Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine

Implications for Stabilization With Improved Arthrodesis

Alexander K. Yu, Catherine M. Siegfried, Brandon Chew, Joseph Hobbs, Abraham Sabersky, Diana Jho, Daniel J. Cook, Jonathan Brad Bellotte, Donald M. Whiting, Boyle C. Cheng

Research output: Contribution to journalArticle

Abstract

METHODS: Six fresh-frozen lumbar cadaveric specimens were used. Each untreated specimen (Intact) underwent biomechanical testing. Next, each specimen had a unilateral transforaminal lumbar interbody fusion performed at L3-L4 using a cage with an integrated load cell. Pedicle screws were also placed at this time. Subsequently, the Isobar was implanted and tested, and finally, a rigid rod replaced the Isobar in the same pedicle screw arrangement.

SUMMARY OF BACKGROUND DATA: Dynamic fusion rods may enhance arthrodesis compared with a rigid rod. Wolff's law implies that bone remodeling and growth may be enhanced through anterior column loading (AL). This is important for dynamic fusion rods because their purpose is to increase AL.

STUDY DESIGN: A comparative biomechanical human cadaveric spine study of a dynamic fusion rod and a traditional titanium rod.

OBJECTIVE: The purpose of this study was to measure and compare the biomechanical metrics associated with a dynamic fusion device, Isobar TTL Evolution, and a rigid rod.

RESULTS: In terms of range of motion, the Isobar performed comparably to the rigid rod and there was no statistical difference found between Isobar and rigid rod. There was a significant difference between the intact and rigid rod and also between intact and Isobar conditions in flexion extension. For interpedicular displacement, there was a significant increase in flexion extension (P=0.017) for the Isobar compared with the rigid rod. Isobar showed increased AL under axial compression compared with the rigid rod (P=0.024).

CONCLUSIONS: Isobar provided comparable stabilization to a rigid rod when using range of motion as the metric, however, AL was increased because of the greater interpedicular displacement of dynamic rod compared with a rigid rod. By increasing interpedicular displacement and AL, it potentially brings clinical benefit to procedures relying on arthrodesis.

Original languageEnglish (US)
Pages (from-to)E325-E330
JournalClinical Spine Surgery
Volume29
Issue number7
DOIs
StatePublished - Aug 1 2016

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Arthrodesis
Articular Range of Motion
Biomechanical Phenomena
Spine
Bone Remodeling
Bone Development
Weight-Bearing
Titanium
Equipment and Supplies
Pedicle Screws

All Science Journal Classification (ASJC) codes

  • Surgery
  • Orthopedics and Sports Medicine
  • Clinical Neurology

Cite this

Yu, Alexander K. ; Siegfried, Catherine M. ; Chew, Brandon ; Hobbs, Joseph ; Sabersky, Abraham ; Jho, Diana ; Cook, Daniel J. ; Bellotte, Jonathan Brad ; Whiting, Donald M. ; Cheng, Boyle C. / Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine : Implications for Stabilization With Improved Arthrodesis. In: Clinical Spine Surgery. 2016 ; Vol. 29, No. 7. pp. E325-E330.
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title = "Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine: Implications for Stabilization With Improved Arthrodesis",
abstract = "METHODS: Six fresh-frozen lumbar cadaveric specimens were used. Each untreated specimen (Intact) underwent biomechanical testing. Next, each specimen had a unilateral transforaminal lumbar interbody fusion performed at L3-L4 using a cage with an integrated load cell. Pedicle screws were also placed at this time. Subsequently, the Isobar was implanted and tested, and finally, a rigid rod replaced the Isobar in the same pedicle screw arrangement.SUMMARY OF BACKGROUND DATA: Dynamic fusion rods may enhance arthrodesis compared with a rigid rod. Wolff's law implies that bone remodeling and growth may be enhanced through anterior column loading (AL). This is important for dynamic fusion rods because their purpose is to increase AL.STUDY DESIGN: A comparative biomechanical human cadaveric spine study of a dynamic fusion rod and a traditional titanium rod.OBJECTIVE: The purpose of this study was to measure and compare the biomechanical metrics associated with a dynamic fusion device, Isobar TTL Evolution, and a rigid rod.RESULTS: In terms of range of motion, the Isobar performed comparably to the rigid rod and there was no statistical difference found between Isobar and rigid rod. There was a significant difference between the intact and rigid rod and also between intact and Isobar conditions in flexion extension. For interpedicular displacement, there was a significant increase in flexion extension (P=0.017) for the Isobar compared with the rigid rod. Isobar showed increased AL under axial compression compared with the rigid rod (P=0.024).CONCLUSIONS: Isobar provided comparable stabilization to a rigid rod when using range of motion as the metric, however, AL was increased because of the greater interpedicular displacement of dynamic rod compared with a rigid rod. By increasing interpedicular displacement and AL, it potentially brings clinical benefit to procedures relying on arthrodesis.",
author = "Yu, {Alexander K.} and Siegfried, {Catherine M.} and Brandon Chew and Joseph Hobbs and Abraham Sabersky and Diana Jho and Cook, {Daniel J.} and Bellotte, {Jonathan Brad} and Whiting, {Donald M.} and Cheng, {Boyle C.}",
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Yu, AK, Siegfried, CM, Chew, B, Hobbs, J, Sabersky, A, Jho, D, Cook, DJ, Bellotte, JB, Whiting, DM & Cheng, BC 2016, 'Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine: Implications for Stabilization With Improved Arthrodesis', Clinical Spine Surgery, vol. 29, no. 7, pp. E325-E330. https://doi.org/10.1097/BSD.0b013e31827588b1

Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine : Implications for Stabilization With Improved Arthrodesis. / Yu, Alexander K.; Siegfried, Catherine M.; Chew, Brandon; Hobbs, Joseph; Sabersky, Abraham; Jho, Diana; Cook, Daniel J.; Bellotte, Jonathan Brad; Whiting, Donald M.; Cheng, Boyle C.

In: Clinical Spine Surgery, Vol. 29, No. 7, 01.08.2016, p. E325-E330.

Research output: Contribution to journalArticle

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T1 - Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine

T2 - Implications for Stabilization With Improved Arthrodesis

AU - Yu, Alexander K.

AU - Siegfried, Catherine M.

AU - Chew, Brandon

AU - Hobbs, Joseph

AU - Sabersky, Abraham

AU - Jho, Diana

AU - Cook, Daniel J.

AU - Bellotte, Jonathan Brad

AU - Whiting, Donald M.

AU - Cheng, Boyle C.

PY - 2016/8/1

Y1 - 2016/8/1

N2 - METHODS: Six fresh-frozen lumbar cadaveric specimens were used. Each untreated specimen (Intact) underwent biomechanical testing. Next, each specimen had a unilateral transforaminal lumbar interbody fusion performed at L3-L4 using a cage with an integrated load cell. Pedicle screws were also placed at this time. Subsequently, the Isobar was implanted and tested, and finally, a rigid rod replaced the Isobar in the same pedicle screw arrangement.SUMMARY OF BACKGROUND DATA: Dynamic fusion rods may enhance arthrodesis compared with a rigid rod. Wolff's law implies that bone remodeling and growth may be enhanced through anterior column loading (AL). This is important for dynamic fusion rods because their purpose is to increase AL.STUDY DESIGN: A comparative biomechanical human cadaveric spine study of a dynamic fusion rod and a traditional titanium rod.OBJECTIVE: The purpose of this study was to measure and compare the biomechanical metrics associated with a dynamic fusion device, Isobar TTL Evolution, and a rigid rod.RESULTS: In terms of range of motion, the Isobar performed comparably to the rigid rod and there was no statistical difference found between Isobar and rigid rod. There was a significant difference between the intact and rigid rod and also between intact and Isobar conditions in flexion extension. For interpedicular displacement, there was a significant increase in flexion extension (P=0.017) for the Isobar compared with the rigid rod. Isobar showed increased AL under axial compression compared with the rigid rod (P=0.024).CONCLUSIONS: Isobar provided comparable stabilization to a rigid rod when using range of motion as the metric, however, AL was increased because of the greater interpedicular displacement of dynamic rod compared with a rigid rod. By increasing interpedicular displacement and AL, it potentially brings clinical benefit to procedures relying on arthrodesis.

AB - METHODS: Six fresh-frozen lumbar cadaveric specimens were used. Each untreated specimen (Intact) underwent biomechanical testing. Next, each specimen had a unilateral transforaminal lumbar interbody fusion performed at L3-L4 using a cage with an integrated load cell. Pedicle screws were also placed at this time. Subsequently, the Isobar was implanted and tested, and finally, a rigid rod replaced the Isobar in the same pedicle screw arrangement.SUMMARY OF BACKGROUND DATA: Dynamic fusion rods may enhance arthrodesis compared with a rigid rod. Wolff's law implies that bone remodeling and growth may be enhanced through anterior column loading (AL). This is important for dynamic fusion rods because their purpose is to increase AL.STUDY DESIGN: A comparative biomechanical human cadaveric spine study of a dynamic fusion rod and a traditional titanium rod.OBJECTIVE: The purpose of this study was to measure and compare the biomechanical metrics associated with a dynamic fusion device, Isobar TTL Evolution, and a rigid rod.RESULTS: In terms of range of motion, the Isobar performed comparably to the rigid rod and there was no statistical difference found between Isobar and rigid rod. There was a significant difference between the intact and rigid rod and also between intact and Isobar conditions in flexion extension. For interpedicular displacement, there was a significant increase in flexion extension (P=0.017) for the Isobar compared with the rigid rod. Isobar showed increased AL under axial compression compared with the rigid rod (P=0.024).CONCLUSIONS: Isobar provided comparable stabilization to a rigid rod when using range of motion as the metric, however, AL was increased because of the greater interpedicular displacement of dynamic rod compared with a rigid rod. By increasing interpedicular displacement and AL, it potentially brings clinical benefit to procedures relying on arthrodesis.

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