Does Preoperative T1 Slope Affect the Revision Rate of Multilevel Posterior Cervical or Cervical-Thoracic Fusions: Multi-Center Analysis

Introduction: This study examines if preoperative T1 slope should be used when planning the caudal instrumented vertebra in multilevel posterior cervical fusions.

Methods: Analysis of multicenter radiographic and clinical databases of patients that underwent a three or more-level posterior cervical fusion for degenerative disease with at least two years of post-operative (post-op) data. Patients were divided into two groups: Group I (fusion ending within the cervical spine) and Group II (fusion extending into the thoracic spine).

Results: There were 168 and 96 patients in Group I and II, respectively. Overall revision rate was 10.4%. Index surgeries ending in the cervical spine (Group I) had a higher rate of revision than those extending into the thoracic spine (Group II), 11.3% and 9.4% respectively, but were not statistically significant. At two years post-op, cervical lordosis had improved in both groups (12.6° and 14.1°), but the difference between groups was not statistically significant. Though there was no significant difference in T1 slope from two-weeks to two years post-operative, it is noted that patients with a cervical caudal level consistently had higher T1 slopes than those that terminated in the thoracic spine, regardless of revision status. Both groups showed significant improvement in pain (Visual Analog Scale) and function (Oswestry Disability Index) outcomes at two years post-op, but there was no statistical advantage of one terminal level over the other.

Conclusion : As with previous studies, this study did not reveal a clear advantage of a cervical or thoracic last instrumented vertebra (LIV) in multilevel posterior cervical fusion. There was no evidence that preoperative T1 slope had an effect on revision rate in either the cervical or thoracic groups. It is noted, however, that though not significant, the cervical group did have higher T1 slopes consistently throughout the analysis. While this individual measure may not be a singular determinant in end level selection, future studies may include preop T1 slope vs. cervical lordosis mismatch in decision making about both appropriate LIV and the need for concomitant anterior interbody or osteotomy procedures.