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

Mapping Intimacies ◽

10.1115/detc2021-67768 ◽

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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Selection of suitable pedicle screw for degenerated cortical and cancellous bone of human lumbar spine: A finite element study

The International Journal of Artificial Organs ◽

10.1177/0391398820964483 ◽

2020 ◽

pp. 039139882096448

Author(s):

Pushpdant Jain ◽

David Chua Sing Ngie ◽

Soh Fong Lim ◽

Bee Huah Lim

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Pedicle Screw ◽

Cancellous Bone ◽

Body Movement ◽

Pedicle Screws ◽

Element Analysis ◽

Moment Conditions ◽

Bone Screw ◽

Selection Of

Pedicular arthrodesis is the traditional procedure in terms of increase in the biomechanical stability with higher fixation rate. The current work aims to identify the effect of three spinal pedicle screws considering cortical and cancellous degeneracy condition. Lumbar section L2-L3 is utilized and various load and moment conditions were applied to depict the various biomechanical parameters for selection of suitable screw. Three dimensional model is considered in finite element analysis to identify the various responses of pedicle screw at bone screw juncture. Computed tomography (CT) images of a healthy male were considered to generate the finite element vertebral model. Generated intact model was further utilized to develop the other implanted models of degenerated cortical and cancellous bone models. The three fused instrumented models with different cortical and cancellous degeneracy conditions were analyzed in finite element analysis. The results were obtained as stress pattern at bone screw boundary and intervertebral disc stress. FE simulated results represents significant changes in the von Mises stress due to various load and moment conditions on degenerated bones during different body movement conditions. Results have shown that among all pedicle screws, the 6.0 mm diameter screw reflects very less stress values at the juncture. Multiple results on biomechanical aspects obtained during the FE study can be considered to design a new stabilization device and may be helpful to plan surgery of critical sections.

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

Bosnian Journal of Basic Medical Sciences ◽

10.17305/bjbms.2009.2767 ◽

2009 ◽

Vol 9 (1) ◽

pp. S77-S82 ◽

Cited By ~ 4

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.

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

Applied Sciences ◽

10.3390/app11041503 ◽

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.

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Alternative Pedicle Screw Design via Biomechanical Evaluation

Applied Sciences ◽

10.3390/app10144746 ◽

2020 ◽

Vol 10 (14) ◽

pp. 4746 ◽

Cited By ~ 1

Author(s):

Jiwoon Kwon ◽

Myung Heon Ha ◽

Moon Gu Lee

Keyword(s):

Spinal Fusion ◽

Pedicle Screw ◽

Bending Strength ◽

Pedicle Screws ◽

The Elderly ◽

Spinal Diseases ◽

Fusion Surgery ◽

Spinal Fusion Surgery ◽

Screw Design ◽

Experimental Apparatus

With the recent increase in the elderly population, many people suffer from spinal diseases, and, accordingly, spinal fusion surgery using pedicle screws has been widely applied to treat them. However, most research on pedicle screw design has been focused on the test results rather than the behavior of the screws and vertebrae. In this study, a design platform with a series of biomechanical tests and analyses were presented for pedicle screw improvement and evaluation. The platform was then applied to an alternative hybrid screw design with quadruple and double threads. An experimental apparatus was developed to investigate the bending strength of the screw, and several tests were performed based on the ASTM F1717 standard. In the experiments, it was confirmed that the alternative pedicle screw has the highest bending strength. To examine the stress distribution of pedicle screws, finite element models were established, through which it was found that the proposed pedicle screw has sufficient mechanical safety to make it acceptable for spinal fusion treatment. Finally, we conclude that the platform has good potential for the design and evaluation of pedicle screws, and the alternative dual screw design is one of the best options for spinal fusion surgery.

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

Applied Sciences ◽

10.3390/app9081525 ◽

2019 ◽

Vol 9 (8) ◽

pp. 1525 ◽

Cited By ~ 1

Author(s):

Shen ◽

Kim ◽

Kang ◽

Yeom

Keyword(s):

Cortical Bone ◽

Pedicle Screw ◽

Bone Quality ◽

Cancellous Bone ◽

Pedicle Screws ◽

Type A ◽

Osteoporotic Bone ◽

Type I ◽

Pullout Strength ◽

Type C

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.

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Comparison of Insertion Time, Pull-out Strength, and Screw-media Interface Area of Customized Pedicle Screw With Different Core and Thread Design Against Commercial Pedicle Screw

10.21203/rs.3.rs-429747/v1 ◽

2021 ◽

Author(s):

Rahadyan Magetsari ◽

Tedjo Rukmoyo ◽

Marda Ade Saputra ◽

Yudha Mathan Sakti

Keyword(s):

Pedicle Screw ◽

Pedicle Screws ◽

Insertion Time ◽

Control Group ◽

Interface Area ◽

Screw Design ◽

Pull Out ◽

Thread Diameter ◽

Screw Group ◽

Pull Out Strength

Abstract Objective: This research aimed to developing customized pedicle screw based on Indonesian vertebral anatomy and compare the insertion time, pull-out strength, and screw-media interface area of different screw design. We have developed 3 different types of pedicle screws (v-thread cylinder-core, square-thread cylinder-core and square-thread conical-core). The thread diameter was calculated from pedicle width of Indonesian population (6 mm). We used commercially available pedicle screw as control group (6.2 mm). Result: The insertion time were significantly difference between v-thread cylinder-core pedicle screw (22,94 s) with commercially available pedicle screw (15.86 s) (p<0.05). The pull-out strength was significantly difference between commercially available pedicle screw (408.60 N) with square-thread conical pedicle screw (836.60 N) (p<0.05). The square-thread conical-core group have the highest interface area (1486.21 mm2). The data comparison showed that the square-thread conical-core customized pedicle screw group has comparable insertion time and has better pull-out strength than commercially available pedicle screw.

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Comparison of insertion time, pull-out strength, and screw-media interface area of customized pedicle screw with different core and thread design against commercial pedicle screw: a pilot study on Indonesian Population

BMC Research Notes ◽

10.1186/s13104-021-05803-5 ◽

2022 ◽

Vol 15 (1) ◽

Author(s):

Rahadyan Magetsari ◽

Tedjo Rukmoyo ◽

Marda Ade Saputra ◽

Yudha Mathan Sakti

Keyword(s):

Pedicle Screw ◽

Pedicle Screws ◽

Insertion Time ◽

Control Group ◽

Interface Area ◽

Screw Design ◽

Pull Out ◽

Indonesian Population ◽

Thread Diameter ◽

Pull Out Strength

Abstract Objective This research aimed to developing customized pedicle screw based on Indonesian vertebral anatomy and compare the insertion time, pull-out strength, and screw-media interface area of different screw design. We have developed 3 different types of pedicle screws (v-thread cylinder-core, square-thread cylinder-core and square-thread conical-core). The thread diameter was calculated from pedicle width of Indonesian population (6 mm). We used commercially available pedicle screw as control group (6.2 mm). Result The insertion time were significantly difference between v-thread cylinder-core pedicle screw (22.94 s) with commercially available pedicle screw (15.86 s) (p < 0.05). The pull-out strength was significantly difference between commercially available pedicle screw (408.60 N) with square-thread conical pedicle screw (836.60 N) (p < 0.05). The square-thread conical-core group have the highest interface area (1486.21 mm2). The data comparison showed that the square-thread conical-core customized pedicle screw group has comparable insertion time and has better pull-out strength than commercially available pedicle screw.

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An Ultrasound Technique of Bone Thickness Estimation for Pedicle Screw Insertion

Journal of Advanced Computational Intelligence and Intelligent Informatics ◽

10.20965/jaciii.2014.p0529 ◽

2014 ◽

Vol 18 (4) ◽

pp. 529-537

Author(s):

Muhamad Khairul Ali Hassan ◽

◽

Kouki Nagamune ◽

Kenichiro Kakutani ◽

Koichiro Maeno ◽

...

Keyword(s):

Pedicle Screw ◽

Cancellous Bone ◽

Pedicle Screws ◽

Screw Placement ◽

Bone Thickness ◽

Ultrasound Technique ◽

Screw Insertion ◽

Pedicle Screw Insertion ◽

Real Time Measurement

Information on bone thickness is useful to surgeons in fixing pedicle screws in place. The quality of pedicle screw insertion continues to increase with the introduction of such techniques as navigation based on computed tomography and fluoroscopy. These techniques reduce error in pedicle screw placement and injury. However, the information reported on the real time measurement of depths drilled through cancellous bone, also known as trabecular bone or sponge bone, by the pedicle screw is minimal. It currently depends on palpation by the physician for judging the boundary between cortical and cancellous bone – an inaccurate technique that may produce errors in screw placement and the risk of injury during surgical processes. Ultrasound is used to help overcome such problems. Bone thickness is estimated in this study using an ultrasound transducer attached to 20 mm of polymethyl methacrylate, a clear glass-like acrylic. The bone thickness of five specimens was measured using ultrasound echo signals. Error in estimating bone thickness was small, 8.121%, showing the accuracy in bone thickness to be more than 90.00% which is suitable for use in estimating bone thickness in pedicle screw insertion.

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The effect of cement augmentation on pedicle screw fixation under various load cases

Bone and Joint Research ◽

10.1302/2046-3758.1012.bjr-2020-0533.r1 ◽

2021 ◽

Vol 10 (12) ◽

pp. 797-806

Author(s):

Yan Chevalier ◽

Maiko Matsuura ◽

Sven Krüger ◽

Hannes Traxler ◽

Christoph Fleege† ◽

...

Keyword(s):

Pedicle Screw ◽

Bone Quality ◽

Pedicle Screws ◽

Bending Stiffness ◽

Cement Augmentation ◽

Fixation Strength ◽

Screw Design ◽

Pull Out ◽

Local Bone ◽

Significant Difference

Aims Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Methods Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S4). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R2 > 0.87) and FV (R2 > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient ( R) = -0.95). Conclusion This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806.

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