Biomechanical Study of Lumbar Spine using Unilateral Pedicle Screw with Tadpole Fixation System

Problems associated with spinal fusion such as adjacent level degeneration and donor site pain have shifted the focus to motion preservation technologies. The Anatomic Facet Replacement System (AFRS™) (Facet Solutions, Inc., Logan, Utah) attempts to address posterior lumbar spine pathologies while preserving stability and natural biomechanics thereby mitigating any potential adjacent level effects resulting from the reduction or elimination of motion as seen in semi-constrained dynamic stabilization and fusion devices. The AFRS™ is comprised of a precision instrumentation set whose design is based upon a comprehensive CT morphology study of the facet joint. It utilizes traditional pedicle screw fixation of its superior and inferior facet implants and is manufactured from a wear resistant alloy called cobalt-chromium-molybdenum. An experimentally validated finite element model was used for the quantification of facet loads and stresses in various components of the facet replacement system and also in the model stabilized using a pedicle screw rigid rod fixation system.

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Stress analysis in a pedicle screw fixation system with flexible rods in the lumbar spine

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1243/09544119jeim611 ◽

2009 ◽

Vol 224 (3) ◽

pp. 477-485 ◽

Cited By ~ 18

Author(s):

Kyungsoo Kim ◽

Won Man Park ◽

Yoon Hyuk Kim ◽

SuKyoung Lee

Keyword(s):

Lumbar Spine ◽

Stress Analysis ◽

Pedicle Screw ◽

Screw Fixation ◽

Pedicle Screw Fixation ◽

Flexible Rods ◽

Fixation System

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Biomechanical study of unilateral pedicle screw combined with contralateral translaminar facet screw in transforaminal lumbar interbody fusion

Clinical Biomechanics ◽

10.1016/j.clinbiomech.2015.05.009 ◽

2015 ◽

Vol 30 (7) ◽

pp. 657-661 ◽

Cited By ~ 5

Author(s):

Beier Luo ◽

Ming Yan ◽

Jinghui Huang ◽

Wei Duan ◽

Zhiping Huang ◽

...

Keyword(s):

Pedicle Screw ◽

Interbody Fusion ◽

Transforaminal Lumbar Interbody Fusion ◽

Biomechanical Study ◽

Lumbar Interbody Fusion ◽

Unilateral Pedicle Screw

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B215 Biomechanical study of unilateral pedicle screw and rod system

The Proceedings of the JSME Conference on Frontiers in Bioengineering ◽

10.1299/jsmebiofro.2011.22.153 ◽

2011 ◽

Vol 2011.22 (0) ◽

pp. 153-154

Author(s):

Takito INUKAI ◽

Norihiko SAKAKIBARA ◽

Zhuo WANG ◽

Yuichi KASAI ◽

Takaya KATO ◽

...

Keyword(s):

Pedicle Screw ◽

Biomechanical Study ◽

Rod System ◽

Unilateral Pedicle Screw

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Influence of posterior pedicle screw fixation at L4–L5 level on biomechanics of the lumbar spine with and without fusion: a finite element method

BioMedical Engineering OnLine ◽

10.1186/s12938-021-00940-1 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Emre Sengul ◽

Ramazan Ozmen ◽

Mesut Emre Yaman ◽

Teyfik Demir

Keyword(s):

Finite Element ◽

Lumbar Spine ◽

Pedicle Screw ◽

Posterior Lumbar Interbody Fusion ◽

Adjacent Segment ◽

Fe Model ◽

Lateral Bending ◽

Adjacent Level ◽

Before And After ◽

Fixation System

Abstract Background Posterior pedicle screw (PS) fixation, a common treatment method for widespread low-back pain problems, has many uncertain aspects including stress concentration levels, effects on adjacent segments, and relationships with physiological motions. A better understanding of how posterior PS fixation affects the biomechanics of the lumbar spine is needed. For this purpose, a finite element (FE) model of a lumbar spine with posterior PS fixation at the L4–L5 segment level was developed by partially removing facet joints (FJs) to imitate an actual surgical procedure. This FE study aimed to investigate the influence of the posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion by determining which physiological motions have the most increase in posterior instrumentation (PI) stresses and FJ loading. Results It was determined that posterior PS fixation increased FJ loading by approximately 35% and 23% at the L3–L4 adjacent level with extension and lateral bending motion, respectively. This increase in FJ loading at the adjacent level could point to the possibility that adjacent segment disease has developed or progressed after posterior lumbar interbody fusion. Furthermore, analyses of peak von Mises stresses on PI showed that the maximum PI stresses of 272.1 MPa and 263.7 MPa occurred in lateral bending and flexion motion before fusion, respectively. Conclusions The effects of a posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion were investigated for all physiological motions. This model could be used as a fundamental tool for further studies, providing a better understanding of the effects of posterior PS fixation by clearing up uncertain aspects.

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Biomechanical Study of Pedicle Screw Fixation Systems for the Lumbar Spine

Lumbar Fusion and Stabilization ◽

10.1007/978-4-431-68234-9_30 ◽

1993 ◽

pp. 288-296

Author(s):

Masatsune Yamagata ◽

Hiroshi Kitahara ◽

Shohei Minami ◽

Kazuhisa Takahashi ◽

Hideshige Moriya ◽

...

Keyword(s):

Lumbar Spine ◽

Pedicle Screw ◽

Screw Fixation ◽

Pedicle Screw Fixation ◽

Biomechanical Study

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Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase

Journal of Neurosurgery Spine ◽

10.3171/2014.10.spine14205 ◽

2015 ◽

Vol 22 (5) ◽

pp. 503-510 ◽

Cited By ~ 44

Author(s):

Steven Wray ◽

Ronnie Mimran ◽

Sasidhar Vadapalli ◽

Snehal S. Shetye ◽

Kirk C. McGilvray ◽

...

Keyword(s):

Bone Mineral Density ◽

Lumbar Spine ◽

Cortical Bone ◽

Pedicle Screw ◽

Bone Quality ◽

Pedicle Screws ◽

Biomechanical Study ◽

Mineral Density ◽

High Quality ◽

Cortical Screw

OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1–5) were used in this study (mean age 57 ± 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p < 0.001) and traditional pedicle screw (48%; p < 0.001) when compared to the traditional trajectory with a traditional pedicle screw within the high-quality bone group. These significant differences were also found in the lowquality bone cohort. All mechanical parameter comparisons (screw type and trajectory) between high-quality and lowquality samples were significant (p < 0.01), and these data were all linearly correlated (r ≥ 0.65) to bone mineral density. Not all mechanical parameters determined from pullout and toggle testing were statistically significant between the 3 screw/trajectory combinations. The incidence of cortical wall breach with the cortical or traditional pedicle screw trajectories was not significantly different. CONCLUSIONS The data demonstrated that the cortical trajectory provides denser bone that allows for utilization of smaller screws to obtain mechanical purchase that is equivalent to long pedicle screws placed in traditional pedicle screw trajectories for both normal- and low-quality bone. Overall, this biomechanical study in cadavers provides evidence that the cortical screw trajectory represents a good option to obtain fixation for the lumbar spine with low-quality bone.

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