Cervical Vertebral Bone Density Measurement

All patients in our hospital underwent three-dimensional reconstructive cervical CT (PHILIPS, Brilliance, slice thickness 1.5 mm, distance 1.5 mm, tube voltage 120 kV) within 1 week before surgery. We use the picture archiving and communication system (PACS) measurement of the C2-C7 HU value. HU values were measured using CT scans according to a previously described method [16 (link)]. The average HU values of each vertebral body were based on the axial plane inferior only to the superior endplate, middle of the vertebral body and axial plane superior only to the inferior endplate. The HU value was measured by placing the largest elliptical region of interest (ROI) at the mid-vertebral body, and the ROI was chosen to include as much trabecular bone as possible and to avoid cortical bone and heterogeneous areas, such as cortical bone margins, osteophytes and osteosclerosis. The average of HU values measured from the three ROIs was regarded as the HU for the individual vertebral (Fig. 1).Fig. 1

Midsagittal (A) and axial CT images demonstrating the measurement of vertebral HU value on the axial plane inferior only to the superior endplate (B), middle of the vertebral (C) and axial plane superior only to the inferior endplate (D) (the first letter C stands for cervical vertebra, which consists of seven segments from top to bottom, denoted by C1-C7, the same as T1)