Comparison of K-Line, T1 Slope and C2–C7 Sagittal Vertical Axis as Predictors of Functional Outcomes Following Surgical Treatment of Cervical Spondylotic Myelopathy: A Retrospective Cohort Study
Abstract
Background: Cervical spondylotic myelopathy is the most common reason for spinal cord impairment in adult patients and is often correlated with unpredictable neurological recovery after surgery, despite appropriate decompressive surgical procedure. Radiographic factors including K-line status, T1 angle and C2-C7 sagittal vertical axis (SVA) have been proposed to be predictive markers for surgical success; yet, their relative significance has not yet been clearly established. Methodology: The present retrospective cohort study comprised 100 cases that had undergone surgical intervention for CSM from January 2023 to December 2025 at a Orthopaedic care hospital. The radiographic parameters evaluated in preoperative examination were K-line, T1 slope and C2-C7 SVA. The functional results were assessed using the mJOA score, NDI, Nurick grade and Hirabayashi recovery index. Correlation analysis, multiple logistic regression and ROC curve analysis were used to assess the predictive power of the radiographic parameters. Results: Post-operative improvement in terms of the mJOA, NDI scores and Nurick grade was significant for all parameters (p <0.001). K-line positive patients showed better neurologic recovery than K-line negative patients (p<0.001). Significant negative correlations were found between T1 slope and C2-C7 SVA whereas cervical lordosis showed a significant positive correlation. K-line positivity and C2-C7 SVA were identified as independent variables with high predictive accuracy on multivariate analysis. ROC analysis showed that C2-C7 SVA had the highest predictive accuracy (AUC=0.842) followed by K-line positivity (AUC=0.801) and T1 slope (AUC=0.742). Conclusion: The cervical spine sagittal vertical axis between C2-C7 is the most accurate prediction for improvement after surgery for CSM. The evaluation of cervical sagittal balance should be considered for pre-operative analysis to improve prognosis, education and surgery planning.