title: Effect of bone cement volume and stiffness on occurrences of adjacent vertebral fractures after vertebroplasty.
abstract: OBJECTIVE
  The purpose of this study is to find the optimal stiffness and volume of bone cement and their biomechanical effects on the adjacent vertebrae to determine a better strategy for conducting vertebroplasty.
  
  
  METHODS
  A three-dimensional finite-element model of a functional spinal unit was developed using computed tomography scans of a normal motion segment, comprising the T11, T12 and L1 vertebrae. Volumes of bone cement, with appropriate mechanical properties, were inserted into the trabecular core of the T12 vertebra. Parametric studies were done by varying the volume and stiffness of the bone cement.
  
  
  RESULTS
  When the bone cement filling volume reached 30% of the volume of a vertebral body, the level of stiffness was restored to that of normal bone, and when higher bone cement exceeded 30% of the volume, the result was stiffness in excess of that of normal bone. When the bone cement volume was varied, local stress in the bony structures (cortical shell, trabecular bone and endplate) of each vertebra monotonically increased. Low-modulus bone cement has the effect of reducing strain in the augmented body, but only in cases of relatively high volumes of bone cement (>50%). Furthermore, varying the stiffness of bone cement has a negligible effect on the stress distribution of vertebral bodies.
  
  
  CONCLUSIONS
  The volume of cement was considered to be the most important determinant in endplate fracture. Changing the stiffness of bone cement has a negligible effect on the stress distribution of vertebral bodies.
authors: Department of Medical System Engineering and Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors: Jin-Myung
authors: JM
authors: Kim
authors: Dong Ah
authors: DA
authors: Shin
authors: Dong-Hak
authors: DH
authors: Byun
authors: Hyung-Sun
authors: HS
authors: Kim
authors: Sohee
authors: S
authors: Kim
authors: Hyoung-Ihl
authors: HI
authors: Kim
keywords: Bone cements; Finite element analysis; Vertebroplasty