gms | German Medical Science

German Congress of Orthopaedics and Traumatology (DKOU 2021)

26. - 29.10.2021, Berlin

Optimizing 3D printed individual human bone samples for biomechanical testing

Meeting Abstract

  • presenting/speaker Felix Wunderlich - Universitätsmedizin Mainz, Zentrum für Orthopädie und Unfallchirurgie, Mainz, Germany
  • Dorothea Mehler - Universitätsmedizin Mainz, Zentrum für Orthopädie und Unfallchirurgie, Mainz, Germany
  • Katharina Degner - Hochschule Rhein Main, Wiesbaden, Germany
  • Christian Glockner - Hochschule Rhein Main, Wiesbaden, Germany
  • Pol Maria Rommens - Universitätsmedizin Mainz, Zentrum für Orthopädie und Unfallchirurgie, Mainz, Germany
  • Dominik Gruszka - Universitätsmedizin Mainz, Zentrum für Orthopädie und Unfallchirurgie, Mainz, Germany

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2021). Berlin, 26.-29.10.2021. Düsseldorf: German Medical Science GMS Publishing House; 2021. DocAB93-1012

doi: 10.3205/21dkou662, urn:nbn:de:0183-21dkou6620

Published: October 26, 2021

© 2021 Wunderlich et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

Text

Objectives: Even though composite human bone models (e.g. Sawbones) used for biomechanical testing are easy to store and are not as expensive as cadaveric specimen, they do not reproduce the unique internal architecture and viscoelastic properties of real human bone. After creating a 3D printed individual human bone sample (3D-IBS) on CT-Scan basis of metacarpals, we aimed to improve its mechanical characteristics in 4 degrees of freedom to match human bone mechanics.

Methods: Based on CT-Scan data of fresh-frozen, macroscopically intact, cadaveric metacarpals (MC 2-5) we created a digital template via 3-layer Standard Tesselation Language (STL) Net matching the 3D printing requirements. For printing we used Polyamid 12 (PA12) as a raw material, which is a thermoplastic linear built plastic material. Four different 3D-IBS samples were developed: 1. Cortical bone as measured in the CT-Scan, cancellous bone grid structure 1.2mm (PA12); 2. Cortical bone thickened 0.5mm with identical grid structure (PA12+); 3. PA12 raw material with mineral fibre additive (PA12HST); 4. Horizontal layering structure rather than vertical structure (PA12H).

The bone templates were augmented with mounting brackets for biomechanical testing. Testing for tension, bending, shearing and torsional force was conducted in a universal testing machine. Forces were applied over 5mm/min. All different 3D-IBS metacarpal samples were tested against Sawbone and fresh frozen cadaveric metacarpals. All samples were loaded to failure.

Results: To the current state of test realization 25 3D-IBS have been tested for tension and torsional forces. Mean maximum load for torsion in human samples was 228.20 Newton (N), basic 3D-IBS PA12 bones showed a mean maximum load of 225.86N, whereas Sawbones had a mean maximum load for torsion of 622.74N. The mean maximum load for torsion in the other samples was the following: PA12+ 313.10N; PA12HST 203.94N; PA12H 207.99N.

Mean maximum load for tension in human samples was 1814.70N, PA12 bones had a mean maximum load of 1446.42N, Sawbones had 3061.80N. Mean maximum load for tension in the other samples was the following: PA12+ 2962.20N; PA12HST 1235.40N; PA12H 1590.60N.

All specimens were also tested for distortion and elongation with mean maximum values as shown in Table 1 [Tab. 1].

Conclusion: 3D-IBS show better similarity to mechanical human bone characteristics in tension and torsional loading than the conventionally used Sawbone. From the current state of our testing, same could be alleged for shearing and bending forces. Further testing with different materials and manufacturing processes is needed to optimize the plastic deformability of our specimens, especially in distortion.