Department of Neurosurgery, University of Michigan Medical School Thoracic Pedicle Screws Thoracic Pedicle Screws Anatomy and Technique Anatomy and Technique Frank La Marca M. D. Frank La Marca M. D. Department of Neurosurgery Department of Neurosurgery University of Michigan University of Michigan
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Department of Neurosurgery, University of Michigan Medical School
Thoracic Pedicle ScrewsThoracic Pedicle ScrewsAnatomy and TechniqueAnatomy and Technique
Frank La Marca M. D.Frank La Marca M. D.
Department of NeurosurgeryDepartment of Neurosurgery
University of MichiganUniversity of Michigan
Department of Neurosurgery, University of Michigan Medical School
Relevant AnatomyRelevant Anatomy
• a = chord lengtha = chord length• b = transverse diameterb = transverse diameter• c = angle of insertionc = angle of insertion• d = pedicle lengthd = pedicle length
Vaccaro et al. JBJS 77(8), 1995.Vaccaro et al. JBJS 77(8), 1995.
Department of Neurosurgery, University of Michigan Medical School
Department of Neurosurgery, University of Michigan Medical School
Basic TechniqueBasic TechniqueHistoryHistory
•Starting pointStarting point– Mid-articular line Mid-articular line
(vertically)(vertically)– Bisection of transverse Bisection of transverse
process (horizontally)process (horizontally)
•Screw directed Screw directed perpendicular to plane of the perpendicular to plane of the posterior elementsposterior elements•Accuracy not documentedAccuracy not documented
Roy-Camille et al. Clin Orth. 203, 1986.Roy-Camille et al. Clin Orth. 203, 1986.
Department of Neurosurgery, University of Michigan Medical School
Basic TechniqueBasic TechniqueHistoryHistory
•Modified starting pointModified starting point– Mid-articular line Mid-articular line
(vertically)(vertically)– Superior border of Superior border of
transverse process at transverse process at juncture with the lamina juncture with the lamina (horizontally)(horizontally)
Xu et al, Spine. 24(2), 1999.Xu et al, Spine. 24(2), 1999.
Vaccaro et al. JBJS 77(8), 1995.Vaccaro et al. JBJS 77(8), 1995.
Department of Neurosurgery, University of Michigan Medical School
•Biomechanically Biomechanically superior anchor pointsuperior anchor point•Can be performed safelyCan be performed safely•Enhance curve Enhance curve correctioncorrection•Save fusion levelsSave fusion levels•Address all curve typesAddress all curve types
Department of Neurosurgery, University of Michigan Medical School
•Significant learning Significant learning curvecurve•CostCost•Radiation exposure (not Radiation exposure (not with free hand with free hand technique)technique)•Neurologic riskNeurologic risk
Department of Neurosurgery, University of Michigan Medical School
•Accuracy = rate of fully Accuracy = rate of fully contained screwscontained screws•Accepted and well-Accepted and well-published for large published for large lumbar pedicleslumbar pedicles•Smaller thoracic Smaller thoracic pedicles may preclude pedicles may preclude full containmentfull containment
Department of Neurosurgery, University of Michigan Medical School
•Volumetric canal Volumetric canal intrusion of hooks vs intrusion of hooks vs screwsscrews•Medial perforation of Medial perforation of thoracic pedicle screwthoracic pedicle screw
– >>2mm c/w intrusion of 2mm c/w intrusion of smallest hooksmallest hook
– >>3mm c/w intrusion of 3mm c/w intrusion of largest hooklargest hook
Department of Neurosurgery, University of Michigan Medical School
•40 patients, 279 T-screws40 patients, 279 T-screws•Flouroscopic guidance, no Flouroscopic guidance, no laminotomieslaminotomies•Post-op CTPost-op CT•99% of screws were fully 99% of screws were fully contained or inserted with contained or inserted with acceptable medial/lateral acceptable medial/lateral wall breechwall breech•No neurologic deficitsNo neurologic deficits•2 screw revisions from 2 screw revisions from anterior perforationanterior perforation
Level N Out Medial Lateral Level N Out Medial Lateral T1-4 39 27(69%) 11% 89%T1-4 39 27(69%) 11% 89%T5-8 77 47(61%) 34% 66%T5-8 77 47(61%) 34% 66%T9-12 163 46(28%) 42% 58%T9-12 163 46(28%) 42% 58%
Belmont et al. Spine. 26(21) 2001.Belmont et al. Spine. 26(21) 2001.
Department of Neurosurgery, University of Michigan Medical School