Laminectomy, durotomy, and piotomy effects on spinal cord intramedullary pressure in severe cervical and thoracic kyphotic deformity: a cadaveric study

Laboratory investigation

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Object

Previous studies have shown that cervical and thoracic kyphotic deformity increases spinal cord intramedullary pressure (IMP). Using a cadaveric model, the authors investigated whether posterior decompression can adequately decrease elevated IMP in severe cervical and thoracic kyphotic deformities.

Methods

Using an established cadaveric model, a kyphotic deformity was created in 16 fresh human cadavers (8 cervical and 8 thoracic). A single-level rostral laminotomy and durotomy were performed to place intraparenchymal pressure monitors in the spinal cord at C-2, C4–5, and C-7 in the cervical study group and at T4–5, T7–8, and T11–12 in the thoracic study group. Intramedullary pressure was recorded at maximal kyphosis. Posterior laminar, dural, and pial decompressions were performed while IMP was monitored. In 2 additional cadavers (1 cervical and 1 thoracic), a kyphotic deformity was created and then corrected.

Results

The creation of the cervical and thoracic kyphotic deformities resulted in significant increases in IMP. The mean increase in cervical and thoracic IMP (change in IMP [ΔIMP]) for all monitored levels was 37.8 ± 7.9 and 46.4 ± 6.4 mm Hg, respectively. After laminectomies were performed, the mean cervical and thoracic IMP was reduced by 22.5% and 18.5%, respectively. After midsagittal durotomies were performed, the mean cervical and thoracic IMP was reduced by 62.8% and 69.9%, respectively. After midsagittal piotomies were performed, the mean cervical and thoracic IMP was reduced by 91.3% and 105.9%, respectively. In 2 cadavers in which a kyphotic deformity was created and then corrected, the ΔIMP increased with the creation of the deformity and returned to zero at all levels when the deformity was corrected.

Conclusions

In this cadaveric study, laminar decompression reduced ΔIMP by approximately 15%–25%, while correction of the kyphotic deformity returned ΔIMP to zero. This study helps explain the pathophysiology of myelopathy in kyphotic deformity and the failure of laminectomy alone for cervical and thoracic kyphotic deformities with myelopathy. In addition, the study emphasizes the need for correction of deformity during operative treatment of kyphotic deformity, the need for maintaining adequate intraoperative blood pressure during operative treatment, and the higher risk of spinal cord injury associated with operative treatment of kyphotic deformity.

Abbreviations used in this paper: IMP = intramedullary pressure; ΔIMP = change in IMP.

Article Information

Address correspondence to: Charles Kuntz IV, M.D., Department of Neurosurgery, University of Cincinnati College of Medicine, ML 0515, 231 Albert Sabin Way, Cincinnati, Ohio 45219. email: charleskuntz@yahoo.com.

Please include this information when citing this paper: published online November 11, 2011; DOI: 10.3171/2011.10.SPINE11377.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Lateral radiographs of the cervical and thoracic spine at the position of the cervical starting lordotic alignment (A), cervical kyphotic deformity (B), thoracic starting kyphotic alignment (C), and thoracic kyphotic deformity (D).

  • View in gallery

    Bar graph showing ΔIMP at C-2 (A), C4–5 (B), C-7 (C), and the mean ΔIMP of the cervical spinal cord (D) prior to induction of kyphosis, at maximal kyphosis, after laminectomy, after midsagittal durotomy, and after incising the midsagittal pia (*p < 0.05).

  • View in gallery

    Bar graph showing the ΔIMP at T4–5 (A), T7–8 (B), T11–12 (C), and the mean thoracic spinal cord ΔIMP (D) prior to induction of kyphosis, at maximal kyphosis, after laminectomy, after midsagittal durotomy, and after incising the midsagittal pia (*p < 0.05).

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