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Preliminary investigations on intradiscal pressures during daily activities: an in vivo study using the merino sheep.

Reitmaier S, Schmidt H, Ihler R, Kocak T, Graf N, Ignatius A, Wilke HJ - PLoS ONE (2013)

Bottom Line: Here, IDPs averaged 3.73 MPa and 1.60 MPa respectively, approximately two to four times higher in the ovine disc compared to human.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.In vivo IDPs were found to be higher in the ovine than in the human disc.

View Article: PubMed Central - PubMed

Affiliation: Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, Ulm, Germany. sandra.reitmaier@uni-ulm.de

ABSTRACT

Purpose: Currently, 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.

Methods: Intradiscal 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.

Results: The 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.

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Concise plottings of continuous pressure records.a) Representative course of IDP throughout three hours of activity and b) one hour of rest for the sheep (gray) and the human (red). Due to the lack of continuous recordings of the human IDP profile during the day, only a trend in the course of the pressure is shown.
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pone-0069610-g005: Concise plottings of continuous pressure records.a) Representative course of IDP throughout three hours of activity and b) one hour of rest for the sheep (gray) and the human (red). Due to the lack of continuous recordings of the human IDP profile during the day, only a trend in the course of the pressure is shown.

Mentions: A continuous three hours of activity decreased the IDP from ~1.0 to ~0.7 MPa (Figure 5a). In contrast, a continuous lying phase of one hour induced an IDP increase from ~0.2 to ~0.4 MPa (Figure 5b). The rate of pressure rise during rest was, with 0.2 MPa/hour, twice as high as the loss in pressure during the activity phase, of 0.1 MPa/hour.


Preliminary investigations on intradiscal pressures during daily activities: an in vivo study using the merino sheep.

Reitmaier S, Schmidt H, Ihler R, Kocak T, Graf N, Ignatius A, Wilke HJ - PLoS ONE (2013)

Concise plottings of continuous pressure records.a) Representative course of IDP throughout three hours of activity and b) one hour of rest for the sheep (gray) and the human (red). Due to the lack of continuous recordings of the human IDP profile during the day, only a trend in the course of the pressure is shown.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722231&req=5

pone-0069610-g005: Concise plottings of continuous pressure records.a) Representative course of IDP throughout three hours of activity and b) one hour of rest for the sheep (gray) and the human (red). Due to the lack of continuous recordings of the human IDP profile during the day, only a trend in the course of the pressure is shown.
Mentions: A continuous three hours of activity decreased the IDP from ~1.0 to ~0.7 MPa (Figure 5a). In contrast, a continuous lying phase of one hour induced an IDP increase from ~0.2 to ~0.4 MPa (Figure 5b). The rate of pressure rise during rest was, with 0.2 MPa/hour, twice as high as the loss in pressure during the activity phase, of 0.1 MPa/hour.

Bottom Line: Here, IDPs averaged 3.73 MPa and 1.60 MPa respectively, approximately two to four times higher in the ovine disc compared to human.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.In vivo IDPs were found to be higher in the ovine than in the human disc.

View Article: PubMed Central - PubMed

Affiliation: Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, Ulm, Germany. sandra.reitmaier@uni-ulm.de

ABSTRACT

Purpose: Currently, 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.

Methods: Intradiscal 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.

Results: The 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 MeSH