Influence of novel design alteration of pedicle screw on pull-out strength

A finite element study

Shota Takenaka, Takashi Kaito, Ken Ishii, Koota Watanabe, Kei Watanabe, Akira Shinohara, Tomohisa Harada, Fumiya Nakada, Yusuke Majima, Morio Matsumoto

Research output: Contribution to journalArticle

Abstract

Background: We conducted a finite element study to assess the effectiveness of a novel pedicle screw design with two alterations in the distal and proximal portions. Methods: Finite element (FE) models of 24 vertebrae were constructed using computed tomographic data. Pull-out strength of 4 different pedicle screws were compared. The basic screw design was a dual threaded one (PS0), in which the proximal portion is double-threaded (cortical thread), and the distal portion is single-threaded (cancellous thread). In PS1, the inter-thread double-core shape was added to PS0 in the distal portion. Compared to PS0, in PS2, the proximal portion was elongated by 5 mm. PS3 had both PS1 and PS2 features. In addition, the 24 vertebrae were classified into 3 groups based on volumetric bone mineral density (vBMD) of the vertebral body: low <120 mg/cm 3 , moderate 120–170 mg/cm 3 , and high >170 mg/cm 3 . Results: The mean pull-out strengths (±SD) were 1137 ± 500 N, 1188 ± 520 N, 1191 ± 512 N, and 1242 ± 538 N for PS0, PS1, PS2, and PS3, respectively. In PS1, there was significant difference in the incremental ratio of pull-out strength to PS0 between the low and high vBMD groups (3.7 ± 1.6% vs. 5.0 ± 1.0%, p = 0.006). In PS2, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (7.6 ± 4.0% vs. 3.3 ± 1.8%, p < 0.001). In PS3, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (12.1 ± 4.8% vs. 8.5 ± 2.1%, p = 0.003). Conclusions: The two design alterations showed the combined additive effect in the PS3 design. The moderate vBMD group has a balanced bone property to reflect the combined effects of the PS1 and PS2 design alterations.

Original languageEnglish
JournalJournal of Orthopaedic Science
DOIs
Publication statusPublished - 2019 Jan 1

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Bone Density
Spine
Pedicle Screws
Bone and Bones

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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Influence of novel design alteration of pedicle screw on pull-out strength : A finite element study. / Takenaka, Shota; Kaito, Takashi; Ishii, Ken; Watanabe, Koota; Watanabe, Kei; Shinohara, Akira; Harada, Tomohisa; Nakada, Fumiya; Majima, Yusuke; Matsumoto, Morio.

In: Journal of Orthopaedic Science, 01.01.2019.

Research output: Contribution to journalArticle

Takenaka, Shota ; Kaito, Takashi ; Ishii, Ken ; Watanabe, Koota ; Watanabe, Kei ; Shinohara, Akira ; Harada, Tomohisa ; Nakada, Fumiya ; Majima, Yusuke ; Matsumoto, Morio. / Influence of novel design alteration of pedicle screw on pull-out strength : A finite element study. In: Journal of Orthopaedic Science. 2019.
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abstract = "Background: We conducted a finite element study to assess the effectiveness of a novel pedicle screw design with two alterations in the distal and proximal portions. Methods: Finite element (FE) models of 24 vertebrae were constructed using computed tomographic data. Pull-out strength of 4 different pedicle screws were compared. The basic screw design was a dual threaded one (PS0), in which the proximal portion is double-threaded (cortical thread), and the distal portion is single-threaded (cancellous thread). In PS1, the inter-thread double-core shape was added to PS0 in the distal portion. Compared to PS0, in PS2, the proximal portion was elongated by 5 mm. PS3 had both PS1 and PS2 features. In addition, the 24 vertebrae were classified into 3 groups based on volumetric bone mineral density (vBMD) of the vertebral body: low <120 mg/cm 3 , moderate 120–170 mg/cm 3 , and high >170 mg/cm 3 . Results: The mean pull-out strengths (±SD) were 1137 ± 500 N, 1188 ± 520 N, 1191 ± 512 N, and 1242 ± 538 N for PS0, PS1, PS2, and PS3, respectively. In PS1, there was significant difference in the incremental ratio of pull-out strength to PS0 between the low and high vBMD groups (3.7 ± 1.6{\%} vs. 5.0 ± 1.0{\%}, p = 0.006). In PS2, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (7.6 ± 4.0{\%} vs. 3.3 ± 1.8{\%}, p < 0.001). In PS3, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (12.1 ± 4.8{\%} vs. 8.5 ± 2.1{\%}, p = 0.003). Conclusions: The two design alterations showed the combined additive effect in the PS3 design. The moderate vBMD group has a balanced bone property to reflect the combined effects of the PS1 and PS2 design alterations.",
author = "Shota Takenaka and Takashi Kaito and Ken Ishii and Koota Watanabe and Kei Watanabe and Akira Shinohara and Tomohisa Harada and Fumiya Nakada and Yusuke Majima and Morio Matsumoto",
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T2 - A finite element study

AU - Takenaka, Shota

AU - Kaito, Takashi

AU - Ishii, Ken

AU - Watanabe, Koota

AU - Watanabe, Kei

AU - Shinohara, Akira

AU - Harada, Tomohisa

AU - Nakada, Fumiya

AU - Majima, Yusuke

AU - Matsumoto, Morio

PY - 2019/1/1

Y1 - 2019/1/1

N2 - Background: We conducted a finite element study to assess the effectiveness of a novel pedicle screw design with two alterations in the distal and proximal portions. Methods: Finite element (FE) models of 24 vertebrae were constructed using computed tomographic data. Pull-out strength of 4 different pedicle screws were compared. The basic screw design was a dual threaded one (PS0), in which the proximal portion is double-threaded (cortical thread), and the distal portion is single-threaded (cancellous thread). In PS1, the inter-thread double-core shape was added to PS0 in the distal portion. Compared to PS0, in PS2, the proximal portion was elongated by 5 mm. PS3 had both PS1 and PS2 features. In addition, the 24 vertebrae were classified into 3 groups based on volumetric bone mineral density (vBMD) of the vertebral body: low <120 mg/cm 3 , moderate 120–170 mg/cm 3 , and high >170 mg/cm 3 . Results: The mean pull-out strengths (±SD) were 1137 ± 500 N, 1188 ± 520 N, 1191 ± 512 N, and 1242 ± 538 N for PS0, PS1, PS2, and PS3, respectively. In PS1, there was significant difference in the incremental ratio of pull-out strength to PS0 between the low and high vBMD groups (3.7 ± 1.6% vs. 5.0 ± 1.0%, p = 0.006). In PS2, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (7.6 ± 4.0% vs. 3.3 ± 1.8%, p < 0.001). In PS3, there was a significant difference in the incremental ratio to PS0 between the moderate and high vBMD groups (12.1 ± 4.8% vs. 8.5 ± 2.1%, p = 0.003). Conclusions: The two design alterations showed the combined additive effect in the PS3 design. The moderate vBMD group has a balanced bone property to reflect the combined effects of the PS1 and PS2 design alterations.

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