K-line tilt as a novel radiographic parameter in cervical sagittal alignment.

ABSTRACT

OBJECTIVE: To investigate the relationship between the K-line tilt and classical cervical parameters such as the C2-C7 sagittal vertical axis (SVA), cervical lordosis, and the T1 slope in cervical sagittal alignment. We assessed whether the K-line tilt can be used as an excellent cervical parameter. METHODS: We reviewed 50 patients aged 60-89 years who visited the spine center outpatient clinic from May 2017 to September 2017 through cervical spine lateral radiography and checked the cervical spine parameters. All targeted patients were randomized without any prejudice. Radiographic measurements included the K-line tilt, C2-C7 lordosis, the C2-C7 SVA, the T1 slope, and T1 slope minus C2-C7 lordosis (T1S-CL). Pearson correlation coefficients were calculated between the K-line tilt and each cervical parameter. RESULTS: Of the 50 patients, 33 were men. The mean age of the patients was 70.84 ± 7.52 years. The mean K-line tilt was 11.28 ± 8.31°. The K-line tilt was correlated with the C2-C7 SVA (r = 0.813, P = 0.000) and T1S-CL (r = 0.315, P = 0.026). CONCLUSION: This study showed that the K-line tilt is also a useful parameter like the C2-C7 SVA and T1S-CL in cervical sagittal alignment. These slides can be retrieved under Electronic Supplementary Material.