title: Can experimental data in humans verify the finite element-based bone remodeling algorithm?
abstract: METHODS
  A finite element analysis-based bone remodeling study in human was conducted in the lumbar spine operated on with pedicle screws. Bone remodeling results were compared to prospective experimental bone mineral content data of patients operated on with pedicle screws.
  
  
  OBJECTIVE
  The validity of 2 bone remodeling algorithms was evaluated by comparing against prospective bone mineral content measurements. Also, the potential stress shielding effect was examined using the 2 bone remodeling algorithms and the experimental bone mineral data.
  
  
  BACKGROUND
  In previous studies, in the human spine, the bone remodeling algorithms have neither been evaluated experimentally nor been examined by comparing to unsystematic experimental data.
  
  
  METHODS
  The site-specific and nonsite-specific iterative bone remodeling algorithms were applied to a finite element model of the lumbar spine operated on with pedicle screws between L4 and L5. The stress shielding effect was also examined. The bone remodeling results were compared with prospective bone mineral content measurements of 4 patients. They were measured after surgery, 3-, 6- and 12-months postoperatively.
  
  
  RESULTS
  After 1 year, there was an average experimental bone loss of 9.78% below the positions of pedicle screws, and the results for the 2 bone remodeling algorithms showed an average bone gain of 8.41% and 1.61%. There were no similarities between the bone remodeling and experimental data.
  
  
  CONCLUSIONS
  The bone remodeling data showed no resemblances when compared to the prospective data of BMC measurements. There was no basis for confirming the validity of the bone remodeling algorithms in this study.
authors.affiliation: Department of Orthopaedic Surgery, National University Hospital of Copenhagen, Copenhagen, Denmark. chwo123@gmail.com
authors.forename: Christian
authors.initials: C
authors.lastname: Wong
authors.forename: P Martin
authors.initials: PM
authors.lastname: Gehrchen
authors.forename: Thomas
authors.initials: T
authors.lastname: Kiaer
mesh_terms: D000328:Adult; D000465:Algorithms; D016723:Bone Remodeling; D020342:Finite Element Analysis / Q000592:standards*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008875:Middle Aged; D011859:Radiography; D015203:Reproducibility of Results; D012107:Research Design / Q000592:standards*