Artificial hip replacement failures - early iterations

Not the failure framing — here used positively, as an early AM application. 3D-printed ceramic molds for custom-fit titanium hips on $50,000 operations. ## Cases mentioned in passing

So Mike Cima and Ely Sachs came along with an inkjet print head and laid down a very thin layer of ceramic, printed the adhesive on top, put another layer of ceramic, printed the thing, and just built it up. A lot of the stuff in the early '90s is developing the computer codes to make the complex structures. What were the early applications? One of the earliest applications was making casting molds for artificial hips. It was actually too expensive for a dentist early on. But an artificial hip is a $50,000 operation. If you can make that metal hip personalized for the patient so it fits right, fifty thousand dollar operation, who cares? You make the mold, you cast the alloy in a regular metal casting shop, but you make the mold. That's how they make the Super Bowl rings, too, still today. They're only going to make a couple hundred Super Bowl rings or World Series rings. You go down to Tiffany's down here in Rhode Island, and you'll see they've got about six 3D printers that are binding ceramics for the mold, and they can customize the design and make 200 molds for your rings, and then they destroy that, and you have to win another Super Bowl and get another design.

Silk was used, and they made silk screws. One of the advantages of silk screws is they're not too stiff. One of the biggest problems we have with medical implants — you break a bone really badly and they go in, they put a metal plate, could be titanium, could be stainless, and they screw it together with titanium or stainless screws. You don't mix metals because they tend to create galvanic corrosion. They're stiff and unyielding compared to the bone. Bone's got a modulus that — it's not on here, but bone is probably down in this range.

Tom's MIT-bellwether argument. "Hip corroders" were the traditional biomedical engineering focus; Tom rejected them in favor of soft tissue engineering when he became department head in 1995. Used both as historical case and as the pivot to the rabbit impact-load research anecdote.

Even today, although no other school would really admit it, what MIT does sort of defines what other universities will do. I can give you a personal example. When I became department head in 1995, on the department strategy list we were supposed to hire someone in biomedical engineering. At that time biomedical engineering meant what I call the hip corroder. My thesis advisor, and his thesis advisor, had been hip corroders. An artificial hip you put in — they would corrode, and they might fail within six months or a year or three years. When they first started putting them in people, they were staying with steel and they were failing in six months. You have an operation where you don't get off the crutches for six months, and the thing fails and you need another operation — that wasn't very good. And I saw, in my career as an undergraduate and then a graduate student, it go from about a one-year or two-year or three-year lifetime to where they were starting to put artificial hips in children 10 years old and expecting them hopefully to last 30 years.