BACKGROUND: Adjacent vertebral fracture after percutaneous kyphoplasty (PKP) has been reported. Many scholars have analyzed that cement leakage into the intervertebral discs is one of the major reasons for subsequent fracture of the adjacent vertebral bodies.
OBJECTIVE: To explore the biomechanical changes of the adjacent vertebral bodies after PKP with bone cement leakage into the intervertebral discs using finite element analysis; to further analyze the causes of adjacent vertebral fractures and to seek for the remedial measures.
METHODS: A three-dimensional finite element model of thoracolumbar spine (T11-L2) was constructed using MIMICS, ABAQUS and other software. Simulation of PKP treatment for L1 vertebral osteoporotic compression fractures was performed to observe whether the cement leakage into the T12-L1 discs has biomechanical effects on the adjacent vertebral bodies of the fractures; a further simulation of prophylactic reinforcement of 2, 3 and 4 mL cement in the vertebral body T12 was performed to observe the Von Mises stress of the ensemble and each of different models under different loads.
RESULTS AND CONCLUSION: The relevant three-dimensional finite element models were successfully established. The maximum Von Mises stress of the adjacent vertebral bodies (T12) and the inferior endplate in the group with cement leakage into the disc(T12-L1) was significantly higher than that in the group without cement leakage. The maximum Von Mises stress of the adjacent vertebral body (T12) decreased to some extent after the prophylactic reinforcement of different doses of bone cement. The prophylactic reinforcement of low dose of bone cement (2-4 mL) did not obviously affect the biomechanical behaviors of the other vertebral bodies and intervertebral discs. These findings indicate that kyphoplasty with bone cement leakage into the intervertebral discs may lead to secondary fractures in the adjacent vertebral bodies; the prophylactic reinforcement of the adjacent vertebral bodies may reduce the occurrence of secondary fractures.