Cancer patients with pelvic sarcomas need a large bone transplantation and implant fixation after resection of the bone defect, but complex implant systems often fall apart in many patients shortly after surgery. A team of researchers from China published “Three-dimensional printed implant for reconstruction of pelvic bone after removal of giant chondrosarcoma: a case report” about a patient who received 3D printed implants for the reconstruction of her pelvic bone after a massive chondrosarcoma (malignant tumor of cartilage-producing cells) was removed.
“In patients who undergo massive tissue removal, individualized implants can be extremely helpful because many large bone defects cannot be easily bridged by standard implants,” the researchers wrote.
3D printing has been used before to make customized pelvic implants for patients. In this case, a 29-year-old woman presented with a lump that had been growing in her left thigh for ten years, and while she had no pain – common with chondrosarcoma – the patient was having some mobility issues. After an X-ray showed a giant tumor “eroding the pubic bone, ischium, and acetabulum,” she was admitted, and further testing showed that the tumor, diagnosed a mucinous chondrosarcoma with a fine needle biopsy, had invaded her inner thigh and shifted her left femoral artery and deep femoral artery.
“After ruling out deficiencies of the circulatory, respiratory, urinary, and gastrointestinal systems, a multidisciplinary discussion was conducted among the oncologists, orthopedic surgeons, and researchers. Considering the large structural defect that would be present after removal of the tumor, intraoperative application of a 3D-printed implant was suggested,” the team explained.
A Siemens CT scanner was used to image the pelvic bone and upper one-third of the femoral bone, and a 3D model was created in Materialise Mimics 17.0 software. The model was imported into Siemens NX software so a surgical guide could be designed, which was 3D printed out of PLA on an UP BOX+ 3D printer from Beijing Tiertime Technology Co., Ltd. The implant itself is made of titanium.
“Although titanium alloys are widely used in orthopedic surgeries because of their outstanding biocompatibility and biomechanical characteristics, some reports have described implant loosening and bone resorption due to the stress shielding effect after the application of titanium implants,” they wrote. “To avoid this effect, we used a porous structure 3D painted implant in which the diameter of each aperture was 200'‰ µm, the extent of porosity was 38%, and the density was 2.8'‰g/m3. Suture anchors for fixation of the muscles and ligaments were designed on the implant according to the 3D-reconstructed CT data.”
During the five-hour surgery, doctors used the 3D printed guide to isolate and resect the tumor once the iliac periosteum was exposed. When they said massive, they meant it – the tumor measured at 12'‰Ã—'‰8'‰Ã—'‰6'‰cm. Luckily, they were able to get clear margins.
After the left superior acetabulum, pubic symphysis, and femoral neck were resected, they removed the cartilage on the right pubic symphysis and used screws to affix the 3D printed titanium implant onto the “bleeding bone bed.” The hip was externally rotated in order to expose the femoral neck, “which was then sawed 1'‰cm superior to the lesser trochanter” before the hip joint was re-positioned. The position of the implants was confirmed using intraoperative C-arm X-ray, and then the hip joint was dislocated. The surgeons filled a 3D printed acetabulum with bone cement, before a polyethylene socket was fixed inside. Once the cement solidified, they inserted femoral stem and femoral head prostheses and restored the joint.
Finally, after determining that joint mobility was intact, they washed the surgical field, repaired all of the muscles, and closed the incision. Post-op, the tumor was dissected, and the diagnosis was confirmed through pathological studies. The surgical site healed successfully with no infection, sutures were removed two weeks post-op, and the patient began physiotherapy two weeks after that, with outpatient visits scheduled every three months.
“The patient achieved rapid recovery after the surgery, and no failure or loosening of the implant occurred after the patient began walking without an external aid,” the researchers wrote. “The length of the left leg and right leg was 72.5 and 71.0'‰cm, respectively. The Harris hip score was 73 at 1 month postoperatively, 79 at 6 months postoperatively, and 92 at 12 months postoperatively.”
At both six months and twelve months post-op, there was no loosening, or failure, of the 3D printed implant.
Using 3D printing to make the implant definitely had its advantages. For instance, because allogeneic bone transplants weren’t needed, the length of the surgery was reduced. Additionally, conventional implants can leave voids, which requires a second surgery to harvest autologous bone grafts in order to fill them; personalized implants negate this. A more functional recovery is possible with a custom 3D printed implant, and the technology also makes the implant more stable, as “3D printing can provide precise locations for the attachment of muscles and ligaments on the implants.”
“3D printing is currently a hot technology that conforms to the principle of precision therapy. It is an appropriate choice in complex orthopedic surgeries. In our case, despite the removal of a large portion of the pelvic bone and surrounding soft tissues, the patient achieved satisfactory mobility without implant loosening,” the team wrote. “Because 3D printing allows precise treatment, usually without the need for multiple intraoperative attempts to mold the acetabular cup, the duration of surgery was controlled within 5 hours, and most of this time was spent on removal of the giant tumor.”
But they did note some disadvantages. The total cost of this surgery was 96,380 Yuan ($13, 768), which is “similar to patients treated with conventional methods,” so there wasn’t a noticeable cost reduction, and the design process “can be time-consuming.”
“However, considering that its advantages far outweigh its disadvantages and that most technical problems can be solved with further research, we are confident that 3D-printed implants will be widely applied in future to benefit millions of patients,” the researchers concluded.
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