Comparison of pullout strength of pedicle screws following revision using larger diameter screws

Varghese, Vicky; Krishnan, Venkatesh; Kumar, Girish

doi:10.1016/j.medengphy.2019.09.008

Cited by 16 publications

(13 citation statements)

References 34 publications

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“…[19] Since transpedicular screws ensure a threedimensional stability over the spine segment motion, they have been considered the gold-standard interventional method for several diseases including spinal deformities, degenerative diseases, tumors, and vertebral fractures. [20,21] Screw pullout is a very common problem encountered by surgeons in clinical follow-up. Several studies have demonstrated loosening of transpedicular screws in 0.8 to 11% of patients.…”

Section: Discussionmentioning

confidence: 99%

“…Meanwhile, according to different studies, the greater diameter of the unthreaded shank may squeeze the surrounding bone onto the peripheral cortex walls of a predrilled hole, which in term increases the frictional resistance and, thus, the grasping power of the inserted screw. [16][17][18]20] Researchers continuously keep parameters design changing in an attempt to obtain the most suitable screw design which may offer the optimal pullout strength to minimize pedicular screw pullout failure as much as possible. [20] In the current study, one the main objectives was to research the holding power of different screw thread profile configurations on the bone-screw construct.…”

Section: Discussionmentioning

confidence: 99%

“…[16][17][18]20] Researchers continuously keep parameters design changing in an attempt to obtain the most suitable screw design which may offer the optimal pullout strength to minimize pedicular screw pullout failure as much as possible. [20] In the current study, one the main objectives was to research the holding power of different screw thread profile configurations on the bone-screw construct. The length and the type of the threaded portion were different for the six pedicle screws.…”

Section: Discussionmentioning

confidence: 99%

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Biomechanical comparison of pullout strengths of six pedicle screws with different thread designs

Karakaşlı

Acar²,

Hüsemoğlu

2021

Jt Dis Relat Surg

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Objectives This study aims to assess the pullout strength of six different pedicle screw thread patterns. Materials and methods A total of 36 sheep spines were divided into six groups including six spines in each group: fully threaded cortical (Type A), fully threaded spongeous (Type B), fully cortical threads in the proximal half and fully spongeous threads in the distal half (Type C), fully spongeous threads in the proximal half and fully cortical threads in the distal half (Type D), unthreaded proximal half with fully spongeous threads in the distal half (Type E), and unthreaded proximal half with fully cortical threads in the distal half (Type F). The axial compression-traction machine was used for biomechanical testing at a pullout rate of 1 mm/min. Results The mean values of pullout strength of the groups A, B, C, D, E, and F were 1112±7.52 N, 986±8.34 N, 646±3.88 N, 676±7.16 N, 609±9.52 N, and 769±6.49 N, respectively. There was a statistically significant difference between the screw groups A and B, C, D, E and F (p=0.036, p=0.028, p=0.04, p=0.039, and p=0.046, respectively). A statistically significant difference was observed between the groups B versus C and E (p=0.037 and p=0.021, respectively). There was no statistically significant difference between the groups B versus D and F (p=0.35 and p=0.61, respectively). Conclusion Fully threaded cortical pedicular screw design exhibited the strongest bone grasp compared to other thread designs. Further studies should be conducted in multidirectional force pattern on human spine to assess the six screw thread designs in a closer real-life setting simulation model.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Biomechanical comparison of pullout strengths of six pedicle screws with different thread designs

Karakaşlı

Acar²,

Hüsemoğlu

2021

Jt Dis Relat Surg

View full text Add to dashboard Cite

show abstract

“…Pull-out tests of screw joints are carried out mostly in orthopaedics/traumatology applications (see [16,[24][25][26][27][28]). Orthopaedic/traumatology surgery often involves the use of bone screws to stabilize fractures via fixation techniques.…”

Section: Introductionmentioning

confidence: 99%

Mechanics of Screw Joints Solved as Beams Placed in a Tangential Elastic Foundation

et al. 2021

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This article deals with a new original analytical solution of deformation, force and stress states in wood screw joints up to the limit values of pulling out/breaking the screw. The screws are under tension. The wood-to-screw interaction is effectively simplified by introducing several physical model variants using a tangential elastic non-linear foundation. The experimental verification of the proposed models using pull-out tests (i.e., pulling out screws from dry spruce wood in laboratory conditions) confirms the correctness of the proposed models of the elastic linear/non-linear foundation. The validity of the model is also analytically and experimentally verified in the biomechanical model of pulling out screws from the femur of a bovine/human cadaver, which confirms and expands the validity of newly designed screw joint models outside the timber structure area.

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“…Besides cement augmentation, changing the screw design, including diameter, length, and thread design, may be used to improve fixation [10][11][12][13]. Because the holding power of the bone-screw interface is poor in osteoporosis, increasing the diameter of the screw may improve fixation and stability [14]. However, the maximum diameter of the screw is limited by the anatomical shape of the pedicle, and so the viable size range for the screw is limited.…”

Section: Introductionmentioning

confidence: 99%

Partial Threading of Pedicle Screws in a Standard Construct Increases Fatigue Life: A Biomechanical Analysis

Chen

Kuo

et al. 2021

Applied Sciences

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This study proposed a pedicle screw design where the proximal 1/3 of the screw is unthreaded to improve fixation in posterior spinal surgery. This design was also expected to reduce the incidence of mechanical failure often observed when an unsupported screw length is exposed outside the vertebra in deformed or degenerated segments. The aim of this study was to evaluate the fatigue life of the novel pedicle screw design using finite element analysis and mechanical testing in a synthetic spinal construct in accordance with American Society for Testing and Materials (ASTM) F1717. The following setups were evaluated: (i) pedicle screw fully inserted into the test block (EXP-FT-01 and EXP-PU-01; full thread (FT), proximal unthread (PU)) and (ii) pedicle screw inserted but leaving an exposed shaft length of 7.6 mm (EXP-FT-02 and EXP-PU-02). Corresponding finite element models FEM-FT-01, FEM-FT-02, FEM-PU-01, and FEM-PU-02 were also constructed and subjected to the same loading conditions as the experimental groups. The results showed that under a 220 N axial load, the EXP-PU-01 group survived the full 5 million cycles, the EXP-PU-02 group failed at 4.4 million cycles on average, and both EXP-FT-01 and EXP-FT-02 groups failed after less than 1.0 million cycles on average, while the fatigue strength of the EXP-FT-02 group was the lowest at 170 N. The EXP-FT-01 and EXP-FT-02 constructs failed through fracture of the pedicle screw, but a rod fractured in the EXP-PU-02 group. In comparison to the FEM-FT-01 model, the maximum von Mises stress on the pedicle screw in the FEM-PU-01 and FEM-PU-02 models decreased by −43% and −27%, respectively. In conclusion, this study showed that having the proximal 1/3 of the pedicle screw unthreaded can reduce the risk of screw fatigue failure when used in deformed or degenerated segments.

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Comparison of pullout strength of pedicle screws following revision using larger diameter screws

Cited by 16 publications

References 34 publications

Biomechanical comparison of pullout strengths of six pedicle screws with different thread designs

Biomechanical comparison of pullout strengths of six pedicle screws with different thread designs

Mechanics of Screw Joints Solved as Beams Placed in a Tangential Elastic Foundation

Partial Threading of Pedicle Screws in a Standard Construct Increases Fatigue Life: A Biomechanical Analysis

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