An analysis of different modalities of bone mineral densitometry evaluation in cage subsidence in anterior cervical discectomy and fusion

Objective To compare the effectiveness of different measurement methods on bone miner density (BMD), including cervical HU of CT, MRI-based cervical vertebral bone quality (C-VBQ), and T value of DEXA, for predicting cage subsidence after single-level ACDF. Methods This is a retrospective study, and patients who underwent single-level ACDF from June 2019 to June 2022 were recruited. We collected preoperative total segmental vertebral height (pre-TSVH), cage subsidence height, cervical angle (CA), T1-slope, straight or reverse cervical curvature, mean HU value of C3–7 (C-HU), mean HU of segment (seg-HU), C-VBQ, segmental C-VBQ (seg-VBQ), and total lumbar T value ( T value). The variables between the two groups were compared by Student's t test or chi-square test. Logistic regression was used to determine the independent risk factors for subsidence. The ROC curve was used to analyze the predictive efficiency of C-HU, seg-HU, C-VBQ, seg-VBQ and T value for cage subsidence. Finally, the correlations of C-HU, seg-HU, C-VBQ, seg-VBQ, T value and subsidence height were analyzed. Results A total of 320 patients were included in this study, and 97 patients (30.31%) had cage subsidence at the last follow-up. The subsidence height was 4.25 ± 0.937 mm in the subsidence group and 1.40 ± 0.726 mm in the nonsubsidence group. There were statistically significant differences between the two groups in bone mineral density-related indexes, including C-HU, seg-HU, C-VBQ, seg-VBQ, and T value ( p < 0.05). Logistic regression analysis showed that C-HU was an independent risk factor for vertebral subsidence after single-level ACDF. ROC curve analysis showed that C-HU had the largest AUC of 0.897 (0.862, 0.933) in predicting vertebral subsidence. Correlation analysis showed that C-HU had a high correlation with the T value ( r = 0.662, p < 0.001), while C-VBQ had a low correlation with the T value ( r = −0.173, p = 0.002), and C-VBQ had a low correlation with subsidence height ( r = 0.135, p = 0.016). Conclusion Our study showed that compared with the C-VBQ and T value, C-HU is more effective for predicting cage subsidence after ACDF. Using the segmental index of C-VBQ or HU could not improve predictive effectiveness. C-VBQ may be insufficient in predicting cage subsidence and estimating BMD.