Fill of the nucleus cavity affects mechanical stability in compression, bending, and torsion of a spine segment, which has undergone nucleus replacement

Amy Arthur, Marco Cannella, Michael Keane, Wamis Singhatat, Edward Vresilovic, Michele Marcolongo

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

STUDY DESIGN.: Axial loading, rotation, and bending were applied to human cadaveric lumbar segments to investigate the changes in disc mechanics with denucleation and incremental delivery of a novel hydrogel nucleus replacement. OBJECTIVE.: The purpose of this study was to investigate the effect of nucleus implant injection pressure/volume relationships on the quasi-static mechanical behavior of the human cadaveric lumbar intervertebral disc to determine if intact biomechanics could be reproduced with nucleus-implanted discs. SUMMARY OF BACKGROUND DATA.: Previous studies have shown that volumetric filling of the nucleus cavity with a compliant nucleus replacement device will affect compressive stiffness of the implanted intervertebral disc, but data regarding restoration of mechanics through cavity pressurization are lacking. METHODS.: A total of 12 intact lumbar anterior column units were loaded in series in axial loading, axial rotation, lateral bending, and flexion/extension (FE). Each segment was fully denucleated and implanted with a hydrogel nucleus replacement using pressurization between 12 psi and 40 psi. Range of motion (ROM), neutral zone (NZ), energy dissipation (HYS), disc height (DH), and stiffness were compared among the intact, denucleated, and implanted conditions. RESULTS.: Denucleation significantly destabilized the segments compared to intact controls as shown by increased ROM, NZ, and HYS, and decreased DH and stiffness through the NZ. As the nucleus cavity was repressurized with increasing volumes of hydrogel implant, the segments were stabilized and DH was restored to the intact level. No significant differences from intact were observed in any loading direction for ROM, NZ, or DH after the segments were implanted with the nucleus replacement device using inflation pressures between 20 psi and 40 psi. CONCLUSION.: Compliant nucleus replacement using inflation pressures of 20 to 40 psi resulted in restoration of intact mechanics. Mechanical function was dependent on the volume of implant injected into the nucleus cavity.

Original languageEnglish (US)
Pages (from-to)1128-1135
Number of pages8
JournalSpine
Volume35
Issue number11
DOIs
StatePublished - May 15 2010

Fingerprint

Hydrogel
Articular Range of Motion
Mechanics
Spine
Intervertebral Disc
Economic Inflation
Weight-Bearing
Pressure
Equipment and Supplies
Biomechanical Phenomena
Injections

All Science Journal Classification (ASJC) codes

  • Clinical Neurology
  • Orthopedics and Sports Medicine

Cite this

Arthur, Amy ; Cannella, Marco ; Keane, Michael ; Singhatat, Wamis ; Vresilovic, Edward ; Marcolongo, Michele. / Fill of the nucleus cavity affects mechanical stability in compression, bending, and torsion of a spine segment, which has undergone nucleus replacement. In: Spine. 2010 ; Vol. 35, No. 11. pp. 1128-1135.
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abstract = "STUDY DESIGN.: Axial loading, rotation, and bending were applied to human cadaveric lumbar segments to investigate the changes in disc mechanics with denucleation and incremental delivery of a novel hydrogel nucleus replacement. OBJECTIVE.: The purpose of this study was to investigate the effect of nucleus implant injection pressure/volume relationships on the quasi-static mechanical behavior of the human cadaveric lumbar intervertebral disc to determine if intact biomechanics could be reproduced with nucleus-implanted discs. SUMMARY OF BACKGROUND DATA.: Previous studies have shown that volumetric filling of the nucleus cavity with a compliant nucleus replacement device will affect compressive stiffness of the implanted intervertebral disc, but data regarding restoration of mechanics through cavity pressurization are lacking. METHODS.: A total of 12 intact lumbar anterior column units were loaded in series in axial loading, axial rotation, lateral bending, and flexion/extension (FE). Each segment was fully denucleated and implanted with a hydrogel nucleus replacement using pressurization between 12 psi and 40 psi. Range of motion (ROM), neutral zone (NZ), energy dissipation (HYS), disc height (DH), and stiffness were compared among the intact, denucleated, and implanted conditions. RESULTS.: Denucleation significantly destabilized the segments compared to intact controls as shown by increased ROM, NZ, and HYS, and decreased DH and stiffness through the NZ. As the nucleus cavity was repressurized with increasing volumes of hydrogel implant, the segments were stabilized and DH was restored to the intact level. No significant differences from intact were observed in any loading direction for ROM, NZ, or DH after the segments were implanted with the nucleus replacement device using inflation pressures between 20 psi and 40 psi. CONCLUSION.: Compliant nucleus replacement using inflation pressures of 20 to 40 psi resulted in restoration of intact mechanics. Mechanical function was dependent on the volume of implant injected into the nucleus cavity.",
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Fill of the nucleus cavity affects mechanical stability in compression, bending, and torsion of a spine segment, which has undergone nucleus replacement. / Arthur, Amy; Cannella, Marco; Keane, Michael; Singhatat, Wamis; Vresilovic, Edward; Marcolongo, Michele.

In: Spine, Vol. 35, No. 11, 15.05.2010, p. 1128-1135.

Research output: Contribution to journalArticle

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T1 - Fill of the nucleus cavity affects mechanical stability in compression, bending, and torsion of a spine segment, which has undergone nucleus replacement

AU - Arthur, Amy

AU - Cannella, Marco

AU - Keane, Michael

AU - Singhatat, Wamis

AU - Vresilovic, Edward

AU - Marcolongo, Michele

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N2 - STUDY DESIGN.: Axial loading, rotation, and bending were applied to human cadaveric lumbar segments to investigate the changes in disc mechanics with denucleation and incremental delivery of a novel hydrogel nucleus replacement. OBJECTIVE.: The purpose of this study was to investigate the effect of nucleus implant injection pressure/volume relationships on the quasi-static mechanical behavior of the human cadaveric lumbar intervertebral disc to determine if intact biomechanics could be reproduced with nucleus-implanted discs. SUMMARY OF BACKGROUND DATA.: Previous studies have shown that volumetric filling of the nucleus cavity with a compliant nucleus replacement device will affect compressive stiffness of the implanted intervertebral disc, but data regarding restoration of mechanics through cavity pressurization are lacking. METHODS.: A total of 12 intact lumbar anterior column units were loaded in series in axial loading, axial rotation, lateral bending, and flexion/extension (FE). Each segment was fully denucleated and implanted with a hydrogel nucleus replacement using pressurization between 12 psi and 40 psi. Range of motion (ROM), neutral zone (NZ), energy dissipation (HYS), disc height (DH), and stiffness were compared among the intact, denucleated, and implanted conditions. RESULTS.: Denucleation significantly destabilized the segments compared to intact controls as shown by increased ROM, NZ, and HYS, and decreased DH and stiffness through the NZ. As the nucleus cavity was repressurized with increasing volumes of hydrogel implant, the segments were stabilized and DH was restored to the intact level. No significant differences from intact were observed in any loading direction for ROM, NZ, or DH after the segments were implanted with the nucleus replacement device using inflation pressures between 20 psi and 40 psi. CONCLUSION.: Compliant nucleus replacement using inflation pressures of 20 to 40 psi resulted in restoration of intact mechanics. Mechanical function was dependent on the volume of implant injected into the nucleus cavity.

AB - STUDY DESIGN.: Axial loading, rotation, and bending were applied to human cadaveric lumbar segments to investigate the changes in disc mechanics with denucleation and incremental delivery of a novel hydrogel nucleus replacement. OBJECTIVE.: The purpose of this study was to investigate the effect of nucleus implant injection pressure/volume relationships on the quasi-static mechanical behavior of the human cadaveric lumbar intervertebral disc to determine if intact biomechanics could be reproduced with nucleus-implanted discs. SUMMARY OF BACKGROUND DATA.: Previous studies have shown that volumetric filling of the nucleus cavity with a compliant nucleus replacement device will affect compressive stiffness of the implanted intervertebral disc, but data regarding restoration of mechanics through cavity pressurization are lacking. METHODS.: A total of 12 intact lumbar anterior column units were loaded in series in axial loading, axial rotation, lateral bending, and flexion/extension (FE). Each segment was fully denucleated and implanted with a hydrogel nucleus replacement using pressurization between 12 psi and 40 psi. Range of motion (ROM), neutral zone (NZ), energy dissipation (HYS), disc height (DH), and stiffness were compared among the intact, denucleated, and implanted conditions. RESULTS.: Denucleation significantly destabilized the segments compared to intact controls as shown by increased ROM, NZ, and HYS, and decreased DH and stiffness through the NZ. As the nucleus cavity was repressurized with increasing volumes of hydrogel implant, the segments were stabilized and DH was restored to the intact level. No significant differences from intact were observed in any loading direction for ROM, NZ, or DH after the segments were implanted with the nucleus replacement device using inflation pressures between 20 psi and 40 psi. CONCLUSION.: Compliant nucleus replacement using inflation pressures of 20 to 40 psi resulted in restoration of intact mechanics. Mechanical function was dependent on the volume of implant injected into the nucleus cavity.

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