Roughing up implants

Medical implants – from catheters that deliver long-term life support to joint replacements – may work better when their surfaces are on the rough side, according to researchers at Ohio State University.

Implants often have surfaces that soft tissue, such as skin and connective tissue, cannot attach to, said Andreas von Recum, a professor of biomedical engineering at the University. So the body in turn forms a tissue capsule around the implant, sealing it off from the rest of the body. That seclusion, however, can lead to a variety of serious problems.

“Being encased in connective tissue seriously compromises an implant’s function,” von Recum said. “And connective tissue can’t tolerate constantly moving against a foreign object. This friction – and ensuing inflammation – kills healthy cells and creates a steadily growing capsule of dead tissue.”

Adding texture to an implant’s surface increased compatibility with connective tissue cells, called fibroblasts, considerably.

And while researchers von Recum and Rakhi Jain, a former doctoral student at Ohio State, conducted their experiments using titanium -commonly used to make implants – all implants can benefit from having a textured surface.

The researchers made the discovery by coating disk-shaped polyester wafers with titanium. Some of the disks were then covered with grooves only several microns deep.

Fibroblasts from mice were left to grow on both the smooth and textured disks for three days. At the end of that time, the researchers used photomicrography – taking an image through a confocal microscope – to determine the distance between cell membranes and disk surfaces.

The distance between the fibroblasts and the surface of the textured disks was immeasurable, suggesting that these cells had adhered to the surface. Conversely, the researchers could measure the distance – although very small, on the order of nanometers – between cell membranes and the surface of a smooth disk.

Adding texture to implants isn’t a new concept; it first gained popularity in the 1960s.

“The problem with those implants was that the scale of roughness was a hundred to a thousand times larger than what we’ve found to be effective,” von Recum said.

“The interface went beyond a layer of connective tissue cells – these old implants essentially became embedded in the body as connective tissue and bone grew into them. Their removal was nearly impossible, as it usually resulted in major bone loss in some types of implants.”

“The technique we’re proposing – and it will be some time before such implants are made and used – doesn’t adhere nearly as strongly to the surrounding tissues,” he concluded.