Intradiscal pressure monitoring in the cervical spine.

Background: Discography has been widely used in the lumbar and cervical spine as a diagnostic tool to identify sources of discogenic pain that may be amenable to surgical treatment. Discography in the cervical spine is currently performed without the benefit of pressure monitoring, and corresponding pressure parameters have not been determined.

Objective: The purpose of this study was to develop the framework for intradiscal pressure monitoring in the cervical spine and the basis for a pressure curve that will reflect clinically significant cervical internal disc disruption. We also sought to determine whether there is any pressure increase in adjacent discs during cervical discography that might result in false-positive diagnosis during in-vivo discography. An additional goal was to establish safe upper parameters for infusion volume and intradiscal pressure in the cervical spine.

Design: Investigation of fresh-frozen discs in the cervical spine.

Methods: Investigated were 26 discs in 5 fresh-frozen cadaveric cervical spines aged 45 to 68 with no prior history of cervical spine disease. A T2 MRI was performed on each specimen and radiographically abnormal discs were noted. Pressure-controlled, fluoroscopically guided discography was performed on each level using a right lateral approach. Opening pressure, rupture pressure, volume infused, and location of rupture were recorded. Pressures were simultaneously recorded at each adjacent disc level using additional pressure monitors and identical needle placement. Immediately following discography, CT was performed on each specimen according to the discography protocol.

Results: Twenty-six discs C2-3 to C7-T1 were grossly intact for evaluation. The median opening pressure was 30 psi (range 14-101 psi). Two discs did not rupture and were pressurized to 367 psi. In 24 discs, the median intradiscal rupture pressure was 40 psi (range 14-171 psi). The median volume infused at rupture was 0.5 ml (range 0.25-1.0 ml). When grouped, the median intradiscal rupture pressure in the C2-3, C3-4, and C7-T1 discs was 53 psi (range 16-171 psi) compared to 36.5 psi (range 14-150 psi) in the C4-5, C5-6, and C6-7 discs (p=0.18). There was no measurable pressure change in any of the 30 adjacent disc levels evaluated.

Conclusion: In the cervical spine, iatrogenic disc injury may be caused at significantly lower pressures and volumes infused than in the lumbar spine. There was no measurable pressure change in any of the adjacent disc levels evaluated at maximum intradiscal pressurization. Further cadaveric testing will be necessary to develop parameters for intradiscal pressure monitoring in the cervical spine.