Analysis of Prevent Adjacent Segment Fractures After Vertebroplasty with Variable Amount of Bone Cement by Using FEA and GRA

Abstract

Aim: Osteoporosis occurs as a result of low bone density and deterioration of bone microarchitecture It is especially seen in the elderly population and is a chronic and progressive disease in which fractures develop even with simple trauma. Osteoporotic vertebrae fractures are common in this disease and vertebroplasty is an effective treatment for the pain relief and stabilization of the vertebral column. In this technique, bone cement is injected into the broken vertebra to strengthen them and reduce the pain. However, vertebra stiffness may cause pressure on the upper and the lower segments, leading to adjacent vertebral fractures. The aim of this study was to investigate the stresses in adjacent segments and the reaction forces in the intervertebral discs following different rates of bone cement injection into the osteoporotic vertebra fracture model. Materials and Methods: An intact lumbar (L) 1-3 spine finite element model was developed from the computed tomography images. The material properties were adapted to simulate osteoporosis. Twenty percent, 40% and 60% of cancellous bone were removed and filled with bone cement instead. The obtained models were subjected to 500 Newton (N) cyclic loading on the axial plane and 5 Newton/meter (N/m) forward flexion, left and the right moment forces. Models were imported into ANSYS Software Version 18 (Canonsburg, PA, USA) and the same boundary conditions were applied in all models in the analyses. Also, the models were compared with ANOVA (Analysis of Variance) and GRA (Grey Relational Analysis) methods. Results: It was determined that there was a significant difference between the stresses in the adjacent vertebrae and discs and the reaction forces that occurred in the discs in the models in which bone cement was injected at different ratios. There was a strong positive correlation between the models in which bone cement was injected at different rates and the equivalent stresses in the disc and vertebrae. Also, the results of ANOVA and GRA supported the results obtained from ANSYS. Conclusion: The amount of bone cement augmentation used in vertebroplasty significantly increases the stresses on adjacent discs and vertebrae. By reducing the amount of cement used, the risk of fracture in the adjacent segments can be decreased.