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Pull-out strength of Caspar cervical screws. Neurosurgery 1992 Dec;31(6):1097-101; discussion 1101

Date

12/01/1992

Pubmed ID

1470320

DOI

10.1227/00006123-199212000-00016

Scopus ID

2-s2.0-0026447655 (requires institutional sign-in at Scopus site)   31 Citations

Abstract

Anterior cervical instrumentation as an adjunct to bone fusion has an important role in cervical spine surgery. Posterior vertebral body cortex purchase is strongly recommended in the use of the Caspar system, although few biomechanical data exist to validate this requirement. In this study, Caspar screws were placed in 43 human cadaveric cervical vertebral bodies, either putting them into the posterior vertebral cortex as identified radiographically or penetrating it by 2 mm as recommended in the literature. Pull-out tests were conducted with tension applied to a connected plate at 0.25 mm/s, and force-deformation data were obtained. Failure typically occurred with clean pull-out; in most instances, cancellous bone remained attached to screw threads. Mean load without posterior cortical purchase was 375 +/- 53 N; with penetration it was 411 +/- 70 N. These differences were nonsignificant. Average deformation to failure was 1.41 +/- 0.10 mm in the group without posterior cortical penetration. In the posterior penetration group, mean deformation was 1.56 +/- 0.16 mm. Again, differences were not significant. Posterior cortical penetration does not improve the pull-out strength of Caspar screws in an isolated vertebral body model, but other biomechanical studies need to be done before insertion methods are altered.

Author List

Maiman DJ, Pintar FA, Yoganandan N, Reinartz J, Toselli R, Woodward E, Haid R

Authors

Frank A. Pintar PhD Professor in the Biomedical Engineering department at Medical College of Wisconsin
Narayan Yoganandan PhD Professor in the Neurosurgery department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Biomechanical Phenomena
Bone Plates
Bone Screws
Cervical Vertebrae
Humans
Spinal Fusion
Tensile Strength