An Experimentally Validated Mathematical Model of Axial Spinal Compression to Visualize Vertebral Compression Fracture

Summary

Here, we provide a predictive model of VCFs to support surgical intervention. Biomechanical fracture patterns of human and porcine cadaveric vertebrae under compression loading were used to verify an FEA model, providing a resource for better visualizing vertebral fracture and supporting using porcine samples in spine research.

Abstract

The finite element analysis (FEA) model established in this study predicts the mechanical behavior of a vertebral body under pure compression loading. Four human and four porcine cadaveric spines were used in the region from T9-T12 (human) and T12-T14 (porcine) to derive biomechanical failure data under pure axial compression. By implementing the data from these axial crush experiments and combining them with computed tomography (CT)-derived three-dimensional (3D) reconstructions of vertebrae, this new model mathematically predicts the behavior of the spine in vertebral compression fractures (VCFs). The development of an accurate mathematical model has the potential to aid surgical intervention of VCFs during vertebroplasty, kyphoplasty, and potentially additional techniques by accurately representing biomechanical behavior. It can be adapted for osteoporosis, fusion, and implant biomechanics cases to improve surgical accuracy. Understanding the vertebral fracture pattern is essential in surgical pre-planning and understanding prior and future risks. The presented method may serve as an additional resource for studying and treating VCF and further supports the use of porcine specimens in spine research.

Introduction

Vertebral Compression Fractures (VCFs) are biomechanical failures of the anterior vertebral body in response to axial compressive load^1,2. There are 1-1.5 million patients experiencing VCFs in the US each year, with notable risk factors including osteoporosis, advanced age, and female sex^3,4,5. Patients with VCFs can experience pain, disability, altered pulmonary or respiratory function, secondary vertebral fracture, and increased mortality risk^6,7. Preferred ....

Protocol

All experiments were performed in accordance with relevant human research ethics and animal care guidelines at the University of Illinois College of Medicine.

1. Sample preparation

NOTE: VCFs are extensively described for the thoracolumbar region, as most wedge compression fractures occur in the mid-thoracic area¹⁹. For this reason, thoracic vertebrae T9-T12 from humans and T12-14 from porcine were used for these experiments (Table 1).

1. Obtain four cadaveric human spines.
2. Obtain four commercially available cadaveric porcine spines.

Results

From the 12 porcine vertebrae, the load-displacement curves obtained for all specimens are depicted in Figure 1, where all experimental data curves showed similar patterns. Results show an average vertebral stiffness and strength of 9.54 ±1.1 kN/mm (range 6.73-13.63 kN/mm) and 10.2 ± 0.86 kN (range 8.1-13 kN). Video analysis of the experimental compression tests demonstrated a common failure pattern across specimens. The failure pattern consisted of three fracture lines. The first two fractu.......

Discussion

While CT-derived FEA is a well-established tool for modeling biomechanical behavior, few studies apply mathematical modeling in conjunction with physical validation in the context of VCFs. This study demonstrates an accurate predictive mathematical model of thoracolumbar VCF, supported by experimental compression of porcine and human cadaveric spines. The model incorporates strength, stiffness, fracture pattern, load mechanics, and material properties to mathematically predict vertebra response to axial load. The morphol.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3-MATIC	Materialise	v15.0
Abaqus/CAE	Simulia	n/a
Analytical Balance	Sigma Aldrich	OH30122634
Cadaveric porcine spines			Local butcher shop, Chicago, IL
CT machine	Siemens	SOMATOM Definition AS
Epredia Shandon Round Tip Bone Saw, Blade: 8 in. x 2.5 in. (20.3 in. 6.4 cm), standard, 11.5 in. (29.2 cm)	Fischer Scientific	40018
Fisherbrand Fine Precision Medium Tipped Tweezers/Forceps	Fischer Scientific	12-000-157
Integra Miltex Sterile Standard Scalpels	Fischer Scientific	12-460-451
Laser cutter machine/3D printer	Fusion3	F400HFR
Mimics Software	Materialise	v2.0
NDI Optotrak Certus	NextGen Ergonomics	Certus Products
Orthopedic Bone Saw	OrthopedicDrills	OTS-1
SPSS Statistics	IBM	v27
Absorbent Underpads with Waterproof Moisture Barrier, 58.4 x 61 cm, 410 mL, Blue, 200/cs	VWR INTERNATIONAL INC	56616-032