Primary stability of anterior lumbar stabilization: interdependence of implant type and endplate retention or removal

Flamme, Christian; Heide, Nadine von der; Heymann, Caroline; Hurschler, Christof

doi:10.1007/s00586-005-0993-4

Cited by 7 publications

(4 citation statements)

References 68 publications

(77 reference statements)

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“…This may in part explain the asymmetrical behavior of the IDP in lateral bending and axial rotation with respect to the right versus the left side. Another declarative aspect is the fact, that we know from previous biomechanical studies with calf spines, that they behave asymmetrically [ 28 - 30 ]. Another possible reason for the not symmetrical distribution of the IDP to both directions in lateral bending and axial rotation can be the position of the pressure measuring sensors.…”

Section: Discussionmentioning

confidence: 99%

In vitro-analysis of kinematics and intradiscal pressures in cervical arthroplasty versus fusion – A biomechanical study in a sheep model with two semi-constrained prosthesis

et al. 2015

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BackgroundAs an alternative technique to arthrodesis of the cervical spine, total disc replacement (TDR) has increasingly been used with the aim of restoration of the physiological function of the treated and adjacent motions segments. The purpose of this experimental study was to analyze the kinematics of the target level as well as of the adjacent segments, and to measure the pressures in the proximal and distal disc after arthrodesis as well as after arthroplasty with two different semi-constrained types of prosthesis.MethodsTwelve cadaveric ovine cervical spines underwent polysegmental (C2-5) multidirectional flexibility testing with a sensor-guided industrial serial robot. Additionally, pressures were recorded in the proximal and distal disc. The following three conditions were tested: (1) intact specimen, (2) single-level arthrodesis C3/4, (3) single-level TDR C3/4 using the Discover® in the first six specimens and the activ® C in the other six cadavers. Statistical analysis was performed for the total range of motion (ROM), the intervertebral ROM (iROM) and the intradiscal pressures (IDP) to compare both the three different conditions as well as the two disc prosthesis among each other.ResultsThe relative iROM in the target level was always lowered after fusion in the three directions of motion. In almost all cases, the relative iROM of the adjacent segments was almost always higher compared to the physiologic condition. After arthroplasty, we found increased relative iROM in the treated level in comparison to intact state in almost all cases, with relative iROM in the adjacent segments observed to be lower in almost all situations. The IDP in both adjacent discs always increased in flexion and extension after arthrodesis. In all but five cases, the IDP in each of the adjacent level was decreased below the values of the intact specimens after TDR. Overall, in none of the analyzed parameters were statistically significantly differences between both types of prostheses investigated.ConclusionThe results of this biomechanical study indicate that single-level implantation of semi-constrained TDR lead to a certain hypermobility in the treated segments with lowering the ROM in the adjacent levels in almost all situations.

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Section: Discussionmentioning

confidence: 99%

In vitro-analysis of kinematics and intradiscal pressures in cervical arthroplasty versus fusion – A biomechanical study in a sheep model with two semi-constrained prosthesis

et al. 2015

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“…The endplates providing the greatest structural stability of the vertebral body 28 are more vulnerable to compression with decreasing BMD: 45 the less cortical bone that is preserved, the greater the loss of stability against compression, and the likelihood that a cage or the edges of a lordosizing device are going to shift increases. 20,26,28,45 Because we worked with osteoporotic bone, we aimed for application of forces close to the cortical periphery when using the lamina spreader, Synex, and lordosizer by leveling instruments flush against endplates, thereby limiting cracks or cuts. With the lordosizer, injury to endplates was less likely, which is explained by its correction method: the higher the bending moments with the correction and distraction process, the more pronounced the point-to-point interface contacts and peak loads between the endplate and edges of the instrument, and thus the higher the risk of device-endplate subsidence.…”

Section: Interrelation Of Correction and Preloadingmentioning

confidence: 99%

Implications of the center of rotation concept for the reconstruction of anterior column lordosis and axial preloads in spinal deformity surgery

Koller

Mayer

Zenner

et al. 2012

SPI

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Object In thoracolumbar deformity surgery, anterior-only approaches are used for reconstruction of anterior column failures. It is generally advised that vertebral body replacements (VBRs) should be preloaded by compression. However, little is known regarding the impact of different techniques for generation of preloads and which surgical principle is best for restoration of lordosis. Therefore, the authors analyzed the effect of different surgical techniques to restore spinal alignment and lordosis as well as the ability to generate axial preloads on VBRs in anterior column reconstructions. Methods The authors performed a laboratory study using 7 fresh-frozen specimens (from T-3 to S-1) to assess the ability for lordosis reconstruction of 5 techniques and their potential for increasing preloads on a modified distractable VBR in a 1-level thoracolumbar corpectomy. The testing protocol was as follows: 1) Radiographs of specimens were obtained. 2) A 1-level corpectomy was performed. 3) In alternating order, lordosis was applied using 1 of the 5 techniques. Then, preloads during insertion and after relaxation using the modified distractable VBR were assessed using a miniature load-cell incorporated in the modified distractable VBR. The modified distractable VBR was inserted into the corpectomy defect after lordosis was applied using 1) a lamina spreader; 2) the modified distractable VBR only; 3) the ArcoFix System (an angular stable plate system enabling in situ reduction); 4) a lordosizer (a customized instrument enabling reduction while replicating the intervertebral center of rotation [COR] according to the COR method); and 5) a lordosizer and top-loading screws ([LZ+TLS], distraction with the lordosizer applied on a 5.5-mm rod linked to 2 top-loading pedicle screws inserted laterally into the vertebra). Changes in the regional kyphosis angle were assessed radiographically using the Cobb method. Results The bone mineral density of specimens was 0.72 ± 22.6 g/cm2. The maximum regional kyphosis angle reconstructed among the 5 techniques averaged 9.7°−16.1°, and maximum axial preloads averaged 123.7–179.7 N. Concerning correction, in decreasing order the LZ+TLS, lordosizer, and ArcoFix System outperformed the lamina spreader and modified distractable VBR. The order of median values for insertion peak load, from highest to lowest, were lordosizer, LZ+TLS, and ArcoFix, which outperformed the lamina spreader and modified distractable VBR. In decreasing order, the axial preload was highest with the lordosizer and LZ+TLS, which both outperformed the lamina spreader and the modified distractable VBR. The technique enabling the greatest lordosis achieved the highest preloads. With the ArcoFix System and LZ+TLS, compression loads could be applied and were 247.8 and 190.6 N, respectively, which is significantly higher than the insertion peak load and axial preload (p < 0.05). Conclusions Including the ability for replication of the COR in instruments designed for anterior column reconstructions, the ability for lordosis restoration of the anterior column and axial preloads can increase, which in turn might foster fusion.

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“…These tolerance values may be determined through dynamic experiments using segments of the cadaver spine [5][6][7][8][9][10], Bending moments are also applied quasi-statically in ex vivo models to evaluate spine mechanics [11] and to assess surgical implants [12,13], Accurate measurement of the applied bending moments in these experiments is essential for the development of optimal injury prevention and treatment strategies for the spine.…”

Section: Introductionmentioning

confidence: 99%

“…Opposing cables are used to produce force couples [6,7,14,15] or driven shafts with universal joints may be used to apply pure moments [16]. Moments may also be applied dynami cally [5] or quasi-statically [11][12][13] using an axial force at an ec centricity to the center of the spine, where the expected moment is the product of force and eccentricity. Loads may be applied with so-called fixed-fixed [8,10,17] or fixed-free [5][6][7] boundary condi tions, which refer to the ability of each side of the specimen to translate and/or rotate.…”

Section: Introductionmentioning

confidence: 99%

Moment Measurements in Dynamic and Quasi-Static Spine Segment Testing Using Eccentric Compression are Susceptible to Artifacts Based on Loading Configuration

Toen

Carter²,

Oxland

et al. 2014

Journal of Biomechanical Engineering

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The tolerance of the spine to bending moments, used for evaluation of injury prevention devices, is often determined through eccentric axial compression experiments using segments of the cadaver spine. Preliminary experiments in our laboratory demonstrated that eccentric axial compression resulted in "unexpected" (artifact) moments. The aim of this study was to evaluate the static and dynamic effects of test configuration on bending moments during eccentric axial compression typical in cadaver spine segment testing. Specific objectives were to create dynamic equilibrium equations for the loads measured inferior to the specimen, experimentally verify these equations, and compare moment responses from various test configurations using synthetic (rubber) and human cadaver specimens. The equilibrium equations were verified by performing quasi-static (5 mm/s) and dynamic experiments (0.4 m/s) on a rubber specimen and comparing calculated shear forces and bending moments to those measured using a six-axis load cell. Moment responses were compared for hinge joint, linear slider and hinge joint, and roller joint configurations tested at quasi-static and dynamic rates. Calculated shear force and bending moment curves had similar shapes to those measured. Calculated values in the first local minima differed from those measured by 3% and 15%, respectively, in the dynamic test, and these occurred within 1.5 ms of those measured. In the rubber specimen experiments, for the hinge joint (translation constrained), quasi-static and dynamic posterior eccentric compression resulted in flexion (unexpected) moments. For the slider and hinge joints and the roller joints (translation unconstrained), extension ("expected") moments were measured quasi-statically and initial flexion (unexpected) moments were measured dynamically. In the cadaver experiments with roller joints, anterior and posterior eccentricities resulted in extension moments, which were unexpected and expected, for those configurations, respectively. The unexpected moments were due to the inertia of the superior mounting structures. This study has shown that eccentric axial compression produces unexpected moments due to translation constraints at all loading rates and due to the inertia of the superior mounting structures in dynamic experiments. It may be incorrect to assume that bending moments are equal to the product of compression force and eccentricity, particularly where the test configuration involves translational constraints and where the experiments are dynamic. In order to reduce inertial moment artifacts, the mass, and moment of inertia of any loading jig structures that rotate with the specimen should be minimized. Also, the distance between these structures and the load cell should be reduced.

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Primary stability of anterior lumbar stabilization: interdependence of implant type and endplate retention or removal

Cited by 7 publications

References 68 publications

In vitro-analysis of kinematics and intradiscal pressures in cervical arthroplasty versus fusion – A biomechanical study in a sheep model with two semi-constrained prosthesis

In vitro-analysis of kinematics and intradiscal pressures in cervical arthroplasty versus fusion – A biomechanical study in a sheep model with two semi-constrained prosthesis

Implications of the center of rotation concept for the reconstruction of anterior column lordosis and axial preloads in spinal deformity surgery

Moment Measurements in Dynamic and Quasi-Static Spine Segment Testing Using Eccentric Compression are Susceptible to Artifacts Based on Loading Configuration

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