Is it necessary to link the bilateral cement during the process of Percutaneous kyphoplasty？

BACKGROUND: To evaluate the clinical and biomechanical results of different types of bone cement distribution post bilateral percutaneous kyphoplasty (PKP) in patients with osteoporotic vertebral compression fractures (OVCF). METHODS: A retrospective study of 227 single-segment OVCF patients from May 2017 to November 2020 were operated with bilateral percutaneous kyphoplasty and injected with the same material and the same volume of bone cement. According to the postoperative imaging data of the patients, the patients were allocated into two groups according to whether the bilateral bone cement in the vertebral body was connected. Further, establishment of a three-dimensional finite element model to evaluate the mechanical property of vertebral bodies after percutaneous kyphoplasty. Loading the model in five motion states (compression, forward bending, backward extension, rotation and lateral bending) for force analysis, and compare the stress difference between the fractured vertebrae and adjacent vertebrae under the two cement distributions. RESULTS: Of the 227 patients, 217 eventually received an average follow-up of 22 months. The restoration rate of vertebral body height, the improvement of kyphotic angle and the degree of postoperative improvement of the visual analog scale for pain (VAS) of the two groups of patients were similar, and there was no significant difference between the groups (P>0.05). There was no significant difference in the rate of bone cement leakage between the two groups (P>0.05). But there was a significant difference in the incidence of recurrent vertebral fractures (new fractures of adjacent vertebral bodies and re-fractures of injured vertebrae) (P< 0.05). There was a significant difference in the von Mises stress between the fractured vertebral body and the cranial adjacent vertebra under the same conditions between the two groups of vertebral body models (P＜0.05). CONCLUSION：Administration of bone cement in the center of vertebrae without distribution to both edges may reduce the risk of re-collapse of the injured vertebrae and fracture of adjacent vertebral body on the cranial side.