Morphometric measurements can improve prediction of progressive vertebral deformity following vertebral damage

Abstract

Purpose

A damaged vertebral body can exhibit accelerated ‘creep’ under constant load, leading to progressive vertebral deformity. However, the risk of this happening is not easy to predict in clinical practice. The present cadaveric study aimed to identify morphometric measurements in a damaged vertebral body that can predict a susceptibility to accelerated creep.

Methods

A total of 27 vertebral trabeculae samples cored from five cadaveric spines (3 male, 2 female, aged 36 to 73 (mean 57) years) were mechanically tested to establish the relationship between bone damage and residual strain. Compression testing of 28 human spinal motion segments (three vertebrae and intervening soft tissues) dissected from 14 cadaveric spines (10 male, 4 female, aged 67 to 92 (mean 80) years) showed how the rate of creep of a damaged vertebral body increases with increasing “damage intensity” in its trabecular bone. Damage intensity was calculated from vertebral body residual strain following initial compressive overload using the relationship established in the compression test of trabecular bone samples.

Results

Calculations from trabecular bone samples showed a strong nonlinear relationship between residual strain and trabecular bone damage intensity (R² = 0.78, P < 0.001). In damaged vertebral bodies, damage intensity was then related to vertebral creep rate (R² = 0.39, P = 0.001). This procedure enabled accelerated vertebral body creep to be predicted from morphological changes (residual strains) in the damaged vertebra.

Conclusion

These findings suggest that morphometric measurements obtained from fractured vertebrae can be used to quantify vertebral damage and hence to predict progressive vertebral deformity.

Appendix

See Figures. 

Fig. 7

Data from 27 trabecular bone samples showing the relationship between trabecular bone damage and residual strain assessed at 0.1 MPa

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Fig. 8

The relationship between increased vertebral creep rate ($\mathrm{ln}{\dot{\varepsilon }}_{c}-\mathrm{ln}{\dot{\varepsilon }}_{0}$) and vertebral damage [$-\mathrm{ln}\left(1-\omega \right)]$ based on data represented in Fig. 7. Mechanical test data were from 25 vertebral bodies. ${\dot{\varepsilon }}_{0}$ is the vertebral creep rate before damage, ${\dot{\varepsilon }}_{c}$ is the vertebral creep rate after damage, and $\omega$ is the damage intensity derived from residual strain measured in the ramp loading/unloading cycle performed after compressive overload

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Fig. 9

Data from 27 trabecular bone samples showing the relationship between trabecular bone damage and residual strain assessed at 0.3 MPa

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Fig. 10

The relationship between increased vertebral creep rate ($\mathrm{ln}{\dot{\varepsilon }}_{c}-\mathrm{ln}{\dot{\varepsilon }}_{0}$) and vertebral damage [$-\mathrm{ln}\left(1-\omega \right)]$ based on data represented in Figure 9. Mechanical test data were from 25 vertebral bodies. ${\dot{\varepsilon }}_{0}$ is the vertebral creep rate before damage, ${\dot{\varepsilon }}_{c}$ is the vertebral creep rate after damage, and $\omega$ is the damage intensity derived from residual strain measured in the ramp loading/unloading cycle performed after compressive overload

10.