Spinal Morphology of Vertebroplasty during Fatigue Loading
Date Issued
2009
Date
2009
Author(s)
hsu, cheng-kun
Abstract
Objective: To explore the refracture mechanism of vertebroplasty. ummary of Background Data: Vertebroplasty is a minimal invasive surgery for spinal compression fracture. The major complications of vertebroplasty are cement leakage and adjacent vertebral failure. In recent year, the incidence of augmented vertebral refracture increases. The mechanism of refracture is, however, not clear.aterials and Methods: Ten fresh 4-level thoracic motion segments (T5~T8,N=3;T9~T12,N=5 ;T8~T11,N=1; T4~T7,N=1) from 6 human spines were used. A series of steel balls (D=1.4 mm) were glued to the canal for determining the canal width in the midsagittal plane. Four steel balls separately embedded into the anterior vertebra for measuring the height of anterior vertebra. Both ends of the specimen were mounted, leaving the center 2 vertebrae free. The lower level of free vertebra was artificially injured and than cement augmented. The injection volume of cement was 3.5 ml and the powder to monomer ratio of the cement was 1.3. All specimens were applied with 650 N, 950 N and 1150 N (mean) compressive fatigue loading. The loading frequency was 5 Hz and the loading period was 5 hours in each loading magnitude. The lateral radiographs were taken in each hour. In the end of the experiment, the failure specimens were cut along the sagittal plane.esults: The vertebral height, spinal canal width and disc height decreased following fatigue loading, and can be partially recovered during 12 hr rest. The vertebral posterior cortex extrusion causes loss of the spinal canal width. The spinal canal width after injury and posterior vertebral height were positively related to the spinal canal width after fatigue, but the bone mineral density and the anterior vertebral height restoration were not correlated to the spinal canal. The dissected specimens showed that the weak posterior bony structure was extruded into spinal canal due to the fatigue loading.onclusion: The fracture of pre-existed vertebral posterior cortex increases the risk of subsequent fracture post vertebroplasty. The refracture mechanism cannot be correlated with the BMD and the anterior vertebral height restoration in this study.
Subjects
compression fracture、vertebroplasty、bone cement、refracture
Type
thesis
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