Non-Contiguous OVCF Patients Had a Higher Risk of AVF After PVP Operation Related to Poor Bone Mineral Density Rather Than Aggravated Stress Concentration

Background: Biomechanical deterioration and low bone mineral density (BMD) are two primary triggers for adjacent vertebral fracture (AVF) after percutaneous vertebroplasty (PVP) operation. Sandwich vertebral body (SVB) refers to a vertebral body situated between two osteoporotic vertebral compressive fractures (OVCF) segments. There exists a contradiction regarding whether the SVB are at a heightened risk of AVF, and the underlying mechanism has yet to be elucidated. Methods: Clinical data of PVP treated OVCF patients were included in this study. Patients were divided into two groups: those with single-level OVCF and those with SVB resulting from non-contiguous two-level OVCF. Statistical comparisons and logistic regression analyses were performed to investigate whether patients with two-level non-contiguous OVCFs constitute a risk factor for AVF. Furthermore, PVP procedures involving single-level and non-contiguous two-level OVCFs were simulated in models with identical bony density. Biomechanical indicators associated with AVF were computed under physiological loading conditions. Results: This study enrolled 173 patients with PVP-treated OVCF, including 134 with single-segment fractures and 39 with non-contiguous two-level fractures. Among these patients, the overall incidence of AVF was 22.39% (30/134) in the single-segment group and 38.46% (15/39) in the non-contiguous two-level group. The incidence of AVF was significantly higher in patients with non-contiguous two-level OVCF (P = 0.044). Correspondingly, HU values were significantly lower in those with two-level OVCF. However, only a lower HU value was judged to be an independent risk factor for AVF. Furthermore, the maximum difference between the two models with identical BMD was found to be less than 5%. The only exception observed was the cortical stress value in the L3 vertebral body under extension loading conditions. In this case, the stress value of the SVB increased by 10.41% compared to the control group (i.e. single-level OVCF at L2), and the difference in stress between groups was not influenced by the presence or absence of compressive load. Conclusion: Patients with two-level non-contiguous OVCF experiences a higher incidence of AVF primarily due to poor BMD, rather than the exacerbation of stress concentration caused by two adjacent segmental cement augmentations.