Biomechanical Testing of a 3D-printed L5 Vertebral Body Model

Authors

Michael A. Bohl, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.Follow
Clinton D. Morgan, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.
Michael A. Mooney, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.
Garrett J. Repp, Department of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.
Jennifer N. Lehrman, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.Follow
Brian P. Kelly, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.Follow
Steve W. Chang, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.Follow
Jay D. Turner, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.
U Kumar Kakarla, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA.

Document Type

Article

Abstract

Background We examined the biomechanical performance of a three-dimensional (3D)-printed vertebra on pedicle screw insertional torque (IT), axial pullout (APO), and stiffness (ST) testing. Materials and methods Seventy-three anatomically identical L5 vertebral body models (146 pedicles) were printed and tested for IT, APO, and ST using single-threaded pedicle screws of equivalent diameter (6.5 mm), length (40.0 mm), and thread pitch (2.6 mm). Print properties (material, cortical thickness [number of shells], cancellous density [in-fill], in-fill pattern, print orientation) varied among models. One-way analysis of variance was performed to evaluate the effects of variables on outcomes. Results The type of material significantly affected IT, APO, and ST (P < 0.001, all comparisons). For acrylonitrile butadiene styrene (ABS) models, in-fill density (25-35%) had a positive linear association with APO (P = 0.002), ST (P = 0.008), and IT (P = 0.10); similarly for the polylactic acid (PLA) models, APO (P = 0.001), IT (P < 0.001), and ST (P = 0.14). For the nylon material type, in-fill density did not affect any tested parameter. For a given in-fill density, material, and print orientation, the in-fill pattern significantly affected IT (P = 0.002) and APO (P = 0.03) but not ST (P = 0.23). Print orientation also significantly affected IT (P < 0.001), APO (P < 0.001), and ST (P = 0.002). Conclusions 3D-printed vertebral body models with specific print parameters can be designed to perform analogously to human bone on pedicle screw tests of IT, APO, and ST. Altering the material, in-fill density, in-fill pattern, and print orientation of synthetic vertebral body models could reliably produce a model that mimics bone of a specific bone mineral density.

Keywords

3d printing, bone mineral density, pedicle screw, spine biomechanics, synthetic bone model

Publication Date

1-15-2019

Publication Title

Cureus

ISSN

2168-8184

Volume

11

Issue

1

First Page

e3893

PubMed ID

30911450

Digital Object Identifier (DOI)

10.7759/cureus.3893

Recommended Citation

Bohl, Michael A.; Morgan, Clinton D.; Mooney, Michael A.; Repp, Garrett J.; Lehrman, Jennifer N.; Kelly, Brian P.; Chang, Steve W.; Turner, Jay D.; and Kakarla, U Kumar, "Biomechanical Testing of a 3D-printed L5 Vertebral Body Model" (2019). Translational Neuroscience. 1205.
https://scholar.barrowneuro.org/neurobiology/1205