MEDICA 2011 Will Highlight Advances in Implant Medicine

Many medical fields use a bone implant of one kind or another, from dentistry to orthopedics to trauma care. In general, such implants should meet multiple criteria, including a surface that will readily integrate with the bone, biocompatibility, absence of toxic substances, and bioresorbability. The implant must also be able to withstand sterilization without losing any positive properties, and be mechanically stable so that patients can use their limbs as soon as possible after the surgery. The MEDICA trade fair this year will highlight several recent innovations that aim to tackle these issues.

Implants that dissolve in the body within a defined period of time represent a particular challenge. The self-dissolving polymers used for this include polylactide (PLA), polyglycolid (PGA), polydioxanon (PDS), poly hydroxy butyric acid (PHB) and polyorthoester (POE). A new procedure is the KLS-Martin (Freiburg, Germany) SonicWeld Rx system, which uses a poly-DL-lactide (PDLLA) pin placed in a predrilled hole that liquefies under ultrasonic energy, penetrating the trabecular spaces that conventional screws cannot reach in both cancellous and cortical bone. The connection is stable within seconds, and the bone pin self-degrades completely. A second surgical intervention is not necessary, implantation time is significantly shorter, and there is no risk of implant fractures.

Another option involves resorbable metal implants, made of magnesium (Mg) and iron (Fe). As implants made of Mg alloys have similar elasticity modules as bone tissue, there is no bone resorption at the implantation location. Over time, the implants dissolve through corrosion, but as they are metal implants, they are very stable and therefore suitable for supporting functions.

Researchers at the Fraunhofer Institute for Manufacturing Technology (Bremen, Germany) and other companies have also developed a degradable iron-based alloy, which in toxicological studies proved to be well tolerated.

Another important area is cardiovascular implants, with special emphasis on implant coating technologies for catheters and stents. The coating materials that can be used include hydrophile polymers and polymers with good gliding properties such as polyvinyl pyrrolidone (PVP), polyethylene glycol / polyethylene oxide (PEG/PEO), polyvinyl alcohol (PVA), as well as hyaluronic acid. As these compounds are often water soluble, they must be stabilized through cross-linking. These stable coatings allow the programmable release of a number of different agents, from small molecules all the way to protein therapeutics.

“Coatings increase functionality, lifetime and cost efficiency, improve the guidance and positioning of parts, and they facilitate handling and reduce the patient's risk of injury,” said Professor Hans-Wilhelm Engels, PhD, head of the innovation community council and head of research in the area of paints, adhesives, and specialties at Bayer Material Science (Leverkusen, Germany). “We are also already working on optimal systems for biodegradable stents.”

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