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  • 1
    Online-Ressource
    Online-Ressource
    Effect of a prosthetic disc nucleus on the mobility and disc height of the L4–5 intervertebral disc postnucleotomy
    Journal of Neurosurgery Publishing Group (JNSPG) ; 2001
    In:  Journal of Neurosurgery: Spine Vol. 95, No. 2 ( 2001-10), p. 208-214
    Details
    In: Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 95, No. 2 ( 2001-10), p. 208-214
    Kurzfassung: Object. Current procedures for treatment of degenerative disc disease may not restore flexibility or disc height to the intervertebral disc. Recently, a prosthetic device, intended to replace the degenerated nucleus pulposus, was developed. In this biomechanical in vitro test the authors study the effect of implanting a prosthetic nucleus in cadaveric lumbar intervertebral discs postnucleotomy and determine if the flexibility and disc height of the L4–5 motion segment is restored. Methods. The prosthetic disc nucleus device consists of two hydrogel pellets, each enclosed in a woven polyethylene jacket. Six human cadaveric lumbar motion segments (obtained in individuals who, at the time of death, were a mean age of 56.7 years) were loaded with moments of ± 7.5 Nm in flexion—extension, lateral bending, and axial rotation. The following states were investigated: intact, postnucleotomy, and after device implantation. Range of motion (ROM) and neutral zone (NZ) measurements were determined. Change in disc height from the intact state was measured after nucleotomy and device implantation, with and without a 200-N preload. Conclusions. Compared with the intact state (100%), the nucleotomy increased the ROM in flexion—extension to 118%, lateral bending to 112%, and axial rotation to 121%; once the device was implanted the ROM was reduced to 102%, 88%, and 90%, respectively. The NZ increased the ROM to 210%, lateral bending to 173%, and axial rotation to 107% after nucleotomy, and 146%, 149%, 44%, respectively, after device implantation. A 200-N preload reduced the intact and postnucleotomy disc heights by approximately 1 mm and 2 mm, respectively. The original intact disc height was restored after implantation of the device. The results of the cadaveric L4–5 flexibility testing indicate that the device can potentially restore ROM, NZ, and disc height to the denucleated segment.
    Materialart: Online-Ressource
    ISSN: 1547-5654
    URL: Article
    DOI: 10.3171/spi.2001.95.2.0208
    RVK:
    XA 55270.1
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 2001
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
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    Effects of neck movements on stability and subsidence in cervical interbody fusion: an in vitro study
    Journal of Neurosurgery Publishing Group (JNSPG) ; 2001
    In:  Journal of Neurosurgery: Spine Vol. 94, No. 1 ( 2001-01), p. 97-107
    Details
    In: Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 94, No. 1 ( 2001-01), p. 97-107
    Kurzfassung: Object. The aim of this in vitro study was to determine the influence of simulated postoperative neck movements on the stabilizing effect and subsidence of four different anterior cervical interbody fusion devices. Emphasis was placed on the relation between subsidence and spinal stability. Methods. The flexibility of 24 human cervical spine specimens was tested before and directly after being stabilized with a WING, BAK/C, AcroMed I/F cage, or with bone cement in standard flexibility tests under 50 N axial preload. Thereafter, 700 pure moment loading cycles (± 2 Nm) were applied in randomized directions to simulate physiological neck movements. Additional flexibility tests in combination with measurements of the subsidence depth were conducted after 50, 100, 200, 300, 500, and 700 loading cycles. In all four groups, simulated postoperative neck movements caused an increase of the range of motion (ROM) ranging from 0.4 to 3.1° and of the neutral zone from 0.1 to 4.2°. This increase in flexibility was most distinct in extension followed by flexion, lateral bending, and axial rotation. After cyclic loading, ROM tended to be lower in the group fitted with AcroMed cages (3.3° in right lateral bending, 3.5° in left axial rotation, 7.8° in flexion, 8.3° in extension) and in the group in which bone cement was applied (5.4°, 2.5°, 7.4°, and 8.8°, respectively) than in those fixed with the WING (6.3°, 5.4°, 9.7°, and 6.9°, respectively) and BAK cages (6.2°, 4.5°, 10.2°, and 11.6°, respectively). Conclusions. Simulated repeated neck movements not only caused an increase of the flexibility but also subsidence of the implants into the adjacent vertebrae. The relation between flexibility increase and subsidence seemed to depend on the implant design: subsiding BAK/C cages partially supported stability whereas subsiding WING cages and AcroMed cages did not.
    Materialart: Online-Ressource
    ISSN: 1547-5654
    URL: Article
    DOI: 10.3171/spi.2001.94.1.0097
    RVK:
    XA 55270.1
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 2001
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
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    Enhanced primary stability through additional cementable cannulated rescue screw for anterior thoracolumbar plate application
    Journal of Neurosurgery Publishing Group (JNSPG) ; 2003
    In:  Journal of Neurosurgery: Spine Vol. 98, No. 1 ( 2003-01), p. 50-55
    Details
    In: Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 98, No. 1 ( 2003-01), p. 50-55
    Kurzfassung: Object. The authors conducted a study to investigate the biomechanical in vitro influence of a new anchorage system for fixation of anterior stabilization devices and the possibility of using additional cement after screw insertion to compensate for poor bone quality. The incidence of osteoporosis-related fractures has increased nearly twofold in the last decade. Because of problems associated with anterior screw fixation such as loosening, mechanical failure, and the weakness of osteoporotic bone, current surgical treatments of vertebral body (VB) fractures are problematic. This is due to poor fixation strength of anterior screws in the adjacent segments. The aim of this study was to determine whether a new cemented and uncemented VB screw provides improved primary stability following placement of anterior instrumentation in cases of fracture. Methods. The primary stability-related parameters of a new uncemented/cemented screw were compared with those of conventional monocortical screw fixation in a burst fracture model in which strut graft and anterior overbridging instrumentation were used. The use of the new uncemented screw improved the range of motion (ROM) of the stabilized spine in flexion—extension by approximately 22%, in rotation by 20%, and in lateral bending by 15%. Additional cementation improved the ROM by approximately 41% in flexion—extension, 32% in rotation, and 30% in lateral bending compared with conventional monocortical screw fixation. Conclusions. The new cannulated screw improves fixation strength and primary stability parameters. It is useful in the initial treatment of fractures in cases of poor bone quality and as a rescue device if previously inserted screws do not remain securely in place.
    Materialart: Online-Ressource
    ISSN: 1547-5654
    URL: Article
    DOI: 10.3171/spi.2003.98.1.0050
    RVK:
    XA 55270.1
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 2003
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
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    Biomechanical evaluation of conventional anulus fibrosus closure methods required for nucleus replacement : Laboratory investigation
    Journal of Neurosurgery Publishing Group (JNSPG) ; 2008
    In:  Journal of Neurosurgery: Spine Vol. 9, No. 3 ( 2008-09), p. 307-313
    Details
    In: Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 9, No. 3 ( 2008-09), p. 307-313
    Kurzfassung: Nucleus replacement implants became increasingly attractive as an alternative to fusion, discectomy, or total disc replacement. The goals of nucleus replacement are to restore disc height and flexibility and to preserve the anatomy. However, implant extrusions have been reported and are the major concern. In this study the authors investigated different conventional surgical methods for anulus closure: suture alone, and fibrin glue and cyanoacrylate glue, alone and with suture. Methods The in vitro testing was conducted using 30 lumbar spinal segments obtained from calves. In each specimen, an incision was made; the nucleus was removed and subsequently replaced by a collagen matrix. The incisions were treated with anulus closure methods in 5 groups of animals. Flexibility was assessed in a spine tester. Subsequently, specimens were exposed to cyclic fatigue loading by using a hydraulic loading frame. Specimens were excentrically loaded in sine waveform up to a maximum of 100,000 cycles with 4–24 Nm at 5 Hz while being rotated at 360°/minute. Results Removal of the nucleus caused a significant loss of stability. The segmental stability could be restored after the implantation. Fatigue testing indicated that suturing was able to sustain 3400 cycles. Fibrin glue failed earlier than cyanoacrylate glue. Both combinations (suture with glue) provided longer stability to the anulus closure. Conclusions The results suggested that closing the anulus incision with suture or fibrin glue alone might not be appropriate. The authors found that the best method was cyanoacrylate glue with suture. Although this method provided the longest duration of closure, it could not sustain the maximum number of fatigue cycles. Conventional methods could improve the outcome compared with using no closure. Nonetheless, the authors' findings highlight the demand for an appropriate anulus reconstruction method or device with good long-term reliability.
    Materialart: Online-Ressource
    ISSN: 1547-5654
    URL: Article
    DOI: 10.3171/SPI/2008/9/9/307
    RVK:
    XA 55270.1
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 2008
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    Evaluation of a new monocortical screw for anterior cervical fusion and plating by a combined biomechanical and clinical study
    Springer Science and Business Media LLC ; 1999
    In:  European Spine Journal Vol. 8, No. 5 ( 1999-10-26), p. 382-387
    Details
    In: European Spine Journal, Springer Science and Business Media LLC, Vol. 8, No. 5 ( 1999-10-26), p. 382-387
    Materialart: Online-Ressource
    ISSN: 0940-6719 , 1432-0932
    URL: Article
    DOI: 10.1007/s005860050191
    Sprache: Unbekannt
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 1999
    ZDB Id: 1472721-3
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
    Online-Ressource
    Minimally invasive ventral spondylodesis for thoracolumbar fracture treatment: surgical technique and first clinical outcome
    Springer Science and Business Media LLC ; 2003
    In:  European Spine Journal Vol. 12, No. 6 ( 2003-12-1), p. 618-624
    Details
    In: European Spine Journal, Springer Science and Business Media LLC, Vol. 12, No. 6 ( 2003-12-1), p. 618-624
    Materialart: Online-Ressource
    ISSN: 0940-6719 , 1432-0932
    URL: Article
    DOI: 10.1007/s00586-003-0564-5
    Sprache: Unbekannt
    Verlag: Springer Science and Business Media LLC
    Publikationsdatum: 2003
    ZDB Id: 1472721-3
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Online-Ressource
    Online-Ressource
    Stabilizing effect of posterior lumbar interbody fusion cages before and after cyclic loading
    Journal of Neurosurgery Publishing Group (JNSPG) ; 2000
    In:  Journal of Neurosurgery: Spine Vol. 92, No. 1 ( 2000-01), p. 87-92
    Details
    In: Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 92, No. 1 ( 2000-01), p. 87-92
    Kurzfassung: Object. The function of interbody fusion cages is to stabilize spinal segments primarily by distracting them as well as by allowing bone ingrowth and fusion. An important condition for efficient formation of bone tissue is achieving adequate spinal stability. However, the initial stability may be reduced due to repeated movements of the spine during everyday activity. Therefore, in addition to immediate stability, stability after cyclic loading is of remarkable relevance; however, this has not yet been investigated. The object of this study was to investigate the immediate stabilizing effect of three different posterior lumbar interbody fusion cages and to clarify the effect of cyclic loading on the stabilization. Methods. Before and directly after implantation of a Zientek, Stryker, or Ray posterior lumbar interbody fusion cage, 24 lumbar spine segment specimens were each evaluated in a spine tester. Pure lateral bending, flexion—extension, and axial rotation moments (± 7.5 Nm) were applied continuously. The motion in each specimen was measured simultaneously. The specimens were then loaded cyclically (40,000 cycles, 5 Hz) with an axial compression force ranging from 200 to 1000 N. Finally, they were tested once again in the spine tester. Conclusions. In general, a decrease of movement in all loading directions was noted after insertion of the Zientek and Ray cages and an increase of movement after implantation of a Stryker cage. In all three cage groups greater stability was demonstrated in lateral bending and flexion than in extension and axial rotation. Reduced stability during cyclic loading was observed in all three cage groups; however, loss of stability was most pronounced when the Ray cage was used.
    Materialart: Online-Ressource
    ISSN: 1547-5654
    URL: Article
    DOI: 10.3171/spi.2000.92.1.0087
    RVK:
    XA 55270.1
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 2000
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 8
    Online-Ressource
    Online-Ressource
    A three-dimensional collagen matrix as a suitable culture system for the comparison of cyclic strain and hydrostatic pressure effects on intervertebral disc cells
    Journal of Neurosurgery Publishing Group (JNSPG) ; 2005
    In:  Journal of Neurosurgery: Spine Vol. 2, No. 4 ( 2005-04), p. 457-465
    Details
    In: Journal of Neurosurgery: Spine, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 2, No. 4 ( 2005-04), p. 457-465
    Kurzfassung: Object. To study intervertebral disc cell mechanobiology, the authors developed experimental systems that allow the application of cyclic strain and intermittent hydrostatic pressure (IHP) on isolated disc cells under equal three-dimensional (3D) culture conditions. The purpose of the study was to characterize disc cell proliferation, viability, morphology, and gene expression in 3D collagen matrices. Methods. The effects of cyclic strain (1, 2, 4, and 8% strain; 1 Hz) and IHP (0.25 MPa, 0.1 Hz) on gene expression (real-time polymerase chain reaction) of anabolic and catabolic matrix proteins were investigated and compared with those derived from mechanically unstimulated controls. Intervertebral disc cells proliferated in the collagen gels (mean viability 91.6%) and expressed messenger RNA for collagen I, collagen II, aggrecan, matrix metalloproteinase (MMP)—2, and MMP-3. Morphologically, both spindle-shaped cells with longer processes and rounded cells were detected in the collagen scaffolds. Cyclic strain increased collagen II and aggrecan expression and decreased MMP-3 expression of anulus fibrosus cells. No significant difference between the four strain magnitudes was found. Intermittent hydrostatic pressure tended to increase collagen I and aggrecan expression of nucleus cells and significantly decreased MMP-2 and -3 expression of nucleus cells, whereas aggrecan expression of anulus cells tended to decrease. Conclusions. Based on these results, the collagen matrix appeared to be a suitable substrate to apply both cyclic strain and IHP to intervertebral disc cells under 3D culture conditions. Individual variations may be influenced by the extent of degeneration of the disc specimens from which the cells were isolated. This experimental setup may be suitable for studying the influence of degeneration on the disc cell response to mechanical stimuli.
    Materialart: Online-Ressource
    ISSN: 1547-5654
    URL: Article
    DOI: 10.3171/spi.2005.2.4.0457
    RVK:
    XA 55270.1
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 2005
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Online-Ressource
    Online-Ressource
    Stabilizing effect of posterior lumbar interbody fusion cages before and after cyclic loading
    Journal of Neurosurgery Publishing Group (JNSPG) ; 1999
    In:  Neurosurgical Focus Vol. 7, No. 6 ( 1999-12), p. E7-
    Details
    In: Neurosurgical Focus, Journal of Neurosurgery Publishing Group (JNSPG), Vol. 7, No. 6 ( 1999-12), p. E7-
    Kurzfassung: The function of interbody fusion cages is to stabilize spinal segments primarily by distracting them as well as by allowing bone ingrowth and fusion. An important condition for efficient formation of bone tissue is achieving adequate spinal stability. However, the initial stability may be reduced due to repeated movements of the spine during everyday activity. Therefore, in addition to immediate stability, stability after cyclic loading is of remarkable relevance; however, this has not yet been investigated. The object of this study was to investigate the immediate stabilizing effect of three different posterior lumbar interbody fusion cages and to clarify the effect of cyclic loading on the stabilization. Before and directly after implantation of a Zientek, Stryker, or Ray posterior lumbar interbody fusion cage, 24 lumbar spine segment specimens were each evaluated in a spine tester. Pure lateral bending, flexion-extension, and axial rotation moments (± 7.5 Nm) were applied continuously. The motion in each specimen was measured simultaneously. The specimens were then loaded cyclically (40,000 cycles, 5 Hz) with an axial compression force ranging from 200 to 1000 N. Finally, they were tested once again in the spine tester. In general, a decrease of movement in all loading directions was noted after insertion of the Zientek and Ray cages and an increase of movement after implantation of a Stryker cage. In all three cage groups greater stability was demonstrated in lateral bending and flexion than in extension and axial rotation. Reduced stability during cyclic loading was observed in all three cage groups; however, loss of stability was most pronounced when the Ray cage was used.
    Materialart: Online-Ressource
    ISSN: 1092-0684
    URL: Article
    DOI: 10.3171/foc.1999.7.6.8
    Sprache: Unbekannt
    Verlag: Journal of Neurosurgery Publishing Group (JNSPG)
    Publikationsdatum: 1999
    ZDB Id: 2026589-X
    Standort Signatur Einschränkungen Verfügbarkeit
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