Hounsfield units vs. vertebral bone quality score: which is a better predictor of screw loosening after single-level lumbar interbody fusion?

PURPOSE

To clarify the ability of the preoperative CT Hounsfield units (HU) of the vertebrae and MRI-based vertebral bone quality (VBQ) score in predicting screw loosening following lumbar interbody fusion.

METHODS

Patients with lumbar degenerative disease who underwent single-level lumbar interbody fusion at five hospitals were enrolled. The HU were assessed at vertebral body and pedicle. The VBQ score was assessed on the T1-weighted sagittal image and defined as the quotient of the median signal intensity of the vertebrae from L1 to L4 divided by the signal intensity of the cerebrospinal fluid. Screw loosening was evaluated by the postoperative CT scans at 12 months or more. Patients were divided into the screw loosening group and no loosening group, and the HU and the VBQ score were compared between the groups.

RESULTS

A total of 107 patients (mean age, 67.8 ± 10.1 years, 62 men) were included. At the vertebral body, the HU of L1, the average HU from L1 to L4, from L1 to L5, and from L1 to S1, and the HU of the upper instrumented vertebra showed a statistically significant difference between the two groups. The average HU of the vertebral body from L1 to L4 showed the highest AUC of 0.651 and sensitivity of 0.818. No significant difference was found in the HU of the pedicle and VBQ score.

CONCLUSION

The preoperative CT HU of the vertebral bodies could reliably predict screw loosening following lumbar interbody fusion. In contrast, the VBQ score did not predict screw loosening.