Selective Laser Melting Benefits Craniofacial Surgery

A new laser technology creates a perfectly fitting cranial implant that consists of a porous material that is replaced by the ingrowth of adjacent bone.

Researchers at the Fraunhofer Institute for Laser Technology (ILT; Aachen, Germany) used selective laser melting (SLM) and a computerized tomography (CT) image template to create a perfectly fitting implant that consists of synthetic polylactide (PLA) and stored granules of tricalcium phosphate (TCP), a combination known as "Resobone". The work processes--from CT imaging, to construction of the implant, through to its completion--are coordinated in such precise sequences that the replacement for a defective zygomatic bone can be produced in just a few hours, while a 5-cm large section of cranium can be done overnight. The technique can be used to close defects of up to 25 cm² in size.

However, unlike conventional synthetic bony substitutes to date, the implant is not made up of a solid mass, but is porous instead. Precise channels permeate the implant at intervals of just a few hundred micrometers; the porous canals create a lattice structure that the adjacent bones can grow into. The synthetic PLA and TCP in "Resobone" ensure rigidity and stimulate the bone‘s natural healing process. As pastes, granulates and semi-finished products, TCP and PLA already have proven to be degradable implants, as the body can catabolize both substances as rapidly as the natural bones can regrow.

"No custom-fit, degradable implants ever existed before now. During the operation, the surgeon had to cut TCP cubes, or the patient‘s own previously removed bone material, to size and insert it into the fissure,” said Simon Höges, Ph.D., project manager at ILT. "In addition, the operations are now fewer in number: Physicians no longer take the bone replacement 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.”

SLM generates a razor-thin laser beam that melts the pulverized material, layer-by-layer, to form structures that may be as delicate as 80 μm - 100 μm long.

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Fraunhofer Institute for Laser Technology