Trans-endplate nucleotomy increases deformation and creep response in axial loading

Wade Johannessen, Jordan M. Cloyd, Grace D. O'Connell, Edward J. Vresilovic, Dawn M. Elliott

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Knowledge of the functional role of the nucleus pulposus is critical for the development and evaluation of disc treatment strategies to restore mechanical function. While previous motion segment studies have shown that nucleotomy alters disc mechanics, disruption of the annulus fibrosus may have influenced these experiments. The objective of this study was to determine the mechanical role of the nucleus pulposus in support of axial loads via a trans-endplate nucleotomy procedure. Sheep motion segments were randomly assigned to three groups: control, limited nucleotomy, and radical nucleotomy. Mechanical testing consisted of 20 cycles of compression-tension, a 1-h creep, and a slow constant-rate compressive ramp test. Nucleotomy led to increased axial deformations, in particular an elongated neutral zone, a greater range of motion, and altered creep behavior. In general, the elastic properties exhibited a graded response with respect to the amount of nucleus material removed. This graded effect can be attributed to swelling of the nucleus pulposus in the limited nucleotomy group, whereas little swelling was observed in the radical group. The findings of the present study indicate that functional evaluation of nucleus pulposus replacements and disc implants should include range of motion measures (including neutral zone) and viscoelastic creep experiments in addition to considering compressive stiffness.

Original languageEnglish (US)
Pages (from-to)687-696
Number of pages10
JournalAnnals of Biomedical Engineering
Issue number4
StatePublished - Apr 2006

All Science Journal Classification (ASJC) codes

  • Biomedical Engineering


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