Shape Memory Alloy Expandable Pedicle Screw to Enhance Fixation in Osteoporotic Bone: Primary Design and Finite Element Simulation

2012 ◽  
Vol 6 (3) ◽  
Author(s):  
Majid Tabesh ◽  
Vijay Goel ◽  
Mohammad H. Elahinia
Keyword(s):  
Finite Element ◽  
Body Temperature ◽  
Shape Memory ◽  
Pedicle Screw ◽  
Stable Solution ◽  
Pedicle Screws ◽  
The Body ◽  
Osteoporotic Bone ◽  
Major Drawback ◽  
Pull Out

The properties of shape memory alloys, specifically the equiatomic intermetallic NiTi, are unique and significant in that they offer simple and effective solutions for some of the biomechanical issues encountered in orthopedics. Pedicle screws, used as an anchoring point for the implantation of spinal instrumentations in the spinal fracture and deformity treatments, entail the major drawback of loosening and backing out in osteoporotic bone. The strength of the screw contact with the surrounding bone diminishes as the bone degrades due to osteoporosis. The SMArtTM pedicle screw design is developed to address the existing issue in degraded bone. It is based on the interaction of bi-stable shape memory-superelastic elements. The bi-stable assembly acts antagonistically and consists of an external superelastic tube that expands the design protrusions when body temperature is attained; also an internal shape memory wire, inserted into the tube, retracts the assembly while locally heated to above the body temperature. This innovative bi-stable solution augments the pull-out resistance while still allowing for screw removal. The antagonistic wire-tube assembly was evaluated and parametrically analyzed as for the interaction of the superelastic tube and shape memory wire using a finite element model developed in COMSOL Multiphysics®. The outcomes of the simulation suggest that shape memory NiTi inserts on the SMArtTM pedicle screw can achieve the desired antagonistic functionality of expansion and retraction. Consequently, a parametric analysis was conducted over the effect of different sizes of wires and tubes. The dimensions for the first sample of this innovative pedicle screw were determined based on the results of this analysis.

Modeling NiTi Superelastic-Shape Memory Antagonistic Beams: A Finite Element Analysis

2009 ◽  
Author(s):  
Majid Tabesh ◽  
Mohammad Elahinia ◽  
Mehdi Pourazady
Keyword(s):  
Finite Element ◽  
Body Temperature ◽  
Shape Memory ◽  
Pedicle Screws ◽  
Experimental Tests ◽  
Element Analysis ◽  
Major Drawback ◽  
Screw Design ◽  
Finite Element Software ◽  
Engineering Sciences

Shape memory alloys (SMA) have received widespread attention from researchers in various fields of engineering sciences due to their exceptional properties of shape memory and superelasticity. NiTi equiatomic alloys among other SMA, show acceptable biocompatibility to be implemented in biomedical applications. Applications of NiTi in biomedical areas specifically orthopedics, demonstrate its unique performance which is not achievable with conventional materials. Pedicle screws, which are used as an anchoring point for implanting spinal instrumentations in spinal fracture and deformity treatments, entail a major drawback; i.e. loosening and back-out. The strength of screw contact with the surrounding bone diminishes as the bone degrades due to osteoporosis. A “Smart” pedicle screw design was developed to address this issue which uses NiTi superelastic-shape memory coils wrapped around it. The smart assembly consists of external superelastic tubing which is responsible for expanding the designed protrusions when they reach body temperature; also an internal shape memory wire inserted into the tubing is sought to retract the assembly when locally heated to above body temperature. The whole assembly was modeled as a beam structure in COMSOL Multiphysics Finite Element software. The behavior of shape memory alloy was defined in the software via its Partial Differential Equation (PDE) module. The SMA model has is a Tanaka-based model and is capable of capturing shape memory effect, superelasticity and hysteresis behavior, and partial transformation in both positive and negative directions. This 1D model was further modified to be included in a 3D framework such that it makes it possible for simulation of a beam under bending. The functionality of the smart screw design can be studied via this FEM model as a future work and the outcomes of the simulation can be compared with experimental tests on the prepared sample of the screw comprising NiTi tubing and wires.

scholarly journals Effects of the Insertion Type and Depth on the Pedicle Screw Pullout Strength: A Finite Element Study

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
K. Jendoubi ◽  
Y. Khadri ◽  
M. Bendjaballah ◽  
N. Slimane
Keyword(s):  
Finite Element ◽  
Pedicle Screw ◽  
Pedicle Screws ◽  
Osteoporotic Bone ◽  
Screw Thread ◽  
Pullout Strength ◽  
Pullout Resistance ◽  
Finite Element Study ◽  
Screw Breakage ◽  
Element Study

Purpose. The pedicle screw is a surgical device that has become widely used in spinal fixation and stabilization. Postsurgical complications such as screw loosening due to fatigue loading and screw breakage still need investigations. Clinical parameters such as the screw insertion type and depth, the bone density, and the patient degree of mobility greatly affect the mechanisms of the implant’s failure/success. Methods. The current finite element study focused on the prediction of the pedicle screw pullout strength under various conditions such as insertion type, insertion depth, bone quality, and loading mode. Results. As depicted in this study, the preservation of the pedicle cortex as in the N1 insertion technique greatly enhances the pullout resistance. In addition, the higher the screw-anchoring depth, permitting to gear a maximum number of threads, the better the protection against premature breakouts of pedicle screws. Conclusions. In agreement with experimental data, the type of insertion in which the first screw thread is placed immediately after the preserved pedicle cortex showed the best pullout resistance for both normal and osteoporotic bone.

Micromechanics of stress transfer in shape memory alloy reinforced three-phase composites

2018 ◽  
Vol 29 (15) ◽  
pp. 3151-3164 ◽  
Author(s):  
Fathollah Taheri-Behrooz ◽  
Mohammad Javad Mahdavizade ◽  
Alireza Ostadrahimi
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Thermal Loading ◽  
Hybrid Composites ◽  
Stress Transfer ◽  
Shape Memory Alloy Wire ◽  
Alloy Wire ◽  
Pull Out

Due to the weak interface in shape memory alloy wire–reinforced composites, the influence of interphase on the mechanical properties and stress distribution of hybrid composites is of considerable importance. In this article, a three-cylinder axisymmetric model using a pull-out test is developed to predict stress transfer and interfacial behavior between shape memory alloy wire, interphase, and matrix. In this article, only superelasticity behavior of the shape memory alloy wire is considered. Based on the stress function method and the principle of minimum complementary energy, stress distribution is derived for three different cases in terms of loading and boundary conditions (thermal loading model, intact model, and partially debonded model). Inhomogeneous interphase and different radial and hoop stress components in each phase are considered to achieve deeper physical understanding. Finite element analysis also performed to simulate stress transfer from the wire to the matrix through the interphase. To evaluate the accuracy of this model, the results of the work are compared with the results of the two-cylinder model proposed by Wang et al. and finite element results.

scholarly journals Highly Tough Hydrogels with the Body Temperature-Responsive Shape Memory Effect

2019 ◽  
Vol 11 (46) ◽  
pp. 43563-43572 ◽  
Author(s):  
Ruixue Liang ◽  
Haojie Yu ◽  
Li Wang ◽  
Long Lin ◽  
Nan Wang ◽  
...  
Keyword(s):  
Body Temperature ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
The Body ◽  
Temperature Responsive

A Pull-Out Resistant Pedicle Screw for the Osteoporotic Spine

2007 ◽  
Author(s):  
Karthik Ponnusamy ◽  
Sravisht Iyer ◽  
Alex Hui ◽  
Gaurav Gupta ◽  
Kartik Trehan ◽  
...  
Keyword(s):  
Bone Mass ◽  
Mass Density ◽  
Pedicle Screws ◽  
Bone Mass Density ◽  
Vertebral Compression Fractures ◽  
Osteoporotic Bone ◽  
Low Bone Mass ◽  
Compression Fractures ◽  
Pull Out ◽  
Increased Risk

Pedicle screws are commonly used in spine surgery to implant and affix metal devices to the spine. These screws are most commonly associated with cases that require rod or plate implantation. Use of pedicle screws in osteoporotic patients, however, is limited because they suffer from low bone mass density (BMD). The low BMD is harmful to patients in two ways — it leads to increased incidence of spinal trauma and also prevents surgeons from instrumenting osteoporotic patients because screws do not achieve the required fixation in osteoporotic patients [1]. The risk of trauma is increased due to the brittle bone and vertebral compression fractures, resulting in spinal misalignment and increased risk of future trauma. Instrumenting these cases with rods or plates, however, is impossible because osteoporotic bone is not strong enough to “hold” pedicle screws in, i.e., prevent screws from pulling out [2, 3].

A Novel Technique for Measuring Pedicle Screw Forces In Situ

2008 ◽  
Author(s):  
Samuel Q. Tia ◽  
Jennifer M. Buckley ◽  
Thuc-Quyen Nguyen ◽  
Jeffrey C. Lotz ◽  
Shane Burch
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Clinical Failure ◽  
Strain Gages ◽  
Destructive Testing ◽  
Novel Technique ◽  
Pull Out ◽  
Pull Out Strength

Long posterior fusion constructs in the lumbar spine cause substantial posteriorly directed loading of the supporting pedicle screws, particularly during patient bending activities. Although there are numerous documented accounts of clinical failure at the pedicle screw-bone interface [1,2], the in situ pull-out strength of pedicle screws in long surgical constructs has not been characterized. Previous biomechanical studies have quantified pedicle screw pull-out force in cadaveric models through destructive testing or in nondestructive cases, through the use of custom-machined pedicle screws instrumented with strain gages [3–6]. However, these techniques involve altering screw geometry and may fail to properly simulate in vivo mechanical loading conditions. The goal of this study was to develop and validate a sensor system for measuring pedicle screw pull-out forces in long posterior constructs in situ during multi-segmental cadaveric testing.

Influence of novel design alteration of pedicle screw on pull-out strength: A finite element study

2020 ◽  
Vol 25 (1) ◽  
pp. 66-72 ◽  
Author(s):  
Shota Takenaka ◽  
Takashi Kaito ◽  
Ken Ishii ◽  
Kota Watanabe ◽  
Kei Watanabe ◽  
...  
Keyword(s):  
Finite Element ◽  
Pedicle Screw ◽  
Finite Element Study ◽  
Pull Out ◽  
Novel Design ◽  
Pull Out Strength ◽  
Element Study

scholarly journals Placement of Guide-Wireless Sharp Percutaneous Pedicle Screws Utilizing Computed Tomography-Navigation and Sentinel Fluoroscopy: 2-Dimensional Operative Video

2019 ◽  
Vol 19 (2) ◽  
pp. E149-E150 ◽  
Author(s):  
Nikolay L Martirosyan ◽  
Joshua T Wewel ◽  
Juan S Uribe
Keyword(s):  
Computed Tomography ◽  
Pedicle Screw ◽  
Pedicle Screws ◽  
Transverse Process ◽  
Screw Placement ◽  
Osteoporotic Bone ◽  
Screw Insertion ◽  
Institutional Review ◽  
Stab Incision ◽  
Anterior Posterior

Abstract Many established techniques exist for minimally invasive pedicle screw placement. Nearly all techniques incorporate the use of a Kershner wire (K-wire) at various points in the work-flow. The use of a K-wire adds an additional step. If its position is lost, it requires repeating all previous steps, and placement is not without complication. The use of a guide-wireless sharp screws allows the surgeon to place a pedicle screw in 1 step with several fluid maneuvers.1 The patient underwent Institutional Review Board-approved consent for this study. Following traditional computed tomography-based navigation, a stab incision is made, followed by fascial dissection with monopolar cautery. The sharp screw is placed percutaneously at the facet-transverse process junction. The precise entry point is confirmed with navigation, followed by a sentinel anterior-posterior fluoroscopic image, verifying the accuracy of the navigation. The cortical bone is traversed by malleting the sharp tip through the cortex. When the cancellous bone is engaged, the screw is then advanced through the pedicle. This set of steps allows for safe, efficient placement of percutaneous pedicle screws without the need for a guidewire. Mal-placement regarding sharp pedicle screw insertion is similar to K-wire-dependent screw placement. Surgeons must be cognoscente of exceptionally sclerotic bone, which can prove difficult to cannulate. Conversely, osteoporotic bone that is liable to a cortical pedicle breach, transverse process fracture, and/or maltrajectory are all considerations when placing a K-wireless, sharp pedicle screw. Anterior-posterior fluoroscopy is utilized to confirm accuracy of image-guided navigation and mitigate malplacement of pedicle screws.

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