New Pedicle Screw Design With Expandable Shell for Low Bone Quality1

2014 ◽  
Vol 8 (2) ◽  
Author(s):  
Teyfik Demir ◽  
Mehmet F. Örmeci
Keyword(s):  
Pedicle Screw ◽  
Screw Design

114. Dual thread screw design provides equivalent fixation to upsized screw diameter in revision pedicle screw instrumentation

2020 ◽  
Vol 20 (9) ◽  
pp. S56
Author(s):  
Joseph L. Laratta ◽  
Ryan Weegens ◽  
Jeffrey L. Gum ◽  
Michael J. Voor ◽  
Leah Y. Carreon ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screw Instrumentation ◽  
Screw Design ◽  
Screw Diameter

scholarly journals Evaluation of the Intrinsic Properties of Pedicle Screws: Do Diameter, Manufacturing and Screw Design Affect Resistance and/or Resistivity

2009 ◽  
Vol 9 (1) ◽  
pp. S77-S82 ◽  
Author(s):  
Worawat Limthongkul ◽  
Jason Savage ◽  
Emmanuel K. Nenonene ◽  
Eldin E. Karaikovic
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Constant Current ◽  
Intrinsic Properties ◽  
Measurement Variability ◽  
Screw Design ◽  
Measured Voltage ◽  
Lower Resistance ◽  
Screw Diameter ◽  
Lower Resistivity

The pedicle screw diameter, composite and design are variables that can affect the threshold of intraoperative electromyographic monitoring. Even though we know that larger diameter objects tend to have less resistance, no study documented the effect that this variable could have on pedicle screw resistance. Using high quality equipment, resistance and resistivity of ten pedicle screws (from four manufacturers) were calculated based on known constant current and measured voltage. Voltage was measured three times for each screw to determine intraobserver measurement variability. Resistance of all screws ranged from 1.4 to 3.9 m ohm (mean = 2.69+/-0.71 m ohm). The screw with largest diameter (7.75 mm) had lower resistance than screws with other diameters. Resistivity of screws ranged from 7.12 to 12.63 micro ohm*m (mean = 9.9+/-1.82 micro ohm*m). Based on the screw design, one manufacturer's pedicle screws (A) had significantly lower resistivity compared to three other manufacturers (p<0.01). Larger diameter screws (7.75 mm in diameter) had lower resistance. Screw design (polyaxial or monoaxial) had no effect on its resistance. Screws of one manufacturer (A) showed lower resistivity compared to those manufactured by other three companies.

An Experimental Study for Establishing an Optimal Pedicle Screw Design According to Bone Mineral Density

2020 ◽  
Vol 44 (8) ◽  
pp. 519-526
Author(s):  
Chan-Hee Song ◽  
Tae Sik Goh ◽  
Jung Sub Lee ◽  
Eun Sun Lee ◽  
Jin-Young Heo ◽  
...  
Keyword(s):  
Bone Mineral Density ◽  
Experimental Study ◽  
Pedicle Screw ◽  
Bone Mineral ◽  
Mineral Density ◽  
Screw Design

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

2021 ◽  
Vol 11 (4) ◽  
pp. 1503
Author(s):  
Fon-Yih Tsuang ◽  
Chia-Hsien Chen ◽  
Lien-Chen Wu ◽  
Yi-Jie Kuo ◽  
Yueh-Ying Hsieh ◽  
...  
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Pedicle Screw ◽  
Pedicle Screws ◽  
Biomechanical Analysis ◽  
Von Mises Stress ◽  
Shaft Length ◽  
Element Analysis ◽  
Screw Design ◽  
Screw Length

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.

Proposal for an Adaptive Bone Screw Design Based on FEA Studies Exemplified by Pedicle Screw

2021 ◽  
Author(s):  
Alexander Seidler ◽  
Lars Mehlhorn ◽  
Philipp Sembdner ◽  
Stefan Holtzhausen ◽  
Ralph Stelzer ◽  
...  
Keyword(s):  
Simulation Model ◽  
Pedicle Screw ◽  
Cancellous Bone ◽  
Adaptive Design ◽  
Pedicle Screws ◽  
Bone Screws ◽  
Design Models ◽  
Bone Screw ◽  
Cad System ◽  
Screw Design

Abstract This paper presents a proposal for a density-adaptive design of bone screws using pedicle screws for spinal fixations as an example. The basis is the analysis and categorization of currently available variants of bone screws, which differ in principle in their thread design because of different application areas (cortical or cancellous bone). These screw variants are investigated in FEA simulations for pullout and bending with regard to occurring stresses. A corresponding simulation model is presented for this purpose. The precise design models for these screws are generated in a CAD system using a self-developed configuration tool. Based on the FEA evaluation, the proposal for a new pedicle screw design, consisting of several thread types merged into each other, is described in detail. By integrating different thread types over the shaft, the respective properties of the bone can thus be optimally utilized.

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