Dissolvable Implants Help Body Replace Missing Cranial Bones
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03 June 2010
Researchers have created a new material for bone implants that can promote the body’s natural healing process while minimising the need for the extra surgeries required in conventional titanium implants...
In a medical emergency, a puncture of the cranium is commonly treated with an implant. While replacements made of titanium just plug holes, a new kind of implant can stimulate the body to regenerate itself: It is customfit and disappears to the same extent that the bone regrows.
The body can heal minor bone injuries itself – but with major injuries, it needs help. That’s when implants come into use. In contrast to titanium–based solutions, degradable implants are intended to replace the missing pieces of bone only until the fissure closes itself up. That may last months or even years, depending on the size of the defect.
The new implant improves the conditions for the healing. Unlike the conventional substitutes, it is not made up as a solid mass, but is porous instead. Precise little channels permeate the implant at intervals of a few hundred micrometres.
“Its precision fit and porous structure, combined with the new biomaterial and promises a total bone reconstruction that was previously impossible to achieve,” said Ralf Smeets of the University Medical Centre of Aachen, Germany.
The porous canals create a lattice structure which the adjacent bones can grow into. Its basic structure consists of synthetic polylactide, or PLA for short. The stored granules from tricalcium phosphate (TCP) ensure rigidity and stimulate the bone’s natural healing process. Through extensive research TCP and PLA already have proven to be degradable implants. The body can catabolise them as rapidly as the natural bones can regrow. But the material can only be applied in places where it will not be subject to severe stress: Thus, the implants will primarily replace missing facial, maxillary and cranial bones.
Currently, they are able to close fissures of up to 25 square centimetres in size. The unique structure was made possible through a process developed at the Fraunhofer Institute in Germany. Using Selective Laser Melting (SLM): A razor–thin laser beam melts the material layer–by–layer to structures that may be as delicate as 80 to 100 micrometres. The patient’s computer tomography serves as the template for the precision–fit production of the implants. A new implant can be produced in just a few hours, while a five–centimetre large section can be done overnight.
In addition to the obvious benefits, there is a considerable gain in time during surgery. The operations are now also fewer in number: Physicians no longer take the bone from the patient’s own pelvic bone. Similarly, they can dispense with the countless follow–up operations on children to exchange long–term implants that don’t grow as the child matures.