Analysis of factors influencing the intravertebral shell phenomenon after posterior reduction internal fixation of thoracolumbar fracture: A case-control study

Abstract

Abstract Background: To investigate the factors influencing the intravertebral shell phenomenon (ISP) after posterior repositioning internal fixation of thoracolumbar fractures and the related factors of evolutionary outcomes and to make recommendations for the prevention and treatment of this phenomenon. Methods: We retrospectively analysed 331 patients with single-segment fractures of the thoracolumbar vertebrae treated with posterior repositioning internal fixation using the posterior pedicle nail system from January 2016 to December 2020. Univariate and multivariate logistic regressions were applied to analyse the factors influencing the ISP. Results: A total of 260 patients (78.5%) were found to have the postoperative ISP. Reduced bone density, preoperative vertebral over-compression, and intraoperative vertebral over-sparing were significantly correlated with the occurrence of postoperative ISP(P<0.05). A total of 166 of the 260 patients were reviewed by CT 1 year after surgery, revealing reduction or healing of the vertebral cavity in 104 patients (62.6%) and enlargement of the vertebral cavity or collapse of the endplate in 62 patients (37.4%). The degree of intraoperative vertebral body repositioning was strongly correlated with the outcome of the intravertebral shellphenomenon (P<0.05). A total of 123 patients (74%) had their internal fixation devices removed 1 year after surgery, which was significantly correlated withthe degree of intraoperative vertebral body repositioning and the outcome of the ISP 1 year after surgery (P<0.05). Conclusion: The ISP occurs commonly after internal fixation of thoracolumbar fractures and is associated with reduced bone density and excessive preoperative compression intraoperative sparing of the vertebrae. At 1 year postoperatively, 37.4% of patients still had enlarged vertebral cavities or endplate collapse, which affected patient access to internal fixation; the impact on patient function needs further study.