Open AccessCan barb thread design improve the pullout strength of bone screws?
Author(s) -
Xiaoreng Feng,
Weichen Qi,
Christian Fang,
William W. Lu,
Frankie Leung,
Bin Chen
Publication year - 2021
Publication title -
bone and joint research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.639
H-Index - 31
ISSN - 2046-3758
DOI - 10.1302/2046-3758.102.bjr-2020-0072.r2
Subject(s) - buttress , thread (computing) , ultimate tensile strength , cancellous bone , screw thread , compressive strength , materials science , finite element method , structural engineering , orthodontics , composite material , engineering , anatomy , medicine , mechanical engineering
Aims To draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws.Methods Buttress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared.Results The barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure.Conclusion Bone screws with a reverse buttress thread design will significantly increase the pullout strength. Cite this article: Bone Joint Res 2021;10(2):105–112.