Opportunistic Use of Intraoperative Computed Tomography for the Assessment of Bone Quality

Single-institution, retrospective cohort study.

Determine whether preoperative and intraoperative computed tomography (CT) Hounsfield units (HU) were reliable, consistent, and had similar diagnostic ability for detecting osteoporosis.

Osteoporosis is common in spine surgical patients and associated with adverse outcomes. Opportunistic use of preoperative CT HU has been shown to estimate bone quality and fracture risk. Spinal navigation systems utilize intraoperative CT, which may offer an opportunity for osteoporosis assessment.

From January 2021 to December 2022, 166 patients who underwent thoracolumbar surgery using spinal navigation and had both preoperative and intraoperative CT scans were included. Regions of interest (ROI) measuring 200 mm2 were placed in the centroid of the L1 vertebral body to measure HU, with HU values >150 indicating normal bone, 110-150 osteopenia, and <110 osteoporosis. Preoperative and intraoperative CT HU were compared using the Pearson correlation. Bland-Altman and Cohen kappa analysis were used to determine agreement.

Mean (SD) age was 61.11 (8.79), BMI was 30.26 (6.09), and 54% were female. Mean preoperative and intraoperative L1 HU were 150.66 (58.33) and 148.41 (57.59), respectively, which were not significantly different (P=0.339). On the basis of HU, normal bone, osteopenia, and osteoporosis were present in 41%, 39%, and 20% of patients based on preoperative CT compared with 37%, 38%, and 25% on intraoperative CT, k=0.91 [95% CI: 0.87-0.95]. Preoperative and intraoperative CT HU had a strong, positive correlation (r=0.982, P<0.001). Bland-Altman demonstrated agreement between preoperative and intraoperative CT HU, with a mean difference of 2.23 [95% CI: -19.70 to 24.16], P=0.427.

Preoperative and intraoperative CT HU values were reliable, consistent, and demonstrated similar diagnostic ability for osteoporosis. Intraoperative HU may be useful for identifying patients at high risk for fracture or adverse surgical outcomes with probable osteoporosis who may require further postoperative bone health evaluation.