title: Can high-friction intraannular material increase screw pullout strength in osteoporotic bone?
abstract: BACKGROUND
  Osteoporotic bone brings unique challenges to orthopaedic surgery, including a higher likelihood of problematic screw stripping in cancellous bone. Currently, there are limited options to satisfactorily repair stripped screws. Additionally, nonstripped screws hold with less purchase in osteoporotic bone.
  
  
  OBJECTIVE
  This study attempts to answer the following questions: (1) Does high-friction intraannular (HFIA) augmentation increase pullout strength in osteoporotic and in severely osteoporotic bone; and (2) can HFIA repair stripped bone thread in osteoporotic and severely osteoporotic bone?
  
  
  METHODS
  We measured screw pullout strength using a synthetic bone model in three groups: (1) predrilled nonstripped control holes as controls; (2) predrilled nonstripped augmented with HFIA; and (3) predrilled stripped holes repaired with HFIA. We tested this in osteoporotic and severely osteoporotic synthetic bone for a total of six test groups. We measured screw pullout force using an electromechanical tensile-testing machine comparing pullout force between the test groups and controls.
  
  
  RESULTS
  HFIA augmentation did not increase pullout force compared with the control group in the osteoporotic bone model (489 ± 175 versus 607 ± 76, respectively; effect size = 0.94 [95% confidence interval {CI}, -1.75 to 0.08], p = 0.06). However, in severely osteoporotic cancellous bone that was augmented, the HFIA material generated more pullout force than the control (51 ± 18 versus 35 ± 16, respectively; effect size = 0.94 [95% CI, -0.02 to 1.82], p = 0.05). In stripped holes, HFIA partially restored pullout strength but remained weaker than controls in both osteoporotic and severely osteoporotic bone models (osteoporotic: 320 ± 59 versus 607 ± 76, respectively; effect size = -4.28 [95% CI, -5.57 to -2.51], p < 0.001; severely osteoporotic: 21 ± 8 versus 35 ± 16, respectively; effect size = -1.13 [95% CI, -2.0 to 0.12], p = 0.027).
  
  
  CONCLUSIONS
  HFIA effectively augmented severely osteoporotic bone for screw purchase, but this effect was not seen for osteoporotic bone. In a model simulating both osteoporotic and severely osteoporotic bone, we found that HFIA can be used to repair stripped screw holes, but the resulting construct remains weaker than nonstripped controls.
  
  
  CONCLUSIONS
  The HFIA material looks promising as a potential solution to stripped screws in osteoporotic bone. However, this material has yet to be tested in human bone. Furthermore, the fine mesh material could be damaged by autoclaving and could break off in vivo causing unknown tissue reactions. We recommend additional testing in a living animal model to better understand how living bone will react to the HFIA material.
authors.affiliation: Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bronsnick
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Harold
authors.forename: Ari
authors.initials: A
authors.lastname: Youderian
authors.forename: Giovanni
authors.initials: G
authors.lastname: Solitro
authors.forename: Farid
authors.initials: F
authors.lastname: Amirouche
authors.forename: Benjamin
authors.initials: B
authors.lastname: Goldberg
mesh_terms: D001696:Biomechanical Phenomena; D001843:Bone Cements; D001863:Bone Screws; D004867:Equipment Design; D017276:Friction; D006801:Humans; D008422:Materials Testing; D010024:Osteoporosis / Q000601:surgery*
chemical_list: D001843:Bone Cements