The combination of a new ceramic material made mostly of hydroxyapatite and the ability of computer design and manufacturing software to produce custom-made implants may produce a major breakthrough in the care of patients who lose bone to cancer or related surgery.
The new material, which was created at the Sandia National Laboratories (USA), is used to build a layered meshwork that is stronger than bone but is porous, which allows new growth of bone tissue and blood vessels to extend through the implant to surrounding bone.

The team of basic scientists and surgeons who developed and tested the ceramic implants believes they can reduce the pain, recovery time, and risk of infection for patients who need bone replacement in the mandible, as well as the skull, spine, or other bony structures. Other potential benefits include avoidance of longer surgical procedures, more predictability of outcome, and lower health care costs.

In the first human test, a woman who had lost part of her mandible was fitted with an implant and had a second portion of lost bone replaced conventionally with a graft from her pelvis.

"Surgeons and patients would love to eliminate both the bone retrieval and implant preparation processes," said lead Sandia scientist Joe Cesarano. "This test showed we can make artificial porous implants prior to surgery that will fit perfectly into the damaged region. The reconstructive procedure would then only require attaching the implant and closing the wound."

The basic process used to manufacture the customized ceramics was developed to allow manufacture of specialty parts for the military in mobile laboratories. Under the control of a computer program, the machine dispenses liquefied ceramic pastes to form shapes of varying complexity along a prearranged path.

To create the simulated bone scaffolding, the machine dispensed a hydroxyapatite mixture in cross-laid slivers each about as thick and as far apart as the diameters of 10 human hairs. "Bone, blood vessels, and collagen love to grow into a structure with pores of that size [500 microns]," said Cesarano. "The material becomes a hard-tissue scaffold for promoting new bone growth."

Before the first human test (a mandibular implant) could be done, surgeon Michael Goldwasser, MD, worked with programmers to modify digital information from a computerized tomogram of the diseased bone to create an exact model for the pre-existing (and replacement) bone. "Eventually, if it could be done electronically, it may be a very simple thing and cost-effective," he said.

"There is nothing inherently expensive about either the materials or the process," added Cesarano.

"We'll see if the clinician, the bioresearcher, and the engineer can come up with a method to implement it," Goldwasser concluded.