Abstract
BACKGROUND: This study aimed to evaluate the predictive value of CT-based S(1) Hounsfield Unit (HU) measurements for postoperative pedicle screw loosening (PSL) in patients with lumbar degenerative diseases who underwent posterior lumbar interbody fusion (PLIF). METHODS: Consecutive patients who underwent PLIF at our institution between January 2016 and June 2024 were retrospectively analyzed. The L(1) and S(1) HU values were obtained using CT, whereas L(1)–L(4) and S(1) vertebral bone quality (VBQ) scores were obtained using MRI. Multivariate logistic regression analysis was performed to identify independent predictors of PSL. The area under the receiver operating characteristic curve (AUC) was used to assess the predictive performance of bone quality parameters. Optimal cutoff values were determined using the Youden index. RESULTS: A total of 285 patients were included. The PSL rate was 21.40% (61/285). The loosening group demonstrated a lower L(1) and S(1) HU values, and higher L(1)–L(4) and S(1) VBQ scores (P < 0.001) than the non-loosening group. Multivariable logistic regression analysis identified lowest instrumented vertebra (LIV) at S(1) (P = 0.001) and L(1) (P < 0.001) and S(1) HU values (P < 0.001) and L(1)–L(4) (P = 0.026) and S(1) VBQ scores (P < 0.001) as independent predictors of PSL. The AUCs for L(1) and S(1) HU values and L(1)–L(4) and S(1) VBQ scores were 0.772, 0.770, 0.730, and 0.753, respectively. CONCLUSIONS: When conventional bone mineral density metrics are unavailable, the S(1) HU value serves as an effective preoperative predictor. Notably, S(1) HU demonstrated a higher discriminative capacity for PSL than the S(1) VBQ score. Furthermore, integrating L(1) and S(1) HU values yielded markedly superior predictive efficiency compared with either parameter assessed independently. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12893-026-03570-3.