BACKGROUND CONTEXT: Recently, attention has been directed to the impact of adult scoliosis or scoliosis treatment on the cervical spine. Several authors have proposed a set of standardized radiographic parameters to help evaluate the cervical spine in patients with adult spinal deformity using fulllength 36-inch radiographs. While this is the standard radiograph used to evaluate spinal deformity, dedicated cervical spine radiographs are more commonly used to evaluate cervical spinal pathology. In order to limit costs and exposure to radiation, there is a need to determine whether a full-length 36-inch radiograph is necessary to evaluate the sagittal parameters of the cervical spine, if a dedicated cervical spine film has already been obtained. PURPOSE: To determine whether there is a correlation between sagittal measures of the spine taken from a dedicated cervical spine radiograph and those taken from a 36-inch spine radiograph. STUDY DESIGN/SETTING: Cross sectional study from a single tertiary spine practice. PATIENT SAMPLE: Patients who had a cervical spine radiograph and 36-inch spine radiograph within four weeks of each other were identified from the billing database. OUTCOME MEASURES: C0-C2, C0-C7, C1-C2 and C2-C7 Sagittal Cobb angles; T1 slope; Chin-brow-vertical angle (CBVA), C1-C7 sagittal vertical axis (SVA), C2-C7 SVA, Center of Gravity-C7 sagittal vertical axis (COG-C7 SVA). METHODS: On separate occasions, de-identified radiographs were evaluated and the following radiographic measures were determined: C0-C2, C0-C7, C1-C2 and C2-C7 Sagittal Cobb angles; T1 slope; CBVA, C1- C7 SVA, C2-C7 SVA and COG-C7 SVA. Paired t-tests and correlation analyses were performed between the corresponding paired radiographic parameter as measured on the cervical spine radiograph and the 36-inch radiograph. Correlation coefficients between 0.60 and 080 indicate a marked degree of correlation; while coefficients between 0.80 and 1.00 indicate robust correlations. RESULTS: Radiographic measurements were collected on 40 patients. There were 33 females and 7 males with a mean age of 48.9 +/- 14.5 years. All correlations were statistically significant at p<0.001. All sagittal Cobb measures showed a marked correlation. The C0-C2 sagittal Cobb had the strongest correlation (r=0.81) and the C2-C7 sagittal Cobb had the weakest (0.62). Among the sagittal balance parameters, the COG-C7 SVA had the weakest correlation (r=0.42) and the C1-C7 SVA (r=0.64) and the C1- C7 SVA (r=0.65) had strong correlations. The T1 slope and the CBVA had correlation coefficients of 0.74 and 0.91 respectively. Paired t-tests showed that there was no statistically significant difference in the measures taken from the cervical radiograph and 36-inch radiograph, except for the C0-C7 sagittal Cobb (p=0.000) with a measurement difference of 7 degrees and the T1 tilt (p=0.000) with a measurement difference of 5 degrees. CONCLUSIONS: Except for COG-C7 SVA, strongcorrelations between most cervical spine parameters taken from a dedicated cervical spine radiograph and those taken from a 36-inch radiograph. Most measures were similar when evaluated from either film. A full-length 36-inch radiograph may not be necessary to evaluate the cervical spine when a dedicated cervical spine radiograph has already been obtained.
Carreon, L. Y., Smith, C. L., Dimar, J. R., & Glassman, S. D. (2016). Correlation of cervical sagittal alignment parameters on full-length spine radiographs compared with dedicated cervical radiographs. Scoliosis and Spinal Disorders, 11(1). https://doi.org/10.1186/s13013-016-0072-0