Tumor resections from the pelvic girdle often pose daunting reconstruction challenges for orthopaedic surgeons. In the September 2, 2020 issue of The Journal of Bone & Joint Surgery, Ji et al. report early results from a series of 80 bone-tumor patients who underwent pelvic reconstruction using a 3D-printed modular hemipelvic endoprosthesis. The 3D-printed interconnected porous component was generated from an electron beam melting process, and the design allowed for the main iliosacral fixation screws to be oriented parallel to the loading axis of the trunk.
The authors detected no acetabular component instability or implant loosening or migration after a mean follow-up of 32.5 months. The mean acetabular tilt on the reconstructed side immediately after surgery was 46.9o, and it was 47.1o at the most recent follow-up. The mean function score (84%, as measured by the Musculoskeletal Tumor Society 93 tool) was higher than the previously reported range of 55% to 72% from recent studies, and the authors say that the 3-month dislocation rate in this series (2.5%) “seems to be the lowest ever reported.” Moreover, histological analysis of specimens from 2 patients who experienced tumor recurrence revealed bone trabeculae extending toward the implant and bone ingrowth within the porous network.
Still, complications occurred in 16 (20%) of the patients, with wound dehiscence being the most prevalent one. Deep infections, relatively common after pelvic reconstruction surgery, occurred in 5 (6.3%) of the patients, which is a lower deep-infection rate than those reported in previous studies.
Despite the stable fixation and “satisfying early functional and radiographic outcomes” with this 3D-printed modular prosthesis, the authors caution that their short-term results “may prove to be insufficient for the assessment of implant viability.” Nevertheless, any innovation that helps address the many surgical challenges in this population of orthopaedic patients is welcome.
OrthoBuzz has reported previously on the 3D printing of implantable skeletal structures (click here for an example), but the materials used were metallic. Now, two new accomplishments with 3D printing have produced material that mimics the physiochemical properties and porous structure of real bone.
First, students from California State University in Long Beach created the LuxNova OsBot 3D printer. The students say that the OsBot can replicate the unique and complex structure of human bone tissue down to the micro and nano levels.
Meanwhile, in China, the Xi’an Particle Cloud Advanced Materials Technology Co. has wrapped up animal testing on a similar bioprinting device and is poised to enter human trials. The device uses both UV light and heat to “laminate” binder material until a bonelike structure is fabricated. In rabbits, the 3D-printed bone exhibited new bone-cell activity on its surface almost immediately after implantation.
Theoretically, surgeons could use 3D-printed bone grafts to replace cancerous or severely traumatized bone tissue, obviating the need for amputation or cadaver grafts.