Adjacent-level range of motion and intradiscal pressure after posterior cervical decompression and fixation: An in vitro human cadaveric model

Ryan M. Kretzer, Wesley Hsu, Nianbin Hu, Hidemasa Umekoji, George I. Jallo, Paul C. McAfee, P. Justin Tortolani, Bryan W. Cunningham

Research output: Contribution to journalArticlepeer-review

Abstract

STUDY DESIGN.: This in vitro human cadaveric study measured adjacent-level kinematics after posterior cervical decompression and fixation. OBJECTIVE.: Quantify adjacent-level changes in range of motion (ROM) and intradiscal pressure after posterior cervical decompression and fixation. SUMMARY OF BACKGROUND DATA.: Optimal length of instrumentation after posterior decompression is unclear. Longer posterior cervical fixation constructs may increase the risk of adjacent-segment degeneration. METHODS.: Eight cervicothoracic spines were evaluated intact, with C3-C6 laminectomy, C3-C6 laminectomy + C3-C6 fixation, C3-C6 laminectomy + C3-C7 fixation, C3-C7 laminectomy, C3-C7 laminectomy + C3-C7 fixation, C3-C7 laminectomy + C2-C7 fixation, C3-C7 laminectomy + C3-T2 fixation, and C3-C7 laminectomy + C2-T2 fixation. Testing included intact moments (±2.0 N•m) in flexion/extension, axial rotation, and lateral bending, with quantification of ROM at C2-C3, C6-C7, and C7-T1 normalized to the intact spine. Intradiscal pressures were also measured at each level. RESULTS.: For the C3-C6 laminectomy group, there were no differences in adjacent-level flexion/extension ROM or intradiscal pressure based on construct length, except at C6-C7, where ROM was significantly decreased when fixation was extended to C7 (P < 0.05). After C3-C7 laminectomy and reconstruction, the greatest increase in C2-C3 flexion/extension ROM and intradiscal pressure occurred in the C3-T2 fixation subgroup (ROM: 348% [P < 0.05]; intradiscal pressure: 319 ± 243 psi [pounds per square inch] vs. 65 ± 41 psi intact [P < 0.05]). At C7-T1, the greatest increase in flexion/extension ROM and intradiscal pressure occurred after C2-C7 fixation (ROM: 531% [P < 0.05]; intradiscal pressure: 152 ± 83 psi vs. 21 ± 14 psi intact [P < 0.05]). CONCLUSION.: For C3-C6 laminectomy, instrumentation to C7 significantly decreased flexion/extension ROM and intradiscal pressure at C6-C7 without significantly increasing either measure at C2-C3 or C7-T1 relative to C3-C6 fixation. In the setting of a C3-C7 laminectomy, when instrumenting to either C2 or T2, consideration should be given to including both levels within these constructs.

Original languageEnglish (US)
Pages (from-to)E778-E785
JournalSpine
Volume37
Issue number13
DOIs
StatePublished - Jun 1 2012

Keywords

  • adjacent segment degeneration
  • biomechanics
  • cervical spondylotic myelopathy
  • cervicothoracic junction
  • intradiscal pressure
  • posterior cervical fixation

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology

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