title: An ex vivo evaluation of an inflatable bone tamp used to reduce fractures within vertebral bodies under load.
abstract: METHODS
  Ex vivo biomechanical study using osteoporotic cadaveric vertebral bodies.
  
  
  OBJECTIVE
  To determine if fracture reduction could be achieved by the inflatable bone tamp (tamp) in vertebral bodies under simulated physiologic loads.
  
  
  BACKGROUND
  Previous ex vivo biomechanical studies showed that kyphoplasty restored vertebral body height with vertebral body endplates under stress-free conditions.
  
  
  METHODS
  Simulated compression fractures were experimentally created in 18 osteoporotic vertebral bodies alternatingly assigned to one of two treatment (tamp inflation) groups: low axial load (111 N) or high axial load (222 N). Each vertebral body was then placed between two platens in a special radiolucent loading fixture and subjected to the preassigned load to simulate in vivo physiologic loading. The tamps were inflated and postreduction heights were measured fluoroscopically. The effect of applied load and condition on vertebral body height was checked for significance (P < 0.05).
  
  
  RESULTS
  Comparing the experimental conditions (initial, postcompression, postinflation), there were no significant vertebral body height differences between the load groups (low load vs. high load). However, vertebral body height differences between conditions within each load group were all significant. For the low-load and high-load groups, mean postinflation heights (24.4 and 24.4 mm) were significantly greater than mean postcompression heights (21.6 and 22.5 mm) but significantly less than initial vertebral body heights (26.6 and 26.3 mm), respectively. Initial heights were fully restored in 22% (two of nine) of vertebral bodies in both groups.
  
  
  CONCLUSIONS
  The inflatable bone tamp restored some of the height lost to compression fractures in vertebral bodies under simulated physiologic loads.
authors.affiliation: Orthopaedic Instrumentation Laboratory, Department of Orthopaedic Surgery, Johns Hopkins University/Johns Hopkins Bayview Medical Center, Baltimore, Maryland 21224-2780, USA. ebulson@jhmi.edu
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Belkoff
authors.forename: Louis E
authors.initials: LE
authors.lastname: Jasper
authors.forename: Sheila S
authors.initials: SS
authors.lastname: Stevens
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D020007:Implants, Experimental; D008954:Models, Biological; D019637:Orthopedic Procedures / Q000295:instrumentation*; D010024:Osteoporosis / Q000150:complications* / Q000000981:diagnostic imaging; D016103:Spinal Fractures / Q000150:complications / Q000473:pathology / Q000601:surgery*; D013131:Spine / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D013314:Stress, Mechanical; D016896:Treatment Outcome; D016474:Weight-Bearing