scholarly journals The role of obesity in the biomechanics and radiological changes of the spine: an in vitro study

2016 ◽  
Vol 24 (4) ◽  
pp. 615-623 ◽  
Author(s):  
Nestor G. Rodriguez-Martinez ◽  
Luis Perez-Orribo ◽  
Samuel Kalb ◽  
Phillip M. Reyes ◽  
Anna G. U. S. Newcomb ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Negative Correlation ◽  
Axial Rotation ◽  
Significant Negative Correlation ◽  
Female Group ◽  
Compression Tests ◽  
Lateral Bending ◽  
Male Group ◽  
Flexion Extension ◽  
Spinal Segments

OBJECT The effects of obesity on lumbar biomechanics are not fully understood. The aims of this study were to analyze the biomechanical differences between cadaveric L4–5 lumbar spine segments from a large group of nonobese (body mass index [BMI] < 30 kg/m2) and obese (BMI ≥ 30 kg/m2) donors and to determine if there were any radiological differences between spines from nonobese and obese donors using MR imaging. METHODS A total of 168 intact L4–5 spinal segments (87 males and 81 females) were tested using pure-moment loading, simulating flexion-extension, lateral bending, and axial rotation. Axial compression tests were performed on 38 of the specimens. Sex, age, and BMI were analyzed with biomechanical parameters using 1-way ANOVA, Pearson correlation, and multiple regression analyses. MR images were obtained in 12 specimens (8 from obese and 4 from nonobese donors) using a 3-T MR scanner. RESULTS The segments from the obese male group allowed significantly greater range of motion (ROM) than those from the nonobese male group during axial rotation (p = 0.018), while there was no difference between segments from obese and nonobese females (p = 0.687). There were no differences in ROM between spines from obese and nonobese donors during flexion-extension or lateral bending for either sex. In the nonobese population, the ROM during axial rotation was significantly greater for females than for males (p = 0.009). There was no significant difference between sexes in the obese population (p = 0.892). Axial compressive stiffness was significantly greater for the obese than the nonobese population for both the female-only group and the entire study group (p < 0.01); however, the difference was nonsignificant in the male population (p = 0.304). Correlation analysis confirmed a significant negative correlation between BMI and resistance to deformation during axial compression in the female group (R = −0.65, p = 0.004), with no relationship in the male group (R = 0.03, p = 0.9). There was also a significant negative correlation between ROM during flexion-extension and BMI for the female group (R = −0.38, p = 0.001), with no relationship for the male group (R = 0.06, p = 0.58). Qualitative analysis using MR imaging indicated greater facet degeneration and a greater incidence of disc herniations in the obese group than in the control group. CONCLUSIONS Based on flexibility and compression tests, lumbar spinal segments from obese versus nonobese donors seem to behave differently, biomechanically, during axial rotation and compression. The differences are more pronounced in women. MR imaging suggests that these differences may be due to greater facet degeneration and an increased amount of disc herniation in the spines from obese individuals.

Correlation of Implant Stability between two Non-Invasive Methods Using Submerged and non submerged healing protocols; A randomized clinical trail

2020 ◽  
Author(s):  
Marwa Abdel AAL ◽  
Mahmoud El Far ◽  
Nora Mohamed Sheta ◽  
Ahmed Fayyad ◽  
Eman El Desouky ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Negative Correlation ◽  
Significant Negative Correlation ◽  
Female Group ◽  
Implant Stability ◽  
Non Invasive ◽  
Male Group ◽  
Primary Implant ◽  
Edentulous Mandible ◽  
The Difference

Various invasive and non-invasive methods have been used for measuring primary implant stability. Periotest damping device, and resonance frequency analysis (RFA) with the Osstell device have been classified as non-invasive methods.In this clinical randomized trial, a general correlation of primary implant stability was recorded using both the Osstell and Periotest device at the day of implant installation and 3 month after healing for the submerged and non submerged   loading protocols. The gender of included patients were investigated in the correlation of the two devices.Eighty completely edentulous patients were recruited, all patients were of age ranging from 50 to 69 years old. A single implant was installed in the midline of the completely edentulous mandible to improve retention of their lower denture. After implant installation, Implant Stability was recorded using the osstel and periotest device. Patients were then randomized into two groups using sealed envelopes; Submerged (S), and Non Submerged (NS). All ISQ and PTV were recorded at the day of implant installation, and 3 month after healing for both groups.When the ISQ was correlated to the (PTV), there was a moderate negative statistically significant correlation between the two readings, correlation coefficient= -0.466, p=0.000 . There tends to be a weak negative correlation between the two devices in the male group ,while there tends to be no correlation between the two devices in the female group After 3 month healing, there was no statistically significant correlation of the readings with in both groups ;NS and S ; Correlation coefficient =-0.014, -0.430, p=0.942, 0.052 respectively.   A strong negative statistically significant correlation between the two devices for the female group for both, NS and the S group. While there was no statistically significant correlation with in the male group for both groups.The present study concluded that there is a significant negative correlation between the two devices when recording primary implant stability, while this significance is lost after 3 month of loading when recording secondary implant stability. Gender would affect the implant stability recording, this would mainly due to the difference in bone density between the male and female group.

Impact of dual-headed pedicle screws on the biomechanics of lumbosacral junction multirod constructs

2021 ◽  
pp. 1-9
Author(s):  
Jakub Godzik ◽  
Bernardo de Andrada Pereira ◽  
Anna G. U. Sawa ◽  
Jennifer N. Lehrman ◽  
Randall J. Hlubek ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Pedicle Screws ◽  
Bending Moment ◽  
Axial Rotation ◽  
Compression Tests ◽  
Lumbosacral Junction ◽  
Lateral Bending ◽  
Repeated Measures Anova ◽  
Flexion Extension ◽  
Left And Right

OBJECTIVEThe objective of this study was to evaluate a novel connector design and compare it with traditional side connectors, such as a fixed-angle connector (FAC) and a variable-angle connector (VAC), with respect to lumbosacral stability and instrumentation strain.METHODSStandard nondestructive flexibility tests (7.5 Nm) and compression tests (400 N) were performed using 7 human cadaveric specimens (L1–ilium) to compare range of motion (ROM) stability, posterior rod strain (RS), and sacral screw bending moment (SM). Directions of motion included flexion, extension, left and right lateral bending, left and right axial rotation, and compression. Conditions included 1) the standard 2-rod construct (2R); 2) the dual-tulip head (DTH) with 4-rod construct (4R); 3) FACs with 4R; and 4) VACs with 4R. Data were analyzed using repeated-measures ANOVA.RESULTSOverall, there were no statistically significant differences in ROM across the lumbosacral junction among conditions (p > 0.07). Compared with 2R, DTH and FAC significantly reduced RS in extension, left axial rotation, and compression (p ≤ 0.03). VAC significantly decreased RS compared with 2R in flexion, extension, left axial rotation, right axial rotation, and compression (p ≤ 0.03), and significantly decreased RS compared with DTH in extension (p = 0.02). DTH was associated with increased SM in left and right axial rotation compared with 2R (p ≤ 0.003) and in left and right lateral bending and left and right axial rotation compared with FAC and VAC (p ≤ 0.02). FAC and VAC were associated with decreased SM compared with 2R in right and left lateral bending (p ≤ 0.03).CONCLUSIONSRS across the lumbosacral junction can be high. Supplemental rod fixation with DTH is an effective strategy for reducing RS across the lumbosacral junction. However, the greatest reduction in RS and SM was achieved with a VAC that allowed for straight (uncontoured) accessory rod placement.

A PARAMETRIC INVESTIGATION OF THE EFFECTS OF CERVICAL DISC PROSTHESES WITH UPWARD AND DOWNWARD NUCLEI ON SPINE BIOMECHANICS

2016 ◽  
Vol 16 (07) ◽  
pp. 1650092 ◽  
Author(s):  
ZEINAB KAMAL ◽  
GHOLAMREZA ROUHI
Keyword(s):  
Cervical Spine ◽  
Axial Rotation ◽  
Torsional Stiffness ◽  
Cervical Disc ◽  
Fe Model ◽  
Lateral Bending ◽  
Biomechanical Behavior ◽  
Flexion Extension ◽  
Spinal Segments ◽  
Ct Data

This work aimed at investigating the influence of Baguera and Discocerv cervical disc prostheses, with mobile downward center of rotation (COR) and fixed upward COR, respectively, on the biomechanical behavior of C4–C6 cervical spine. For this purpose, using computed tomography (CT) data, a parametric nonlinear finite element (FE) model of intact C4–C6 spinal segments was developed, and an artificial disc was implanted at C5–C6 level. To assess the influence of implants on the biomechanics of cervical spine, the FE models were analyzed in flexion, extension, lateral bending, and axial rotation, and the results were presented in the range of motion (ROM) curves, and torsional stiffness. Results of this study, in agreement with the literature, suggested that both Baguera and Discocerv implants might be able to preserve the motion, and limit the alteration of the biomechanics of adjacent levels. Except for the possible confliction of adjacent vertebrae at the implanted level with Baguera implant in lateral bending, results of this study also indicated that the movability and downward COR of Baguera disc prosthesis caused ROMs of the implanted segment to be more similar to the intact model than Discocerv implant. Moreover, the upward COR of Discocerv implant may result in over-distraction on facets in the maximal flexion, with the ratio of 1.22 versus 1.36, and consequently facet syndrome during extension for Bageura and Discocerv disc prostheses, respectively.

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.

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.

The cervical end of an occipitocervical fusion: a biomechanical evaluation of 3 constructs

2008 ◽  
Vol 9 (3) ◽  
pp. 296-300 ◽  
Author(s):  
Michael A. Finn ◽  
Daniel R. Fassett ◽  
Todd D. Mccall ◽  
Randy Clark ◽  
Andrew T. Dailey ◽  
...  
Keyword(s):  
Tracking System ◽  
Plate Fixation ◽  
Axial Rotation ◽  
Lateral Mass ◽  
Lateral Bending ◽  
Cross Link ◽  
3D Tracking ◽  
Flexion Extension ◽  
Biomechanical Evaluation ◽  
Rotation Motion

Object Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link. Methods Ten intact human cadaveric spines (Oc–C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested. Results All constructs demonstrated a significant increase in stiffness after instrumentation. The C1L-C2P construct was equivalent to the TASF in all moments. The C1L-C2L was significantly weaker than the C1L-C2P construct in all moments and significantly weaker than the TASF in lateral bending. The addition of a cross-link made no difference in the stiffness of any construct. Conclusions All constructs provide significant immediate stability in the destabilized occipitocervical junction. Although the C1L-C2P construct performed best overall, the TASF was similar, and either one can be recommended. Decreased stiffness of the C1L-C2L construct might affect the success of clinical fusion. This construct should be reserved for cases in which anatomy precludes the use of the other two.

scholarly journals Biomechanical evaluation of the ProDisc-C stability following graded posterior cervical injury

2018 ◽  
Vol 29 (5) ◽  
pp. 515-524
Author(s):  
Michael D. Staudt ◽  
Doron Rabin ◽  
Ali A. Baaj ◽  
Neil R. Crawford ◽  
Neil Duggal
Keyword(s):  
Axial Rotation ◽  
Control Group ◽  
Lateral Bending ◽  
Cervical Injury ◽  
Cervical Arthroplasty ◽  
Posterior Surgery ◽  
Flexion Extension ◽  
Posterior Element ◽  
And Control ◽  
Flexion And Extension

OBJECTIVEThere are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.METHODSFourteen human cadaveric cervical spines (C3–T1 or C2–7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.RESULTSRange of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).CONCLUSIONSForaminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.

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.

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