<i>In vitro</i>
            and
            <i>in silico</i>
            investigations of disc nucleus replacement

Reitmaier, Sandra; Shirazi‐Adl, A.; Bashkuev, Maxim; Wilke, Hans–Joachim; Gloria, Antonio; Schmidt, Hendrik

doi:10.1098/rsif.2012.0016

Cited by 54 publications

(19 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finite element analyses showed that a destroyed interface is one possible reason for the strong differences between DEF-NUC and INTACT (Reitmaier et al, 2012). The model predicted a 10% drop in IDP during the creep phases after replacing the native nucleus material.…”

Section: Discussionmentioning

confidence: 90%

Hydrogels for nucleus replacement—Facing the biomechanical challenge

Reitmaier

Wolfram

Ignatius

et al. 2012

Journal of the Mechanical Behavior of Biomedical Materials

Self Cite

View full text Add to dashboard Cite

Hydrogels are considered promising for disc regeneration strategies. However, it is currently unknown whether the destruction of the natural interface between nucleus and surrounding structures caused by nucleotomy and an inadequate annulus closure diminishes the mechanical competence of the disc. This in vitro study aimed to clarify these mechanisms and to evaluate whether hydrogels are able to restore the biomechanical behaviour of the disc. Nucleus pressure in an ovine intervertebral disc was measured in vivo during day and night and adapted to an in vitro axial compressive diurnal (15min) and night (30min) load. Effects of different defects on disc height and nucleus pressure were subsequently measured in vitro using 30 ovine motion segments. Following cases were considered: intact; annulus incision repaired by suture and glue; annulus incision with removal and re-implantation of nucleus tissue; and two different hydrogels repaired by suture and glue. The intradiscal pressure in vivo was 0.75MPa during day and 0.5MPa during night corresponding to an in vitro axial compressive force of 130 and 58N, respectively. The compression test showed that neither the implantation of hydrogels nor the re-implantation of the natural nucleus, assumed as being the ideal implant, was able to restore the mechanical functionality of an intact disc. Results indicate the importance of the natural anchorage of the nucleus with its surrounding structures and the relevance of an appropriate annulus closure. Therefore, hydrogels that are able to mimic the mechanical behaviour of the native nucleus may fail in restoring the mechanical behaviour of the disc.

show abstract

Section: Discussionmentioning

confidence: 90%

Hydrogels for nucleus replacement—Facing the biomechanical challenge

Reitmaier

Wolfram

Ignatius

et al. 2012

Journal of the Mechanical Behavior of Biomedical Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…Lasting 24 hours, the time frame of IDP measurement in the current study is comparably short and degenerative changes due to disc puncture therefore are not expected. Additionally, a 4 mm cut in the annulus was shown not to significantly impair axial compressive stiffness and IDP of the ovine intervertebral disc [45,46]. …”

Section: Discussionmentioning

confidence: 99%

Preliminary Investigations on Intradiscal Pressures during Daily Activities: An In Vivo Study Using the Merino Sheep

et al. 2013

Self Cite

View full text Add to dashboard Cite

PurposeCurrently, no studies exist, which attest the suitability of the ovine intervertebral disc as a biomechanical in vivo model for preclinical tests of new therapeutic strategies of the human disc. By measuring the intradiscal pressure in vivo, the current study attempts to characterize an essential biomechanical parameter to provide a more comprehensive physiological understanding of the ovine intervertebral disc.MethodsIntradiscal pressure (IDP) was measured for 24 hours within the discs L2-L3 and L4-L5 via a piezo-resistive pressure sensor in one merino sheep. The data were divided into an activity and a recovery phase and the corresponding average pressures for both phases were determined. Additionally, IDPs for different static and dynamic activities were analyzed and juxtaposed to human data published previously. After sacrificing the sheep, the forces corresponding to the measured IDPs were examined ex vivo in an axial compression test.ResultsThe temporal patterns of IDP where pressure decreased during activity and increased during rest were comparable between humans and sheep. However, large differences were observed for different dynamic activities such as standing up or walking. Here, IDPs averaged 3.73 MPa and 1.60 MPa respectively, approximately two to four times higher in the ovine disc compared to human. These IDPs correspond to lower ex vivo derived axial compressive forces for the ovine disc in comparison to the human disc. For activity and rest, average ovine forces were 130 N and 58 N, compared to human forces of 400-600 N and 100 N, respectively.Conclusions In vivo IDPs were found to be higher in the ovine than in the human disc. In contrast, axial forces derived ex vivo were markedly lower in comparison to humans. Both should be considered in future preclinical tests of intradiscal therapies using the sheep. The techniques used in the current study may serve as a protocol for measuring IDP in a variety of large animal models.

show abstract

“…Mechanical evaluation of nucleus replacements often focuses on the intrinsic mechanical properties of the gel and its immediate effects on disc mechanical response [18][19][20][21][22]. More extensive mechanical testing is completed with the aim of testing failure properties [23,24].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of an In Situ Gelable and Injectable Hydrogel Treatment to Preserve Human Disc Mechanical Function Undergoing Physiologic Cyclic Loading Followed by Hydrated Recovery

Showalter

Elliott

Chen

et al. 2015

Journal of Biomechanical Engineering

View full text Add to dashboard Cite

Despite the prevalence of disc degeneration and its contributions to low back problems, many current treatments are palliative only and ultimately fail. To address this, nucleus pulposus replacements are under development. Previous work on an injectable hydrogel nucleus pulposus replacement composed of n-carboxyethyl chitosan, oxidized dextran, and teleostean has shown that it has properties similar to native nucleus pulposus, can restore compressive range of motion in ovine discs, is biocompatible, and promotes cell proliferation. The objective of this study was to determine if the hydrogel implant will be contained and if it will restore mechanics in human discs undergoing physiologic cyclic compressive loading. Fourteen human lumbar spine segments were tested using physiologic cyclic compressive loading while intact, following nucleotomy, and again following treatment of injecting either phosphate buffered saline (PBS) (sham, n ¼ 7) or hydrogel (implant, n ¼ 7). In each compressive test, mechanical parameters were measured immediately before and after 10,000 cycles of compressive loading and following a period of hydrated recovery. The hydrogel implant was not ejected from the disc during 10,000 cycles of physiological compression testing and appeared undamaged when discs were bisected following all mechanical tests. For sham samples, creep during cyclic loading increased (þ15%) from creep during nucleotomy testing, while for implant samples creep strain decreased (À3%) toward normal. There was no difference in compressive modulus or compressive strains between implant and sham samples. These findings demonstrate that the implant interdigitates with the nucleus pulposus, preventing its expulsion during 10,000 cycles of compressive loading and preserves disc creep within human L5-S1 discs. This and previous studies provide a solid foundation for continuing to evaluate the efficacy of the hydrogel implant.

show abstract

In vitro and in silico investigations of disc nucleus replacement

Cited by 54 publications

References 30 publications

Hydrogels for nucleus replacement—Facing the biomechanical challenge

Hydrogels for nucleus replacement—Facing the biomechanical challenge

Preliminary Investigations on Intradiscal Pressures during Daily Activities: An In Vivo Study Using the Merino Sheep

Evaluation of an In Situ Gelable and Injectable Hydrogel Treatment to Preserve Human Disc Mechanical Function Undergoing Physiologic Cyclic Loading Followed by Hydrated Recovery

Contact Info

Product

Resources

About