A biomechanical comparison of three anterior thoracolumbar implants after corpectomy: are two screws better than one?

Object A flexibility experiment using human cadaveric thoracic spine specimens was performed to determine biomechanical differences among thoracolumbar two-screw plate, single-screw plate, and dual-rod systems. A secondary goal was to investigate differences in the ability of the systems to stabilize the spine after a one- or two-level corpectomy. Methods The authors evaluated 21 cadaveric spines implanted with a titanium mesh cage and three types of anterior thoracolumbar supplementary instrumentation after one-level thoracic corpectomies. Pure moments were applied quasistatically while three-dimensional motion was measured optoelectronically. The lax zone, stiff zone, and range of motion (ROM) were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Corpectomies were expanded to two levels, and testing was repeated with longer hardware. Biomechanical testing showed that the single-bolt plate system was no different from the dual-rod system with two screws in limiting ROM. The single-bolt plate system performed slightly better than the two-screw plate system. Across the same two levels, there was an average of 19% more motion after a two-level corpectomy than after a one-level corpectomy. In general, however, the difference across the different loading modes was insignificant. Conclusions Biomechanically, the single-screw plate system is equivalent to a two-screw dual-rod and a two-screw plate system. All three systems performed similarly in stabilizing the spine after one- or two-level corpectomies.

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Biomechanical Model for Testing Cage Subsidence in the Osteoporotic Spine Under Permanent Maximum Load

10.21203/rs.3.rs-107903/v1 ◽

2020 ◽

Author(s):

Stefan Schleifenbaum ◽

Robin Heilmann ◽

Riemer Elena ◽

Rebekka Reise ◽

Christoph-Eckhard Heyde ◽

...

Keyword(s):

Biomechanical Testing ◽

Biomechanical Model ◽

Primary Stability ◽

Maximum Load ◽

Axial Rotation ◽

Point Of View ◽

Force Transmission ◽

Flexion Extension ◽

Cage Subsidence ◽

Rod System

Abstract BackgroundFusions in cases of reduced bone density are a tough challenge. As not only does bone quality have an influence on force transmission, these forces must be bridged for much longer time, as a fusion takes longer than in bone-healthy patients. However, cage subsidence or displacement results to loss of reposition and pain. From a biomechanical point of view, the majority of current studies have focussed on the range of motion or have shown test setups for single component tests. Definite setups for biomechanical testing of the primary stability of a 360° fusion using a screw rod system and cage on the osteoporotic spine are missing. The aim of this study is to develop a test stand to provide information about the bone-implant interface under reproducible conditions.MethodsAfter pre-testing with artificial bone, human functional spine units were tested with 360° fusion in TLIF technique. The movement sequences was conducted in flexion, extension, right-left lateral bending and right-left axial rotation on an osteoporotic human model.ResultsDuring the testings of human cadavers, 4 vertebrae were fully tested and were inconspicuous even after radiological and macroscopic examination. 1 vertebra showed a subsidence of 2mm and 1 vertebra had a cage collapsed into the vertebra.ConclusionsThis setup is suitable for biomechanical testing of cyclical continuous loads on the osteoporotic spine. The embedding method is stable and ensures a purely monosegmental setup. The optical monitoring provides a very accurate indication of cage movement, which correlates with the macroscopic and radiological results.

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In Vitro Biomechanical Analysis of a New Lumbar Low-Profile Locking Screw-Plate Construct Versus a Standard Top-Loading Cantilevered Pedicle Screw-Rod Construct

Neurosurgery ◽

10.1227/01.neu.0000363701.76835.bf ◽

2010 ◽

Vol 66 (2) ◽

pp. E404-E406 ◽

Cited By ~ 7

Author(s):

Neil R. Crawford ◽

Şeref Doğan ◽

K. Zafer Yüksel ◽

Octavio Villasana-Ramos ◽

Julio C. Soto-Barraza ◽

...

Keyword(s):

Range Of Motion ◽

Pedicle Screw ◽

Axial Rotation ◽

Biomechanical Analysis ◽

Posterior Fixation ◽

Low Profile ◽

Flexion Extension ◽

Rod System ◽

Plate System

Abstract OBJECTIVE A standard top-loading lumbar pedicle screw-rod system is compared with a pedicle screw-plate system with smaller-diameter screws, more medial entry, and lower profile to assess the relative stability, strength, and resistance to fatigue of the 2 systems. METHODS Seven human cadaveric specimens were studied with each surgical construct. Nondestructive, nonconstraining pure moments were applied to specimens to induce flexion, extension, lateral bending, and axial rotation while recording L5–S1 motion optoelectronically. After initial tests, specimens were fatigued for 10 000 cycles and retested to assess early postoperative loosening. Specimens were then loaded to failure in hyperextension. RESULTS The standard screw-rod construct reduced range of motion to a mean of 20% of normal, whereas the screw-plate construct reduced range of motion to 13% of normal. Differences between systems were not significant in any loading mode (P > 0.06). The 14% loosening of the screw-rod system with fatigue was not significantly different from the 10% loosening observed with the screw-plate system (P > 0.15). Mean failure loads of 30 Nm for screw-rod and 37 Nm for screw-plate were also not significantly different (P = 0.38). CONCLUSION Posterior fixation at L5–S1 using the low-profile screw-plate system offers stability, resistance to fatigue, and resistance to failure equivalent to fixation using a standard cantilevered pedicle screw-rod system.

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Kinematics and Laxity of Ulnohumeral Joint Under Valgus-Varus Stress

Journal of Musculoskeletal Research ◽

10.1142/s021895779800007x ◽

1998 ◽

Vol 02 (01) ◽

pp. 45-54 ◽

Cited By ~ 39

Author(s):

Shinji Tanaka ◽

Kai-Nan An ◽

Bernard F. Morrey

Keyword(s):

Elbow Joint ◽

Three Dimensional ◽

Elbow Flexion ◽

Axial Rotation ◽

Joint Laxity ◽

Treatment Modalities ◽

Trochlear Groove ◽

Flexion Extension ◽

Varus Stress ◽

Baseline Information

Three-dimensional kinematics of the ulnohumeral joint under simulated active elbow joint flexion-extension was obtained by using an electromagnetic tacking device. The joint motion was analyzed based on Eulerian angle description. In order to minimize the effect of "downstream cross-talk" on calculation of the three Eulerian angles, an optimal axis to best represent flexion-extension of the elbow joint was established. This axis, on average, is close to the line joining the centers of the capitellum and the trochlear groove. Furthermore, joint laxity under valgus-varus stress was also examined. With the weight of the forearm as the stress, maximums of 7.6° valgus-varus laxity and 5.3° axial rotation laxity were observed within a range of elbow flexion. The results of this study provide useful baseline information on joint laxity for the evaluation of elbow joints with implant replacements and other surgical treatment modalities.

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Biomechanical Analysis of Allograft Spacer Failure as a Function of Cortical-Cancellous Ratio in Anterior Cervical Discectomy/Fusion: Allograft Spacer Alone Model

Applied Sciences ◽

10.3390/app10186413 ◽

2020 ◽

Vol 10 (18) ◽

pp. 6413

Author(s):

Ji-Won Kwon ◽

Hwan-Mo Lee ◽

Tae-Hyun Park ◽

Sung Jae Lee ◽

Young-Woo Kwon ◽

...

Keyword(s):

Three Dimensional ◽

Element Model ◽

Axial Rotation ◽

Biomechanical Analysis ◽

Flexion Extension ◽

Hybrid Motion ◽

Anterior Cervical Discectomy Fusion ◽

Flexion And Extension ◽

Additional Fixation ◽

Lateral Walls

The design and ratio of the cortico-cancellous composition of allograft spacers are associated with graft-related problems, including subsidence and allograft spacer failure. Methods: The study analyzed stress distribution and risk of subsidence according to three types (cortical only, cortical cancellous, cortical lateral walls with a cancellous center bone) and three lengths (11, 12, 14 mm) of allograft spacers under the condition of hybrid motion control, including flexion, extension, axial rotation, and lateral bending,. A detailed finite element model of a previously validated, three-dimensional, intact C3–7 segment, with C5–6 segmental fusion using allograft spacers without fixation, was used in the present study. Findings: Among the three types of cervical allograft spacers evaluated, cortical lateral walls with a cancellous center bone exhibited the highest stress on the cortical bone of spacers, as well as the endplate around the posterior margin of the spacers. The likelihood of allograft spacer failure was highest for 14 mm spacers composed of cortical lateral walls with a cancellous center bone upon flexion (PVMS, 270.0 MPa; 250.2%) and extension (PVMS: 371.40 MPa, 344.2%). The likelihood of allograft spacer subsidence was also highest for the same spacers upon flexion (PVMS, 4.58 MPa; 28.1%) and extension (PVMS: 12.71 MPa, 78.0%). Conclusion: Cervical spacers with a smaller cortical component and of longer length can be risk factors for allograft spacer failure and subsidence, especially in flexion and extension. However, further study of additional fixation methods, such as anterior plates/screws and posterior screws, in an actual clinical setting is necessary.

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The 6-Plus–Person Lift Transfer Technique Compared With Other Methods of Spine Boarding

Journal of Athletic Training ◽

10.4085/1062-6050-43.1.6 ◽

2008 ◽

Vol 43 (1) ◽

pp. 6-13 ◽

Cited By ~ 47

Author(s):

Gianluca Del Rossi ◽

Mary Beth H. Horodyski ◽

Bryan P. Conrad ◽

Christian P. Di Paola ◽

Matthew J. Di Paola ◽

...

Keyword(s):

Spinal Injury ◽

Three Dimensional ◽

Axial Rotation ◽

Linear Displacement ◽

Angular Motion ◽

Spinal Segment ◽

Spinal Motion ◽

Spinal Immobilization ◽

Flexion Extension ◽

Spine Board

Abstract Context: To achieve full spinal immobilization during on-the-field management of an actual or potential spinal injury, rescuers transfer and secure patients to a long spine board. Several techniques can be used to facilitate this patient transfer. Objective: To compare spinal segment motion of cadavers during the execution of the 6-plus–person (6+) lift, lift-and-slide (LS), and logroll (LR) spine-board transfer techniques. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Eight medical professionals (1 woman, 7 men) with 5 to 32 years of experience were enlisted to help carry out the transfer techniques. In addition, test conditions were performed on 5 fresh cadavers (3 males, 2 females) with a mean age of 86.2 ± 11.4 years. Main Outcomes Measure(s): Three-dimensional angular and linear motions initially were recorded during execution of transfer techniques, initially using cadavers with intact spines and then after C5-C6 spinal segment destabilization. The mean maximal linear displacement and angular motion obtained and calculated from the 3 trials for each test condition were included in the statistical analysis. Results: Flexion-extension angular motion, as well as anteroposterior and distraction-compression linear motion, did not vary between the LR and either the 6+ lift or LS. Compared with the execution of the 6+ lift and LS, the execution of the LR generated significantly more axial rotation (P = .008 and .001, respectively), more lateral flexion (P = .005 and .003, respectively), and more medial-lateral translation (P = .003 and .004, respectively). Conclusions: A small amount of spinal motion is inevitable when executing spine-board transfer techniques; however, the execution of the 6+ lift or LS appears to minimize the extent of motion generated across a globally unstable spinal segment.

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FINITE ELEMENT MODELING OF HUMAN THORACIC SPINE

Journal of Musculoskeletal Research ◽

10.1142/s0218957704001302 ◽

2004 ◽

Vol 08 (04) ◽

pp. 133-144 ◽

Cited By ~ 3

Author(s):

Tian-Xia Qiu ◽

Ee-Chon Teo

Keyword(s):

Finite Element ◽

Thoracic Spine ◽

Three Dimensional ◽

Axial Rotation ◽

Torsional Stiffness ◽

Fe Model ◽

Thoracic Vertebrae ◽

Fundamental Information ◽

Flexion Extension ◽

Scoliosis Correction

Mathematical models, which can accurately represent the geometric, material and physical characteristics of the human spine structure, are useful in predicting biomechanical behaviors of the spine. In this study, a three-dimensional finite element (FE) model of thoracic spine (T1–T12) was developed, based on geometrical data of embalmed thoracic vertebrae (T1–T12) obtained from a precise flexible digitizer, and validated against published thoracolumbar experimental results in terms of the torsional stiffness of the whole thoracic spine (T1–T12) under axial torque alone and combined with distraction and compression loads. The torsional stiffness was increased by over 60% with application of a 425 N distraction force. A trend in increasing torsional stiffness with increasing distraction forces was detected. The validated model was then loaded under moment rotation in three anatomical planes to determine the ranges of motion (ROMs). The ROMs were approximately 37°, 31°, 32°, 51° for flexion, extension, lateral bending and axial rotation, respectively. These results may offer an insight to better understanding the kinematics of the human thoracic spine and provide clinically relevant fundamental information for the evaluation of spinal stability and instrumented devices functionality for optimal scoliosis correction.

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Biomechanical analysis of Goel technique for C1–2 fusion

Journal of Neurosurgery Spine ◽

10.3171/2011.1.spine10446 ◽

2011 ◽

Vol 14 (5) ◽

pp. 639-646 ◽

Cited By ~ 27

Author(s):

Jon Park ◽

Justin K. Scheer ◽

T. Jesse Lim ◽

Vedat Deviren ◽

Christopher P. Ames

Keyword(s):

Motion Tracking ◽

Tracking System ◽

Testing Machine ◽

Pedicle Screws ◽

Axial Rotation ◽

Biomechanical Analysis ◽

Lateral Bending ◽

Flexion Extension ◽

Rod System ◽

Harms Technique

Object The Goel technique, in which C1–2 intraarticular spacers are used, may be performed to restore stability to a disrupted atlantoaxial complex in conjunction with the Harms technique of placing polyaxial screws and bilateral rods. However, it has yet to be determined biomechanically whether the addition of the C1–2 joint spacers increases the multiaxial rigidity of the fixation construct. The goal of this study was to quantify changes in multiaxial rigidity of the combined Goel-Harms technique with the addition of C1–2 intraarticular spacers. Methods Seven cadaveric cervical spines (occiput–C2) were submitted to nondestructive flexion-extension, lateral bending, and axial rotation tests in a material testing machine spine tester. The authors applied 1.5 Nm at a rate of 0.1 Nm/second and held it constant for 10 seconds. The specimens were loaded 3 times, and data were collected on the third cycle. Testing of the specimens was performed for the following groups: 1) intact (I); 2) with the addition of C-1 lateral mass/C-2 pedicle screws and rod system (I+SR); 3) with C1–2 joint capsule incision, decortication (2 mm on top and bottom of each joint [that is, the C-1 and C-2 surface) and addition of bilateral C1–2 intraarticular spacers at C1–2 junction to the screws and rods (I+SR+C); 4) after removal of the posterior rods and only the bilateral spacers in place (I+C); 5) after removal of spacers and further destabilization with simulated odontoidectomy for a completely destabilized case (D); 6) with addition of posterior rods to the destabilized case (D+SR); and 7) with addition of bilateral C1–2 intraarticular spacers at C1–2 junction to the destabilized case (D+SR+C). The motion of C-1 was measured by a 3D motion tracking system and the motion of C-2 was measured by the rotational sensor of the testing system. The range of motion (ROM) and neutral zone (NZ) across C-1 and C-2 were evaluated. Results For the intact spine test groups, the addition of screws/rods (I+SR) and screws/rods/cages (I+SR+C) significantly reduced ROM and NZ compared with the intact spine (I) for flexion-extension and axial rotation (p < 0.05) but not lateral bending (p > 0.05). The 2 groups were not significantly different from each other in any bending mode for ROM and NZ, but in the destabilized condition the addition of screws/rods (D+SR) and screws/rods/cages (D+SR+C) significantly reduced ROM and NZ compared with the destabilized spine (D) in all bending modes (p < 0.05). Furthermore, the addition of the C1–2 intraarticular spacers (D+SR+C) significantly reduced ROM (flexion-extension and axial rotation) and NZ (lateral bending) compared with the screws and rods alone (D+SR). Conclusions Study result indicated that both the Goel and Harms techniques alone and with the addition of the C1–2 intraarticular spacers to the Goel-Harms technique are advantageous for stabilizing the atlantoaxial segment. The Goel technique combined with placement of a screw/rod construct appears to result in additional construct rigidity beyond the screw/rod technique and appears to be more useful in very unstable cases.

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Biomechanical Assessment of a PEEK Rod System for Semi-Rigid Fixation of Lumbar Fusion Constructs

Journal of Biomechanical Engineering ◽

10.1115/1.4004862 ◽

2011 ◽

Vol 133 (8) ◽

Cited By ~ 42

Author(s):

Matthew F. Gornet ◽

Frank W. Chan ◽

John C. Coleman ◽

Brian Murrell ◽

Russ P. Nockels ◽

...

Keyword(s):

Lumbar Fusion ◽

Dynamic Performance ◽

Load Sharing ◽

Axial Rotation ◽

Rigid Fixation ◽

Peek Rods ◽

Significant Difference ◽

Flexion Extension ◽

Rod System

The concept of semi-rigid fixation (SRF) has driven the development of spinal implants that utilize nonmetallic materials and novel rod geometries in an effort to promote fusion via a balance of stability, intra- and inter-level load sharing, and durability. The purpose of this study was to characterize the mechanical and biomechanical properties of a pedicle screw-based polyetheretherketone (PEEK) SRF system for the lumbar spine to compare its kinematic, structural, and durability performance profile against that of traditional lumbar fusion systems. Performance of the SRF system was characterized using a validated spectrum of experimental, computational, and in vitro testing. Finite element models were first used to optimize the size and shape of the polymeric rods and bound their performance parameters. Subsequently, benchtop tests determined the static and dynamic performance threshold of PEEK rods in relevant loading modes (flexion-extension (F/E), axial rotation (AR), and lateral bending (LB)). Numerical analyses evaluated the amount of anteroposterior column load sharing provided by both metallic and PEEK rods. Finally, a cadaveric spine simulator was used to determine the level of stability that PEEK rods provide. Under physiological loading conditions, a 6.35 mm nominal diameter oval PEEK rod construct unloads the bone-screw interface and increases anterior column load (approx. 75% anterior, 25% posterior) when compared to titanium (Ti) rod constructs. The PEEK construct’s stiffness demonstrated a value lower than that of all the metallic rod systems, regardless of diameter or metallic composition (78% < 5.5 mm Ti; 66% < 4.5 mm Ti; 38% < 3.6 mm Ti). The endurance limit of the PEEK construct was comparable to that of clinically successful metallic rod systems (135N at 5 × 106 cycles). Compared to the intact state, cadaveric spines implanted with PEEK constructs demonstrated a significant reduction of range of motion in all three loading directions (> 80% reduction in F/E, p < 0.001; > 70% reduction in LB, p < 0.001; > 54% reduction in AR, p < 0.001). There was no statistically significant difference in the stability provided by the PEEK rods and titanium rods in any mode (p = 0.769 for F/E; p = 0.085 for LB; p = 0.633 for AR). The CD HORIZON® LEGACY™ PEEK Rod System provided intervertebral stability comparable to currently marketed titanium lumbar fusion constructs. PEEK rods also more closely approximated the physiologic anteroposterior column load sharing compared to results with titanium rods. The durability, stability, strength, and biomechanical profile of PEEK rods were demonstrated and the potential advantages of SRF were highlighted.

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In vitro evaluation of a lateral expandable cage and its comparison with a static device for lumbar interbody fusion: a biomechanical investigation

Journal of Neurosurgery Spine ◽

10.3171/2013.12.spine13798 ◽

2014 ◽

Vol 20 (4) ◽

pp. 387-395 ◽

Cited By ~ 8

Author(s):

Sabrina A. Gonzalez-Blohm ◽

James J. Doulgeris ◽

Kamran Aghayev ◽

William E. Lee ◽

Jake Laun ◽

...

Keyword(s):

Pedicle Screw ◽

Haptic Feedback ◽

Biomechanical Testing ◽

Axial Rotation ◽

Pedicle Screw Fixation ◽

Interbody Cage ◽

Disc Space ◽

Significance Level ◽

Flexion Extension

Object Through in vitro biomechanical testing, the authors compared the performance of a vertically expandable lateral lumbar interbody cage (EC) under two different torque-controlled expansions (1.5 and 3.0 Nm) and with respect to an equivalent lateral lumbar static cage (SC) with and without pedicle screw fixation. Methods Eleven cadaveric human L2–3 segments were evaluated under the following conditions: 1) intact; 2) discectomy; 3) EC under 1.50 Nm of torque expansion (EC-1.5Nm); 4) EC under 3.00 Nm of torque expansion (EC-3.0Nm); 5) SC; and 6) SC with a bilateral pedicle screw system (SC+BPSS). Load-displacement behavior was evaluated for each condition using a combination of 100 N of axial preload and 7.5 Nm of torque in flexion and extension (FE), lateral bending (LB), and axial rotation (AR). Range of motion (ROM), neutral zone stiffness (NZS), and elastic zone stiffness (EZS) were statistically compared among conditions using post hoc Wilcoxon signed-rank comparisons after Friedman tests, with a significance level of 0.05. Additionally, any cage height difference between interbody devices was evaluated. When radiographic subsidence was observed, the specimen's data were not considered for the analysis. Results The final cage height in the EC-1.5Nm condition (12.1 ± 0.9 mm) was smaller (p < 0.001) than that in the EC-3.0Nm (13.9 ± 1.1 mm) and SC (13.4 ± 0.8 mm) conditions. All instrumentation reduced (p < 0.01) ROM with respect to the injury and increased (p ≤ 0.01) NZS in flexion, extension, and LB as well as EZS in flexion, LB, and AR. When comparing the torque expansions, the EC-3.0Nm condition had smaller (p < 0.01) FE and AR ROM and greater (p ≤ 0.04) flexion NZS, extension EZS, and AR EZS. The SC condition performed equivalently (p ≥ 0.10) to both EC conditions in terms of ROM, NZS, and EZS, except for EZS in AR, in which a marginal (p = 0.05) difference was observed with respect to the EC-3.0Nm condition. The SC+BPSS was the most rigid construct in terms of ROM and stiffness, except for 1) LB ROM, in which it was comparable (p = 0.08) with that of the EC-1.5Nm condition; 2) AR NZS, in which it was comparable (p > 0.66, Friedman test) with that of all other constructs; and 3) AR EZS, in which it was comparable with that of the EC-1.5Nm (p = 0.56) and SC (p = 0.08) conditions. Conclusions A 3.0-Nm torque expansion of a lateral interbody cage provides greater immediate stability in FE and AR than a 1.5-Nm torque expansion. Moreover, the expandable device provides stability comparable with that of an equivalent (in size, shape, and bone-interface material) SC. Specifically, the SC+BPSS construct was the most stable in FE motion. Even though an EC may seem a better option given the minimal tissue disruption during its implantation, there may be a greater chance of endplate collapse by over-distracting the disc space because of the minimal haptic feedback from the expansion.

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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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