Introduction: Previous studies have shown that kyphotic deformity significantly increases spinal cord intramedullary pressure(IMP). IMP changes in scoliotic deformity have not been studied to our knowledge. An in-vitro cadaveric model is used to define the relationship between main thoracic scoliotic deformity and spinal cord IMP.

Methods: In six fresh-frozen cadavers, a progressive scoliotic deformity was created. Cadavers were positioned sitting with physiologic thoracic coronal and sagittal alignment, head stabilized with skull clamp and spine segmentally instrumented from occiput to L3. The T3/T4 ligamentum flavum was removed, dura opened, and 3 pressure sensors were advanced caudally to T4/T5, T7/T8 and T10/T11 within the cord parenchyma. A stepwise main thoracic T4-T11 scoliotic deformity with rostral and caudal compensatory curves was then induced by coronally bending thoracic rods and closing lateral segmental osteotomies by compressing on the concavity and distracting on convexity. At each step, fluoroscopic images and pressure measurements were obtained; the T4-T11 Cobb angle was measured.

Results: The creation of main thoracic scoliotic deformity did not significantly increase IMP. The mean main thoracic maximal scoliotic deformity created was 77±2 degrees (range:71-84). At maximal deformity, the mean IMP change at T4/5, T7/8, T10/11 was 2±2mm Hg, 1±1mm Hg and 1±1mm Hg, respectively. This differs significantly from previously published data demonstrating a significant marked increase in IMP for progressive cervical and thoracic kyphotic deformity. In one cadaver, a kyphotic deformity was created following coronal curve testing, confirming the previously reported impact of kyphosis on IMP.

Conclusions: In this cadaveric study, main thoracic scoliotic deformity did not significantly increase IMP. These findings correlate with presentation of isolated main thoracic scoliotic deformity patients with cosmetic and pulmonary symptoms without myelopathic symptoms. This study helps explain the relative absence of myelopathy in isolated main thoracic coronal plane deformity.

Patient Care: A pathophysiological explanation is proposed to help explain the the relative absence of myelopathy in isolated main thoracic coronal plane deformity. This correlates with clinical presentation such that cosmetic and pulmonary symptoms without myelopathy predominate in the isolated main thoracic scoliotic deformity patient.

Learning Objectives: By the conclusion of this presentation, participants should be able to: 1) Identify the relationship between spinal deformity and spinal cord intramedullary pressure 2) Discuss the possible pathophysiologic basis for the relative absence of myelopathy in scoliosis

References: 1. Farley CW, Curt BA, Pettigrew DB, Holtz JR, Dollin N, Kuntz C 4th. Spinal cord intramedullary pressure in thoracic kyphotic deformity: a cadaveric study. Spine (Phila Pa 1976). 2012 Feb 15;37(4):E224-30. 2. Winestone JS, Farley CW, Curt BA, Chavanne A, Dollin N, Pettigrew DB, Kuntz C. Laminectomy, durotomy, and piotomy effects on spinal cord intramedullary pressure in severe cervical and thoracic kyphotic deformity: a cadaveric study. J Neurosurg Spine. 2012 Feb;16(2):195-200. Epub 2011 Nov 11.