Biomechanical effects of different vertebral heights after augmentation of osteoporotic vertebral compression fracture: a three-dimensional finite element analysis

Abstract

Background: Clinical results have shown that different vertebral heights have been restored post-augmentation of osteoporotic vertebral compression fractures (OVCFs) and the treatment results are consistent. However, no significant results regarding biomechanical effects post-augmentation have been found with different types of vertebral deformity or vertebral heights by biomechanical analysis. Therefore, the present study aimed to investigate the biomechanical effects between different vertebral heights of OVCFs before and after augmentation using three-dimensional finite element analysis.

Methods: Four patients with OVCFs of T12 underwent computed tomography (CT) of the T11-L1 levels. The CT images were reconstructed as simulated three-dimensional finite-element models of the T11-L1 levels (before and after the T12 vertebra was augmented with cement). Four different kinds of vertebral height models included Genant semi-quantitative grades 0, 1, 2, and 3, which simulated unilateral augmentation. These models were assumed to represent vertical compression and flexion, left flexion, and right flexion loads, and the von Mises stresses of the T12 vertebral body were assessed under different vertebral heights before and after bone cement augmentation.

Results: Data showed that the von Mises stresses significantly increased under four loads of OVCFs of the T12 vertebral body before the operation from grade 0 to grade 3 vertebral heights. The maximum stress of grade 3 vertebral height pre-augmentation was produced at approximately 200%, and at more than 200% for grade 0. The von Mises stresses were significantly different between different vertebral heights preoperatively. The von Mises stresses of the T12 vertebral body significantly decreased in four different loads and at different vertebral body heights (grades 0-3) after augmentation. There was no significant difference between the von Mises stresses of grade 0, 1, and 3 vertebral heights postoperatively. The von Mises stress significantly decreased between pre-augmentation and post-augmentation in T12 OVCF models of grade 0-3 vertebral heights.

Conclusion: Vertebral augmentation can sufficiently reduce von Mises stresses at different heights of OVCFs of the vertebral body, although this technique does not completely restore vertebral height to the anatomical criteria.

Keywords: Osteoporotic vertebral compression fracture; Vertebral augmentation; Von Mises stress.

Fig. 1

Computed tomography images of 4 patients with T12 osteoporotic vertebral compression fractures after vertebral augmentation. a–d Cross-section images of grade 0–3 vertebral height; e–h sagittal images of grade 0–3 vertebral height

Fig. 2

T11-L1 three-dimensional model and T12 fracture model

Fig. 3

T11-L1 three-dimensional model and the T12 vertebral body after augmentation

Fig. 4

T11-L1 finite element analysis model

Fig. 5

Nephograms of the von Mises stresses on fresh T12 osteoporotic vertebral compression fractures. The side and upper end-plate are shown

Fig. 6

The von Mises stresses on fresh T12 osteoporotic vertebral compression fractures

Fig. 7

Nephograms of the von Mises stresses on T12 osteoporotic vertebral compression fractures after augmentation. The side and upper end-plate are shown

Fig. 8

The von Mises stresses on the T12 vertebral body after augmentation

Fig. 9

Comparison of the von Mises stresses before and after augmentation