Quantifying Bone Quality Using Computed Tomography Hounsfield Units in the Mid-sagittal View of the Lumbar Spine

Abstract

Background: Computed tomography Hounsfield unit (HU) is an alternative tool to the dual energy x-ray absorptiometry scan T-score to quantify the bone quality. DEXA scan can overestimate the bone mineral density. We studied the correlation of the vertebral mid-axial and mid-sagittal HU to the T-score. Methods: We retrospectively reviewed the electronic medical records of patients who underwent dual energy x-ray absorptiometry and computed tomography scans within 1 year. Age, sex, mid-axial and mid-sagittal HU, and T-score were collected and statistically analyzed. Results: We identified 100 patients with computed tomography of the L1-L4. There were 80 female and 20 male patients. The average age was 60.25 years (±12.54 years). Nineteen patients were diagnosed with degenerative spine disease. There were 56 patients with a normal T-score, 33 with osteopenia, and 11 with osteoporosis. The average HU for the mid-sagittal view was 163 (±59) for L1, 159 (±62) for L2, 151 (±59) for L3, and 150 (±62) for L4. The mid-axial and mid-sagittal HU were positively correlated to the DEXA T-score (P < 0.001). The HU was 177 (95% CI: 160–194) for normal T-scores, 132 (120–143) for T-scores indicating osteopenia, and 106 (88–124) for T-scores indicating osteoporosis (P < 0.001). Post hoc analysis showed no difference between osteopenia and osteoporosis (P = 0.46). Conclusions: Mid-sagittal HU is positively correlated to the T-score, similar to the mid-axial HU. Therefore, it can be used to acquire a general overview of the bone quality before spinal instrumentation.