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Technical Brief

Creating Physiologically Realistic Vertebral Fractures in a Cervine Model

[+] Author and Article Information
Nicole C. Corbiere

Department of Mechanical and Aeronautical Engineering,
Clarkson University,
Potsdam, NY 13699

Kathleen A. Lewicki

Department of Mechanical and Aeronautical Engineering,
Clarkson University,
Potsdam, NY 13699;
Thayer School of Engineering,
Dartmouth College,
Hanover, NH 03755

Kathleen A. Issen

Department of Mechanical and Aeronautical Engineering,
Clarkson University,
Potsdam, NY 13699

Laurel Kuxhaus

Department of Mechanical and Aeronautical Engineering,
Clarkson University,
Potsdam, NY 13699
e-mail: lkuxhaus@clarkson.edu

1Corresponding author.

Manuscript received October 4, 2013; final manuscript received February 6, 2014; accepted manuscript posted March 6, 2014; published online May 6, 2014. Assoc. Editor: Kristen Billiar.

J Biomech Eng 136(6), 064504 (May 06, 2014) (4 pages) Paper No: BIO-13-1464; doi: 10.1115/1.4027059 History: Received October 04, 2013; Revised February 06, 2014; Accepted March 06, 2014

Approximately 50% of women and 25% of men will have an osteoporosis-related fracture after the age of 50, yet the micromechanical origin of these fractures remains unclear. Preventing these fractures requires an understanding of compression fracture formation in vertebral cancellous bone. The immediate research goal was to create clinically relevant (midvertebral body and endplate) fractures in three-vertebrae motion segments subject to physiologically realistic compressional loading conditions. Six three-vertebrae motion segments (five cervine, one cadaver) were potted to ensure physiologic alignment with the compressive load. A 3D microcomputed tomography (microCT) image of each motion segment was generated. The motion segments were then preconditioned and monotonically compressed until failure, as identified by a notable load drop (48–66% of peak load in this study). A second microCT image was then generated. These three-dimensional images of the cancellous bone structure were inspected after loading to qualitatively identify fracture location and type. The microCT images show that the trabeculae in the cervine specimens are oriented similarly to those in the cadaver specimen. In the cervine specimens, the peak load prior to failure is highest for the L4–L6 motion segment, and decreases for each cranially adjacent motion segment. Three motion segments formed endplate fractures and three formed midvertebral body fractures; these two fracture types correspond to clinically observed fracture modes. Examination of normalized-load versus normalized-displacement curves suggests that the size (e.g., cross-sectional area) of a vertebra is not the only factor in the mechanical response in healthy vertebral specimens. Furthermore, these normalized-load versus normalized-displacement data appear to be grouped by the fracture type. Taken together, these results show that (1) the loading protocol creates fractures that appear physiologically realistic in vertebrae, (2) cervine vertebrae fracture similarly to the cadaver specimen under these loading conditions, and (3) that the prefracture load response may predict the impending fracture mode under the loading conditions used in this study.

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Figures

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Fig. 1

Load frame fixture with potted specimen

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Fig. 2

MicroCT image of cross-section from (a) cervine L4 lumbar vertebra and (b) cadaver L4 lumbar vertebra

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Fig. 3

Load–displacement curves for all three-vertebra motion segments. Dashed lines indicate endplate fractures and solid lines indicate midvertebral body fractures. The cadaver specimen curve is marked (H).

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Fig. 4

Fracture type and location (indicated by arrows) for each motion segment. (Supplemental material for 3D fly-through videos of each cervine specimen is available under the “Supplemental Data” tab for this paper on the ASME Digital Collection)

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Fig. 5

Normalized-load versus normalized-displacement curves for all vertebral motion segments. Dashed lines indicate endplate fractures and solid lines indicate midvertebral body fractures. The cadaver specimen curve is marked (H).

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