Biomechanics of a novel minimally invasive lumbar interspinous spacer: effects on kinematics, facet loads, and foramen height.

Bruno C.R. Lazaro, Leonardo B.C. Brasiliense, Anna G.U. Sawa, Phillip M. Reyes, Nicholas Theodore, Volker K.H. Sonntag, Neil R. Crawford

Research output: Contribution to journalArticle

Abstract

OBJECTIVE: To study the alteration to normal biomechanics after insertion of a lumbar interspinous spacer (ISS) in vitro by nondestructive cadaveric flexibility testing. METHODS: Seven human cadaveric specimens were studied before and after ISS placement at L1-L2. Angular range of motion, lax zone, stiff zone, sagittal instantaneous axis of rotation (IAR), foraminal height, and facet loads were compared between conditions. Flexion, extension, lateral bending, and axial rotation were induced using pure moments (7.5 Nm maximum) while recording motion optoelectronically. The IAR was measured during loading with a 400 N compressive follower. Foraminal height changes were calculated using rigid body methods. Facet loads were assessed from surface strain and neural network analysis. RESULTS: After ISS insertion, range of motion and stiff zone during extension were significantly reduced (P < .01). Foraminal height was significantly reduced from flexion to extension in both normal and ISS-implanted conditions; there was significantly less reduction in foraminal height during extension with the ISS in place. The ISS reduced the mean facet load by 30% during flexion (P < .02) and 69% during extension (P < .015). The IAR after ISS implantation was less than 1 mm from the normal position (P > .18). CONCLUSION: The primary biomechanical effect of the ISS was reduced extension with associated reduced facet loads and smaller decrease in foraminal height. The ISS had little effect on sagittal IAR or on motion or facet loads in other directions.

Original languageEnglish (US)
JournalNeurosurgery
Volume66
Issue number3 Suppl Operative
StatePublished - Mar 2010
Externally publishedYes

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Biomechanical Phenomena
Articular Range of Motion

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

Cite this

Lazaro, B. C. R., Brasiliense, L. B. C., Sawa, A. G. U., Reyes, P. M., Theodore, N., Sonntag, V. K. H., & Crawford, N. R. (2010). Biomechanics of a novel minimally invasive lumbar interspinous spacer: effects on kinematics, facet loads, and foramen height. Neurosurgery, 66(3 Suppl Operative).

Biomechanics of a novel minimally invasive lumbar interspinous spacer : effects on kinematics, facet loads, and foramen height. / Lazaro, Bruno C.R.; Brasiliense, Leonardo B.C.; Sawa, Anna G.U.; Reyes, Phillip M.; Theodore, Nicholas; Sonntag, Volker K.H.; Crawford, Neil R.

In: Neurosurgery, Vol. 66, No. 3 Suppl Operative, 03.2010.

Research output: Contribution to journalArticle

Lazaro, BCR, Brasiliense, LBC, Sawa, AGU, Reyes, PM, Theodore, N, Sonntag, VKH & Crawford, NR 2010, 'Biomechanics of a novel minimally invasive lumbar interspinous spacer: effects on kinematics, facet loads, and foramen height.', Neurosurgery, vol. 66, no. 3 Suppl Operative.
Lazaro BCR, Brasiliense LBC, Sawa AGU, Reyes PM, Theodore N, Sonntag VKH et al. Biomechanics of a novel minimally invasive lumbar interspinous spacer: effects on kinematics, facet loads, and foramen height. Neurosurgery. 2010 Mar;66(3 Suppl Operative).
Lazaro, Bruno C.R. ; Brasiliense, Leonardo B.C. ; Sawa, Anna G.U. ; Reyes, Phillip M. ; Theodore, Nicholas ; Sonntag, Volker K.H. ; Crawford, Neil R. / Biomechanics of a novel minimally invasive lumbar interspinous spacer : effects on kinematics, facet loads, and foramen height. In: Neurosurgery. 2010 ; Vol. 66, No. 3 Suppl Operative.
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AU - Lazaro, Bruno C.R.

AU - Brasiliense, Leonardo B.C.

AU - Sawa, Anna G.U.

AU - Reyes, Phillip M.

AU - Theodore, Nicholas

AU - Sonntag, Volker K.H.

AU - Crawford, Neil R.

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N2 - OBJECTIVE: To study the alteration to normal biomechanics after insertion of a lumbar interspinous spacer (ISS) in vitro by nondestructive cadaveric flexibility testing. METHODS: Seven human cadaveric specimens were studied before and after ISS placement at L1-L2. Angular range of motion, lax zone, stiff zone, sagittal instantaneous axis of rotation (IAR), foraminal height, and facet loads were compared between conditions. Flexion, extension, lateral bending, and axial rotation were induced using pure moments (7.5 Nm maximum) while recording motion optoelectronically. The IAR was measured during loading with a 400 N compressive follower. Foraminal height changes were calculated using rigid body methods. Facet loads were assessed from surface strain and neural network analysis. RESULTS: After ISS insertion, range of motion and stiff zone during extension were significantly reduced (P < .01). Foraminal height was significantly reduced from flexion to extension in both normal and ISS-implanted conditions; there was significantly less reduction in foraminal height during extension with the ISS in place. The ISS reduced the mean facet load by 30% during flexion (P < .02) and 69% during extension (P < .015). The IAR after ISS implantation was less than 1 mm from the normal position (P > .18). CONCLUSION: The primary biomechanical effect of the ISS was reduced extension with associated reduced facet loads and smaller decrease in foraminal height. The ISS had little effect on sagittal IAR or on motion or facet loads in other directions.

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