Dr. Daniel Penello: The development of a 3D-printed finger and challenges of this debut procedure

Written by Alan Condon | August 09, 2019 | Print  |

Daniel Penello, MD, successfully implanted a custom 3D-printed finger bone in an iron worker, Robert Smith, who was facing amputation after a heavy steel beam crushed his finger.

Dr. Penello of Alexander Orthopaedic Associates in St. Petersburg, Fla., is an orthopedic surgeon with fellowship training in hand and upper extremity surgery.

Mr. Smith coordinated with Dr. Penello over a five month period to refine the development of the 3D-printed finger, which was designed by Additive Orthopedics in Little Silver, N.J.

Here, Dr. Penello details the development process of the implant, challenges of the procedure and how he sees 3D printing and regenerative medicine progressing in orthopedics.

Question: Can you tell me about the development process? What did the implant consist of?

Dr. Daniel Penello: It was titanium-based and we made one side smooth; that part was going to be the external part. The internal part that was integrated with the patient's own bone was a porous coating so they 3D-printed a lattice work on the inside of the prosthesis so his bone would grow into that lattice work. So that bone will become part of his body.

Q: I believe this is the first procedure with this type of 3D implant. What was most challenging surgical aspect of the procedure?

DP: I think it was the size because it was such a small bone but in an important area of the body — in the fingertip. The size made it difficult as I did not have much bone to work with. The patient had crushed most of the bone only leaving a small remnant and that's what I needed to attach the prosthesis to. We did a lot of design work in the simulated surgeries using computer programs to achieve the most solid fixation or integration of junction between the prosthesis and his own bone without damaging his own bone in the process.

Because he was left with such a small amount of bone, if I made a mistake and shattered that bone while trying to put the prosthesis in, then he'd end up with an amputation. Also, no one had ever made a prosthesis for this bone before, so I didn't have any prior art to base it off. I tried to pull concepts from knee, hip and shoulder replacements and use those principles.

Q: How do you see procedures like this and 3D printing developing in orthopedics?

DP: I think 3D printing will be used for developing standard hardware. A lot of the standard hardware that we use now can be 3D-printed rather than machine. Most of the hearing aids made of plastic are 3D-printed and made to fit the ear canal of each patient. I think 3D-printed prostheses for other joint replacements will happen sooner than we think.

Down the road what we really want to be able to do is 3D-print organic tissue. There is research being done on this where scientists are trying to print liver cells or print heart or kidney cells. I think in the future that has the potential in orthopedics to rebuild tendons and 3D-printed organic bone that's alive, as opposed to something artificial like this. What that will involve is 3D printing as a scaffold or biogel and colonizing it with the appropriate cells.

Q: How do you approach the physician-patient conversation when you're detailing a procedure that hasn't been done before?

DP: I've always worried about the medical legal environment here. You need to do this on the right patient because if something went wrong, you're treading into uncharted waters. When I spoke with the patient I used the comparison of a boiled hotdog — he had flesh there but no structural support at the tip of his finger. When he tried to pinch something or turn a nut with the top of his finger he just didn't have any strength, the finger was like jelly.

Q: What was the development process like working with Additive Orthopedics and designing the implant?

DP: The first meeting was the longest one. I outlined what I wanted to achieve, then we got a CT scan of the injured finger and the uninjured finger on the other hand. Additive Orthopedics used the uninjured finger as a template. The engineers took the principals we discussed and we came up with version one of the prosthesis. They showed me the 3D rendering of the prosthesis and we virtually simulated the surgery on a computer. I would say, 'Oh, you've got a screw there and I can't put a screw there because that's going to violate his nail or compromise his tendon,' which was working. Then they would get rid of that screw and find something else that would work.

Q: Do you see yourself taking on more of these types of surgeries down the line?

DP: I'd be very happy to do it again and I think now that I've completed the process once, the second one is going to be a little easier and I'll know exactly what to expect. Right now, 3D printing is being used for more complicated situations so it's hard to know how much crossover there's going to be between this situation and the next one. The next one might be completely different. I think there is a learning curve with everything, and having gone through the process once, it will make it easier for everyone involved the second time.

More articles on Q+As:
Why Dr. Dominic Thomas Kleinhenz joined University Orthopedics and the biggest obstacle in spine
Dr. Stephen Hochschuler: Future trends in spine – telemedicine, robotics, AI & more
Dr. Christopher Kager: The standout spine procedure in his career, future of biologics & more

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