LAUSR

Measuring the sagittal canal diameter (SCD) is crucial for cervical spine assessment. A small SCD predisposes patients to myelopathy. Stenosis is less common at the C1 level than at the levels below C2. The existing literature regarding hypoplastic stenosis at the C1 level includes a few case reports; based on the literature, C1 hypoplasia seems to be more common in Chinese populations. Normative values of C1 SCD may help in the evaluation of potential cervical stenosis in a given clinical situation; they were reported as adequately powered for defining pure C1 hypoplasia. However, there is a paucity of data on C1 SCD in Chinese populations compared with those in other populations [Supplemental Table 1, http://links.lww.com/CM9/A538]. Among several measurement methods, in vivo computed tomography (CT)-based measurements have been validated and found to be as accurate as measurements in cadaver studies. Thus, we aimed to use CT-based measurements to establish normative values for C1 SCD in Chinese adults and to define C1 hypoplasia.