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Appl. Sci. 2019, 9(8), 1525; https://doi.org/10.3390/app9081525

Comparison of the Pullout Strength of Pedicle Screws According to the Thread Design for Various Degrees of Bone Quality

1
Spine Center and Department of Orthopedic Surgery, Seoul National University College of Medicine and Seoul National University Bundang Hospital, 166 Gumiro, Bundang-gu, Sungnam 463-707, Korea
2
Department of Mechanical Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 100-011, Korea
*
Author to whom correspondence should be addressed.
Received: 4 March 2019 / Revised: 31 March 2019 / Accepted: 6 April 2019 / Published: 12 April 2019
(This article belongs to the Special Issue Biomaterials and Biofabrication)
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Abstract

Although dual-threaded pedicle screws have been developed, the advantages over single-threaded screws remain controversial. We aimed to investigate the biomechanical performance of two types of dual-threaded pedicle screw by comparing their pullout strength with that of a single-threaded screw in relation to bone quality. Four types of pedicle screw with different thread patterns were designed. Type I: single-threaded screw; Type II: double-threaded screw; Type III: dual-threaded screw; Type IV: a newly designed double dual-threaded screw. Five types of polyurethane foams simulating various degrees of bone quality were used. These were: Type A: cancellous bone; Type B: cancellous bone with cortical bone in the upper margin; Type C: osteoporotic cancellous bone; Type D: osteoporotic cancellous bone with cortical bone in the upper margin; and Type E: osteoporotic bone with cortical bone in the upper and lower margins. A comparison of the pullout strength of Type I, II, and III screws in Type A, B, C and D bone specimens was performed. Type C and E bone specimens were used for comparisons among Type I, II, and IV screws. Compared to the single-threaded screw, the dual-threaded pedicle screws exhibited higher pullout strength in normal-quality bone and significantly lower pullout strength in compromised osteoporotic bone. However, the double dual-threaded screw exhibited better pullout biomechanics in osteoporotic bone with bi-cortical bone. View Full-Text
Keywords: pedicle screw; dual-threaded; pullout strength; polyurethane foam block pedicle screw; dual-threaded; pullout strength; polyurethane foam block
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Shen, F.; Kim, H.-J.; Kang, K.-T.; Yeom, J.S. Comparison of the Pullout Strength of Pedicle Screws According to the Thread Design for Various Degrees of Bone Quality. Appl. Sci. 2019, 9, 1525.

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