Biomechanical Testing of 3D-Printed Implants for the Fixation of OTA Type B Ankle Fractures

Abstract

Background:

3D printing is a cost-effective manufacturing approach that offers several advantages for health care delivery, including rapid prototyping, precise customization to patient anatomy and user specifications, and the capability to produce implants directly at the point of care. The purpose of this study was to test whether 3D-printed carbon fiber–reinforced polyetheretherketone (CF-PEEK) one-third tubular plates are statistically equivalent, within prespecified margins, to stainless steel plates in simulated early weightbearing and torsion.

Methods:

Carbon fiber–reinforced polyetheretherketone one-third tubular plates were designed and printed using Fused Deposition Modeling printers by study authors. These were compared to traditionally manufactured plates using 4-point bend tests. A cadaveric biomechanical comparison between fractures stabilized using 3D-printed plates and traditional manufactured plates was performed. Matched-pairs specimens underwent axial cyclic loading and torsional load to failure.

Results:

Ten matched paired specimens underwent mechanical testing. All specimens survived 100 000 cycles loaded to 875 N. Torque at failure did not significantly differ between groups (P = .14). During torsional load to failure, all 10 specimens (100%) with the traditional plate failed because of screw pullout. Five specimens (50%) with the 3D plate failed because of screw pullout and 5 (50%) failed because of plate fracture. Fifteen plates (five 3D, five 3D post autoclave, 5 traditional) underwent 4-point bending test. Stiffness was significantly lower in the 3D plates (P < .0001). The coefficient of variation was 0.06 for the 3D-printed plates and 0.01 for the traditional manufactured plates, demonstrating high consistency within groups.

Conclusion:

In conclusion, this cadaveric study found that nonsterilized CF-PEEK plates demonstrated statistically equivalent displacement and torque at failure to stainless steel plates. However, they exhibited reduced stiffness and a higher incidence of plate fracture. Additionally, autoclave sterilization had a significant impact on the mechanical properties of the CF-PEEK plates. These findings underscore the need for additional biomechanical and clinical studies to assess the performance of 3D-printed implants and to refine sterilization protocols.

Clinical Relevance:

These results suggest that constructs using 3D-printed CF-PEEK plates can perform statistically equivalently (within prespecified margins) to stainless steel constructs in simulated early weightbearing and torsion, despite different material properties. The impact of sterilization, however, must be considered, and alternatives to autoclaving are recommended.