Hennepin County Medical Center has marked a new era in medicine: One in which 3-D printers are used not just for anatomical models and surgical practice, but to create real implants in real patients.

And it came just in time for construction worker Justin Siltala, who was injured last fall when a shovel handle snapped, driving a long wooden shard through his eye socket and into his brain.

With Siltala's case and a handful of others, the Minneapolis hospital has become one of the first in the United States to use a Swedish technology known as OssDsign to create craniofacial bone replacements made of calcium phosphate and 3D-printed titanium that fit precisely in patients.

The shard "stuck into his brain by a good 4 or 5 inches," said Dr. Uzma Samadani, the HCMC neurosurgeon who operated on Siltala. "It was really deep in there, and it broke the bone in two different places."

Step one was delicately removing the wooden splinter, which had pushed aside Siltala's eyeball and pierced the skull. Then surgeons had to figure out how to repair the broken bone. Surgeons worried that the existing fragments could have been tainted by fungus or mold spores in the wood, so they needed a replacement.

"I was concerned about the infection risk," Samadani said.

Three-dimensional printing has gained increasing importance in health care in the last decade.

Doctors originally used the technology to create anatomical models that they could use for planning and practicing complex procedures. Mayo Clinic was an early adopter in 2005, when it created a model for a life-threatening separation surgery of conjoined twins.

Since then, the sharing of 3-D designs has increased rapidly. The National Institutes of Health in 2014 created a 3-D print exchange for that purpose, and just last month Mayo held a national conference on the future of collaborative 3-D printing in medicine.

But in the last five years, surgeons have focused more and more on the technology's ability to make implants.

In 2013, doctors in Michigan gained emergency permission from the U.S. Food and Drug Administration to use 3-D printing to create a tracheal splint to prevent a child's airway from collapsing. Since then, companies have emerged offering 3-D printing solutions for dental, facial, spinal and other implants.

OssDsign gained FDA approval last January; HCMC has now used its facial-bone implant technology in nine surgeries.

Siltala remembers very little about the accident on Nov. 1, when a chunk of asphalt suddenly splintered, shattered the shovel handle that he was holding, and propelled a wooden shard into his skull. A co-worker had to hold Siltala on the ground and pin his arms, because he was instinctively trying to pull the shard out.

That Siltala survived was miraculous, Samadani said, because the blow would have been fatal if the wood had entered at just a slightly different angle. It pushed his eyeball aside, rather than destroying it, so that corrective surgery was able to save it.

For some accident victims with skull fractures, the best choice is to immediately implant manually shaped titanium scaffolds that will encourage bone growth over time, Samadani said. But they don't always fit perfectly, and they can result in facial deformities. Samadani said she has had to perform corrective surgeries on Vietnam veterans who had operations decades ago, because the titanium used in emergency wartime surgeries eventually protruded back out of the aging bone and caused complications.

But Siltala appeared stable enough after the shovel fragment was removed that Samadani felt confident waiting and leaving a temporary gap in his skull while a 3-D bone replacement was printed to provide an exact fit.

"It's as much about trying to make the patient look normal, or even good, as it is about trying to get a graft that will work," she said.

Siltala, who was back at HCMC last week, lives in Dassel, Minn., with his wife and six children. He said his recovery has been steady — he has taken physical and occupational therapy at HCMC to regain clear eyesight and to restore lost strength, balance and cognition.

But when he touches his skin above the bone implant, he can't feel any difference. Samadani "said it would be the best, and I obviously trusted her," he said, joking that "I'm far from a brain surgeon myself."

Siltala passed a driving simulation last month, and he immediately went out for a drive that lasted 100 miles.

"Just because I could," he said.

To pass the time and get exercise, he splits wood and feeds the two wood stoves in his house, but he said he is looking forward to working again.

A hunter and collector, Siltala now has possession of the shovel fragments that injured him. And he has asked HCMC pathologists to give him his missing fragment of skull.

Jeremy Olson • 612-673-7744