Experimental investigation of pull-out performance of pedicle screws at different polyurethane (PU) foam densities

2021 ◽  
pp. 095441192110025
Author(s):  
Ahmet Çetin ◽  
Durmuş Ali Bircan
Keyword(s):  
Pedicle Screws ◽  
Poor Quality ◽  
Osteoporotic Bone ◽  
Foam Density ◽  
Pull Out ◽  
Pu Foam ◽  
Screw Diameter ◽  
Critical Materials ◽  
Materials Used ◽  
Force Displacement

Pedicle bone screws are one of the most critical materials used in spinal orthopaedic operations. Screw loosening and pull-out (PO) are basic complications encountered during or after surgery. Pull-out Strength (POS) of the bone is one of the significant parameters to understand the mechanical behaviour of a screw fixed to poor quality or osteoporotic bone. This study investigates how the POS of a pedicle screw is affected by the factors of the screw diameter and the polyurethane (PU) foam density by experimental analysis. In the experiments, two different diameter (5.5 and 6.5 mm) of conical pedicle screws and five different density (0.08, 0.16, 0.24, 0.32 and 0.48 g·cm−3) PU foams were used. According to the force-displacement curves obtained from experimental results, the POS increased with the increases in screw diameter and PU foam density.

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].

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.

scholarly journals The evaluation of long-term screw pull-out rates following posterior thoracolumbar fusion surgery with short and thin pedicle screws

2019 ◽  
pp. 178-182
Author(s):  
Umit Kocaman ◽  
Hakan Yilmaz
Keyword(s):  
Pedicle Screws ◽  
Fusion Surgery ◽  
Pull Out ◽  
Transpedicular Screw ◽  
Thoracic Pedicle Screws ◽  
Pedicle Length ◽  
Neurocentral Junction ◽  
Male Patients ◽  
Lumbar Pedicle

Background. The aim of this study was to evaluate screw pull-out rates after fusion operations with short and thin pedicle screws.Methods. A total of 200 posterior lumbar and thoracolumbar fusion operations performed at our clinic with short and thin pedicle screws (5.5x35 mm) were retrospectively evaluated. The patients were assessed with computed tomography postoperatively on the day of surgery and at the 6th month. Single groove retraction of the transpedicular screw was evaluated as pull-out. The results were evaluated by the 'number of pull-out cases / total number of cases' and also the 'total number of pull-out screws / total number of screws used' ratios. Results. There were 112 (56%) female and 88 (44%) male patients with a mean age of 58 years. The total number of screws used in the 200 cases was 1188. There were 88 (7.4%) thoracic pedicle screws, 1056 (88.9%) lumbar pedicle screws and 44 (3.7%) sacral pedicle screws used. No pull-out was found in the control CTs taken postoperatively. Left side T11 and T12 pull-out was observed in one case and left L4 pull-out was observed in another case in the control CTs taken at the postoperative 6th month. Pull-out was observed in 2 (1%) of the 200 cases and 3 (0.25%) of the 1188 screws.Conclusions. All the short and thin pedicle screws used had passed the pedicle length and neurocentral junction. The use of a 5.5x35 mm screws in fusion operations is less invasive than using longer and thicker screws while the pull-out rates may be similar.

Pullout strength for cannulated pedicle screws with bone cement augmentation in severely osteoporotic bone: Influences of radial hole and pilot hole tapping

2009 ◽  
Vol 24 (8) ◽  
pp. 613-618 ◽  
Author(s):  
Lih-Huei Chen ◽  
Ching-Lung Tai ◽  
Po-Liang Lai ◽  
De-Mei Lee ◽  
Tsung-Tin Tsai ◽  
...  
Keyword(s):  
Bone Cement ◽  
Pedicle Screws ◽  
Cement Augmentation ◽  
Osteoporotic Bone ◽  
Pullout Strength ◽  
Pilot Hole

scholarly journals Evaluation of C2 pedicle screw placement via the freehand technique by neurosurgical trainees

2018 ◽  
Vol 29 (3) ◽  
pp. 235-240 ◽  
Author(s):  
Martin H. Pham ◽  
Joshua Bakhsheshian ◽  
Patrick C. Reid ◽  
Ian A. Buchanan ◽  
Vance L. Fredrickson ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Medical Center ◽  
Pedicle Screws ◽  
Screw Placement ◽  
Pedicle Screw Placement ◽  
C2 Pedicle Screw ◽  
Canal Diameter ◽  
Screw Length ◽  
Freehand Technique ◽  
Screw Diameter

OBJECTIVEFreehand placement of C2 instrumentation is technically challenging and has a learning curve due the unique anatomy of the region. This study evaluated the accuracy of C2 pedicle screws placed via the freehand technique by neurosurgical resident trainees.METHODSThe authors retrospectively reviewed all patients treated at the LAC+USC Medical Center undergoing C2 pedicle screw placement in which the freehand technique was used over a 1-year period, from June 2016 to June 2017; all procedures were performed by neurosurgical residents. Measurements of C2 were obtained from preoperative CT scans, and breach rates were determined from coronal reconstructions on postoperative scans. Severity of breaches reflected the percentage of screw diameter beyond the cortical edge (I = < 25%; II = 26%–50%; III = 51%–75%; IV = 76%–100%).RESULTSNeurosurgical residents placed 40 C2 pedicle screws in 24 consecutively treated patients. All screws were placed by or under the guidance of Pham, who is a postgraduate year 7 (PGY-7) neurosurgical resident with attending staff privileges, with a PGY-2 to PGY-4 resident assistant. The authors found an average axial pedicle diameter of 5.8 mm, axial angle of 43.1°, sagittal angle of 23.0°, spinal canal diameter of 25.1 mm, and axial transverse foramen diameter of 5.9 mm. There were 17 screws placed by PGY-2 residents, 7 screws placed by PGY-4 residents, and 16 screws placed by the PGY-7 resident. The average screw length was 26.0 mm, with a screw diameter of 3.5 mm or 4.0 mm. There were 7 total breaches (17.5%), of which 4 were superior (10.0%) and 3 were lateral (7.5%). There were no medial breaches. The breaches were classified as grade I in 3 cases (42.9%), II in 3 cases (42.9%), III in 1 case (14.3%), and IV in no cases. There were 3 breaches that occurred via placement by a PGY-2 resident, 3 breaches by a PGY-4 resident, and 1 breach by the PGY-7 resident. There were no clinical sequelae due to these breaches.CONCLUSIONSFreehand placement of C2 pedicle screws can be done safely by neurosurgical residents in early training. When breaches occurred, they tended to be superior in location and related to screw length choice, and no breaches were found to be clinically significant. Controlled exposure to this unique anatomy is especially pertinent in the era of work-hour restrictions.

scholarly journals Possible Usage of Cannulated Pedicle Screws without Cement Augmentation

2014 ◽  
Vol 11 (3) ◽  
pp. 149-155 ◽  
Author(s):  
Teyfik Demir
Keyword(s):  
Pedicle Screws ◽  
Pedicle Screw Fixation ◽  
Cement Augmentation ◽  
Control Group ◽  
Pullout Strength ◽  
Screw Design ◽  
Pullout Tests ◽  
Pu Foam ◽  
Common Problems ◽  
Testing Protocols

Background: The use of pedicle screws is becoming increasingly popular for spinal surgery practice as the technology advances. Screw pullout due to bone quality and loading conditions is one of the most common problems observed after pedicle screw fixation. Several solutions were studied to prevent screw pullout. These can be investigated under three main categories: screw design, expandable screws and cement augmentation.Objective: This study aimed to investigate the pullout performance of cannulated screws without cement augmentation on synthetic foams.Methods: Artificial fusion process for PU is described and validated in our previous studies. For this study six newly designed cannulated pedicle screws were artificially fused to PU foam and pullout test were conducted according to ASTM F543 standard testing protocols.Results: According to the results of post-fusion pullout tests, worst performed cannulated screw design was S3H on healthy bone simulating PU foam. However, pullout strength of unilaterally three holes including (S3H) design was purchased with two times higher loads when compared to control group. Solid cored screws were purchased with 671 N where this value was 1450 N for S3H design.Conclusions: This study provided that using cannulated pedicle screws without cement augmentation for the cases with healthy bone can be a reliable alternative to classical screws. To the knowledge of the authors this is the first post-fusion study investigating cannulated pedicle screws without cement augmentation.

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.

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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