scholarly journals Design of a Dynamic Stabilization Spine Implant

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.

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

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.

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

2020 ◽  
Vol 43 (12) ◽  
pp. 803-810 ◽  
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.

Effect of Facetectomy on the Three-Dimensional Biomechanical Properties of the Fourth Canine Cervical Functional Spinal Unit: A Cadaveric Study

2017 ◽  
Vol 30 (06) ◽  
pp. 430-437 ◽  
Author(s):  
Nadja Bösch ◽  
Martin Hofstetter ◽  
Alexander Bürki ◽  
Beatriz Vidondo ◽  
Fenella Davies ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Motion Analysis ◽  
Testing Machine ◽  
Three Dimensional ◽  
Axial Rotation ◽  
Biomechanical Properties ◽  
Lateral Bending ◽  
Coupled Motion ◽  
Functional Spinal Unit ◽  
Flexion Extension

Abstract Objective To study the biomechanical effect of facetectomy in 10 large breed dogs (>24 kg body weight) on the fourth canine cervical functional spinal unit. Methods Canine cervical spines were freed from all muscles. Spines were mounted on a six-degrees-of-freedom spine testing machine for three-dimensional motion analysis. Data were recorded with an optoelectronic motion analysis system. The range of motion wasdetermined inall threeprimary motionsaswellasrange of motion of coupled motions on the intact specimen, after unilateral and after bilateral facetectomy. Repeated-measures analysis of variance models were used to assess the changes of the biomechanical properties in the three treatment groups considered. Results Facetectomy increased range of motion of primary motions in all directions. Axial rotation was significantly influenced by facetectomy. Coupled motion was not influenced by facetectomy except for lateral bending with coupled motion axial rotation. The coupling factor (coupled motion/primary motion) decreased after facetectomy. Symmetry of motion was influenced by facetectomy in flexion–extension and axial rotation, but not in lateral bending. Clinical Significance Facet joints play a significant role in the stability of the cervical spine and act to maintain spatial integrity. Therefore, cervical spinal treatments requiring a facetectomy should be carefully planned and if an excessive increase in range of motion is expected, complications should be anticipated and reduced via spinal stabilization.

Hybrid dynamic stabilization: a biomechanical assessment of adjacent and supraadjacent levels of the lumbar spine

2012 ◽  
Vol 17 (3) ◽  
pp. 232-242 ◽  
Author(s):  
Prasath Mageswaran ◽  
Fernando Techy ◽  
Robb W. Colbrunn ◽  
Tara F. Bonner ◽  
Robert F. McLain
Keyword(s):  
Lumbar Spine ◽  
Lumbar Fusion ◽  
Industrial Robot ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Dynamic Stabilization ◽  
Follower Load ◽  
Lateral Bending ◽  
Intact Specimen ◽  
Flexion Extension

Object The object of this study was to evaluate the effect of hybrid dynamic stabilization on adjacent levels of the lumbar spine. Methods Seven human spine specimens from T-12 to the sacrum were used. The following conditions were implemented: 1) intact spine; 2) fusion of L4–5 with bilateral pedicle screws and titanium rods; and 3) supplementation of the L4–5 fusion with pedicle screw dynamic stabilization constructs at L3–4, with the purpose of protecting the L3–4 level from excessive range of motion (ROM) and to create a smoother motion transition to the rest of the lumbar spine. An industrial robot was used to apply continuous pure moment (± 2 Nm) in flexion-extension with and without a follower load, lateral bending, and axial rotation. Intersegmental rotations of the fused, dynamically stabilized, and adjacent levels were measured and compared. Results In flexion-extension only, the rigid instrumentation at L4–5 caused a 78% decrease in the segment's ROM when compared with the intact specimen. To compensate, it caused an increase in motion at adjacent levels L1–2 (45.6%) and L2–3 (23.2%) only. The placement of the dynamic construct at L3–4 decreased the operated level's ROM by 80.4% (similar stability as the fusion at L4–5), when compared with the intact specimen, and caused a significant increase in motion at all tested adjacent levels. In flexion-extension with a follower load, instrumentation at L4–5 affected only a subadjacent level, L5–sacrum (52.0%), while causing a reduction in motion at the operated level (L4–5, −76.4%). The dynamic construct caused a significant increase in motion at the adjacent levels T12–L1 (44.9%), L1–2 (57.3%), and L5–sacrum (83.9%), while motion at the operated level (L3–4) was reduced by 76.7%. In lateral bending, instrumentation at L4–5 increased motion at only T12–L1 (22.8%). The dynamic construct at L3–4 caused an increase in motion at T12–L1 (69.9%), L1–2 (59.4%), L2–3 (44.7%), and L5–sacrum (43.7%). In axial rotation, only the placement of the dynamic construct at L3–4 caused a significant increase in motion of the adjacent levels L2–3 (25.1%) and L5–sacrum (31.4%). Conclusions The dynamic stabilization system displayed stability characteristics similar to a solid, all-metal construct. Its addition of the supraadjacent level (L3–4) to the fusion (L4–5) did protect the adjacent level from excessive motion. However, it essentially transformed a 1-level lumbar fusion into a 2-level lumbar fusion, with exponential transfer of motion to the fewer remaining discs.

scholarly journals Biomechanical Analysis of an Anterior Cervical Discectomy and Fusion Pseudarthrosis Model Revised With Machined Interfacet Allograft Spacers

2019 ◽  
Vol 10 (8) ◽  
pp. 973-981
Author(s):  
Raymond J. Hah ◽  
Ram Alluri ◽  
Paul A. Anderson
Keyword(s):  
Range Of Motion ◽  
Study Design ◽  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Anterior Cervical Discectomy ◽  
Lateral Bending ◽  
Cervical Discectomy ◽  
Single Level ◽  
Flexion Extension ◽  
Potential Applications

Study Design: Biomechanics study. Objectives: To evaluate the biomechanical advantage of interfacet allograft spacers in an unstable single-level and 2-level anterior cervical discectomy and fusion (ACDF) pseudoarthrosis model. Methods: Nine single-level and 8 two-level ACDF constructs were tested. Range of motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) at 1.5 N m were collected in 4 testing configurations: (1) intact spine, (2) ACDF with interbody graft and plate/screw, (3) ACDF with interbody graft and plate/loosened screws (loose condition), and (4) ACDF with interbody graft and plate/loosened screws supplemented with interfacet allograft spacers (rescue condition). Results: All fixation configurations resulted in statistically significant decreases in range of motion in all bending planes compared with the intact spine ( P < .05). One Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 60.0%, 64.9%, and 72.9%, respectively. Loosening the ACDF screws decreased these reductions to 40.9%, 44.6%, and 52.1%. The addition of interfacet allograft spacers to the loose condition increased these reductions to 74.0%, 84.1%, and 82.1%. Two Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 72.0%, 71.1%, and 71.2%, respectively. Loosening the ACDF screws decreased these reductions to 55.4%, 55.3%, and 51.3%. The addition of interfacet allograft spacers to the loose condition significantly increased these reductions to 82.6%, 91.2%, and 89.3% ( P < .05). Conclusions: Supplementation of a loose ACDF construct (pseudarthrosis model) with interfacet allograft spacers significantly increases stability and has potential applications in treating cervical pseudarthrosis.

Biomechanical Consequences of Cervical Spondylectomy Versus Corpectomy

2008 ◽  
Vol 63 (suppl_4) ◽  
pp. ONS303-ONS308 ◽  
Author(s):  
Şeref Doğan ◽  
Seungwon Baek ◽  
Volker K.H. Sonntag ◽  
Neil R. Crawford
Keyword(s):  
Range Of Motion ◽  
Axial Rotation ◽  
Posterior Fixation ◽  
Spinal Stability ◽  
Angular Range ◽  
Anterior Instrumentation ◽  
Lateral Bending ◽  
Cervical Corpectomy ◽  
Flexion Extension ◽  
Anterior Plating

Abstract Objective: To evaluate the differences in spinal stability and stabilizing potential of instrumentation after cervical corpectomy and spondylectomy. Methods: Seven human cadaveric specimens were tested: 1) intact; 2) after grafted C5 corpectomy and anterior C4–C6 plate; 3) after adding posterior C4–C6 screws/rods; 4) after extending posteriorly to C3–C7; 5) after grafted C5 spondylectomy, anterior C4–C6 plate, and posterior C4–C6 screws/rods; and 6) after extending posteriorly to C3–C7. Pure moments induced flexion, extension, lateral bending, and axial rotation; angular motion was recorded optically. Results: After corpectomy, anterior plating alone reduced the angular range of motion to a mean of 30% of normal, whereas added posterior short- or long-segment hardware reduced range of motion significantly more (P &lt; 0.003), to less than 5% of normal. Constructs with posterior rods spanning C3–C7 were stiffer than constructs with posterior rods spanning C4–C6 during flexion, extension, and lateral bending (P &lt; 0.05), but not during axial rotation (P &gt; 0.07). Combined anterior and C4–C6 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during lateral bending (P = 0.019) and axial rotation (P = 0.001). Combined anterior and C3–C7 posterior fixation exhibited greater stiffness after corpectomy than after spondylectomy during extension (P = 0.030) and axial rotation (P = 0.0001). Conclusion: Circumferential fixation provides more stability than anterior instrumentation alone after cervical corpectomy. After corpectomy or spondylectomy, long circumferential instrumentation provides better stability than short circumferential fixation except during axial rotation. Circumferential fixation more effectively prevents axial rotation after corpectomy than after spondylectomy.

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

2016 ◽  
Vol 17 (4) ◽  
pp. 497-503 ◽  
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.

Numerical investigation on the stability of human upper cervical spine (C1–C3)

2021 ◽  
pp. 1-13
Author(s):  
Waseem Ur Rahman ◽  
Wei Jiang ◽  
Guohua Wang ◽  
Zhijun Li
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Axial Rotation ◽  
Upper Cervical Spine ◽  
Fe Model ◽  
Facet Joints ◽  
Flexion Extension ◽  
Upper Cervical ◽  
The Stability

BACKGROUND: The finite element method (FEM) is an efficient and powerful tool for studying human spine biomechanics. OBJECTIVE: In this study, a detailed asymmetric three-dimensional (3D) finite element (FE) model of the upper cervical spine was developed from the computed tomography (CT) scan data to analyze the effect of ligaments and facet joints on the stability of the upper cervical spine. METHODS: A 3D FE model was validated against data obtained from previously published works, which were performed in vitro and FE analysis of vertebrae under three types of loads, i.e. flexion/extension, axial rotation, and lateral bending. RESULTS: The results show that the range of motion of segment C1–C2 is more flexible than that of segment C2–C3. Moreover, the results from the FE model were used to compute stresses on the ligaments and facet joints of the upper cervical spine during physiological moments. CONCLUSION: The anterior longitudinal ligaments (ALL) and interspinous ligaments (ISL) are found to be the most active ligaments, and the maximum stress distribution is appear on the vertebra C3 superior facet surface under both extension and flexion moments.

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

2021 ◽  
Vol 11 (13) ◽  
pp. 5764
Author(s):  
Jen-Chung Liao ◽  
Michael Jian-Wen Chen ◽  
Tung-Yi Lin ◽  
Weng-Pin Chen
Keyword(s):  
Finite Element ◽  
Axial Rotation ◽  
Vertebral Compression Fractures ◽  
Lateral Bending ◽  
Compression Fractures ◽  
Significant Difference ◽  
Flexion Extension ◽  
Von Mises ◽  
Von Mises Stresses ◽  
Osteoporotic Compression Fractures

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.

scholarly journals Comprehensive biomechanical analysis of three reconstruction techniques following total sacrectomy: an in vitro human cadaveric model

2017 ◽  
Vol 27 (5) ◽  
pp. 570-577 ◽  
Author(s):  
Mohamed Macki ◽  
Rafael De la Garza-Ramos ◽  
Ashley A. Murgatroyd ◽  
Kenneth P. Mullinix ◽  
Xiaolei Sun ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Axial Compression ◽  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Iliac Screws ◽  
Intact Condition ◽  
Cadaveric Model

OBJECTIVEAggressive sacral tumors often require en bloc resection and lumbopelvic reconstruction. Instrumentation failure and pseudarthrosis remain a clinical concern to be addressed. The objective in this study was to compare the biomechanical stability of 3 distinct techniques for sacral reconstruction in vitro.METHODSIn a human cadaveric model study, 8 intact human lumbopelvic specimens (L2–pelvis) were tested for flexion-extension range of motion (ROM), lateral bending, and axial rotation with a custom-designed 6-df spine simulator as well as axial compression stiffness with the MTS 858 Bionix Test System. Biomechanical testing followed this sequence: 1) intact spine; 2) sacrectomy (no testing); 3) Model 1 (L3–5 transpedicular instrumentation plus spinal rods anchored to iliac screws); 4) Model 2 (addition of transiliac rod); and 5) Model 3 (removal of transiliac rod; addition of 2 spinal rods and 2 S-2 screws). Range of motion was measured at L4–5, L5–S1/cross-link, L5–right ilium, and L5–left ilium.RESULTSFlexion-extension ROM of the intact specimen at L4–5 (6.34° ± 2.57°) was significantly greater than in Model 1 (1.54° ± 0.94°), Model 2 (1.51° ± 1.01°), and Model 3 (0.72° ± 0.62°) (p < 0.001). Flexion-extension at both the L5–right ilium (2.95° ± 1.27°) and the L5–left ilium (2.87° ± 1.40°) for Model 3 was significantly less than the other 3 cohorts at the same level (p = 0.005 and p = 0.012, respectively). Compared with the intact condition, all 3 reconstruction groups statistically significantly decreased lateral bending ROM at all measured points. Axial rotation ROM at L4–5 for Model 1 (2.01° ± 1.39°), Model 2 (2.00° ± 1.52°), and Model 3 (1.15° ± 0.80°) was significantly lower than the intact condition (5.02° ± 2.90°) (p < 0.001). Moreover, axial rotation for the intact condition and Model 3 at L5–right ilium (2.64° ± 1.36° and 2.93° ± 1.68°, respectively) and L5–left ilium (2.58° ± 1.43° and 2.93° ± 1.71°, respectively) was significantly lower than for Model 1 and Model 2 at L5–right ilium (5.14° ± 2.48° and 4.95° ± 2.45°, respectively) (p = 0.036) and L5–left ilium (5.19° ± 2.34° and 4.99° ± 2.31°) (p = 0.022). Last, results of the axial compression testing at all measured points were not statistically different among reconstructions.CONCLUSIONSThe addition of a transverse bar in Model 2 offered no biomechanical advantage. Although the implementation of 4 iliac screws and 4 rods conferred a definitive kinematic advantage in Model 3, that model was associated with significantly restricted lumbopelvic ROM.

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