The Effect of Nucleotomy on Lumbar Spine Mechanics in Compression and Shear Loading

Frei, Hanspeter; Oxland, Thomas R.; Ráthonyi, Gábor K.; Nolte, L.-P.

doi:10.1097/00007632-200110010-00007

Cited by 111 publications

(82 citation statements)

References 25 publications

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“…This minimal access will also enable us to test different sealing methods in further studies. The denucleation exhibited an unstable situation for specimens, which was in agreement with previous findings [7,9,24].…”

Section: Discussionsupporting

confidence: 92%

Is a collagen scaffold for a tissue engineered nucleus replacement capable of restoring disc height and stability in an animal model?

et al. 2006

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The idea of a tissue engineered nucleus implant is to seed cells in a three-dimensional collagen matrix. This matrix may serve as a scaffold for a tissue engineered nucleus implant. The aim of this study was to investigate whether implantation of the collagen matrix into a spinal segment after nucleotomy is able to restore disc height and flexibility. The implant basically consists of condensed collagen type-I matrix. For clinical use, this matrix will be used for reinforcing and supporting the culturing of nucleus cells. In experiments, matrixes were concentrated with barium sulfate for X-ray purposes and cell seeding was disclaimed in order to evaluate the biomechanical performance of the collagen material. Six bovine lumbar functional spinal units, aging between 5 and 6 months, were used for the biomechanical in-vitro test. In each specimen, an oblique incision was performed, the nucleus was removed and replaced by a collagen-type-I matrix. Specimens were mounted in a custom-built spine tester, and subsequently exposed to pure moments of 7.5 Nm to move within the three anatomical planes. Each tested stage (intact, nucleotomy and implanted) was evaluated for range of motion, neutral zone and change in disc height. Removal of the nucleus significantly reduced disc height by 0.84 mm in respect to the intact stage and caused an instability in the segment. Through the implantation of the tissue engineered nucleus it was possible to restore this height and stability loss, and even to increase slightly the disc height of 0.07 mm compared with the intact stage. There was no statistical difference between the stability provided by the implant and intact stage. Results of movements in lateral bending and axial rotation showed the same trend compared to flexion/extension. However, implant extrusions have been observed in three of six cases during the flexibility assessment. The results of this study directly reflect the efficacy of vital nucleus replacement to restore disc height and to provide stability to intervertebral discs. However, from a biomechanical point of view, the challenge is to employ an appropriate annulus fibrosus sealing method, which is capable to keep the nucleus implant in place over a long-time period. Securing the nucleus implant inside the disc is one of the most important biomechanical prerequisites if such a tissue engineered implant shall have a chance for clinical application.

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Section: Discussionsupporting

confidence: 92%

Is a collagen scaffold for a tissue engineered nucleus replacement capable of restoring disc height and stability in an animal model?

et al. 2006

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“…By calculating the stress distribution for the entire motion segment, it was demonstrated how much the overall stresses are affected by various parameters, especially by bone density. These changes cannot be accessed with experimental methods except at discrete locations [9]. In addition, the variability resulting from different cadaver specimens used in experimental studies was removed.…”

Section: Discussionmentioning

confidence: 99%

Factors influencing stresses in the lumbar spine after the insertion of intervertebral cages: finite element analysis

et al. 2002

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IntroductionIntervertebral cages in the lumbar spine have been a promising advancement in spinal fusion. The final goal of the procedure is to relieve low back pain, one of today's major and most expensive health care problems. A large number of cages exist, which are different in design, material and surgical implanting approach. Several clinical follow-up studies have been published, mostly reporting high fusion rates, even though the criteria for success are inconsistent [1,5,17,18,23,25,30,31]. Additionally, there have been reports of mechanical failure, subsidence and migration [23,39,42]. The success of a cage insertion, which is regarded as fusion, and thereby stabilisation, of the spine, in addition to the biological factors, may be dependent on other parameters, including material properties of the vertebrae or the cage, geometry of the implant, and the interface between the bone and the cage [23,25,39,43].Hence, experimental and finite element studies have been carried out to investigate the influence of these facAbstract Intervertebral cages in the lumbar spine have been an advancement in spinal fusion to relieve low back pain. Even though initial stability is accepted as a requirement for fusion, there are other factors. The load transfer and its effect on the tissues adjacent to the cage may also play an essential role, which is not easily detectable with experimental tests. In this study the effects of an intervertebral cage insertion on a lumbar functional spinal unit were investigated using finite element analyses. The influences of cage material, cancellous bone density and spinal loading for the stresses in a functional spinal unit were evaluated. Three-dimensional (3D) finite element models of L2-L3 were developed for this purpose. An anterior approach for a monobloc, boxshaped cage was modelled. Models with cage were compared to the corresponding intact ones. The results showed that inserting a cage increased the maximum von Mises stress and changed the load transfer in the adjacent structures. Varying the cage material or the loading conditions had a much smaller influence than varying the cancellous bone density. The denser the cancellous bone, the more the stress was concentrated underneath the cage, while the remaining regions were unloaded. This study showed that the density of the underlying cancellous bone is a more important factor for the biomechanical behaviour of a motion segment stabilized with a cage, and its eventual clinical success, than the cage material or the applied load. Inserting an intervertebral cage markedly changed the load transfer. The altered stress distribution may trigger bone remodelling and explain damage of the underlying vertebrae.

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“…Rigid (Adams et al, 1996;Polikeit et al, 2003;Pollintine et al, 2004;Shirazi-Adl et al, 1984) as well as hinged (Dooris et al, 2001;Frei et al, 2002Frei et al, , 2001 loading fixtures have been used. A hinged loading fixture allows rotation of the most cranial vertebra during load application while a rigid one does not.…”

Section: Introductionmentioning

confidence: 99%

Applying a follower load delivers realistic results for simulating standing

Rohlmann

Zander

Rao

et al. 2009

Journal of Biomechanics

155

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The Effect of Nucleotomy on Lumbar Spine Mechanics in Compression and Shear Loading

Abstract: Nucleotomy resulted in decreased disc pressure, decreased endplate deformation, and modified loading patterns onto the inferior vertebra in compression loading. However, nucleotomy did not appreciably affect the behavior of the disc in shear loading.

Cited by 111 publications

References 25 publications

Is a collagen scaffold for a tissue engineered nucleus replacement capable of restoring disc height and stability in an animal model?

Is a collagen scaffold for a tissue engineered nucleus replacement capable of restoring disc height and stability in an animal model?

Factors influencing stresses in the lumbar spine after the insertion of intervertebral cages: finite element analysis

Applying a follower load delivers realistic results for simulating standing

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