Biomechanical advantage of the index-level pedicle screw in unstable thoracolumbar junction fractures: Presented at the 2010 Joint Spine Section Meeting - Laboratory investigation

Ali A. Baaj, Phillip M. Reyes, Ali S. Yaqoobi, Juan S. Uribe, Fernando Vale Diaz, Nicholas Theodore, Volker K.H. Sonntag, Neil R. Crawford

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Object. Unstable fractures at the thoracolumbar junction often require extended, posterior, segmental pedicular fixation. Some surgeons have reported good clinical outcomes with short-segment constructs if additional pedicle screws are inserted at the fractured level. The goal of this study was to quantify the biomechanical advantage of the index-level screw in a fracture model. Methods. Six human cadaveric T10-L4 specimens were tested. A 3-column injury at L-1 was simulated, and 4 posterior constructs were tested as follows: one-above-one-below (short construct) with/without index-level screws, and two-above-two-below (long construct) with/without index-level screws. Pure moments were applied quasistatically while 3D motion was measured optoelectronically. The range of motion (ROM) and lax zone across T12-L2 were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Results. All constructs significantly reduced the ROM and lax zone in the fractured specimens. With or without index-level screws, the long-segment constructs provided better immobilization than the short-segment constructs during all loading modes. Adding an index-level screw to the short-segment construct significantly improved stability during flexion and lateral bending; there was no significant improvement in stability when an index-level screw was added to the long-segment construct. Overall, bilateral index-level screws decreased the ROM of the 1-level construct by 25% but decreased the ROM of the 2-level construct by only 3%. Conclusions. In a fracture model, adding index-level pedicle screws to short-segment constructs improves stability, although stability remains less than that provided by long-segment constructs with or without index-level pedicle screws. Therefore, highly unstable fractures likely require extended, long-segment constructs for optimum stability.

Original languageEnglish (US)
Pages (from-to)192-197
Number of pages6
JournalJournal of Neurosurgery: Spine
Volume14
Issue number2
DOIs
StatePublished - Feb 1 2011

Fingerprint

Articular Range of Motion
Spine
Joints
Phthiraptera
Immobilization
Pedicle Screws
Wounds and Injuries

Keywords

  • Biomechanical study
  • Pedicle screw
  • Spine fracture
  • Thoracolumbar junction

ASJC Scopus subject areas

  • Surgery
  • Neurology
  • Clinical Neurology

Cite this

Biomechanical advantage of the index-level pedicle screw in unstable thoracolumbar junction fractures : Presented at the 2010 Joint Spine Section Meeting - Laboratory investigation. / Baaj, Ali A.; Reyes, Phillip M.; Yaqoobi, Ali S.; Uribe, Juan S.; Vale Diaz, Fernando; Theodore, Nicholas; Sonntag, Volker K.H.; Crawford, Neil R.

In: Journal of Neurosurgery: Spine, Vol. 14, No. 2, 01.02.2011, p. 192-197.

Research output: Contribution to journalArticle

Baaj, Ali A. ; Reyes, Phillip M. ; Yaqoobi, Ali S. ; Uribe, Juan S. ; Vale Diaz, Fernando ; Theodore, Nicholas ; Sonntag, Volker K.H. ; Crawford, Neil R. / Biomechanical advantage of the index-level pedicle screw in unstable thoracolumbar junction fractures : Presented at the 2010 Joint Spine Section Meeting - Laboratory investigation. In: Journal of Neurosurgery: Spine. 2011 ; Vol. 14, No. 2. pp. 192-197.
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abstract = "Object. Unstable fractures at the thoracolumbar junction often require extended, posterior, segmental pedicular fixation. Some surgeons have reported good clinical outcomes with short-segment constructs if additional pedicle screws are inserted at the fractured level. The goal of this study was to quantify the biomechanical advantage of the index-level screw in a fracture model. Methods. Six human cadaveric T10-L4 specimens were tested. A 3-column injury at L-1 was simulated, and 4 posterior constructs were tested as follows: one-above-one-below (short construct) with/without index-level screws, and two-above-two-below (long construct) with/without index-level screws. Pure moments were applied quasistatically while 3D motion was measured optoelectronically. The range of motion (ROM) and lax zone across T12-L2 were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Results. All constructs significantly reduced the ROM and lax zone in the fractured specimens. With or without index-level screws, the long-segment constructs provided better immobilization than the short-segment constructs during all loading modes. Adding an index-level screw to the short-segment construct significantly improved stability during flexion and lateral bending; there was no significant improvement in stability when an index-level screw was added to the long-segment construct. Overall, bilateral index-level screws decreased the ROM of the 1-level construct by 25{\%} but decreased the ROM of the 2-level construct by only 3{\%}. Conclusions. In a fracture model, adding index-level pedicle screws to short-segment constructs improves stability, although stability remains less than that provided by long-segment constructs with or without index-level pedicle screws. Therefore, highly unstable fractures likely require extended, long-segment constructs for optimum stability.",
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T1 - Biomechanical advantage of the index-level pedicle screw in unstable thoracolumbar junction fractures

T2 - Presented at the 2010 Joint Spine Section Meeting - Laboratory investigation

AU - Baaj, Ali A.

AU - Reyes, Phillip M.

AU - Yaqoobi, Ali S.

AU - Uribe, Juan S.

AU - Vale Diaz, Fernando

AU - Theodore, Nicholas

AU - Sonntag, Volker K.H.

AU - Crawford, Neil R.

PY - 2011/2/1

Y1 - 2011/2/1

N2 - Object. Unstable fractures at the thoracolumbar junction often require extended, posterior, segmental pedicular fixation. Some surgeons have reported good clinical outcomes with short-segment constructs if additional pedicle screws are inserted at the fractured level. The goal of this study was to quantify the biomechanical advantage of the index-level screw in a fracture model. Methods. Six human cadaveric T10-L4 specimens were tested. A 3-column injury at L-1 was simulated, and 4 posterior constructs were tested as follows: one-above-one-below (short construct) with/without index-level screws, and two-above-two-below (long construct) with/without index-level screws. Pure moments were applied quasistatically while 3D motion was measured optoelectronically. The range of motion (ROM) and lax zone across T12-L2 were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Results. All constructs significantly reduced the ROM and lax zone in the fractured specimens. With or without index-level screws, the long-segment constructs provided better immobilization than the short-segment constructs during all loading modes. Adding an index-level screw to the short-segment construct significantly improved stability during flexion and lateral bending; there was no significant improvement in stability when an index-level screw was added to the long-segment construct. Overall, bilateral index-level screws decreased the ROM of the 1-level construct by 25% but decreased the ROM of the 2-level construct by only 3%. Conclusions. In a fracture model, adding index-level pedicle screws to short-segment constructs improves stability, although stability remains less than that provided by long-segment constructs with or without index-level pedicle screws. Therefore, highly unstable fractures likely require extended, long-segment constructs for optimum stability.

AB - Object. Unstable fractures at the thoracolumbar junction often require extended, posterior, segmental pedicular fixation. Some surgeons have reported good clinical outcomes with short-segment constructs if additional pedicle screws are inserted at the fractured level. The goal of this study was to quantify the biomechanical advantage of the index-level screw in a fracture model. Methods. Six human cadaveric T10-L4 specimens were tested. A 3-column injury at L-1 was simulated, and 4 posterior constructs were tested as follows: one-above-one-below (short construct) with/without index-level screws, and two-above-two-below (long construct) with/without index-level screws. Pure moments were applied quasistatically while 3D motion was measured optoelectronically. The range of motion (ROM) and lax zone across T12-L2 were measured during flexion, extension, left and right lateral bending, and left and right axial rotation. Results. All constructs significantly reduced the ROM and lax zone in the fractured specimens. With or without index-level screws, the long-segment constructs provided better immobilization than the short-segment constructs during all loading modes. Adding an index-level screw to the short-segment construct significantly improved stability during flexion and lateral bending; there was no significant improvement in stability when an index-level screw was added to the long-segment construct. Overall, bilateral index-level screws decreased the ROM of the 1-level construct by 25% but decreased the ROM of the 2-level construct by only 3%. Conclusions. In a fracture model, adding index-level pedicle screws to short-segment constructs improves stability, although stability remains less than that provided by long-segment constructs with or without index-level pedicle screws. Therefore, highly unstable fractures likely require extended, long-segment constructs for optimum stability.

KW - Biomechanical study

KW - Pedicle screw

KW - Spine fracture

KW - Thoracolumbar junction

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