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Eur Radiol Exp. 2019 Jan 22;3(1):1. doi: 10.1186/s41747-018-0080-3.

Quantitative CT-based bone strength parameters for the prediction of novel spinal implant stability using resonance frequency analysis: a cadaveric study involving experimental micro-CT and clinical multislice CT.

Author information

1
Department of Orthopedic surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo, Japan.
2
Department of Orthopedic surgery, International University of Health and Welfare School of Medicine, Narita, Chiba, Japan.
3
Department of Environmental and Occupational Health, School of Medicine, Toho University, Tokyo, Japan.
4
Department of Dentistry and Oral Surgery, Keio University School of Medicine, Shinjuku, Tokyo, Japan.
5
Department of Radiology, Keio University School of Medicine, Shinjuku, Tokyo, Japan.
6
Department of Orthopedic surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo, Japan. nagura@keio.jp.
7
Department of Clinical Biomechanics, Keio University School of Medicine, Shinjuku, Tokyo, Japan. nagura@keio.jp.

Abstract

BACKGROUND:

To predict conventional test forces (peak torque and pull-out force) and a new test force (implant stability quotient [ISQ] value of a spinal pedicle screw) from computed tomography (CT) parameters, including micro-architectural parameters, using high-resolution micro-CT and clinical multislice CT (MSCT) in human cadaveric vertebrae.

METHODS:

Micro-CT scans before/after screw insertion (n = 68) and MSCT scans before screw insertion (n = 58) of human cadaveric vertebrae were assessed for conventional test forces and ISQ value. Three-dimensional volume position adjustment between pre-insertion micro-CT and MSCT scans and post-insertion scans (micro-CT) was performed to extract the volume of the cancellous bone surrounding the pedicle screw. The following volume bone mineral density and micro-architectural parameters were calculated: bone volume fraction, bone surface density (bone surface/total volume (BS/TV)), trabecular thickness, trabecular separation, trabecular number, structure model index, and number of nodes (branch points) of the cancellous bone network/total volume (NNd/TV) using Spearman's rank correlation coefficient with Bonferroni correction.

RESULTS:

Conventional test forces showed the strongest correlation with BS/TV: peak torque, ρ = 0.811, p = 4.96 × 10-17(micro-CT) and ρ = 0.730, p = 7.87 × 10-11 (MSCT); pull-out force, ρ = 0.730, p = 1.64 × 10-12 (micro-CT) and ρ = 0.693, p = 1.64 × 10-9 (MSCT). ISQ value showed the strongest correlation with NNd/TV: ρ = 0.607, p = 4.01 × 10-8 (micro-CT) and ρ = 0.515, p = 3.52 × 10-5 (MSCT).

CONCLUSIONS:

Test forces, including the ISQ value, can be predicted using micro-CT and MSCT parameters. This is useful for establishing a preoperative fixation strength evaluation system.

KEYWORDS:

Bone density; Pedicle screws; Resonance frequency analysis; Torque; X-ray (microtomography)

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