title: Biomechanical comparison of augmented versus non-augmented sacroiliac screws in a novel hemi-pelvis test model.
abstract: Operative treatment of sacral insufficiency fractures is frequently being complicated by osteopenic bone properties. Cement augmentation of implanted sacroiliac screws may lead to superior construct stability and prevent mechanical complications. A novel hemi-pelvis test model with dissected symphysis was developed. Five fresh-frozen cadaveric pelvises were vertically osteotomized at the sacrum on both sides and fixed with sacroiliac screws in both corridors of the first sacral vertebral body. One side was randomly augmented with bone cement. Cyclic testing consisting of torsional loading (±2.5 Nm) combined with progressively increasing axial loading (+50 N compression, -10 N traction, ±0,01 N/cycle) was performed until failure; simulated physiological loads derived from inverse dynamic calculations. The fixation was analyzed fluoroscopically quantifying screw migrations and assessing failure mechanisms. Failure modes were cut-out, pull-out, screw-out, and washer penetration. Motion at fracture site was analyzed via optical motion tracking. Unscrewing was provoked four times with non-augmented and twice with augmented screws. When focusing on the sacral region only, cement augmentation significantly improved screw fixation in terms of increased number of cycles to failure (p = 0.043). However, when considering overall construct stability, there was no significant difference between augmented and non-augmented state due to washer penetration at the iliac bone. The generated hemi-pelvis model was found to be valid due to the reproduction of the clinically observed failure mode (unscrewing). Unscrewing was not fully prevented by cement augmentation. Augmentation effects stability at the screw tip, but particularly in porotic bone, failure may shift to the next weak point. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1485-1493, 2017.
authors: AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.|Department for Trauma-, Hand- and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus 1, Building W1, Münster, 48149, Germany.
authors: Niklas
authors: N
authors: Grüneweller
authors: Department for Trauma-, Hand- and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus 1, Building W1, Münster, 48149, Germany.
authors: Michael J
authors: MJ
authors: Raschke
authors: AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.
authors: Ivan
authors: I
authors: Zderic
authors: AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.
authors: Daniel
authors: D
authors: Widmer
authors: Department for Trauma-, Hand- and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus 1, Building W1, Münster, 48149, Germany.
authors: Dirk
authors: D
authors: Wähnert
authors: AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.
authors: Boyko
authors: B
authors: Gueorguiev
authors: AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.
authors: Robert Geoff
authors: RG
authors: Richards
authors: Department for Trauma and Reconstructive Surgery, Vivantes Hospital Friedrichshain, Landsberger Allee 49, Berlin, 10249, Germany.
authors: Thomas
authors: T
authors: Fuchs
authors: AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.
authors: Markus
authors: M
authors: Windolf
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012446:Sacroiliac Joint / Q000601:surgery; D012447:Sacrum / Q000293:injuries* / Q000601:surgery
keywords: augmentation; insufficiency fracture; osteoporosis; sacral fracture; screw