Prediction of Pedicle Screw Loosening for Lumbar Fusion Surgery with Preoperative Volume of Interest- Based Hounsfield Units in Lumbar Vertebral Bodies on Computed Tomography

Objective This study aimed to evaluate the relationship between pedicle screw loosening and Hounsfield unit (HU) values measured using the volume of interest (VOI) method on preoperative computed tomography (CT) scans in patients undergoing lumbar spinal fusion surgery. Methods A retrospective cohort study was conducted on 82 patients who underwent single-level lumbar interbody fusion with bilateral pedicle screw fixation between October 2015 and October 2022 at four medical institutions. HU values at L1-L5 were measured using the VOI method. All measurements were performed by a single independent observer blinded to screw loosening status. Receiver operating characteristic curve analysis was used to determine the optimal HU cutoff values for predicting screw loosening. Results Of the 82 patients, 26 developed pedicle screw loosening. The loosening group had significantly lower HU values at all vertebral levels (p < 0.05). The mean HU across L1-L5 was 235.7 ± 35.2 in the loosening group and 283.2 ± 65.6 in the non-loosening group (p < 0.001). HU values at all vertebral levels demonstrated predictive value for screw loosening. The mean HU value over L1-L5 showed moderate predictive ability, with an area under the curve of 0.723, a sensitivity of 88.5% and a specificity of 50.0%. Conclusions Preoperative HU measurement using the VOI method on CT scans provides valuable insight into bone quality and demonstrates moderate predictive ability for assessing the risk of pedicle screw loosening. This method may serve as a practical tool for preoperative planning, guiding surgical strategies, and improving outcomes in lumbar fusion surgery.