Warning line for preventing bone cement leakage in the surgery of percutaneous kyphoplasty for osteoporotic vertebral compression fractures
Authors: Li Dongyue , Tao Luming , Su Qingjun , Zhang Xinuo , Wu Xingrui 
Published: October 2024

Background
With the increasing aging of society, osteoporotic fractures have gradually become a serious problem affecting the quality of life of elderly individuals. Osteoporotic vertebral compression fractures (OVCFs) are the most common complication of osteoporosis. Percutaneous kyphoplasty (PKP) has achieved good clinical efficacy in the treatment of OVCFs. However, how to reduce the bone cement leakage rate and improve safety during PKP surgery remains an urgent issue to be addressed in clinical practice. Therefore, the aim of this study was to identify a line, called the “warning line”, to determine whether there is leakage of bone cement during PKP surgery.
Methods
From February 2018 to September 2022, patients with OVCFs treated with PKP by a single surgeon at our center were included in the study. After screening from intraoperative X-ray images, we selected patients whose bone cement diffusion reached the posterior margin of the vertebral body, resulting in a total of 88 patients and 106 vertebral bodies. Clinical general data were recorded. Postoperative three-dimensional CT scans were used to assess bone cement leakage at the posterior margin. Vertebral bodies with bone cement reaching the apex of the posterior margin depression without leakage were designated Group A, whereas those with leakage were designated Group B. We compared the age, bone density, balloon pressure, contrast dose, and bone cement volume between the two groups. The posterior vertebral wall was divided into three equal parts in the postoperative three-dimensional CT scans, and the leakage rates at different positions of the posterior vertebral wall were analysed. Lateral X-ray images were used in Group A. Line a was marked as the posterior vertebral margin. Line b was marked as the apex of cement diffusion, parallel to line a. Line c was marked as the anterior vertebral margin. Line b was designated the warning line, and the ratio of ab/ac was calculated.
Results
All 88 patients successfully underwent surgery, with a significant decrease in the postoperative VAS score. No neurological complications occurred in any patient. On the basis of three-dimensional CT images of the 106 vertebral bodies, the posterior vertebral wall cement leakage rate was 58.5%. There were 44 vertebral bodies in Group A and 62 in Group B. No significant differences were found between the two groups in terms of age, bone density, balloon pressure, contrast dose, or cement volume (P > 0.05). In the sagittal images of the three-dimensional CT images, the bone cement leakage rates in the upper third, middle third, and lower third of the posterior vertebral wall were 25%, 61.1%, and 66.7%, respectively, with statistically significant differences in leakage rates at different positions (P < 0.05). In Group A, the ab/ac ratio in the lateral X-ray images was 6.8 ± 2.17%, indicating that the warning line was approximately 6.8% of the sagittal diameter from the posterior vertebral margin.
Conclusions
PKP is a relatively safe treatment for OVCFs. Most bone cement leakage occurs in the middle and lower thirds of the posterior vertebral wall. When the apex of cement diffusion remains anterior to the warning line in PKP surgery, the posterior vertebral wall cement leakage rate is low.