Journal
JOURNAL OF NEUROSURGERY-SPINE
Volume 12, Issue 5, Pages 503-508Publisher
AMER ASSOC NEUROLOGICAL SURGEONS
DOI: 10.3171/2009.11.SPINE09408
Keywords
misplacement; pedicle screw; thoracic spine; pullout strength; cadaver
Categories
Ask authors/readers for more resources
Object. The object of this study was to investigate the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of thoracic pedicle screws. Methods. Forty human thoracic vertebrae (T6-11) from human cadavers were studied. Before pedicle screws were inserted, the specimens were separated into 4 groups according to the type of screw used: 1) standard pedicle screw (no cortical perforation); 2) screw with medial cortical perforation; 3) screw with lateral cortical perforation: and 4) airball screw (a screw that completely missed the vertebral body). Consistency among the groups for bone mineral density, pedicle diameter, and screw insertion depth was evaluated. Finally. each screw was pulled out at a constant displacement rate of 10 mm/minute while ultimate strength was recorded. Results. Compared with well-placed pedicle screws, medially misplaced screws had 8% greater mean pullout strength (p = 0.482) and laterally misplaced screws had 21% less mean pullout strength (p = 0.059). The difference in mean pullout strength between screws with medial and lateral cortical perforations was significant (p = 0.013). Airball screws had only 66% of the mean pullout strength of well-placed screws (p = 0.009) and had 16% lower mean pullout strength than laterally misplaced screws (p = 0.395). Conclusions. This in vitro study showed a significant difference in mean pullout strength between medial and lateral misplaced pedicle screws. Moreover, airball screws were associated with a significant loss of pullout strength. (DOI: 10.3171/2009.11.SPINE09408)
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available