Influence of thread design on anchorage of pedicle screws in cancellous bone: an experimental and analytical analysis

Threads of modern pedicle screws can vary greatly in design. It is difficult to assess which interplay of design features is particularly advantageous for screw anchorage. This study aims to increase the understanding of the anchorage behaviour between screw and cancellous bone. Pull-out tests of si...

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Bibliographic Details
Published in:Scientific reports 2022-05, Vol.12 (1), p.8051-15, Article 8051
Main Authors: Weidling, Martin, Heilemann, Martin, Schoenfelder, Stephan, Heyde, Christoph E.
Format: Article
Language:English
Subjects:
639/166/988
692/1537/805
692/698/1671/63
692/700/806
Biomechanical Phenomena
Bone and Bones
Bone density
Cancellous Bone
Design
Humanities and Social Sciences
multidisciplinary
Orthopedics
Pedicle Screws
Plastic surgery
R&D
Research & development
Science
Science (multidisciplinary)
Titanium alloys
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Description
Summary:Threads of modern pedicle screws can vary greatly in design. It is difficult to assess which interplay of design features is particularly advantageous for screw anchorage. This study aims to increase the understanding of the anchorage behaviour between screw and cancellous bone. Pull-out tests of six pedicle screws in two sizes each were performed on three densities of biomechanical test material. More general screw characteristics were derived from the screw design and evaluated using the test data. Selected screws were tested on body donor material. Some screw characteristics, such as compacting, are well suited to compare the different thread designs of screws with tapered core. The combination of two characteristics, one representing bone compacting and one representing thread flank area, appears to be particularly advantageous for assessing anchorage behaviour. With an equation derived from these characteristics, the pull-out strength could be calculated very accurately (mean deviation 1%). Furthermore, findings are corroborated by tests on donor material. For screws with tapered core, the design demands for good anchorage against pull-out from cancellous bone change with material density. With sufficient bone quality, screws with a high compacting effect are advantageous, while with low bone density a high thread flank area also appears necessary for better screw anchorage.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-022-11824-2