Biomechanical effects of osteoporosis vertebral augmentation on the adjacent intervertebral levels using a three-dimensional finite element analysis / 中华创伤骨科杂志

ABSTRACT

Objective To investigate effects of volume,distribution and leakage of bone cement in ver- tebroplasty on the adjacent intervertebral bodies using an experimentally calibrated and anatomically accurate fi- nite-element model of elderly L4-L5 vertebral bodies.Methods Computed tomography(CT)scanning was done,at 1 mm intervals,on L4-L5 vertebral bodies of the lumbar spine of an old man cadaver that had no abnormal findings on rnentgenograms.The L4-L5 motion segment data were obtained from the CT scans to establish in computer a three-dimensional finite element model of L4-L5 functional spinal unit(FSU)with the software Ansys 7.0.Compressive load after virtual vertebroplasty on the damaged model,unipedicular and bipedieolar injections and leakage of cement into the intervertebral space,and the resulting endplate and disc stresses of the adjacent vertebral bodies were analyzed in various spatial distributions of the filling material and different loading conditions. An anatomically accurate finite-element model of elderly L4-L5 vertebral bodies was developed.Results The FSU study suggested that changes in stress and strain at adjacent levels were minimal.Furthermore,endplale and disc stresses of the adjacent vertebral bodies were not influenced by bone cement filling volumes or distributions except under bending,whereas asymmetric distribution and leakage of bone cement to the disk increased the stress of adjacent endplates.Conclusion Since asymmetric distribution and significant leakage of cement into the intervertebral space can increase the stresses of endplates of adjacent vertebral bodies and may lead to a fracture, symmetric placement of cement in operation should be achieved and leakage of cement avoided.