MECHANISM AND RISK FACTORS OF ADJACENT VERTEBRAL FAILURE POST PERCUTANEOUS VERTEBROPLASTY – A STRAIN ENERGY DENSITY APPROACH

Percutaneous vertebroplasty (PV) is an effective treatment procedure for com-pression fracture of osteoporotic vertebra; however, adjacent vertebral failure (AVF) is a frequently observed complication of PV. The mechanism and risk factors of AVF are not yet clear and this problem has attracted a lot of research effort in the medical community. The purpose of this study is to analyze the mechanism and risk factors of AVF post cement augmentation using a strain energy density (SED) approach. Fresh porcine spine specimens (L1-L5) were used. The effect of cement augmentation on the SED of vertebral bodies (VB), including the damaged VB and both adjacent cra-nial and caudal VBs, was analyzed. The result showed that the SED of the adjacent VBs did not increase after cement augmentation; however, the accumulated energy in the VBs of the whole spine motion segment decreased significantly after cement augmentation. This globally reduced energy is speculated to be absorbed by the disc between VBs. It is reasonable to believe that AVF may be initiated from the stressed disc. This study also suggests that poor bone quality and flexion compression are the two risk factors for AVF. Key Words: strain energy density, percutaneous vertebroplasty, adjacent vertebral failure, bone qualit