An investigation of skin deformation around percutaneous devices

According to the literature one of the primary failure models of percutaneous devices (PDs) in soft tissue implantation sites is that of mechanically induced trauma along the implant/tissue interface. In order to avoid such avulsion, subcutaneous flanges have been incorporated into PD designs to provide a better distribution of stresses along the implant/tissue interface. Tissue necrosis and inflammation were then observed to be most pronounced around the rim of the subcutaneous flange. It was the goal of this study to develop and test PDs with subcutaneous flanges of varying stiffnesses in order to allow the flange to distribute stresses into the surrounding tissues more evenly, thereby reducing the likelihood of failure due to avulsion. PDs were tested with flanges of constant thickness or varying linearly, reducing toward the flange rim. They were evaluated using an in-vitro testing method which was designed to simulate the situation of an implanted PD subjected to external loading. The results indicated that the stiffness characteristics of the subcutaneous flange had a substantial effect on the behavior of the devices under loading. A PD having a radial stiffness decrease would improve the likelihood of implant survival in the clinical situation due to the reduction of mechanically induced trauma along the implant/tissue interface.