Fig 1.
Schematic overview of C5 palsy rate for single level ACDF (A), single level corpectomy (B) or two level corpectomy (C) for the respective cervical level (not all levels shown). The cervical spine is shown in the sagittal view with the spinal cord marked in blue, the surrounding cerebrospinal fluid in yellow and a schematic stenotic narrowing in red. D-F shows representative corresponding lateral X-ray images of the surgical results. Single level ACDF (D), single level corpectomy (E) and two level corpectomy (F). Integrated tables G-I display the additional statistical values to the corresponding surgical strategies, including the overall C5 palsy rate for the respective surgical approach. Statistical analysis applied routine cross tables and chi2 testing.
Fig 2.
Sagittal schematic of the surgical spine to illustrate C5 palsy rate of two level hybrid constructs, i.e. combination of corpectomy and ACDF, for the levels C4-7 (A) and C3-6 (B). Statistical values are summarized in C, including overall C5 incidence rate for hybrid constructs on all levels around the vulnerable level of C4/C5. Additional information on other possible surgical constructs around the level of C4/C5 is presented in D, allowing for the direct comparison of C5 palsy rate of the different surgical strategies. Statistical analysis applied routine cross tables and chi2 testing.
Fig 3.
Multivariate regression analysis of predictive outcome parameters for C5 palsy rate as illustrated by forest plots (A). Dots indicate the odds-ratio (OR) and whiskers for 95% confidence interval (CI). Integrated table (B) shows the corresponding statistical values including the p-value after regression analysis.
Fig 4.
Illustration of the cervical spinal nerve roots exiting the spinal cord (left). The right side schematically depicts the angle, including the superior and inferior rootlets of the individual nerve root, emphasizing the distinct nerve root exit of C5 as formerly described by Hung et al. and Alleyne et al. [19,20]. Sagittal T2w magnetic resonance imaging of the cervical spine before (B) and after (C) dorsal decompression. This image highlights the dorsal shift of the spinal cord due to decompression. Figure D and E schematically explain the postulated hypothesis on the pathophysiological basis of C5 nerve root palsy. A slowly established ventral stenosis (D) results in a dorsal shift of the myelon, leading to a stretched C5 nerve root (blue), as depicted in the axial view. Ventral decompression through ACDF consecutively leads to a ventral shift of the spinal cord with kinking of the nerve root. A dorsal stenosis (E) represents an analogous situation with dorsal shifting of the spinal cord after laminectomy and fusion, as suggested by the screws. Additional information on the pathophysiological basis can be found in supporting information S1 Video.