1. Vertebral compression fracture is a common clinical manifestation in osteoporosis. Kyphoplasty has become a popular tool to address painful thoracic and lumbar compression fracture. By inflating a balloon within a vertebral body to create a void, thereby reducing the fracture, and then depositing polymethylmethacrylate (PMMA) or Calcium phosphate based cement into the void to augment the vertebral body. Many clinical trials have reported favorable early results for transpedicular vertebral cement reinforcement. Previously studies as finite element analysis, biomechanical tests and clinical studies have indirectly associated new adjacent vertebral fractures following augmentation to altered loading. These risk factors, the weaker anterior vertebral wall and superior endplate cleft, were often happened when compression fracture occurred. Impact of cement leakage into disks on the development of adjacent vertebral compression fractures was also reported. There is only a limited understanding how the load shift of the intervertebral disc after a kyphoplasty with PMMA or Calcium phosphate based cement under different these risk factors. We hypothesized that adjacent fractures may result from a shift in stiffness and load following rigid augmentation. In same situation, the intervertebral disc should be showed altered disc pressure profile. Both filler materials could restore the total strength and stiffness level of treated vertebral body. With an intact endplate during compression fracture period, the two augmented cements shows no significantly difference in restoring of strength and stiffness. With a damaged endplate, overgrowth stiffness located superior endplate by using PMMA maybe show a impact factor for further adjacent deformity. The change of pressure in disc with a damaged endplate was supposed to develop abnormal intradiscal pressure in flexion also been shown to increase loading of the adjacent anterior vertebral cortex. The PMMA and CaP cement played a different role in different risk factors. Our study indicated a compression fracture treated with kyphoplasty by PMMA or CaP based cement must be evaluated according the damaged structures in an osteoporotic vertebral compression fracture. Introduction Discussion Suitability evaluation of restoring the intervertebral disc mechanics in treating osteoprotic vertebral fracture using kyphoplasty with PMMA or calcium-p based cement Hao Ju. Lo, Hung-Ming Chen The Orthopaedic Department, Ren-Ai Branch, Taipei City Hospital, Taiwan Methods I have no financial relationships to disclose PMMA vs CaP : Increased to almost 20% in any type. Results Augmentation increased the pressure in the nucleus pulposus and the adjacent endplate under PMMA and CaP cement. The stresses and strains in the vertebrae close to an augmentation were increased, and change their distribution with different risk factors. In PMMA groups, higher stresses and strains were noted over endplate and disc when risk factors exist compared with CaP cement. The pressure in a bulge of the augmented endplate and disc were increased to almost 20% of its value before the augmentation, resulting in a stiffening of the intervertebral disc. The increase of in the inward bulge of the endplate adjacent to the one augmented may be the cause of the adjacent fractures. In CaP cement, in leakage model, seem to show more suitable in mechanics if leakage happened. (material properties adapted to simulate osteoporosis Reference 1.Shinya Nouda, MD, Seiji Tomita, MD, Akihiro Kin, Kunihiko Kawahara, MD, and Mitsuo Kinoshita, MD, 2009 Adjacent Vertebral Body Fracture Following Vertebroplasty With Polymethylmethacrylate or Calcium Phosphate Cement., SPINE Volume 34, Number 24, pp 2613–2618 2.A. Jay Khanna, MD,, Samuel Lee, MSc, Marta Villarraga, PhD, Jonathan Gimbel, PhD, Duane Steffey, PhD, Jeffrey Schwardt, PhD, 2008 Biomechanical evaluation of kyphoplasty with calcium phosphate cement in a 2-functional spinal unit vertebral compression fracture model, The Spine Journal 8, 770–777 3.Hans-Joachim Wilke, PhD, Ulrich Mehnert, MD, Lutz E. Claes, PhD, 2006, Biomechanical Evaluation of Vertebroplasty and Kyphoplasty With Polymethyl Methacrylate or Calcium Phosphate Cement Under Cyclic Loading, SPINE Volume 31, Number 25, pp 2934–2941 4.Antonius Rohlmann Thomas Zander Georg Bergmann, 2006, Spinal loads after osteoporotic vertebral fractures treated by vertebroplasty or kyphoplasty, Eur Spine J 15: 1255–1264 5.Peter G. Campbell A James S. Harrop, 2008, Incidence of fracture in adjacent levels in patients treated with balloon kyphoplasty: a review of the literature, Curr Rev Musculoskelet Med 1:61–64