Offset Laminar Hooks Decrease Bending Moments of Pedicle Screws During In Situ Contouring

Spine ◽  
1997 ◽  
Vol 22 (4) ◽  
pp. 376-381 ◽  
Author(s):  
Scott A. Yerby ◽  
John R. Ehteshami ◽  
Robert F. McLain
Keyword(s):  
Pedicle Screws ◽  
Bending Moments ◽  
Laminar Hooks

Biomechanical evaluation of pedicle screws versus pedicle and laminar hooks in the thoracic spine

2006 ◽  
Vol 6 (4) ◽  
pp. 444-449 ◽  
Author(s):  
Andrew Cordista ◽  
Bryan Conrad ◽  
MaryBeth Horodyski ◽  
Sheri Walters ◽  
Glenn Rechtine
Keyword(s):  
Thoracic Spine ◽  
Pedicle Screws ◽  
Biomechanical Evaluation ◽  
Laminar Hooks

Anterior transvertebral interbody cage with posterior transdiscal pedicle screw instrumentation for high-grade spondylolisthesis

2006 ◽  
Vol 20 (3) ◽  
pp. 1-7 ◽  
Author(s):  
Will Forest Beringer ◽  
Jean-Pierre Mobasser ◽  
Dean Karahalios ◽  
Eric Alfred Potts
Keyword(s):  
Pedicle Screw ◽  
Degenerative Spondylolisthesis ◽  
Pedicle Screws ◽  
Pedicle Screw Fixation ◽  
Technical Note ◽  
Slip Angle ◽  
Fibular Graft ◽  
High Grade ◽  
Shear Forces

✓Adult high-grade degenerative spondylolisthesis represents the extreme end of the spectrum for spondylolisthesis and is consequently rarely encountered. Surgical management of high-grade spondylolisthesis requires constructs capable of resisting the shear forces at the slipped L5–S1 interspace. The severity of the slip, sacral inclination, and slip angle may make conventional approaches to 360° fusion difficult or hazardous. Transdiscal pedicle screw fixation, transvertebral fibular graft fusion, and transvertebral cage fixation are techniques that have been developed to establish anterior column load sharing and to resist shear forces at the L5–S1 interspace, given the anatomical constraints accompanying high-grade spondylolisthesis. In this technical note the authors describe the procedure for implanting an in situ anterior L5–S1 transvertebral cage and performing L4–5 anterior lumbar interbody fusion, followed by placement of posterior S1–L5 vertebral body transdiscal pedicle screws for management of high-grade spondylolisthesis.

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 Impact of subgrade and backfill stiffness on values and distribution of bending moments in integral box bridge

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Andrzej Helowicz
Keyword(s):  
Reinforced Concrete ◽  
Parametric Analysis ◽  
Bridge Structure ◽  
Bending Moments ◽  
Structural Elements ◽  
Subgrade Reaction ◽  
Bridge Design ◽  
Modulus Of Subgrade Reaction ◽  
The Impact

Abstract The article presents parametric analysis regarding the impact of subgrade and backfill stiffness on values and distribution of bending moments in the structural elements of a small integral box bridge made of cast in situ reinforced concrete. The analyzed parameters are the modulus of subgrade reaction under and behind the bridge structure (kv kh). At the beginning, the author presents the integral box bridge and selected parts of the bridge design. In particular, the author focuses on the method of modeling of the subgrade stiffness parameters under and behind the bridge structure, as well as their impact on the values and distribution of bending moments in the bridge structural elements. The bridge was designed by the author and built on the M9 motorway between the towns of Waterford and Kilcullen in Ireland. In conclusions, the author shares his knowledge and experience relating to the design of small integral bridges and culverts and puts forward recommendations as to further research on these type of structures in Poland.

Comparative Experimental Study of Hook and Pedicle Fixation Systems Used at Surgical Treatment of Spine Deformities

2012 ◽  
Vol 19 (3) ◽  
pp. 20-24 ◽  
Author(s):  
A. A Kuleshov ◽  
I. N Lisyansky ◽  
M. S Vetrile ◽  
N. S Gavryushenko ◽  
L. V Fomin
Keyword(s):  
Static Load ◽  
Testing Machine ◽  
Pedicle Screws ◽  
Cyclic Loads ◽  
Pedicle Fixation ◽  
Pull Out ◽  
Spine Deformities ◽  
Laminar Hooks ◽  
Vertebral Arch ◽  
Pull Out Strength

Using human cadaver spines we compared the stiffness of pedicle screws and laminar hooks under cyclic and static pull-out loads. Transpedicular and hook fixation (sub- and supralaminar) of cadaveric thoracic spine segments was performed. Axial pull-out strength was measured using w+b (walter + bai ag) servoelectric testing machine (LFV-10-T50, Switzerland). Static pull-out tests were performed on 7 spine blocks with transpedicular and 7 blocks with hook fixation. The same blocks were tested under cyclic loads. At cyclic pull-out loading 800 N strength with 5 Hz frequency was applied. It was shown that at increasing static load hook implants could bear 1417 N at average. At higher loads the vertebral arch was destroyed. Transpedicular implants could bear 2286 N at average and at higher loads the screw migrated from the arch root. Cyclic tests showed that hooks could bear 2935 cycles at average and at prolonged loading the arch was destroyed. The hooks could bear the full; program of cyclic loads without destruction (18 000 cycles).

Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization

2010 ◽  
Vol 12 (2) ◽  
pp. 183-189 ◽  
Author(s):  
Hakan Bozkuş ◽  
Mehmet Şenoğlu ◽  
Seungwon Baek ◽  
Anna G. U. Sawa ◽  
Ali Fahir Özer ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Stress Shielding ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Bending Moments ◽  
Axial Loads ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Lumbar Stabilization

Object It is unclear how the biomechanics of dynamic posterior lumbar stabilization systems and traditional rigid pedicle screw-rod systems differ. This study examined the biomechanical response of a hinged-dynamic pedicle screw compared with a standard rigid screw used in a 1-level pedicle screw-rod construct. Methods Unembalmed human cadaveric L3–S1 segments were tested intact, after L4–5 discectomy, after rigid pedicle screw-rod fixation, and after dynamic pedicle screw-rod fixation. Specimens were loaded using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording motion optoelectronically. Specimens were then loaded in physiological flexion-extension while applying 400 N of compression. Moment and force across instrumentation were recorded from pairs of strain gauges mounted on the interconnecting rods. Results The hinged-dynamic screws allowed an average of 160% greater range of motion during flexion, extension, lateral bending, and axial rotation than standard rigid screws (p < 0.03) but 30% less motion than normal. When using standard screws, bending moments and axial loads on the rods were greater than the bending moments and axial loads on the rods when using dynamic screws during most loading modes (p < 0.05). The axis of rotation shifted significantly posteriorly more than 10 mm from its normal position with both devices. Conclusions In a 1-level pedicle screw-rod construct, hinged-dynamic screws allowed a quantity of motion that was substantially closer to normal motion than that allowed by rigid pedicle screws. Both systems altered kinematics similarly. Less load was borne by the hinged screw construct, indicating that the hinged-dynamic screws allow less stress shielding than standard rigid screws.

scholarly journals Biomechanical demands on posterior fusion instrumentation during lordosis restoration procedures

2016 ◽  
Vol 25 (3) ◽  
pp. 345-351 ◽  
Author(s):  
Calvin C. Kuo ◽  
Audrey Martin ◽  
Connor Telles ◽  
Jeremi Leasure ◽  
Alex Iezza ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Posterior Fusion ◽  
Strain Gauges ◽  
Peak Loads ◽  
Significant Difference ◽  
Fluoroscopic Imaging ◽  
Cantilever Bending ◽  
Instrumentation Failure

OBJECTIVE The goal of this study was to investigate the forces placed on posterior fusion instrumentation by 3 commonly used intraoperative techniques to restore lumbar lordosis: 1) cantilever bending; 2) in situ bending; and 3) compression and/or distraction of screws along posterior fusion rods. METHODS Five cadaveric torsos were instrumented with pedicle screws at the L1–5 levels. Specimens underwent each of the 3 lordosis restoration procedures. The pedicle screw pullout force was monitored in real time via strain gauges that were mounted unilaterally at each level. The degree of correction was noted through fluoroscopic imaging. The peak loads experienced on the screws during surgery, total demand on instrumentation, and resting loads after corrective maneuvers were measured. RESULTS A mean overall lordotic correction of 10.9 ± 4.7° was achieved. No statistically significant difference in lordotic correction was observed between restoration procedures. In situ bending imparted the largest loads intraoperatively with an average of 1060 ± 599.9 N, followed by compression/distraction (971 ± 534.1 N) and cantilever bending (705 ± 413.0 N). In situ bending produced the largest total demand and postoperative loads at L-1 (1879 ± 1064.1 and 487 ± 118.8 N, respectively), which were statistically higher than cantilever bending and compression/distraction (786 ± 272.1 and 138 ± 99.2 N, respectively). CONCLUSIONS In situ bending resulted in the highest mechanical demand on posterior lumbar instrumentation, as well as the largest postoperative loads at L-1. These results suggest that the forces generated with in situ bending indicate a greater chance of intraoperative instrumentation failure and postoperative proximal pedicle screw pullout when compared with cantilever bending and/or compression/distraction options. The results are aimed at optimizing correction and fusion strategies in lordosis restoration cases.

scholarly journals Analytical solution for the resistance of composite beams subjected to bending

2020 ◽  
Vol 323 ◽  
pp. 01013
Author(s):  
Marek Lechman
Keyword(s):  
Analytical Solution ◽  
Bending Moment ◽  
Composite Beams ◽  
Bending Moments ◽  
Equilibrium Equations ◽  
Good Convergence ◽  
Linear Elastic ◽  
Eurocode 2 ◽  
Strain Relationship

The paper deals with the resistance of steel and concrete composite beams, named BH beams, subjected to bending. They are structurally connected with prefabricated or cast in situ slabs, forming floor slab system. The beams under consideration consist of the reinforced concrete (RC) rectangular core placed inside a reversed TT welded profile. The stress-strain relationship for concrete in compression of the RC core is assumed for nonlinear analysis according to Eurocode 2. For reinforcing and profile steels linear elastic – ideal plastic model is applied. The normalized ultimate bending moment determining the resistance of the BH beam is derived by integrating the equilibrium equations of the bending moments about the horizontal axis of the RC core rectangle, taking into account the physical and geometrical relationships. The presented model was verified by tests carried out on two BH beams subjected to bending. The comparisons made indicated good convergence between the analytical solution and the experimental results in ultimate bending moments.

scholarly journals Finite Element Analysis of I-Girder Bridge

2021 ◽  
Vol 9 (8) ◽  
pp. 2084-2097
Author(s):  
Mohd Nadeem
Keyword(s):  
Prestressed Concrete ◽  
Concrete Bridge ◽  
Bending Moments ◽  
Railway Bridge ◽  
Dead Load ◽  
Shear Forces ◽  
Bending Resistance ◽  
Girder Bridge ◽  
Deck Slab

Abstract: In India railway bridge structures are widely designed with the method suggested by IRS – Concrete bridge code 1997.This Code of Practice applies to the use of plain, reinforced and prestressed concrete in railway bridge construction. It covers both in-situ construction and manufacture of precast units. The Code gives detailed specifications for materials and workmanship for concrete, reinforcement and prestressing tendons used in the construction of railway bridges. After defining the loads, forces and their combinations and requirements for the limit state design, particular recommendations are given for plain concrete, reinforced concrete and prestressed concrete bridge construction. The design of I-Girder bridge superstructure (deck slab and PSC I-beam) are done by calculating bending moments, shear forces, bending resistance in transverse direction, bending resistance in longitudinal direction, checking flexural cracking. The Design of PSC I-Girders is done for Bending moments and Shear forces by Dead Load, Super Imposed Dead Load (SIDL) and Live Loads (LL). The Shrinkage strain, Creep Strain and effect of Temperature rise and fall are also determined. The design is complete for Pre-stressing cables, un-tensioned reinforcements, End cross girder, Shear connectors. I-girder superstructures are the most commonly used superstructures at cross-over location in metro bridges in india, as it has the wide deck slab and it easily permits metro’s to change tracks. I-Girder superstructure construction is component wise construction unlike U-Girders. I-Girders are constructed in casting yard and its deck slab is cast in situ, parapets are also installed on later stage. Keywords: SIDL effects, Live Load effects, Derailment effect, with or without 15% future PT margin

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