Disc collapse aggravates vertebral recollapse following percutaneous kyphoplasty: a clinical review and biomechanical study.

Abstract

<h4>Background</h4>Promoting uniform load distribution is an essential biomechanical function of intervertebral discs (IVDs), but disc degeneration (DD) may compromise this and lead to localized stress concentration. However, whether DD can trigger stress concentration on the cement-augmented vertebral body and result in more severe augmented vertebral recollapse has yet to be determined. The aim of this study was to investigate clarify this issue and provide theoretical guidance regarding the mechanism underlying this complication.<h4>Methods</h4>Augmented vertebrae height was measured immediately after surgery and at 1-year follow-up in patients with percutaneous kyphoplasty (PKP)-treated osteoporotic vertebral compressive fracture (OVCF) to assess the recollapse status. Differences in vertebral recollapse height were compared between patients with and without disc fibrosis and collapse. Independent risk factors for vertebral recollapse were identified via linear regression analysis, with statistical significance set at P<0.05. Additionally, PKP simulations were performed on models with and without disc fibrosis and collapse to investigate stress value changes.<h4>Results</h4>Significantly larger vertebral recollapse height was observed in patients with disc collapse. Conversely, the vertebral recollapse height was comparable between patients with and without disc fibrosis in both the cranial and caudal sides. Moreover, disc collapse in both cranial and caudal IVDs was regarded as an independent risk factor for more severe vertebral recollapse (P=0.02 and P=0.025, respectively). In the comparison of models without disc collapse, a higher stress value on cancellous bone was noted in the disc collapse model. However, only slight differences were found in stress values between the control model and the model of disc fibrosis.<h4>Conclusions</h4>Disc collapse can impair the biomechanical function of IVDs and induce localized stress concentration in adjacent bony structures. This alteration may aggravate recollapse of the cement-augmented vertebral bodies among patients with OVCF.