scholarly journals Rescue Augmentation: Increased Stability in Augmentation After Initial Loosening of Pedicle Screws

2020 ◽  
pp. 219256822091912
Author(s):  
Lukas Weiser ◽  
Gerd Huber ◽  
Kay Sellenschloh ◽  
Klaus Püschel ◽  
Michael M. Morlock ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Bone Density ◽  
Fatigue Testing ◽  
Quantitative Computed Tomography ◽  
Pedicle Screws ◽  
Fatigue Loading ◽  
Cement Augmentation ◽  
Fatigue Load ◽  
The Impact

Study Design: Biomechanical study. Objectives: Failure of pedicle screws is a major problem in spinal surgery not only postoperatively, but also intraoperatively. The aim of this study was to evaluate whether cement augmentation may restore mounting of initially loosened pedicle screws. Methods: A total of 14 osteoporotic or osteopenic human cadaveric vertebral bodies (L2)—according to quantitative computed tomography (QCT)—were instrumented on both sides by conventional pedicle screws and cement augmented on 1 side. In vitro fatigue loading (cranial-caudal sinusoidal, 0.5 Hz) with increasing peak force (100 N + 0.1 N/cycles) was applied until a screw head displacement of 5.4 mm (∼20°) was reached. After loosening, the nonaugmented screw was rescue augmented, and fatigue testing was repeated. Results: The fatigue load reached 207.3 N for the nonaugmented screws and was significantly ( P = .009) exceeded because of initial cement augmentation (300.6 N). The rescue augmentation after screw loosening showed a fatigue load of 370.1 N which was significantly higher ( P < .001) compared with the nonaugmented screws. The impact of bone density on fatigue strength decreased from the nonaugmented to the augmented to the rescue-augmented screws and shows the greatest effect of cement augmentation on fatigue strength at low bone density. Conclusions: Rescue augmentation leads to similar or higher fatigue strengths compared with those of the initially augmented screws. Therefore, the cement augmentation of initially loosened pedicle screws is a promising option to restore adequate screw stability.

scholarly journals Cortical threaded pedicle screw improves fatigue strength in decreased bone quality

2020 ◽  
Author(s):  
Lukas Weiser ◽  
Kay Sellenschloh ◽  
Klaus Püschel ◽  
Michael M. Morlock ◽  
Lennart Viezens ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Pedicle Screw ◽  
Bone Quality ◽  
Quantitative Computed Tomography ◽  
Pedicle Screws ◽  
Fatigue Load ◽  
Head Displacement ◽  
Significant Difference ◽  
Vertebral Bodies

Abstract Purpose Inadequate anchoring of pedicle screws in vertebrae with poor bone quality is a major problem in spine surgery. The aim was to evaluate whether a modified thread in the area of the pedicle could significantly improve the pedicle screw fatigue strength. Methods Fourteen human cadaveric vertebral bodies (L2 and L3) were used for in vitro testing. Bone density (BMD) was determined by quantitative computed tomography. Vertebral bodies were instrumented by standard pedicle screws with a constant double thread on the right pedicle and a partial doubling of the threads–quad thread–(cortical thread) in the area of the pedicle on the left pedicle. Pulsating sinusoidal, cyclic load (0.5 Hz) with increasing peak force (100 N + 0.1 N/cycles) was applied orthogonal to the screw axis. The baseline force remained constant (50 N). Fatigue test was terminated after exceeding 5.4-mm head displacement (~ 20° screw tilting). Results The mean fatigue load at failure was 264.9 N (1682 cycles) for the standard screws and was increased significantly to 324.7 N (2285 cycles) by the use of cortical threaded screws (p = 0.014). This effect is particularly evident in reduced BMD (standard thread 241.2 N vs. cortical thread 328.4 N; p = 0.016), whereas in the group of vertebrae with normal BMD no significant difference could be detected (standard thread 296.5 N vs. cortical thread 319.8 N; p = 0.463). Conclusions Compared to a conventional pedicle screw, the use of a cortical threaded pedicle screw promises superior fatigue load in vertebrae with reduced bone quality.

Evaluation of Total Ankle Arthroplasty Using Highly Crosslinked Ultrahigh-Molecular-Weight Polyethylene Subjected to Physiological Loading

2019 ◽  
Vol 40 (8) ◽  
pp. 880-887 ◽  
Author(s):  
Jeffrey E. Bischoff ◽  
Mehul A. Dharia ◽  
Justin S. Hertzler ◽  
Oliver N. Schipper
Keyword(s):  
Fatigue Strength ◽  
Fatigue Testing ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Fatigue Loading ◽  
Strength Properties ◽  
Total Ankle Arthroplasty ◽  
Wear Properties ◽  
Ankle Arthroplasty ◽  
Walking Gait

Background: Highly crosslinked polyethylene (HXLPE) was developed for its superior wear properties in comparison to conventional polyethylene (CPE). Concern over fatigue resistance has prevented widespread adoption of HXLPE for use in total ankle arthroplasty (TAA). The aim of this study was to determine whether HXLPE has sufficient fatigue strength for total ankle arthroplasty under simulated physiologically relevant motion profiles and loading in the ankle. Methods: Physiologic load and motion profiles representative of walking gait were incorporated into a computational model of a semiconstrained, fixed-bearing TAA to determine the loading state with highest stresses in the HXLPE bearing. Subsequent fatigue testing to 10 million cycles (Mc) at 5600 N was performed to assess bearing strength. Results: Peak stresses in the bearing were predicted at peak axial load and peak dorsiflexion during gait, occurring near heel off. All samples withstood 10 Mc of fatigue loading at that orientation without polyethylene bearing fracture. Conclusion: HXLPE had sufficient fatigue strength to withstand 10 Mc of loading at more than 5 times body weight at the point of peak stresses during simulated gait in total ankle arthroplasty. Clinical Relevance: HXLPE may be mechanically strong enough to withstand the in vivo demands of the ankle. Improvements in wear afforded by HXLPE can be obtained without compromising sufficient polyethylene strength properties in total ankle arthroplasty.

scholarly journals Fatigue Strength as a Function of Preloading in Dynamic Fatigue Testing of Glass and Ceramics

1996 ◽  
Author(s):  
Sung R. Choi ◽  
Jonathan A. Salem ◽  
John P. Gyekenyesi
Keyword(s):  
Fatigue Strength ◽  
Failure Time ◽  
Fatigue Testing ◽  
Slow Crack Growth ◽  
Fatigue Loading ◽  
Soda Lime ◽  
Ceramic Materials ◽  
Soda Lime Glass ◽  
Testing Time ◽  
Dynamic Fatigue

The solution of fatigue strength as a function of preloading in dynamic fatigue testing was obtained analytically and numerically. The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter (n), and for n ≥ 20 the effect is negligible up to a preloading of 90 %. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens in room-temperature distilled water. This result showed that one can apply a preloading corresponding up to 90 % of fatigue strength for most glass and ceramic materials, resulting in a dramatic saving of testing time in dynamic fatigue testing. The key feature that makes this technique feasible is that most of the slow crack growth under dynamic fatigue loading occurs close to failure time where a dynamic fatigue strength is defined.

Sour Service Corrosion Fatigue Testing of Flowline Welds

2007 ◽  
Author(s):  
Fraser McMaster ◽  
Hugh Thompson ◽  
Michelle Zhang ◽  
David Walters ◽  
Jonathan Bowman
Keyword(s):  
Corrosion Fatigue ◽  
Wall Thickness ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Production Quality ◽  
Process Selection ◽  
Circumferential Welds ◽  
The Impact ◽  
Sour Service

An examination of the corrosion-fatigue behavior of production quality welds in X65-type pipes was performed. Due to the low cycle operational nature of the production flowline system, the fatigue test frequency was substantially lower (0.01Hz vs. 0.33Hz) than typically utilized during corrosion-fatigue testing. Also the tests were performed at higher stress ranges than previous sour service fatigue tests, which to date have targeted riser fatigue loading regimes. Stress-life (S-N) samples were removed from segments of pipe with outside diameters of 10.75 inch (wall thickness of 1.30 inch) and 9.625 inch (wall thickness of 1.26 inch) containing fully inspected, production-quality circumferential welds. Environments examined included laboratory air conditions as well as deoxygenated brine supplemented by a gas mix of H2S and N2. For all environmental tests performed, the dissolved oxygen levels were maintained at less than 10 ppb during all testing. The measured fatigue life decrease in the curved pipe segments was in the range of 8–110 times due to the combined effect of the material and fluid property variables examined. The results of this work clearly illustrated the impact of sour-service corrosion fatigue, in welded carbon steel pipes, to the multitude of variables involved. Nevertheless, the foregoing experimental work clearly demonstrated the importance of performing environmental relevant testing when considering material and process selection for offshore applications.

Experimental Study on the Fatigue Strength of the Bogie Frame for Tilting Railway Vehicles

2006 ◽  
Vol 321-323 ◽  
pp. 590-593 ◽  
Author(s):  
Nam Po Kim ◽  
Jung Seok Kim ◽  
Sung Il Seo ◽  
Tae Won Park
Keyword(s):  
Experimental Study ◽  
Fatigue Strength ◽  
Fatigue Loading ◽  
Load Test ◽  
Static Load Test ◽  
Fatigue Load ◽  
Loading Test ◽  
Bogie Frame ◽  
Goodman Diagram ◽  
Tilting Train

This paper shows the experimental study to evaluate the fatigue strength of a bogie frame for Korean tilting train. The various load cases were established based on the international standard (UIC615-4) and the special tilting load case, which is unique in the tilting train, was derived by dynamic analysis and logical assumption of operation under worst tilting condition. The experimental study was conducted by means of two ways, both static and fatigue loading test. Through the static load test, the safety against fatigue was assessed using Goodman diagram of the material used. The fatigue load test was carried out up to 1x107cycles. The fatigue strength was assessed by fatigue crack inspection by means of NDT test at the stage of 6x106cycles and 1x107cycles.

Vertebral bone density evaluated by dual-energy X-ray absorptiometry and quantitative computed tomography in vitro

Bone ◽  
1998 ◽  
Vol 23 (3) ◽  
pp. 283-290 ◽  
Author(s):  
E.N. Ebbesen ◽  
J.S. Thomsen ◽  
H. Beck-Nielsen ◽  
H.J. Nepper-Rasmussen ◽  
Li Mosekilde
Keyword(s):  
Computed Tomography ◽  
Bone Density ◽  
Quantitative Computed Tomography ◽  
Dual Energy ◽  
Vertebral Bone ◽  
X Ray

Fatigue Strength as a Function of Preloading in Dynamic Fatigue Testing of Glass and Ceramics

1997 ◽  
Vol 119 (3) ◽  
pp. 493-499 ◽  
Author(s):  
S. R. Choi ◽  
J. P. Gyekenyesi
Keyword(s):  
Fatigue Strength ◽  
Failure Time ◽  
Fatigue Testing ◽  
Slow Crack Growth ◽  
Fatigue Loading ◽  
Soda Lime ◽  
Ceramic Materials ◽  
Soda Lime Glass ◽  
Testing Time ◽  
Dynamic Fatigue

The solution of fatigue strength as a function of preloading in dynamic fatigue (constant stress-rate) testing was obtained analytically and numerically. The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter (n), and for n ≥ 20 the effect is negligible up to a preloading of 90 percent. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens in room-temperature distilled water. This result showed that one can apply a preloading corresponding up to 90 percent of fatigue strength for most glass and ceramic materials, resulting in a dramatic saving of testing time in dynamic fatigue testing. The key feature that makes this technique feasible is that most of the slow crack growth under dynamic fatigue loading occurs close to failure time where the dynamic fatigue strength is defined.

scholarly journals Flexibility and fatigue evaluation of oblique as compared with anterior lumbar interbody cages with integrated endplate fixation

2016 ◽  
Vol 24 (1) ◽  
pp. 54-59 ◽  
Author(s):  
Andrew L. Freeman ◽  
William J. Camisa ◽  
Glenn R. Buttermann ◽  
James R. Malcolm
Keyword(s):  
Fatigue Testing ◽  
Plate Fixation ◽  
Pedicle Screws ◽  
Test Group ◽  
Pedicle Screw Fixation ◽  
Pullout Resistance ◽  
Pullout Tests ◽  
Cage Subsidence ◽  
Fatigue Evaluation

OBJECT This study was undertaken to quantify the in vitro range of motion (ROM) of oblique as compared with anterior lumbar interbody devices, pullout resistance, and subsidence in fatigue. METHODS Anterior and oblique cages with integrated plate fixation (IPF) were tested using lumbar motion segments. Flexibility tests were conducted on the intact segments, cage, cage + IPF, and cage + IPF + pedicle screws (6 anterior, 7 oblique). Pullout tests were then performed on the cage + IPF. Fatigue testing was conducted on the cage + IPF specimens for 30,000 cycles. RESULTS No ROM differences were observed in any test group between anterior and oblique cage constructs. The greatest reduction in ROM was with supplemental pedicle screw fixation. Peak pullout forces were 637 ± 192 N and 651 ± 127 N for the anterior and oblique implants, respectively. The median cage subsidence was 0.8 mm and 1.4 mm for the anterior and oblique cages, respectively. CONCLUSIONS Anterior and oblique cages similarly reduced ROM in flexibility testing, and the integrated fixation prevented device displacement. Subsidence was minimal during fatigue testing, most of which occurred in the first 2500 cycles.

The Impact of Degenerative Spinal Changes on the Correlation of Peripheral and Axial Bone Density

1994 ◽  
Vol 33 (04) ◽  
pp. 138-143 ◽  
Author(s):  
W. Börner ◽  
P. Schneider
Keyword(s):  
Computed Tomography ◽  
Lumbar Spine ◽  
Bone Density ◽  
Distal Radius ◽  
Bone Mineral ◽  
Quantitative Computed Tomography ◽  
Axial Skeleton ◽  
Mineral Concentration ◽  
The Impact ◽  
Peripheral Skeleton

SummaryResults of bone density measurements by quantitative computed tomography of the peripheral skeleton (pQCT) were compared with those of measurements at the axial skeleton with a view to study the effects of degenerative spinal changes on the validity of bone densitometry of the lumbar spine. 556 consecutive patients were examined by dual-energy x-ray absorptiometry (DXA) of the spine and by peripheral quantitative computed tomography (pQCT) of the distal radius. There were significant differences between the bone mineral values at the distal radius and those at the spine, depending on the degree of spinal degeneration. As expected, spinal degenerations showed a highly significant age dependence. With increasing degeneration the correlations between the radius total bone mineral concentration and the bone density of the lumbar spine decreased from r = 0.45 to 0.23 in women and from r = 0.64 to 0.28 in men. We conclude that the value of spinal DXA is reduced in patients with degenerative spinal disease, compared to the pQCT at the peripheral skeleton.

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