Biomechanical Analysis of Multilevel Posterior Cervical Spinal Fusion Constructs

Timothy P. Murphy*, Donald F. Colantonio, Anthony H. Le, Donald R. Fredericks, Cody D. Schlaff, Erik B. Holm, Arjun S. Sebastian, Alfred J. Pisano, Melvin D. Helgeson, Scott C. Wagner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Study Design: Controlled Laboratory Study Objective: To compare multilevel posterior cervical fusion (PCF) constructs stopping at C7, T1, and T2 under cyclic load to determine the range of motion (ROM) between the lowest instrumented level and lowest instrumented-adjacent level (LIV-1). Summary of Background Data: PCF is a mainstay of treatment for various cervical spine conditions. The transition between the flexible cervical spine and rigid thoracic spine can lead to construct failure at the cervicothoracic junction. There is little evidence to determine the most appropriate level at which to stop a multilevel PCF. Methods: Fifteen human cadaveric cervicothoracic spines were randomly assigned to 1 of 3 treatment groups: PCF stopping at C7, T1, or T2. Specimens were tested in their native state, following a simulated PCF, and after cyclic loading. Specimens were loaded in flexion-extension), lateral bending, and axial rotation. Three-dimensional kinematics were recorded to evaluate ROM. Results: The C7 group had greater flexion-extension motion than the T1 and T2 groups following instrumentation (10.17±0.83 degree vs. 2.77±1.66 degree and 1.06±0.55 degree, P <0.001), and after cyclic loading (10.42±2.30 degree vs. 2.47±0.64 degree and 1.99±1.23 degree, P<0.001). There was no significant difference between the T1 and T2 groups. The C7 group had greater lateral bending ROM than both thoracic groups after instrumentation (8.81±3.44 degree vs. 3.51±2.52 degree, P=0.013 and 1.99±1.99 degree, P=0.003) and after cyclic loading. The C7 group had greater axial rotation motion than the thoracic groups (4.46±2.27 degree vs. 1.26±0.69 degree, P=0.010; and 0.73±0.74 degree, P=0.003) following cyclic loading. Conclusion: Motion at the cervicothoracic junction is significantly greater when a multilevel PCF stops at C7 rather than T1 or T2. This is likely attributable to the transition from a flexible cervical spine to a rigid thoracic spine. Although this does not account for in vivo fusion, surgeons should consider extending multilevel PCF constructs to T1 when feasible. Level of Evidence: Not applicable.

Original languageEnglish
Pages (from-to)E212-E217
JournalClinical Spine Surgery
Issue number5
StatePublished - 1 Jun 2023
Externally publishedYes


  • adjacent segment disease
  • biomechanical
  • cervical fusion
  • cervicothoracic junction
  • distal junctional kyphosis
  • posterior fusion
  • upper thoracic spine


Dive into the research topics of 'Biomechanical Analysis of Multilevel Posterior Cervical Spinal Fusion Constructs'. Together they form a unique fingerprint.

Cite this