Relationship Between T1 Slope and Cervical Alignment Following Multilevel Posterior Cervical Fusion Surgery: Impact of T1 Slope Minus Cervical Lordosis
Study Design. Retrospective study. Objective. To assess the relationship between sagittal alignment of the cervical spine and patient reported health related quality of life scores following multilevel posterior cervical fusion, and to explore whether an analogous relationship exists in the cervical spine using T1 slope minus C2 C7 lordosis (T1S CL) Summary of Background Data. A recent study demonstrated that, similar to the thoracolumbar spine, the severity of disability increases with sagittal malalignment following cervical reconstruction surgery. Methods. From 2007 to 2013, 38 consecutive patients underwent multilevel posterior cervical fusion for cervical stenosis, myelopathy, and deformities. 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 health related quality of life. Results. C2 C7 SVA positively correlated with neck disability index (NDI) scores (r 0.495) C2 C7 lordosis (P 0.001) and T1S CL (P 0.002) changes correlated with NDI score changes after surgery. For significant correlations between C2 C7 SVA and NDI scores, regression models predicted a threshold C2 C7 SVA value of 50 mm, beyond which correlations were most significant. The T1S CL also correlated positively with C2 C7 SVA and NDI scores (r 0.871 and r 0.470, respectively) Results of the regression analysis indicated that a C2 C7 SVA value of 50 mm corresponded to a T1S CL value of 26.1deg. Conclusion. This study showed that disability of the neck increased with cervical sagittal malalignment following surgical reconstruction and a greater T1S CL mismatch was associated with a greater degree of cervical malalignment. Specifically, a mismatch greater than 26.1deg corresponded to positive cervical sagittal malalignment, defined as C2 C7 SVA greater than 50 mm. Level of Evidence: 3
Spine