Relationship between C2 slope with sagittal parameters and clinical function of degenerative cervical kyphosis

PURPOSE: To explore the relationship between C2 slope with sagittal parameters and clinical function of degenerative cervical kyphosis (DCK). METHODS: A retrospective analysis of 127 patients with degenerative cervical spondylosis treated in our spinal deformity center from January 2019 to June 2022. Patients were categorized into two groups and compared based on C2-7 angle (C2-7 ≥ 5° as kyphosis group, C2-7 < 5° as lordosis group). Pearson correlation or Spearman correlation was used to analyze the relationship between C2S and conventional radiological parameters and health -related quality-of-life (HRQOL) outcomes as measured by the EuroQol 5 dimension questionnaire (EQ5D), NRS, and the neck disability index (NDI). The cutoff value of C2S was determined by a receiver operating characteristic (ROC) curve. RESULTS: There were 127 patients who met inclusion criteria (79 men and 48 women). Average 56.00 ± 10.27 years old (range 31–81 years old). C2S of kyphosis group is higher than non-kyphosis group. Aggravating cervical kyphosis increases cSVA positively. For all patients, C2S demonstrated a significant correlation with the O-C2 angle, C2-7 angle, cSVA, and TS-CL (p < 0.05). NRS, NDI and EQ5D-VAS scores revealed a significant correlation with C2S and cSVA (p < 0.01). For the subgroup of patients presenting with DCK, ROC curves demonstrated the cutoff values of C2S as 26.3°, and 30.5°, according to a cSVA of 40 mm, and severe disability expressed by NDI, respectively. CONCLUSION: On the basis of retaining the consistency of cranio-cervical and cervico-thoracic structure, C2S can better analyze the sagittal alignment of DCK patients than TS-CL and has good practicability in clinical application and HRQOL evaluation.