Evaluating the contact anatomy and contact bone volume of spinal screws using a novel drilled surface image

April 12, 2023

. 2023 Apr 10;18(4):e0282737.

doi: 10.1371/journal.pone.0282737.

eCollection 2023.

Affiliations

¹ Department of Radiology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
² Department of Medical Imaging and Radiological Technology, Yuanpei University of Medical Technology, Hsinchu, Taiwan.
³ Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan.
⁴ Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan.
⁵ x-Dimension Center for Medical Research and Translation, China Medical University Hospital, Taichung, Taiwan.
⁶ 3D Printing Medical Research Institute, Asia University, Taichung, Taiwan.
⁷ Department of Neurosurgery, China Medical University Hsinchu Hospital, Hsinchu, Taiwan.

Free PMC article

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Yun-Xuan Tang et al.

PLoS One.

2023.

Free PMC article

. 2023 Apr 10;18(4):e0282737.

doi: 10.1371/journal.pone.0282737.

eCollection 2023.

Affiliations

¹ Department of Radiology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
² Department of Medical Imaging and Radiological Technology, Yuanpei University of Medical Technology, Hsinchu, Taiwan.
³ Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan.
⁴ Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan.
⁵ x-Dimension Center for Medical Research and Translation, China Medical University Hospital, Taichung, Taiwan.
⁶ 3D Printing Medical Research Institute, Asia University, Taichung, Taiwan.
⁷ Department of Neurosurgery, China Medical University Hsinchu Hospital, Hsinchu, Taiwan.

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Abstract

Intraoperative navigation systems have been widely applied in spinal fusion surgery to improve the implantation accuracy of spinal screws using orthogonal tomographic and surface-rendering imaging. However, these images contain limited anatomical information and no information on bone volume contact by the implanted screw, which has been proven to affect the stability of implanted screws. This study proposed a novel drilled surface imaging technique that displays anatomical integration properties to calculate the contact bone volume (CBV) of the screws implanted along an implantation trajectory. A cylinder was used to represent the area traversed by the screws, which was manually rotated and translated to a predetermined implantation trajectory according to a vertebra model obtained using computed tomography (CT) image volumes. The drilled surface image was reconstructed by interpolating the CT numbers at the predefined sampling points on the cylinder surface. The anatomical integration property and CBV of the screw implanted along the transpedicular trajectory (TT) and cortical bone trajectory (CBT) were evaluated and compared. The drilled surface image fully revealed the contact anatomical structure of the screw under the trajectories, improving the understanding of the anatomical integration of the screw and surrounding tissues. On average, the CBV of the CBT was 30% greater than that of the TT. The proposed drilled surface image may be applied in preoperative planning and integrated into intraoperative navigation systems to evaluate the anatomical integration and degree of bone contact of the screw implanted along a trajectory.

Copyright: © 2023 Tang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

**Fig 1**

(A) Cylinder placed along the CBT path. (B) coronal and (C) sagittal CT images of a lumbar spine labeled with sampling points redefined from the coordinates of postdisplacement cylindrical mesh model vertexes.

**Fig 2. Rod location in the area traversed by a screw and the corresponding reconstructed drilled surface image.**

Fig 3. (A) and (B) display drilled surface images reconstructed from rods placed to represent the area traversed by a screw according to the TT and CBT paths in the fourth vertebrae of the same section and the converted CBV map.

**Fig 4. CBV maps reconstructed and converted according the (A) TT and (B) CBT paths on the same side of the fourth vertebrae in patients aged 26–100 years, with the total CBV marked on the map.**

**Fig 5. Relationship between age and total CBV in both the TT and CBT paths on both sides of the fourth vertebrae.**

**Fig 6**

(A) Relationship between total CBV of the TT and CBT paths on the same side of the fourth vertebrae. (B) Relationship between implantation depth of the TT and CBT paths on the same side of the fourth vertebrae.

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MeSH terms

Grant support

YXT was funded by the Shin Kong Wu Ho-Su Memorial Hospital (https://www.skh.org.tw/skh/index.html) under Contract SKH-8302-106-NDR-03. CTS was funded by the China Medical University (https://www.cmu.edu.tw/) under Contract CMU109-N-11. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.