Subcutaneous microfabricated surfaces inhibit epithelial recession and promote long-term survival of percutaneous implants

The long-term success of percutaneous devices is compromised by problems such as infection, mechanical avulsion and epithelial downgrowth. The objective of this study was to test the effects of microfabricated surfaces on tissue integration and long-term survival of percutaneous implants, using a modified implant design and a two-stage surgical method. Hexagonal titanium-coated epoxy implants were constructed with separate subcutaneous and percutaneous components, so that the effects of surface topography on connective tissue could be separated from the effects on epithelium. Subcutaneous components with 30-μm-deep micromachined grooves, 120-μm-deep tapered pits, or smooth control surfaces were secured to the calvarial bone of rats by a titanium pin. After 8 weeks, a percutaneous smooth-surfaced component was secured to the subcutaneous component. Dental impression materials were used to make models of the components and adjacent tissues at weekly intervals and tissue recession around the implants was measured. Some implants were removed at intervals up to 24 weeks and processed for histology. Connective-tissue ingrowth and mineralized tissue were noticed on the micromachined surfaces, whereas a thick capsule and epithelial downgrowth were observed on smooth control surfaces. On all implants, recession occurred most rapidly in the first 3 weeks, but was significantly reduced relative to the smooth controls only on implants with micromachined grooved subcutaneous surfaces (p<0.05). In addition, the time before failure was significantly (p<0.05) longer for implants with grooved subcutaneous surfaces than implants with smooth and pitted subcutaneous surfaces. This study indicated that an impression technique could be used to monitor tissue recession on percutaneous devices, and that micromachined grooved surfaces located subcutaneously improved the performance and longevity of percutaneous devices by promoting tissue integration.