Introduction: Complete radiographic evaluation is essential in the surgical treatment of cervical spondylotic myelopathy (CSM). Prior studies correlated cervical sagittal imbalance and kyphosis with disability and worse health-related quality of life (HR-QOL). However, little is known about the elevated angle at the C2-C3 disc space (C2-C3 angle) and its correlation with post-operative outcomes. The present study is the first to consider C2-C3 angle as an additional radiographic predictor of clinical outcomes, and we propose the routine evaluation of C2-C3 angle to help optimize surgical outcomes.

Methods: Retrospective chart review was performed to identify CSM patients who underwent surgeries from 2009 to 2017, and to obtain their demographics, rates of reoperation from instrumentation failure, and HR-QOL. Cervical sagittal alignment variables were measured using the pre- and post-op radiographs. Univariate logistic regressions were used to explore the association between dependent and independent variables, and a multivariable logistic regression model was created using stepwise variable selection as reference by including all independent variables. Nonparametric methods were used to estimate the areas under the receiver operating characteristic (ROC) curves.

Results: We identified 164 patients who had complete pre-and post-operative radiographic and outcomes data. The overall rate of instrumentation failure requiring reoperation was 15.2% (25/164). Only the post-operative C2-C3 angle, sagittal vertical axis, and T1 tilt were found to be significantly associated with the odds of instrumentation failure. The ROC analysis demonstrated that C2-C3 angle was the most accurate of the models.

Conclusions: In our retrospective analysis of post-operative outcomes of patients with CSM, significant association was found between the C2-C3 angle and post-operative clinical outcomes. We propose that C2-C3 angle be used as an additional parameter of cervical sagittal alignment and predictor for the operative outcomes. C2-C3 angle may also be useful intra-operatively, to serve as a surrogate measure to the global cervical balance.

Patient Care: CSM is a common but frequently undiagnosed manifestation of degenerative process. Although there is uncertainty regarding the determination of the optimal approach, the operative objective to achieve decompression, deformity correction, and stabilization remains clear. Our proposed routine evaluation of C2-C3 angle can be a valuable additional radiogrphic tool to optimize the pre-op planning with the degree of deformity correction necessary, intra-operative evaluation of the global cervical sagittal balance, and post-operative assessment of clinical outcomes.

Learning Objectives: By the conclusion of this session, participants will be able to: 1) Identify the essential cervical alignment measurements, including the C2-C3 disc angle; 2) Utilize the appropriately measured radiographic variables as predictors of clinical post-operative outcomes; 3) Routinely evaluate the C2-C3 angle pre-, intra-, and post-operatively to help minimize surgical complications and optimize outcomes.

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