title: Radiofrequency-activated PMMA-augmentation through cannulated pedicle screws: A cadaver study to determine the biomechanical benefits in the osteoporotic spine.
abstract: BACKGROUND
  PMMA-augmentation of pedicle screws strengthens the bone-screw-interface reducing cut-out risk. Injection of fluid cement bears a higher risk of extravasation, with difficulty of application because of inconsistent viscosity and limited injection time.
  
  
  OBJECTIVE
  To test a new method of cement augmentation of pedicle screws using radiofrequency-activated PMMA, which is suspected to be easier to apply and have less extravasations.
  
  
  METHODS
  Twenty-seven fresh-frozen human cadaver lumbar spines were divided into 18 osteoporotic (BMD ≤ 0.8 g/cm2) and 9 non-osteoporotic (BMD > 0.8 g/cm2) vertebral bodies. Bipedicular cannulated pedicle screws were implanted into the vertebral bodies; right screws were augmented with ultra-high viscosity PMMA, whereas un-cemented left pedicle screws served as negative controls. Cement distribution was controlled with fluoroscopy and CT scans. Axial pullout forces of the screws were measured with a material testing machine, and results were analyzed statistically.
  
  
  RESULTS
  Fluoroscopy and CT scans showed that in all cases an adequately big cement depot with homogenous form and no signs of extravasation was injected. Pullout forces showed significant differences (p < 0.001) between the augmented and non-augmented pedicle screws for bone densities below 0.8 g/cm2 (661.9 N ± 439) and over 0.8 g/cm2 (744.9 N ± 415).
  
  
  CONCLUSIONS
  Pullout-forces were significantly increased in osteoporotic as well as in non-osteoporotic vertebral bodies without a significant difference between these groups using this standardized, simple procedure with increased control and less complications like extravasation.
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.|Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Karius
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.|Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Deborre
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.
authors.forename: D C
authors.initials: DC
authors.lastname: Wirtz
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Burger
authors.affiliation: Institute of Anatomy, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Prescher
authors.affiliation: Department of Orthopaedics, University Hospital Marburg, Marburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Fölsch
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Kabir
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Pflugmacher
authors.affiliation: Department of Orthopaedics and Trauma Surgery, Hospital Wermelskirchen, Wermelskirchen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Goost
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008422:Materials Testing; D010024:Osteoporosis / Q000601:surgery*; D065289:Pedicle Screws; D019904:Polymethyl Methacrylate; D011475:Prosthesis Failure; D011846:Radio Waves
chemical_list: D019904:Polymethyl Methacrylate
keywords: Osteoporosis; PMMA; biomechanical analysis; pedicle screw; polymethylmethacrylate; spinal fractures; spondylodesis