Prediction of Pedicle Screw Loosening For Lumbar Fusion Surgery With Preoperative Volume Of Interest-Based Hounsfield Units in Lumbar Vertebral Bodies On Computed Tomography

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To assess whether preoperative Hounsfield unit (HU) values measured using the volume of interest (VOI) method on computed tomography (CT) scans predict pedicle screw loosening after single-level lumbar fusion surgery. SUMMARY OF BACKGROUND DATA: Pedicle screw loosening is a major complication after spinal fusion surgery, particularly in patients with osteoporosis. While CT-derived HU values using region of interest (ROI) analysis have been associated with bone quality, the 3-dimensional VOI method enables volumetric assessment of the vertebral body. However, the clinical utility of VOI-based HU values for predicting screw loosening remains unclear. METHODS: We retrospectively analyzed 82 patients who underwent single-level lumbar interbody fusion with bilateral pedicle screw fixation. HU values at L1-L5 were measured using a 3D VOI technique. Screw loosening was assessed using follow-up CT scans taken at least 12 months after surgery. Differences in HU values between the loosening and nonloosening groups were evaluated. Receiver operating characteristic (ROC) curve analysis was performed to determine cutoff HU values and predictive performance. RESULTS: Pedicle screw loosening was observed in 26 out of 82 patients (31.7%). HU values were significantly lower in the loosening group across all vertebral levels (P<0.05). The mean HU value across L1-L5 was 235.7±35.2 HU in the loosening group and 283.2±65.6 HU in the nonloosening group (P<0.001). The average HU value across L1-L5 showed moderate predictive performance for screw loosening, with an area under the curve (AUC) of 0.723, a sensitivity of 88.5%, and a specificity of 50.0%. CONCLUSIONS: Preoperative VOI-based HU values were significantly associated with pedicle screw loosening after single-level lumbar fusion surgery and demonstrated moderate predictive performance. VOI-based HU assessment may serve as a potential adjunctive tool for preoperative risk stratification of pedicle screw loosening.