# Preoperative black line sign predicts progressive kyphosis after percutaneous kyphoplasty in osteoporotic vertebral compression fractures

## TL;DR

This study shows that a black line sign on MRI before surgery can predict worsening spine curvature after a procedure for broken vertebrae in osteoporosis patients.

## Contribution

The black line sign is identified as a novel independent predictor of progressive kyphosis after percutaneous kyphoplasty.

## Key findings

- Patients with the black line sign had a 75% incidence of progressive kyphosis compared to 16.2% in those without it.
- The black line sign was a significant independent risk factor with an odds ratio of 9.827 for progressive kyphosis.
- Those with the black line sign experienced greater vertebral height loss and worse clinical outcomes post-surgery.

## Abstract

This study aimed to evaluate the black line sign (BLS) on preoperative MR–STIR images as a predictor of progressive kyphosis (PK) following percutaneous kyphoplasty (PKP) for osteoporotic vertebral compression fractures (OVCFs). The goal of this study was to assess its significance in identifying patients at greater risk for postoperative kyphotic deformities and to refine clinical management strategies.

This single-center retrospective study analyzed 182 patients with OVCFs who underwent PKP between January 2019 and December 2022. Patients were categorized into two groups based on the presence or absence of BLS on preoperative MRI: the BLS group and the non-black line sign (NBLS) group. Radiological and clinical outcomes were compared between these two groups. Both univariate and multivariate analyses were performed to identify risk factors associated with the development of PK.

At the 1-year follow-up, the BLS group presented significantly greater vertebral height loss and kyphotic angle differences than did the NBLS group. Furthermore, the visual analog scale and Oswestry Disability Index scores were notably higher in the BLS group (P < 0.001). The incidence of PK in the BLS group was 75.0% (39/52), which was significantly greater than the 16.2% (21/130) observed in the NBLS group (P < 0.001). Cumulative event analysis revealed that a greater proportion of patients in the BLS group developed PK over the follow-up period. Both the log-rank test and Cox regression analysis demonstrated statistically significant differences (P < 0.001). Multivariate regression analysis revealed that BLS was a significant independent risk factor for PK, with an odds ratio of 9.827 (P < 0.001).

The black line sign on preoperative MR–STIR images is a significant predictor of PK after PKP for OVCFs. Clinicians should consider closer monitoring, external bracing, and aggressive osteoporosis treatment for patients with BLS to reduce the risk of postoperative kyphotic deformities.

The online version contains supplementary material available at 10.1186/s40001-026-03898-9.