors may contribute to the success of a percutaneous device ... 

Importance of flange/stem ratio and the weight of the device in stabilizing and anchoring the percutaneous device. 

Kono K, Mori T, Koyanagi H, Grieeith BP and Kormos RL (1998) Fine trabecularized carbon ideal material and texture for percutaneous device system ofpermanent I ft ventricular assist device. 

Aoki H, Akao M, Shin Y, Tsuji T, Togawa T (1987) Sintered hydroxylapatite for percutaneous devices and its clinical application. Med Progr Technol 12 213... 

Nosocomial bloodborne infections in hospitalized patients are associated with a two- to threefold increase in mortality. The origin of infection is usually either cannula-related or infusate-related. Cannula-related infections include those derived from percutaneous devices used for vascular access (e.g., needles, hubs, and plastic catheters). Maki reports that between 5 and 25% of intravascular devices are microbially colonized at the time of vascular withdrawal [25]. Large numbers of microorganisms are observed on the intravascular portion of the cannula or its tip (Fig. 1). 

Porous materials used in soft tissue applications include polyurethane, polyamide, and polyester velours used in percutaneous devices. Porous reconstituted coUagen has been used in artificial skin, and braided polypropylene has been used in artificial ligaments. As in the case of bone implants, the porosity encourages tissue ingrowth which anchors the device. 

The problem of obtaining a functional and viable interface between the tissue (skin) and an implant (percutaneous device) is primarily due to the following factors. First, although initial attachment of the tissue into the interstices of the implant surface occurs, attachment cannot be maintained for a sustained time since the dermal tissue cells turn over continuously. Downgrowth of epithelium around the implant or overgrowth on the implant leads to extrusion or invagination, respectively. Second, any opening near... 

No percutaneous devices are completely satisfactory. Nevertheless, some researchers believe that hydroxyapatite maybe part of a successful approach. In one experimental trial, a hydroxyapatite-based percutaneous device was associated with less epidermal downgrowth (1 mm after 17 months vs. 4.6 mm after 3 months) when compared with a sUicone rubber control specimen in the dorsal skin of canines. Researchers have also investigated coatings such as laminin-5 which has been shown to enhance epithelial attachment. 

Artificial ear implants capable of processing speech have been developed with electrodes to stimulate cochlear nerve cells. Cochlear implants also have a speech processor that transforms sound waves into electrical impulses that can be conducted through coupled external and internal coils. The electrical impulses can be transmitted directly by means of a percutaneous device. 

Polymers which can adhere to soft tissues are also necessary. They could be used as part of a percutaneous device to prevent tuimel infection through the dead space between the skin tissue and the material surface. We have demonstrated that... 

Brecker, S. J. D. (Ed). (2006). Percutaneous device closure of the atrial septum. United Kingdom Informa Heathcare. 

Clift P and Thorne S. Clinical presentation of the atrial septal defect in adults. In S. J. D. Brecker, ed. Percutaneous Device Closure of the Atrial Septum. United Kingdom Informa Heathcare 2006. 

On the other hand, the lack of adhesiveness causes infection when the implants were used as percutaneous devices. Ikada et al. [83] immobilized collagen onto the surface of a silicone device to prevent infection and epidermal downgrowth when a silicone percutaneous device was implanted. The surface of PAS can be modified by discharge treatment and a subsequent surface graft that polymerizes [84] and immobilizes biomolecules. By using this method, the hydrophobic surface of PAS was changed to hydrophilic or bioadhesive. PAS seems to be useful as implant material for both purposes. 

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