Hounsfield unit to serum pentosidine ratio predicts screw loosening after lumbar interbody fusion.

PURPOSE

This study aimed to identify whether the ratio of the vertebral Hounsfield unit to serum pentosidine (H/P ratio), which reflects bone density and quality, can predict screw loosening after spinal fusion surgery.

METHODS

A retrospective case-control study was conducted in 35 patients (mean age 71 ± 10.4 years, 18 men) who underwent spinal interbody fusion for lumbar spine disease between June 2020 and February 2022. Screw loosening was evaluated by computed tomography at 12 months postoperatively. Information was collected on patient background characteristics, including age, sex, body mass index, diagnosis, dialysis status, smoking history, diabetes, steroid use, and osteoporosis. Imaging parameters, the surgical method used, number of fixed intervertebral segments, intervertebral level (including L5/S1 or not), and the H/P ratio were also investigated. Risk factors associated with screw loosening and pseudarthrosis were examined in univariable and multivariable logistic regression analyses. A P-value of < 0.05 was considered statistically significant.

RESULTS

Screw loosening occurred in 14 of 35 patients (40%). Multivariate analysis revealed that the H/P ratio (odds ratio 0.09, confidence interval 0.02-0.53, P = 0.007) was a significant risk factor for screw loosening at 12 months postoperatively.

CONCLUSION

This study demonstrates that the H/P ratio, which reflects both bone density and deterioration of bone quality in the vertebral body, may serve as a predictor of screw loosening at 12 months after lumbar spinal surgery.