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Spinal Cord Intramedullary Pressure in Thoracic Kyphotic Deformity: A Cadaveric Study.
MedLine Citation:
PMID:  21857404     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
ABSTRACT: Study Design. In vitro cadaveric study of thoracic spinal cord intramedullary pressure (IMP) in kyphotic deformity.Objective. To define the relationship between thoracic spinal kyphotic deformity and spinal cord intramedullary pressure.Summary of Background Data. Previous studies of asymptomatic volunteers have revealed that there is wide variation in regional sagittal neutral upright thoracic spinal alignment with "normal" thoracic T4-T12 kyphosis ranging up to approximately +69° for 98.5% of the asymptomatic adult population. We sought to determine if IMP changes in response to increasing thoracic kyphosis.Methods. In eight fresh-frozen cadavers, a progressive kyphotic deformity was created. Cadavers were positioned sitting with physiological thoracic kyphosis, head stabilized using a skull clamp and spine segmentally instrumented from occiput to L2. The T3/T4 ligamentum flavum was removed, dura opened, and 3 pressure sensors were advanced caudally to T4/T5, T7/T8 and T11/T12 within the cord parenchyma. A step-wise thoracic kyphotic deformity was then induced by sequentially releasing and retightening the skull clamp while distracting posterior short segment rods and closing anterior segmental osteotomies. After each step, fluoroscopic images and pressure measurements were obtained; the T4-T12 Cobb angle was measured.Results. Minor IMP increases of 2-5 mm Hg were observed at one or more spinal cord levels in 1 of 8 cadavers when the Cobb angle < +51° and in 4 of 8 cadavers when > +51° and < +63°. For Cobb angles > +51° and < +63°, a statistically significant, minor increase in IMP was detected at the T7/T8 level only (p = 0.02). At Cobb angles exceeding +63°, ΔIMP progressively increased at one or more spinal cord levels in 8 of 8 cadavers. Cobb angles ranging from +63° to +149° resulted in statistically significant increases in IMP ranging to > 50 mm Hg. ΔIMP did not correlate with segmental spinal cord diameter (stenosis).Conclusion. Thoracic kyphosis less than +51° resulted in no meaningful increase in IMP while kyphosis measuring +51° to +63° resulted in minor increases in IMP. After the thoracic kyphosis exceeded +63°, IMP increased significantly. ΔIMP with spinal alignment may help explain the wide range of "normal" thoracic neutral upright sagittal alignment in studies of asymptomatic adult individuals and may help further define thoracic kyphotic deformity.
Authors:
Chad W Farley; Bradford A Curt; David B Pettigrew; Jeffrey R Holtz; Neal Dollin; Charles Kuntz
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-8-18
Journal Detail:
Title:  Spine     Volume:  -     ISSN:  1528-1159     ISO Abbreviation:  -     Publication Date:  2011 Aug 
Date Detail:
Created Date:  2011-8-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7610646     Medline TA:  Spine (Phila Pa 1976)     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
1The UC Neuroscience Institute: Department of Neurosurgery, University of Cincinnati College of Medicine, Mayfield Clinic and Spine Institute, Cincinnati, Ohio 2Department of Medical Education, University of Cincinnati College of Medicine, Cincinnati, Ohio.
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