title: Vertebroplasty increases compression of adjacent IVDs and vertebrae in osteoporotic spines.
abstract: BACKGROUND
  Approximately 25% of vertebroplasty patients experience subsequent fractures within 1 year of treatment, and vertebrae adjacent to the cemented level are up to three times more likely to fracture than those further away. The increased risk of adjacent fractures postaugmentation raises concerns that treatment of osteoporotic compression fractures with vertebroplasty may negatively impact spine biomechanics.
  
  
  OBJECTIVE
  To quantify the biomechanical effects of vertebroplasty on adjacent intervertebral discs (IVDs) and vertebral bodies (VBs).
  
  
  METHODS
  A biomechanics study was conducted using cadaveric thoracolumbar spinal columns from elderly women (age range, 51-98 years).
  
  
  METHODS
  Five level motion segments (T11-L3) were assigned to a vertebroplasty treated or untreated control group (n=10/group) such that bone mineral density (BMD), trabecular architecture, and age were similar between groups. Compression fractures were created in the L1 vertebra of all specimens, and polymethylmethacrylate bone cement was injected into the fractured vertebra of vertebroplasty specimens. All spine segments underwent cyclic axial compression for 115,000 cycles. Microcomputed tomography imaging was performed before and after cyclic loading to quantify compression in adjacent VBs and IVDs.
  
  
  RESULTS
  Cyclic loading increased strains 3% on average in the vertebroplasty group when compared with controls after 115,000 cycles. This global strain manifested locally as approximately fourfold more compression in the superior VB (T12) and two- to fourfold higher axial and circumferential deformations in the superior IVD (T12-L1) of vertebroplasty-treated specimens when compared with untreated controls. Low BMD and high cement fill were significant factors that explained the increased strain in the vertebroplasty-treated group.
  
  
  CONCLUSIONS
  These data indicate that vertebroplasty alters spine biomechanics resulting in increased compression of adjacent VB and IVD in severely osteoporotic women and may be the basis for clinical reports of adjacent fractures after vertebroplasty.
authors: Division of Solid and Fluid Mechanics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA. Electronic address: srinidhi.nagaraja@fda.hhs.gov.
authors: Srinidhi
authors: S
authors: Nagaraja
authors: Hassan K
authors: HK
authors: Awada
authors: Maureen L
authors: ML
authors: Dreher
authors: Shikha
authors: S
authors: Gupta
authors: Scott W
authors: SW
authors: Miller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000473:pathology*; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000473:pathology*; D054854:Vertebroplasty / Q000009:adverse effects*
keywords: Adjacent segment disease; Biomechanics; Osteoporosis; Vertebral compression fracture; Vertebroplasty