Cervical and First Thoracic Spine Hounsfield Units Assessment and Relationship to Clinical Outcomes and Cervical Sagittal Parameters in Patients Undergoing Anterior Cervical Spine Surgery

This study had 3 objectives: to compare bone mineral density (BMD) from 3 axial slices, subchondral trabecular bone 2 mm inferior to the cranial endplate, middle of the vertebral body, and subchondral trabecular bone 2 mm superior to the caudal endplate; assess BMD variations and correlations of C1-T1 vertebrae; and correlate BMD with clinical outcomes and cervical sagittal parameters in patients undergoing anterior cervical discectomy and fusion. The study enrolled 71 patients who underwent anterior cervical discectomy and fusion between March 2017 and January 2020. Patient demographics, clinical outcomes, cervical sagittal parameters, and Hounsfield units (HUs) of C1-T1 vertebrae were recorded. Analysis of variance was performed to compare HUs from the axial slices. Pearson correlation coefficient was performed to calculate the relationship between mean HUs of C1-T1 and to assess correlations of mean HUs with clinical outcomes and cervical sagittal parameters. There were no significant differences between HUs of 3 axial levels. Mean HUs were highest in the mid-cervical spine (C4). Significant correlations in mean HUs among all measured spinal levels were observed. Age, sex, and body mass index were not related to mean HUs. Visual analog scale, Neck Disability Index, and Patient Health Questionnaire-9 scores were not related to HUs before and after surgery. There were significant correlations among mean HUs of C2-T1 vertebrae, C2-C7 sagittal vertical axis, and cranial tilt. Mean HUs of C4 had the strongest correlation with C2-C7 sagittal vertical axis. To our knowledge, this is the first study of cranial and caudal subchondral trabecular BMD using HUs and comparing them with the middle of the vertebral body and study of correlations between mean HUs of C1-T1 vertebrae and clinical outcomes and cervical sagittal parameters. Correcting C2-C7 sagittal vertical axis and cranial tilt would improve BMD of C1-T1 vertebrae.