Clinical Impact of T1 Slope Minus Cervical Lordosis After Multilevel Posterior Cervical Fusion Surgery: A Minimum 2-Year Follow Up Data.

Study Design: Retrospective study.

Objective: To assess the long-term relationship between sagittal alignment of the cervical spine and patient-reported health-related quality-of-life (HRQOL) scores after multilevel posterior cervical fusion, and to explore whether an analog of T1 slope minus C2-C7 lordosis ('T1S-CL') impacts on patients' clinical outcomes.

Background: A 6-month follow-up study demonstrated that, similar to the thoracolumbar spine, the severity of disability increases with sagittal malalignment after cervical reconstruction surgery.

Methods: From 2007 to 2014, 31 consecutive patients having multilevel posterior cervical fusion for cervical stenosis, myelopathy, and deformities met inclusion criteria. To determine the true impact of the alignment on HRQOL, patients who have pseudarthrosis, a misplaced screw, junctional pathologies, or adjacent level disc herniation were excluded. Radiographic measurements included: C0-C2 lordosis, C2-C7 lordosis, C2-C7 sagittal vertical axis (SVA), T1 slope, and T1S-CL. Pearson correlation coefficients were calculated between pairs of radiographic measures and HRQOL.

Results: C2-C7 SVA positively correlated with neck disability index (NDI) scores (r = 0.550). For significant correlations between C2-C7 SVA and NDI scores, regression models predicted a threshold C2-C7 SVA value of 43.5 mm, beyond which correlations were most significant. The T1S-CL also correlated positively with C2-C7 SVA and NDI scores (r = 0.827 and r = 0.618, respectively). Results of the regression analysis indicated that a C2-C7 SVA value of 43.5 mm corresponded to a T1S-CL value of 22.2°.

Conclusion: This minimum 2-year follow-up study showed that disability of the neck increased with cervical sagittal malalignment after surgical reconstruction and a greater T1S-CL mismatch was associated with a greater degree of cervical malalignment. Specifically, a T1S-CL mismatch greater than 22.2° corresponded to severe disability (NDI>25) and positive cervical sagittal malalignment, defined as C2-C7 SVA greater than 43.5 mm.

Level Of Evidence: 4.