Case 9: Missing bones? Just print them.
Florida surgeon performs first complete midfoot reconstruction using 3D printing and is paving the way for future advancements.
"Creativity is thinking up new things. Innovation is doing new things." ~Theodore Levitt
This is a 54-year-old female who presented to the office complaining of severe progressive foot pain and swelling without any significant history of an injury. Over several years she saw several doctors to see what she could do to combat her pain. She went through multiple MRIs, several rounds of physical therapy, had numerous cortisone injections, and had multiple pairs of inserts made without any lasting relief. During this time, the pain persisted as she watched her arch collapse further into a debilitating deformity.
When she presented to the office, she was ready to discuss surgical reconstruction. Her foot problem had progressed to the point where it was having a dramatic impact on her (and her husband’s) quality of life. Radiographically, she had a significant mid-arch sag with severe cystic formation though the entire midfoot. It was obvious that there was a loss of bone integrity and structure.
Preoperative radiographs. Note the significant loss of integrity of the midfoot bone stock.
A full rheumatological workup was performed and she was sent for a CT scan and a WBC scan to discover the cause and rule out an infectious nature. Although this seemed to have similarities to Charcot neuropathic arthropathy, there was no loss of protective sensation and no history of diabetes. The only thing that stood out from her workup was a critically low vitamin D level and severe osteoporosis. The patient was placed on a vitamin D regimen and she was started on Forteo.
Based on the radiographic workup and CT scan it was obvious that the bone in the midfoot was not viable and there would be a need to do an extensive amount of resection to get to a healthier level of bone capable of healing. Traditionally, this would be done with cadaveric bone and/or an autograft. The only problem would be the amount of bone needed to span the non-viable area. As we know there is an inverse relationship of the amount of graft needed and the ability to incorporate the graft.
When using allograft, the body would need to break down the graft bone at the same rate or slower than the body’s ability to lay down new bone. That is a big ask of a body and arch that has already proven to be challenged where fabrication of new bone is dysfunctional at best.
CT scan confirmed significant loss of bone integrity across the entire midfoot including the Lisfranc, naviculocuneiform and 4th and 5th metatarsal cuboid joints with extensive fragmentation and cystic formation.
The other option would be to drastically reshape and shorten the foot. This was not something that the patient had interest in. In the past, I have taken these more traditional approaches on similar cases. While I have had several good results, I can also say that in my career I experienced several cases where I did an extensive midfoot fusion with bone grafting using cadaveric bone with a bulky medical column fusion plate, a reinforced Charcot style plate or TMT beaming, only to watch graft slowly disintegrate, the hardware break, and the arch drift back into deformity eventually needing further reconstruction. Anyone who has experienced a similar outcome knows that these are not easy revisions, especially with compromised bone stock quality as an underlying issue. This is perhaps where thinking “outside” the box and investigating the advantages of 3D printing may be helpful.
When a rocket scientist investigates the root cause of a failure after a launch that goes horribly wrong, they will not only identify the main reason for failure, but also look for new ways or methods to avoid a similar result.
If bone integration is a concern in the first place, how can we rely on the body to break down grafted bone across a rather large void and replace it with healthy, stable and viable bone throughout the healing process?
Also, when it comes to cadaveric graft, there are no two specimens that are alike. We do not know who they came from, what their age was, nor the status of their overall bone health.
Enter 3D printing. Not only can we control the shape of the intended graft, but we can also optimize the porosity and microgeometry at the metal to bone interface to stimulate bone cell integration and enhance stability via increased osteoconductivity1. We know through literature that bone integration into the metallic bone scaffolding does not need to go deep, just a few millimeters, to significantly reduce the stress to the metal to bone interface, which is key to graft integration2. The shape is only limited to the designing surgeon and additive manufacturing engineering team’s combination of both scientific and creative abilities.
Schematic of Additive Orthopaedics 3D printed wedge replacement (and actual 3D printed constructs) of the midfoot medially with a cuboid replacement and fusion interface into the calcaneus and 4th metatarsal cuboid joint and resurfacing of the 5th metatarsal cuboid joint.
In this case, a decision was made to fuse the subtalar joint, perform a wedge resection through the medial column to include the Lisfranc, talonavicular and naviculocuneiform joints and to replace the cuboid by creating a calcaneocuboid joint and 4th cuboid-metatarsal joint fusion and resurfacing of the 5th metatarsal and cuboid joint using Additive Orthopaedics 3D printed custom implants. Fixation was achieved with the use of Paragon 28 Joust fusion beams (7.5, 5.5 and 5.0mms) and Paragon28 Jaws staple. The tibialis anterior tendon was reflected and then reapproximated medially with a Stryker Ikonix bone anchor.
The patient will be non-weightbearing for 10 weeks and will utilize a bone growth stimulator. Therapy will start with the weightbearing portion of her recovery and it is anticipated that the patient will utilize an articulated AFO for 4-6 months post-op. We will plan to repeat a CT scan at postoperative month 6 to ensure proper bone integration into the implant.
1-week postoperative views of the 3D printed implants and fixation.
1. Hong JY, Ko SY, Lee W, Chang YY, Kim SH, Yun JH. Enhancement of Bone Ingrowth into a Porous Titanium Structure to Improve Osseointegration of Dental Implants: A Pilot Study in the Canine Model. Materials (Basel). 2020;13(14):3061. Published 2020 Jul 8. doi:10.3390/ma13143061
2. Cheong VS, Fromme P, Coathup MJ, Mumith A, Blunn GW. Partial Bone Formation in Additive Manufactured Porous Implants Reduces Predicted Stress and Danger of Fatigue Failure. Ann Biomed Eng. 2020;48(1):502-514. doi:10.1007/s10439-019-02369-zJoust