Comparison of the predictive roles of CT- and MRI-based endplate regional osteoporosis status measurements for cage subsidence after posterior lumbar interbody fusion.

OBJECTIVE: This study aimed to compare the efficacy of endplate Hounsfield unit (HU) values and endplate bone quality (EBQ) scores in predicting cage subsidence (CS) after posterior lumbar interbody fusion (PLIF) in older patients and identify the most discriminative bone mineral density (BMD) assessment indicator. METHODS: This retrospective analysis included consecutive patients who underwent PLIF at the authors' institution between January 2016 and February 2024. Clinical data were collected for all patients. Propensity scores were used to match patients with and without CS, and the matched cohort was subjected to conditional logistic regression to investigate the association between radiographic factors and CS. L1 and endplate HU values were derived from CT scans, whereas vertebral bone quality (VBQ) and EBQ scores were derived from MR images. Receiver operating characteristic curve analysis was conducted to assess the predictive value of endplate HU values and EBQ scores for CS and further compare their predictive value with that of L1 HU values and VBQ scores. RESULTS: This study included 130 matched patients. The CS group demonstrated lower L1 (p < 0.001) and endplate HU (p < 0.001) values and higher VBQ (p = 0.002) and EBQ (p < 0.001) scores compared with the non-CS group. The conditional logistic regression analysis identified L1 HU value (OR 0.99, 95% CI 0.97-0.99; p = 0.036), endplate HU value (OR 0.99, 95% CI 0.98-0.99; p = 0.044), VBQ score (OR 2.40, 95% CI 1.34-4.32; p = 0.038), and EBQ score (OR 4.46, 95% CI 2.16-9.18; p = 0.003) as independent predictors of CS, demonstrating areas under the curve of 0.722, 0.815, 0.648, and 0.782, respectively. The optimal cutoff for the endplate HU value in predicting CS was 262.11 (sensitivity 83.08%, specificity 73.85%). CONCLUSIONS: Endplate HU values indicated a relatively higher predictive performance for CS compared with EBQ scores and served as the most discriminative BMD indicator in patients who underwent PLIF. Measuring the endplate HU value preoperatively helps surgeons select a more appropriate surgical plan and is expected to improve patient outcomes.