Biomechanical Comparison of Vertebroplasty, Kyphoplasty, Vertebrae Stent for Osteoporotic Vertebral Compression Fractures—A Finite Element Analysis

Vertebroplasty (VP), balloon kyphoplasty (BKP), and vertebral stent (VS) are usually used for treating osteoporotic compression fractures. However, these procedures may pose risks of secondary adjacent level fractures. This study simulates finite element models of osteoporotic compression fractures treated with VP, BKP, and VS Vertebral resection method was used to simulate vertebra fracture with Young’s modulus set at 70 MPa to replicate osteoporosis. A follower load of (1175 N for flexion, and 500 N for all others) was applied in between vertebral bodies to simulate the muscle force. Moment loadings of 7.5 N-m in flexion, extension, lateral bending, axial rotation were applied respectively. The VS model had the highest von Mises stresses on the bone cement under all different loading conditions (flexion/5.91 MPa; extension/3.74 MPa; lateral bending/3.12 MPa; axial rotation/3.54 MPa). The stress distribution and maximum von Mises stresses of the adjacent segments, T11 inferior endplate and L1 superior endplate, showed no significant difference among three surgical models. The postoperative T12 stiffness for VP, BKP, and VS are 2898.48 N/mm, 4123.18 N/mm, and 4690.34 N/mm, respectively. The VS model led to superior surgical vertebra stiffness without significantly increasing the risks of adjacent fracture.

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Biomechanical Comparison of Vertbroplasty, Kyphoplasty, Vertebrae Stent for Osteoporotic Vertebral Compression Fractures -A Finite Element Analysis

10.21203/rs.3.rs-490557/v1 ◽

2021 ◽

Author(s):

Jen-Chung Liao ◽

Michael Jian-Wen Chen ◽

Tung-Yi Lin ◽

Weng-Pin Chen

Keyword(s):

Finite Element ◽

Body Height ◽

Compressive Force ◽

Axial Rotation ◽

Vertebral Compression Fractures ◽

Lateral Bending ◽

Compression Fractures ◽

Significant Difference ◽

Von Mises ◽

Von Mises Stresses

Abstract Vertebroplasty (VP), balloon kyphoplasty (BKP), and vertebral stent (VS) are usually used for osteoporotic compression fracture. However, these procedures may pose risks of secondary adjacent level fractures. This study simulates finite element models of osteoporotic compression fractures treated with VP, BKP, and VS. Vertebral resection method was used to simulate vertebra fracture with Young’s modulus set at 70 MPa to replicate osteoporosis. A compressive force of 1000N was applied on the T11 vertebra while the L1 vertebra were fully constrained as boundary condition. Moment loadings of 4.2 N-m in flexion, 1.0 N-m in extension, 2.6 N-m in lateral bending, and 3.4 N-m in axial rotation were applied. The VS model had the highest von Mises stresses on the bone cement under all different loading conditions (flexion/5.91 Mpa; extension/3.74 Mpa; lateral bending/3.12 Mpa; axial rotation/3.54 Mpa). The stress distribution and maximum von Mises stresses of the adjacent segments, T11 inferior endplate and L1 superior endplate, showed no significant difference among three surgical models. The postoperative T12 stiffness for VP, BKP, and VS are 2898.48 N/mm, 4123.18 N/mm, and 4690.34 N/mm, respectively. VS is the most effective surgical method to maintain vertebral body height without significantly increasing the risks of adjacent fracture.

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Design and development of a novel expanding flexible rod device (FRD) for stability in the lumbar spine: A finite-element study

The International Journal of Artificial Organs ◽

10.1177/0391398820917390 ◽

2020 ◽

Vol 43 (12) ◽

pp. 803-810 ◽

Cited By ~ 2

Author(s):

Masud Rana ◽

Sandipan Roy ◽

Palash Biswas ◽

Shishir Kumar Biswas ◽

Jayanta Kumar Biswas

Keyword(s):

Finite Element ◽

Lumbar Spine ◽

Range Of Motion ◽

Pedicle Screw ◽

Axial Rotation ◽

Von Mises Stress ◽

Lateral Bending ◽

Intact Bone ◽

Flexion Extension ◽

Von Mises

The aim of this study is to design a novel expanding flexible rod device, for pedicle screw fixation to provide dynamic stability, based on strength and flexibility. Three-dimensional finite-element models of lumbar spine (L1-S) with flexible rod device on L3-L4-L5 levels are developed. The implant material is taken to be Ti-6Al-4V. The models are simulated under different boundary conditions, and the results are compared with intact model. In natural model, total range of motion under 10 Nm moment were found 66.7°, 24.3° and 13.59°, respectively during flexion–extension, lateral bending and axial rotation. The von Mises stress at intact bone was 4 ± 2 MPa and at bone, adjacent to the screw in the implanted bone, was 6 ± 3 MPa. The von Mises stress of disc of intact bone varied from 0.36 to 2.13 MPa while that of the disc between the fixed vertebra of the fixation model reduced by approximately 10% for flexion and 25% for extension compared to intact model. The von Mises stresses of pedicle screw were 120, 135, 110 and 90 MPa during flexion, extension, lateral bending, and axial rotation, respectively. All the stress values were within the safe limit of the material. Using the flexible rod device, flexibility was significantly increased in flexion/extension but not in axial rotation and lateral bending. The results suggest that dynamic stabilization system with respect to fusion is more effective for homogenizing the range of motion of the spine.

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Finite element analysis of wedge and biconcave deformity in four different height restoration after augmentation of osteoporotic vertebral compression fractures

Journal of Orthopaedic Surgery and Research ◽

10.1186/s13018-021-02225-8 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Xiao-Hua Zuo ◽

Yin-Bing Chen ◽

Peng Xie ◽

Wen-Dong Zhang ◽

Xiang-Yun Xue ◽

...

Keyword(s):

Finite Element ◽

Three Dimensional ◽

Axial Rotation ◽

Vertebral Compression Fractures ◽

Neutral Position ◽

Element Analysis ◽

Flexion Extension ◽

Dimensional Finite Element ◽

Von Mises ◽

Three Dimensional Finite Element

Abstract Purpose Biomechanical comparison of wedge and biconcave deformity of different height restoration after augmentation of osteoporotic vertebral compression fractures was analyzed by three-dimensional finite element analysis (FEA). Methods Three-dimensional finite element model (FEM) of T11-L2 segment was constructed from CT scan of elderly osteoporosis patient. The von Mises stresses of vertebrae, intervertebral disc, facet joints, displacement, and range of motion (ROM) of wedge and biconcave deformity were compared at four different heights (Genant 0–3 grade) after T12 vertebral augmentation. Results In wedge deformity, the stress of T12 decreased as the vertebral height in neutral position, flexion, extension, and left axial rotation, whereas increased sharply in bending at Genant 0; L1 and L2 decreased in all positions excluding flexion of L2, and T11 increased in neutral position, flexion, extension, and right axial rotation at Genant 0. No significant changes in biconcave deformity. The stress of T11-T12, T12-L1, and L1-L2 intervertebral disc gradually increased or decreased under other positions in wedge fracture, whereas L1-L2 no significant change in biconcave fracture. The utmost overall facet joint stress is at Genant 3, whereas there is no significant change under the same position in biconcave fracture. The displacement and ROM of the wedge fracture had ups and downs, while a decline in all positions excluding extension in biconcave fracture. Conclusions The vertebral restoration height after augmentation to Genant 0 affects the von Mises stress, displacement, and ROM in wedge deformity, which may increase the risk of fracture, whereas restored or not in biconcave deformity.

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Biomechanical feasibility of semi-rigid stabilization and semi-rigid lumbar interbody fusion: a finite element study

BMC Musculoskeletal Disorders ◽

10.1186/s12891-021-04958-3 ◽

2022 ◽

Vol 23 (1) ◽

Author(s):

Chia-En Wong ◽

Hsuan-Teh Hu ◽

Li-Hsing Kao ◽

Che-Jung Liu ◽

Ke-Chuan Chen ◽

...

Keyword(s):

Finite Element ◽

Strain Energy ◽

Lumbar Fusion ◽

Axial Rotation ◽

Von Mises Stress ◽

Peek Cage ◽

Lateral Bending ◽

Interspinous Spacer ◽

Flexion Extension ◽

Von Mises

Abstract Background Semi-rigid lumbar fusion offers a compromise between pedicle screw-based rigid fixation and non-instrumented lumbar fusion. However, the use of semi-rigid interspinous stabilization (SIS) with interspinous spacer and ligamentoplasty and semi-rigid posterior instrumentation (SPI) to assist interbody cage as fusion constructs remained controversial. The purpose of this study is to investigate the biomechanical properties of semi-rigidly stabilized lumbar fusion using SIS or SPI and their effect on adjacent levels using finite element (FE) method. Method Eight FE models were constructed to simulate the lumbosacral spine. In the non-fusion constructs, semi-rigid stabilization with (i) semi-rigid interspinous spacer and artificial ligaments (PD-SIS), and (ii) PI with semi-rigid rods were simulated (PD + SPI). For fusion constructs, the spinal models were implanted with (iii) PEEK cage only (Cage), (iv) PEEK cage and SIS (Cage+SIS), (v) PEEK cage and SPI (Cage+SPI), (vi) PEEK cage and rigid PI (Cage+PI). Result The comparison of flexion-extension range of motion (ROM) in the operated level showed the difference between Cage+SIS, Cage+SPI, and Cage+PI was less than 0.05 degree. In axial rotation, ROM of Cage+SIS were greater than Cage+PI by 0.81 degree. In the infrajacent level, while Cage+PI increased the ROM by 24.1, 27,7, 25.9, and 10.3% and Cage+SPI increased the ROM by 26.1, 30.0, 27.1, and 10.8% in flexion, extension, lateral bending and axial rotation respectively, Cage+SIS only increased the ROM by 3.6, 2.8, and 11.2% in flexion, extension, and lateral bending and reduced the ROM by 1.5% in axial rotation. The comparison of the von Mises stress showed that SIS reduced the adjacent IVD stress by 9.0%. The simulation of the strain energy showed a difference between constructs less than 7.9%, but all constructs increased the strain energy in the infradjacent level. Conclusion FE simulation showed semi-rigid fusion constructs including Cage+SIS and Cage+SPI can provide sufficient stabilization and flexion-extension ROM reduction at the fusion level. In addition, SIS-assisted fusion resulted in less hypermobility and less von Mises stress in the adjacent levels. However, SIS-assisted fusion had a disadvantage of less ROM reduction in lateral bending and axial rotation. Further clinical studies are warranted to investigate the clinical efficacy and safety of semi-rigid fusions.

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Rod Stress Prediction in Spinal Alignment Surgery With Different Supplementary Rod Constructing Techniques: A Finite Element Study

Volume 1B: 38th Computers and Information in Engineering Conference ◽

10.1115/detc2018-85601 ◽

2018 ◽

Author(s):

Ming Xu ◽

Thomas Scholl ◽

Pedro Berjano ◽

Jazmin Cruz ◽

James Yang

Keyword(s):

Finite Element ◽

Contact Region ◽

Element Model ◽

Axial Rotation ◽

Von Mises Stress ◽

Lateral Bending ◽

Flexion Extension ◽

Single Cross ◽

Von Mises ◽

Double Cross

Rod fracture and nonunion are common complications associated with pedicle subtraction osteotomies (PSO). Supplementary rods and interbody cage (IB) are added to reduce the primary rod stress. As supplementary rods, delta rods and cross rods have been proposed to reduce more stress on the primary rods compared to conventional supplementary rods (accessary rods) in PSO. The objective of this study is to investigate the effects of cross rods and delta rods on reducing primary rod stress in PSO subject. A validated 3D finite element model of a T12-S1 spine segment with 25° PSO at L3 and bilateral rods fixation from T12-S1 was used to compare different rod configurations: 1) PSO and two primary rods (PSO+2P); 2) PSO with an IB at L2-L3 (PSO+2P+IB); 3) PSO with accessory rods and an IB at L2-L3 (PSO+2P+IB+2A); 4) PSO with delta rods and an IB at L2-L3 (PSO+2P+IB+2D); 5) PSO with single cross rod and an IB at L2-L3 (PSO+2P+IB+1C); 6) PSO with double cross rods and an IB at L2-L3 (PSO+2P+IB+2C). The spine model was loaded with a follower load of 400 N combined with pure moments of 7.5 Nm in flexion, extension, right lateral bending, and right axial rotation. Von Mises stress of the primary rods were predicted for all test conditions. The PSO without IB condition had the largest primary rod stress in flexion. With IB at L2-L3, the rod stress in flexion reduced by 15%. Adding 2 conventional supplementary rods reduced the rod stress in flexion by 29%, which was achieved by adding single cross rod. The maximum von Mises stress occurred in the middle of the primary rods without supplementary rods whereas the maximum stress concentrated adjacent to the contact region between the connectors and the primary rods. Delta rods and double cross rods reduced the most rod stress in flexion, which were by 33% and 32% respectively. Under lateral bending, 2 delta rods reduced the most primary rod stress (−33%). Under axial rotation, the single cross rod reduced the most primary rod stress (−48%). Interbody cages and supplementary rods reduced the primary rod stress in a comparable way. Primary rod stress with 2 delta rods and double cross rods were comparable, which were marginally lower than those with conventional supplementary rods. Adding single cross rod was comparable to adding 2 conventional accessory rods in rod stress reduction in flexion. Under lateral bending, delta rods reduced most rod stress whereas under axial rotation, cross rods reduced most rod stress. This study suggested that both delta rods and cross rods reduce more primary rod stress than conventional accessory rods do.

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How the height and the area of the annulus fibrosus affect the range of motion behavior: A stochastic analysis

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420718805896 ◽

2018 ◽

Vol 233 (10) ◽

pp. 1985-1992

Author(s):

Héctor E Jaramillo S

Keyword(s):

Finite Element ◽

Range Of Motion ◽

Annulus Fibrosus ◽

Element Model ◽

Axial Rotation ◽

Disc Height ◽

Lateral Bending ◽

Analytic Equation ◽

Geometrical Properties ◽

Flexion Extension

The annulus fibrosus has substantial variations in its geometrical properties (among individuals and between levels), and plays an important role in the biomechanics of the spine. Few works have studied the influence of the geometrical properties including annulus area, anterior / posterior disc height, and over the range of motion, but in general these properties have not been reported in the finite element models. This paper presents a probabilistic finite element analyses (Abaqus 6.14.2) intended to assess the effects of the average disc height ( hp) and the area ( A) of the annulus fibrosus on the biomechanics of the lumbar spine. The annulus model was loaded under flexion, extension, lateral bending, and axial rotation and analyzed for different combinations of hpand A in order to obtain their effects over the range of motion. A set of 50 combinations of hp(mean = 18.1 mm, SD = 3.5 mm) and A (mean = 49.8%, SD = 4.6%) were determined randomly according to a normal distribution. A Yeoh energy function was used for the matrix and an exponential function for the fibers. The range of motion was more sensitive to hpthan to A. With regard to the range of motion the segment was more sensitive in the following order: flexion, axial rotation, extension, and lateral bending. An increase of the hpproduces an increase of the range of motion, but this decreases when A increases. Comparing the range of motion with the experimental data, on average, 56.0% and 73.0% of the total of data were within the experimental range for the L4–L5 and L5–S1 segments, respectively. Further, an analytic equation was derived to obtain the range of motion as a function of the hpand A. This equation can be used to calibrate a finite element model of the spine segment, and also to understand the influence of each geometrical parameter on the range of motion.

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Design of a Dynamic Stabilization Spine Implant

Journal of Medical Devices ◽

10.1115/1.3147482 ◽

2009 ◽

Vol 3 (2) ◽

Author(s):

J. Bryndza ◽

A. Weiser ◽

M. Paliwal

Keyword(s):

Finite Element ◽

Range Of Motion ◽

Mechanical Testing ◽

Computational Analysis ◽

Axial Rotation ◽

Dynamic Stabilization ◽

Facet Joints ◽

Lateral Bending ◽

Functional Spinal Unit ◽

Flexion Extension

Arthritis, degenerative disc disease, spinal stenosis, and other ailments lead to the deterioration of the facet joints of the spine, causing pain and immobility in patients. Dynamic stabilization and arthroplasty of the facet joints have advantages over traditional fusion methods by eliminating pain while maintaining normal mobility and function. In the present work, a novel dynamic stabilization spine implant design was developed using computational analysis, and the final design was fabricated and mechanically tested. A model of a fused L4–L5 Functional Spinal Unit (FSU) was developed using Pro/Engineer (PTC Corporation, Needham, MA). The model was imported into commercial finite element analysis software Ansys (Ansys Inc., Canonsburg, PA), and meshed with the material properties of bone, intervertebral disc, and titanium alloy. Physiological loads (600N axial load, 10 N-m moment) were applied to the model construct following the protocol developed by others. The model was subjected to flexion/extension, axial rotation, and lateral bending, and was validated with the results reported by Kim et al. The validated FSU was used as a base to design and evaluate novel spine implant designs, using finite element anlysis. A comparison of the flexion-extension curve of six designs and an intact spine was carried out. Range of motion of the new designs showed up to 4 degrees in flexion and extension, compared to less than one degree flexion/extension in a fused spine. The design that reproduced normal range of motion best was optimized, fabricated and prepared for mechanical testing. The finalized dynamic stabilization design with spring insert was implanted into a L4-L5 FSU sawbone (Pacific Research Laboratories, Vashon, WA) using Stryker Xia pedicle screws. The construct was potted using PMMA, and was subjected to flexion/extension, axial rotation, and lateral bending loads using MTS mechanical testing machine. The stiffness of the design was assessed and compared with computational analysis results.

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Development and initial evaluation of a finite element model of the pediatric craniocervical junction

Journal of Neurosurgery Pediatrics ◽

10.3171/2015.8.peds15334 ◽

2016 ◽

Vol 17 (4) ◽

pp. 497-503 ◽

Cited By ~ 6

Author(s):

Rinchen Phuntsok ◽

Marcus D. Mazur ◽

Benjamin J. Ellis ◽

Vijay M. Ravindra ◽

Douglas L. Brockmeyer

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Material Properties ◽

Element Model ◽

Axial Rotation ◽

Craniocervical Junction ◽

Lateral Bending ◽

Fem Method ◽

Flexion Extension ◽

Ligament Stiffness

OBJECT There is a significant deficiency in understanding the biomechanics of the pediatric craniocervical junction (CCJ) (occiput–C2), primarily because of a lack of human pediatric cadaveric tissue and the relatively small number of treated patients. To overcome this deficiency, a finite element model (FEM) of the pediatric CCJ was created using pediatric geometry and parameterized adult material properties. The model was evaluated under the physiological range of motion (ROM) for flexion-extension, axial rotation, and lateral bending and under tensile loading. METHODS This research utilizes the FEM method, which is a numerical solution technique for discretizing and analyzing systems. The FEM method has been widely used in the field of biomechanics. A CT scan of a 13-month-old female patient was used to create the 3D geometry and surfaces of the FEM model, and an open-source FEM software suite was used to apply the material properties and boundary and loading conditions and analyze the model. The published adult ligament properties were reduced to 50%, 25%, and 10% of the original stiffness in various iterations of the model, and the resulting ROMs for flexion-extension, axial rotation, and lateral bending were compared. The flexion-extension ROMs and tensile stiffness that were predicted by the model were evaluated using previously published experimental measurements from pediatric cadaveric tissues. RESULTS The model predicted a ROM within 1 standard deviation of the published pediatric ROM data for flexion-extension at 10% of adult ligament stiffness. The model's response in terms of axial tension also coincided well with published experimental tension characterization data. The model behaved relatively stiffer in extension than in flexion. The axial rotation and lateral bending results showed symmetric ROM, but there are currently no published pediatric experimental data available for comparison. The model predicts a relatively stiffer ROM in both axial rotation and lateral bending in comparison with flexion-extension. As expected, the flexion-extension, axial rotation, and lateral bending ROMs increased with the decrease in ligament stiffness. CONCLUSIONS An FEM of the pediatric CCJ was created that accurately predicts flexion-extension ROM and axial force displacement of occiput–C2 when the ligament material properties are reduced to 10% of the published adult ligament properties. This model gives a reasonable prediction of pediatric cervical spine ligament stiffness, the relationship between flexion-extension ROM, and ligament stiffness at the CCJ. The creation of this model using open-source software means that other researchers will be able to use the model as a starting point for research.

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Finite element analysis of wedge and biconcave deformity in four different height restoration after augmentation of osteoporotic vertebral compression fracture

10.21203/rs.3.rs-38291/v1 ◽

2020 ◽

Author(s):

Xiao-Hua Zuo ◽

Ying-Bing Chen ◽

Peng Xie ◽

Wen-Dong Zhang ◽

Xiang-Yun Xue ◽

...

Keyword(s):

Finite Element ◽

Three Dimensional ◽

Axial Rotation ◽

Neutral Position ◽

Element Analysis ◽

Flexion Extension ◽

Dimensional Finite Element ◽

Von Mises ◽

Three Dimensional Finite Element ◽

Wedge Fracture

Abstract Purpose Biomechanical comparison of wedge and biconcave deformity of different height restoration after augmentation of osteoporotic vertebral compression fractures was analyzed by three-dimensional finite element analysis (FEA). Methods Three-dimensional finite element model (FEM) of T11-L2 segment was constructed from CT scan of elderly osteoporosis patient. The von Mises stresses of vertebrae, intervertebral disc, facet joints, displacement, and range of motion (ROM) of wedge and biconcave deformity were compared at four different heights (Genant 0–3 grade) after T12 vertebral augmentation. Results In wedge deformity, the stress of T12 decreased as the vertebral height in neutral position, flexion, extension and left axial rotation, whereas increased sharply in bending at Genant 0; L1 and L2 decreased in all positions excluding flexion of L2, and T11 increased in neutral position, flexion, extension, and right axial rotation at Genant 0. No significant changes in biconcave deformity. The stress of T11-T12, T12-L1, and L1-L2 intervertebral disc gradually increased or decreased under other positions in wedge fracture, whereas L1-L2 no significant change in biconcave fracture. The utmost overall facet joint stress is at Genant 3, whereas there is no significant change under the same position in biconcave fracture. The displacement and ROM of the wedge fracture had ups and downs, while a decline in all positions excluding extension in biconcave fracture. Conclusions The vertebral restoration height after augmentation to Genant 0 affects the von Mises stress, displacement, and ROM in wedge deformity, which may increase the risk of fracture; Whereas restored or not in biconcave deformity.

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Biomechanical analysis of occipitocervical stabilization techniques: emphasis on integrity of osseous structures at the occipital implantation sites

Journal of Neurosurgery Spine ◽

10.3171/2020.1.spine191331 ◽

2020 ◽

Vol 33 (2) ◽

pp. 138-147

Author(s):

Bryan W. Cunningham ◽

Kyle B. Mueller ◽

Kenneth P. Mullinix ◽

Xiaolei Sun ◽

Faheem A. Sandhu

Keyword(s):

Fatigue Testing ◽

Plate Fixation ◽

Axial Rotation ◽

Biomechanical Analysis ◽

Lateral Bending ◽

Mineral Density ◽

Plate Group ◽

Significant Difference ◽

Flexion Extension ◽

Implantation Sites

OBJECTIVEThe objective of the current study was to quantify and compare the multidirectional flexibility properties of occipital anchor fixation with conventional methods of occipitocervical screw fixation using nondestructive and destructive investigative methods.METHODSFourteen cadaveric occipitocervical specimens (Oc–T2) were randomized to reconstruction with occipital anchors or an occipital plate and screws. Using a 6-degree-of-freedom spine simulator with moments of ± 2.0 Nm, initial multidirectional flexibility analysis of the intact and reconstructed conditions was performed followed by fatigue loading of 25,000 cycles of flexion-extension (x-axis, ± 2.0 Nm), 15,000 cycles of lateral bending (z-axis, ± 2.0 Nm), and 10,000 cycles of axial rotation (y-axis, ± 2.0 Nm). Fluoroscopic images of the implantation sites were obtained before and after fatigue testing and placed on an x-y coordinate system to quantify positional stability of the anchors and screws used for reconstruction and effect, if any, of the fatigue component. Destructive testing included an anterior flexural load to construct failure. Quantification of implant, occipitocervical, and atlantoaxial junction range of motion is reported as absolute values, and peak flexural failure moment in Newton-meters (Nm).RESULTSAbsolute value comparisons between the intact condition and 2 reconstruction groups demonstrated significant reductions in segmental flexion-extension, lateral bending, and axial rotation motion at the Oc–C1 and C1–2 junctions (p < 0.05). The average bone mineral density at the midline keel (1.422 g/cm3) was significantly higher compared with the lateral occipital region at 0.671 g/cm3 (p < 0.05). There were no significant differences between the occipital anchor and plate treatments in terms of angular rotation (degrees; p = 0.150) or x-axis displacement (mm; p = 0.572), but there was a statistically significant difference in y-axis displacement (p = 0.031) based on quantitative analysis of the pre- and postfatigue fluoroscopic images (p > 0.05). Under destructive anterior flexural loading, the occipital anchor group failed at 90 ± 31 Nm, and the occipital plate group failed at 79 ± 25 Nm (p > 0.05).CONCLUSIONSBoth reconstructions reduced flexion-extension, lateral bending, and axial rotation at the occipitocervical and atlantoaxial junctions, as expected. Flexural load to failure did not differ significantly between the 2 treatment groups despite occipital anchors using a compression-fit mechanism to provide fixation in less dense bone. These data suggest that an occipital anchor technique serves as a biomechanically viable clinical alternative to occipital plate fixation.

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