scholarly journals A novel auxetic structure based bone screw design: Tensile mechanical characterization and pullout fixation strength evaluation

2020 ◽  
Vol 188 ◽  
pp. 108424 ◽  
Author(s):  
Yan Yao ◽  
Lizhen Wang ◽  
Jian Li ◽  
Shan Tian ◽  
Ming Zhang ◽  
...  
Keyword(s):  
Mechanical Characterization ◽  
Fixation Strength ◽  
Strength Evaluation ◽  
Bone Screw ◽  
Screw Design ◽  
Pullout Fixation ◽  
Auxetic Structure

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.

scholarly journals Time-related changes in the fixation strength of titanium bone screw after implantation.

1994 ◽  
Vol 40 (1) ◽  
pp. 88-106
Author(s):  
Takahiro YAMATSUTA ◽  
Akira YAMAGUCHI ◽  
Koichi NISHIMURA
Keyword(s):  
Fixation Strength ◽  
Bone Screw

Interfacial sliding properties of bone screw materials and their effect on screw fixation strength

2014 ◽  
Vol 12 (2) ◽  
pp. 90-96
Author(s):  
Arto P. Koistinen ◽  
Hannu Korhonen ◽  
Heikki Kröger ◽  
Reijo Lappalainen
Keyword(s):  
Screw Fixation ◽  
Fixation Strength ◽  
Bone Screw ◽  
Interfacial Sliding

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

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.

Pullout Strength of Screws in Foal Third Metacarpal Bone after Overdrilling a 4.5 mm Hole

1998 ◽  
Vol 11 (04) ◽  
pp. 200-204 ◽  
Author(s):  
K. Kelly ◽  
G. S. Martin ◽  
D. J. Burba ◽  
S. A. Sedrish ◽  
R. M. Moore
Keyword(s):  
Cortical Bone ◽  
Metacarpal Bone ◽  
Pullout Strength ◽  
Cancellous Screw ◽  
Bone Screw ◽  
Screw Insertion ◽  
Holding Power ◽  
Cortical Screw ◽  
Metaphyseal Bone

SummaryThe purpose of the study was to determine and to compare the in vitro pullout strength of 5.5 mm cortical versus 6.5 mm cancellous bone screws inserted in the diaphysis and metaphysis of foal third metacarpal (MCIII) bones in threaded 4.5 mm cortical bone screw insertion holes that were then overdrilled with a 4.5 mm drill bit. This information is relevant to the selection of a replacement screw if a 4.5 mm cortical screw is stripped during orthopaedic surgery. In vitro pullout tests were performed in two independent cadaver studies, each consisting of 12 foal MCIII bones. Two 4.5 mm cortical screws were placed either in the mid-diaphysis (study 1) or distal metaphysis (study 2) of MCIII bones. The holes were then overdrilled with a 4.5 mm bit and had either a 5.5 mm cortical or a 6.5 mm cancellous screw inserted; screw pullout tests were performed at a rate of 0.04 mm/s until screw or bone failure occurred.The bone failed in all of the tests in the diaphyseal and metaphyseal bone. The holding power for 6.5 mm cancellous screws was significantly (p <0.05) greater than for 5.5 mm cortical screws in both the diaphysis and metaphysis. There was not any difference in the holding power of screws in either the diaphysis or the metaphysis between proximal and distal screw holes.If a 4.5 mm cortical bone screw strips in MCIII diaphyseal or metaphyseal bone of foals, a 6.5 mm cancellous screw would provide greater holding power than a 5.5 mm cortical screw.In order to provide information regarding selection of a replacement screw if a 4.5 mm cortical screw is stripped, the in vitro pullout strength was determined for 5.5 mm cortical and 6.5 mm cancellous screws inserted in third metacarpal diaphyseal and metaphyseal bone of foals in which threaded 4.5 mm cortical bone screw insertion holes had been overdrilled with a 4.5 mm bit. The holding power of the 6.5 mm cancellous screw was significantly greater than the 5.5 mm cortical screw in both the diaphysis and metaphysis of foal third metacarpal bone. Thus, it appears that if a 4.5 mm cortical screw is stripped during orthopaedic surgery in foals, a 6.5 mm cancellous screw would provide superior holding power.

The “Mixing” of Implant Systems

1991 ◽  
Vol 4 (02) ◽  
pp. 38-45 ◽  
Author(s):  
F. Baumgart
Keyword(s):  
Stainless Steel ◽  
Additional Risk ◽  
Bone Screw ◽  
Application Technique ◽  
Quality Controls ◽  
Implant Materials ◽  
Osteosynthesis Plate ◽  
Potential Problems ◽  
Manufacturing Procedure

SummaryThe so-called “mixing” of implants and instruments from different producers entertain certain risks.The use of standardized implant materials (e.g. stainless steel ISO 5832/1) from different producers is necessary but is not sufficient to justify the use of an osteosynthesis plate from one source and a bone screw from another.The design, dimensions, tolerances, manufacturing procedure, quality controls, and application technique of the instruments and implants also vary according to make. This can lead to damage, failure or fracture of the biomechanical system called “osteosynthesis” and hence the failure of the treatment undertaken. In the end, it is the patient who pays for these problems.Some examples also illustrate the potential problems for the staff and institutions involved.The use of a unique, consistent, well-tested, and approved set of implants and instruments is to be strongly recommended to avoid any additional risk.

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