Comparative analysis of endplate volumetric bone mineral density and endplate vertebral bone quality for predicting cage subsidence in lateral lumbar interbody fusion

OBJECTIVE The aim of this study was to compare the predictive efficacy of quantitative CT (QCT)–based endplate volumetric bone mineral density (EP-vBMD) and MRI-based endplate vertebral bone quality (EBQ) score for cage subsidence (CS) after lateral lumbar interbody fusion (LLIF). METHODS A retrospective study was conducted on patients who underwent single-level LLIF in conjunction with pedicle screw fixation at the authors’ institution between January 2019 and April 2023. The volumetric bone mineral density (vBMD) was measured based on preoperative CT using phantom-less QCT software. Measurement of the VBQ score was based on preoperative MRI. CS was defined as a decrease of more than 2 mm in the midpoint height of the intervertebral space. The receiver operating characteristic (ROC) curve of the EP-vBMD and EBQ for predicting CS was drawn, and the predictive efficacy of the two methods was compared using the Delong test. Clinical outcomes, including the visual analog scale for low back pain (VAS-BP), VAS for leg pain (VAS-LP), and Oswestry Disability Index (ODI) scores were assessed preoperatively, postoperatively, and at the 1-year follow-up. RESULTS Ninety-seven patients who underwent LLIF were included in this study, including 31 patients with CS and 66 patients with no CS (NCS). No significant differences were observed between the two groups in VAS-BP, VAS-LP, or ODI scores preoperatively, postoperatively, or at the 1-year follow-up (all p > 0.05). The EP-vBMD of the CS group was lower than that of the NCS group, and EBQ was higher than that of the NCS group. The area under the ROC curve (AUC) of EP-vBMD for predicting CS was larger than that of global and segmental vBMD. The AUC of the EBQ for predicting CS was larger than that of global and segmental VBQ, and the AUC of EP-vBMD was larger than that of the EBQ. The combined prediction model of EP-vBMD and EBQ had the largest AUC value (0.899), but it was not significantly different from EP-vBMD alone (p = 0.547). CONCLUSIONS The regional endplate BMD assessment based on QCT and MRI can effectively predict CS after LLIF, and it has better predictive efficiency than the global or surgical segmental vertebrae BMD measurement. EP-vBMD is superior to EBQ in predicting CS. The prediction efficiency of EP-vBMD combined with EBQ was better than EBQ alone, but not better than EP-vBMD.